12 files changed, 555 insertions, 287 deletions

diff --git a/application/bookmark/Bookmark.php b/application/bookmark/Bookmark.php
index 1beb8be2..4238ef25 100644
--- a/application/bookmark/Bookmark.php
+++ b/application/bookmark/Bookmark.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Shaarli\Bookmark;
 
 use DateTime;
@@ -17,7 +19,7 @@ use Shaarli\Bookmark\Exception\InvalidBookmarkException;
 class Bookmark
 {
     /** @var string Date format used in string (former ID format) */
-    const LINK_DATE_FORMAT = 'Ymd_His';
+    public const LINK_DATE_FORMAT = 'Ymd_His';
 
     /** @var int Bookmark ID */
     protected $id;
@@ -52,32 +54,37 @@ class Bookmark
     /** @var bool True if the bookmark can only be seen while logged in */
     protected $private;
 
+    /** @var mixed[] Available to store any additional content for a bookmark. Currently used for search highlight. */
+    protected $additionalContent = [];
+
     /**
      * Initialize a link from array data. Especially useful to create a Bookmark from former link storage format.
      *
-     * @param array $data
+     * @param array  $data
+     * @param string $tagsSeparator Tags separator loaded from the config file.
+     *                              This is a context data, and it should *never* be stored in the Bookmark object.
      *
      * @return $this
      */
-    public function fromArray($data)
+    public function fromArray(array $data, string $tagsSeparator = ' '): Bookmark
     {
-        $this->id = $data['id'];
-        $this->shortUrl = $data['shorturl'];
-        $this->url = $data['url'];
-        $this->title = $data['title'];
-        $this->description = $data['description'];
-        $this->thumbnail = isset($data['thumbnail']) ? $data['thumbnail'] : null;
-        $this->sticky = isset($data['sticky']) ? $data['sticky'] : false;
-        $this->created = $data['created'];
+        $this->id = $data['id'] ?? null;
+        $this->shortUrl = $data['shorturl'] ?? null;
+        $this->url = $data['url'] ?? null;
+        $this->title = $data['title'] ?? null;
+        $this->description = $data['description'] ?? null;
+        $this->thumbnail = $data['thumbnail'] ?? null;
+        $this->sticky = $data['sticky'] ?? false;
+        $this->created = $data['created'] ?? null;
         if (is_array($data['tags'])) {
             $this->tags = $data['tags'];
         } else {
-            $this->tags = preg_split('/\s+/', $data['tags'], -1, PREG_SPLIT_NO_EMPTY);
+            $this->tags = tags_str2array($data['tags'] ?? '', $tagsSeparator);
         }
         if (! empty($data['updated'])) {
             $this->updated = $data['updated'];
         }
-        $this->private = $data['private'] ? true : false;
+        $this->private = ($data['private'] ?? false) ? true : false;
 
         return $this;
     }
@@ -93,24 +100,29 @@ class Bookmark
      *   - the URL with the permalink
      *   - the title with the URL
      *
+     * Also make sure that we do not save search highlights in the datastore.
+     *
      * @throws InvalidBookmarkException
      */
-    public function validate()
+    public function validate(): void
     {
-        if ($this->id === null
+        if (
+            $this->id === null
             || ! is_int($this->id)
             || empty($this->shortUrl)
             || empty($this->created)
-            || ! $this->created instanceof DateTimeInterface
         ) {
             throw new InvalidBookmarkException($this);
         }
         if (empty($this->url)) {
-            $this->url = '/shaare/'. $this->shortUrl;
+            $this->url = '/shaare/' . $this->shortUrl;
         }
         if (empty($this->title)) {
             $this->title = $this->url;
         }
+        if (array_key_exists('search_highlight', $this->additionalContent)) {
+            unset($this->additionalContent['search_highlight']);
+        }
     }
 
     /**
@@ -119,11 +131,11 @@ class Bookmark
      *   - created: with the current datetime
      *   - shortUrl: with a generated small hash from the date and the given ID
      *
-     * @param int $id
+     * @param int|null $id
      *
      * @return Bookmark
      */
-    public function setId($id)
+    public function setId(?int $id): Bookmark
     {
         $this->id = $id;
         if (empty($this->created)) {
@@ -139,9 +151,9 @@ class Bookmark
     /**
      * Get the Id.
      *
-     * @return int
+     * @return int|null
      */
-    public function getId()
+    public function getId(): ?int
     {
         return $this->id;
     }
@@ -149,9 +161,9 @@ class Bookmark
     /**
      * Get the ShortUrl.
      *
-     * @return string
+     * @return string|null
      */
-    public function getShortUrl()
+    public function getShortUrl(): ?string
     {
         return $this->shortUrl;
     }
@@ -159,9 +171,9 @@ class Bookmark
     /**
      * Get the Url.
      *
-     * @return string
+     * @return string|null
      */
-    public function getUrl()
+    public function getUrl(): ?string
     {
         return $this->url;
     }
@@ -171,7 +183,7 @@ class Bookmark
      *
      * @return string
      */
-    public function getTitle()
+    public function getTitle(): ?string
     {
         return $this->title;
     }
@@ -181,7 +193,7 @@ class Bookmark
      *
      * @return string
      */
-    public function getDescription()
+    public function getDescription(): string
     {
         return ! empty($this->description) ? $this->description : '';
     }
@@ -191,7 +203,7 @@ class Bookmark
      *
      * @return DateTimeInterface
      */
-    public function getCreated()
+    public function getCreated(): ?DateTimeInterface
     {
         return $this->created;
     }
@@ -201,7 +213,7 @@ class Bookmark
      *
      * @return DateTimeInterface
      */
-    public function getUpdated()
+    public function getUpdated(): ?DateTimeInterface
     {
         return $this->updated;
     }
@@ -209,11 +221,11 @@ class Bookmark
     /**
      * Set the ShortUrl.
      *
-     * @param string $shortUrl
+     * @param string|null $shortUrl
      *
      * @return Bookmark
      */
-    public function setShortUrl($shortUrl)
+    public function setShortUrl(?string $shortUrl): Bookmark
     {
         $this->shortUrl = $shortUrl;
 
@@ -223,14 +235,14 @@ class Bookmark
     /**
      * Set the Url.
      *
-     * @param string $url
-     * @param array  $allowedProtocols
+     * @param string|null $url
+     * @param string[]    $allowedProtocols
      *
      * @return Bookmark
      */
-    public function setUrl($url, $allowedProtocols = [])
+    public function setUrl(?string $url, array $allowedProtocols = []): Bookmark
     {
-        $url = trim($url);
+        $url = $url !== null ? trim($url) : '';
         if (! empty($url)) {
             $url = whitelist_protocols($url, $allowedProtocols);
         }
@@ -242,13 +254,13 @@ class Bookmark
     /**
      * Set the Title.
      *
-     * @param string $title
+     * @param string|null $title
      *
      * @return Bookmark
      */
-    public function setTitle($title)
+    public function setTitle(?string $title): Bookmark
     {
-        $this->title = trim($title);
+        $this->title = $title !== null ? trim($title) : '';
 
         return $this;
     }
@@ -256,11 +268,11 @@ class Bookmark
     /**
      * Set the Description.
      *
-     * @param string $description
+     * @param string|null $description
      *
      * @return Bookmark
      */
-    public function setDescription($description)
+    public function setDescription(?string $description): Bookmark
     {
         $this->description = $description;
 
@@ -271,11 +283,11 @@ class Bookmark
      * Set the Created.
      * Note: you shouldn't set this manually except for special cases (like bookmark import)
      *
-     * @param DateTimeInterface $created
+     * @param DateTimeInterface|null $created
      *
      * @return Bookmark
      */
-    public function setCreated($created)
+    public function setCreated(?DateTimeInterface $created): Bookmark
     {
         $this->created = $created;
 
@@ -285,11 +297,11 @@ class Bookmark
     /**
      * Set the Updated.
      *
-     * @param DateTimeInterface $updated
+     * @param DateTimeInterface|null $updated
      *
      * @return Bookmark
      */
-    public function setUpdated($updated)
+    public function setUpdated(?DateTimeInterface $updated): Bookmark
     {
         $this->updated = $updated;
 
@@ -301,7 +313,7 @@ class Bookmark
      *
      * @return bool
      */
-    public function isPrivate()
+    public function isPrivate(): bool
     {
         return $this->private ? true : false;
     }
@@ -309,11 +321,11 @@ class Bookmark
     /**
      * Set the Private.
      *
-     * @param bool $private
+     * @param bool|null $private
      *
      * @return Bookmark
      */
-    public function setPrivate($private)
+    public function setPrivate(?bool $private): Bookmark
     {
         $this->private = $private ? true : false;
 
@@ -323,9 +335,9 @@ class Bookmark
     /**
      * Get the Tags.
      *
-     * @return array
+     * @return string[]
      */
-    public function getTags()
+    public function getTags(): array
     {
         return is_array($this->tags) ? $this->tags : [];
     }
@@ -333,13 +345,18 @@ class Bookmark
     /**
      * Set the Tags.
      *
-     * @param array $tags
+     * @param string[]|null $tags
      *
      * @return Bookmark
      */
-    public function setTags($tags)
+    public function setTags(?array $tags): Bookmark
     {
-        $this->setTagsString(implode(' ', $tags));
+        $this->tags = array_map(
+            function (string $tag): string {
+                return $tag[0] === '-' ? substr($tag, 1) : $tag;
+            },
+            tags_filter($tags, ' ')
+        );
 
         return $this;
     }
@@ -357,11 +374,11 @@ class Bookmark
     /**
      * Set the Thumbnail.
      *
-     * @param string|bool $thumbnail Thumbnail's URL - false if no thumbnail could be found
+     * @param string|bool|null $thumbnail Thumbnail's URL - false if no thumbnail could be found
      *
      * @return Bookmark
      */
-    public function setThumbnail($thumbnail)
+    public function setThumbnail($thumbnail): Bookmark
     {
         $this->thumbnail = $thumbnail;
 
@@ -369,11 +386,29 @@ class Bookmark
     }
 
     /**
+     * Return true if:
+     *   - the bookmark's thumbnail is not already set to false (= not found)
+     *   - it's not a note
+     *   - it's an HTTP(S) link
+     *   - the thumbnail has not yet be retrieved (null) or its associated cache file doesn't exist anymore
+     *
+     * @return bool True if the bookmark's thumbnail needs to be retrieved.
+     */
+    public function shouldUpdateThumbnail(): bool
+    {
+        return $this->thumbnail !== false
+            && !$this->isNote()
+            && startsWith(strtolower($this->url), 'http')
+            && (null === $this->thumbnail || !is_file($this->thumbnail))
+        ;
+    }
+
+    /**
      * Get the Sticky.
      *
      * @return bool
      */
-    public function isSticky()
+    public function isSticky(): bool
     {
         return $this->sticky ? true : false;
     }
@@ -381,11 +416,11 @@ class Bookmark
     /**
      * Set the Sticky.
      *
-     * @param bool $sticky
+     * @param bool|null $sticky
      *
      * @return Bookmark
      */
-    public function setSticky($sticky)
+    public function setSticky(?bool $sticky): Bookmark
     {
         $this->sticky = $sticky ? true : false;
 
@@ -393,17 +428,19 @@ class Bookmark
     }
 
     /**
-     * @return string Bookmark's tags as a string, separated by a space
+     * @param string $separator Tags separator loaded from the config file.
+     *
+     * @return string Bookmark's tags as a string, separated by a separator
      */
-    public function getTagsString()
+    public function getTagsString(string $separator = ' '): string
     {
-        return implode(' ', $this->getTags());
+        return tags_array2str($this->getTags(), $separator);
     }
 
     /**
      * @return bool
      */
-    public function isNote()
+    public function isNote(): bool
     {
         // We check empty value to get a valid result if the link has not been saved yet
         return empty($this->url) || startsWith($this->url, '/shaare/') || $this->url[0] === '?';
@@ -416,33 +453,65 @@ class Bookmark
      *   - multiple spaces will be removed
      *   - trailing dash in tags will be removed
      *
-     * @param string $tags
+     * @param string|null $tags
+     * @param string      $separator Tags separator loaded from the config file.
      *
      * @return $this
      */
-    public function setTagsString($tags)
+    public function setTagsString(?string $tags, string $separator = ' '): Bookmark
     {
-        // Remove first '-' char in tags.
-        $tags = preg_replace('/(^| )\-/', '$1', $tags);
-        // Explode all tags separted by spaces or commas
-        $tags = preg_split('/[\s,]+/', $tags);
-        // Remove eventual empty values
-        $tags = array_values(array_filter($tags));
+        $this->setTags(tags_str2array($tags, $separator));
 
-        $this->tags = $tags;
+        return $this;
+    }
+
+    /**
+     * Get entire additionalContent array.
+     *
+     * @return mixed[]
+     */
+    public function getAdditionalContent(): array
+    {
+        return $this->additionalContent;
+    }
+
+    /**
+     * Set a single entry in additionalContent, by key.
+     *
+     * @param string     $key
+     * @param mixed|null $value Any type of value can be set.
+     *
+     * @return $this
+     */
+    public function addAdditionalContentEntry(string $key, $value): self
+    {
+        $this->additionalContent[$key] = $value;
 
         return $this;
     }
 
     /**
+     * Get a single entry in additionalContent, by key.
+     *
+     * @param string $key
+     * @param mixed|null $default
+     *
+     * @return mixed|null can be any type or even null.
+     */
+    public function getAdditionalContentEntry(string $key, $default = null)
+    {
+        return array_key_exists($key, $this->additionalContent) ? $this->additionalContent[$key] : $default;
+    }
+
+    /**
      * Rename a tag in tags list.
      *
      * @param string $fromTag
      * @param string $toTag
      */
-    public function renameTag($fromTag, $toTag)
+    public function renameTag(string $fromTag, string $toTag): void
     {
-        if (($pos = array_search($fromTag, $this->tags)) !== false) {
+        if (($pos = array_search($fromTag, $this->tags ?? [])) !== false) {
             $this->tags[$pos] = trim($toTag);
         }
     }
@@ -452,9 +521,9 @@ class Bookmark
      *
      * @param string $tag
      */
-    public function deleteTag($tag)
+    public function deleteTag(string $tag): void
     {
-        if (($pos = array_search($tag, $this->tags)) !== false) {
+        if (($pos = array_search($tag, $this->tags ?? [])) !== false) {
             unset($this->tags[$pos]);
             $this->tags = array_values($this->tags);
         }
diff --git a/application/bookmark/BookmarkArray.php b/application/bookmark/BookmarkArray.php
index 3bd5eb20..b9328116 100644
--- a/application/bookmark/BookmarkArray.php
+++ b/application/bookmark/BookmarkArray.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Shaarli\Bookmark;
 
 use Shaarli\Bookmark\Exception\InvalidBookmarkException;
@@ -70,7 +72,8 @@ class BookmarkArray implements \Iterator, \Countable, \ArrayAccess
      */
     public function offsetSet($offset, $value)
     {
-        if (! $value instanceof Bookmark
+        if (
+            ! $value instanceof Bookmark
             || $value->getId() === null || empty($value->getUrl())
             || ($offset !== null && ! is_int($offset)) || ! is_int($value->getId())
             || $offset !== null && $offset !== $value->getId()
@@ -187,13 +190,13 @@ class BookmarkArray implements \Iterator, \Countable, \ArrayAccess
     /**
      * Returns a bookmark offset in bookmarks array from its unique ID.
      *
-     * @param int $id Persistent ID of a bookmark.
+     * @param int|null $id Persistent ID of a bookmark.
      *
      * @return int Real offset in local array, or null if doesn't exist.
      */
-    protected function getBookmarkOffset($id)
+    protected function getBookmarkOffset(?int $id): ?int
     {
-        if (isset($this->ids[$id])) {
+        if ($id !== null && isset($this->ids[$id])) {
             return $this->ids[$id];
         }
         return null;
@@ -205,7 +208,7 @@ class BookmarkArray implements \Iterator, \Countable, \ArrayAccess
      *
      * @return int next ID.
      */
-    public function getNextId()
+    public function getNextId(): int
     {
         if (!empty($this->ids)) {
             return max(array_keys($this->ids)) + 1;
@@ -214,13 +217,14 @@ class BookmarkArray implements \Iterator, \Countable, \ArrayAccess
     }
 
     /**
-     * @param $url
+     * @param string $url
      *
      * @return Bookmark|null
      */
-    public function getByUrl($url)
+    public function getByUrl(string $url): ?Bookmark
     {
-        if (! empty($url)
+        if (
+            ! empty($url)
             && isset($this->urls[$url])
             && isset($this->bookmarks[$this->urls[$url]])
         ) {
diff --git a/application/bookmark/BookmarkFileService.php b/application/bookmark/BookmarkFileService.php
index c9ec2609..6666a251 100644
--- a/application/bookmark/BookmarkFileService.php
+++ b/application/bookmark/BookmarkFileService.php
@@ -1,10 +1,12 @@
 <?php
 
+declare(strict_types=1);
 
 namespace Shaarli\Bookmark;
 
-
+use DateTime;
 use Exception;
+use malkusch\lock\mutex\Mutex;
 use Shaarli\Bookmark\Exception\BookmarkNotFoundException;
 use Shaarli\Bookmark\Exception\DatastoreNotInitializedException;
 use Shaarli\Bookmark\Exception\EmptyDataStoreException;
@@ -47,15 +49,19 @@ class BookmarkFileService implements BookmarkServiceInterface
     /** @var bool true for logged in users. Default value to retrieve private bookmarks. */
     protected $isLoggedIn;
 
+    /** @var Mutex */
+    protected $mutex;
+
     /**
      * @inheritDoc
      */
-    public function __construct(ConfigManager $conf, History $history, $isLoggedIn)
+    public function __construct(ConfigManager $conf, History $history, Mutex $mutex, bool $isLoggedIn)
     {
         $this->conf = $conf;
         $this->history = $history;
+        $this->mutex = $mutex;
         $this->pageCacheManager = new PageCacheManager($this->conf->get('resource.page_cache'), $isLoggedIn);
-        $this->bookmarksIO = new BookmarkIO($this->conf);
+        $this->bookmarksIO = new BookmarkIO($this->conf, $this->mutex);
         $this->isLoggedIn = $isLoggedIn;
 
         if (!$this->isLoggedIn && $this->conf->get('privacy.hide_public_links', false)) {
@@ -63,7 +69,7 @@ class BookmarkFileService implements BookmarkServiceInterface
         } else {
             try {
                 $this->bookmarks = $this->bookmarksIO->read();
-            } catch (EmptyDataStoreException|DatastoreNotInitializedException $e) {
+            } catch (EmptyDataStoreException | DatastoreNotInitializedException $e) {
                 $this->bookmarks = new BookmarkArray();
 
                 if ($this->isLoggedIn) {
@@ -79,25 +85,29 @@ class BookmarkFileService implements BookmarkServiceInterface
             if (! $this->bookmarks instanceof BookmarkArray) {
                 $this->migrate();
                 exit(
-                    'Your data store has been migrated, please reload the page.'. PHP_EOL .
+                    'Your data store has been migrated, please reload the page.' . PHP_EOL .
                     'If this message keeps showing up, please delete data/updates.txt file.'
                 );
             }
         }
 
-        $this->bookmarkFilter = new BookmarkFilter($this->bookmarks);
+        $this->bookmarkFilter = new BookmarkFilter($this->bookmarks, $this->conf);
     }
 
     /**
      * @inheritDoc
      */
-    public function findByHash($hash)
+    public function findByHash(string $hash, string $privateKey = null): Bookmark
     {
         $bookmark = $this->bookmarkFilter->filter(BookmarkFilter::$FILTER_HASH, $hash);
         // PHP 7.3 introduced array_key_first() to avoid this hack
         $first = reset($bookmark);
-        if (! $this->isLoggedIn && $first->isPrivate()) {
-            throw new Exception('Not authorized');
+        if (
+            !$this->isLoggedIn
+            && $first->isPrivate()
+            && (empty($privateKey) || $privateKey !== $first->getAdditionalContentEntry('private_key'))
+        ) {
+            throw new BookmarkNotFoundException();
         }
 
         return $first;
@@ -106,7 +116,7 @@ class BookmarkFileService implements BookmarkServiceInterface
     /**
      * @inheritDoc
      */
-    public function findByUrl($url)
+    public function findByUrl(string $url): ?Bookmark
     {
         return $this->bookmarks->getByUrl($url);
     }
@@ -115,10 +125,10 @@ class BookmarkFileService implements BookmarkServiceInterface
      * @inheritDoc
      */
     public function search(
-        $request = [],
-        $visibility = null,
-        $caseSensitive = false,
-        $untaggedOnly = false,
+        array $request = [],
+        string $visibility = null,
+        bool $caseSensitive = false,
+        bool $untaggedOnly = false,
         bool $ignoreSticky = false
     ) {
         if ($visibility === null) {
@@ -126,8 +136,8 @@ class BookmarkFileService implements BookmarkServiceInterface
         }
 
         // Filter bookmark database according to parameters.
-        $searchtags = isset($request['searchtags']) ? $request['searchtags'] : '';
-        $searchterm = isset($request['searchterm']) ? $request['searchterm'] : '';
+        $searchTags = isset($request['searchtags']) ? $request['searchtags'] : '';
+        $searchTerm = isset($request['searchterm']) ? $request['searchterm'] : '';
 
         if ($ignoreSticky) {
             $this->bookmarks->reorder('DESC', true);
@@ -135,7 +145,7 @@ class BookmarkFileService implements BookmarkServiceInterface
 
         return $this->bookmarkFilter->filter(
             BookmarkFilter::$FILTER_TAG | BookmarkFilter::$FILTER_TEXT,
-            [$searchtags, $searchterm],
+            [$searchTags, $searchTerm],
             $caseSensitive,
             $visibility,
             $untaggedOnly
@@ -145,7 +155,7 @@ class BookmarkFileService implements BookmarkServiceInterface
     /**
      * @inheritDoc
      */
-    public function get($id, $visibility = null)
+    public function get(int $id, string $visibility = null): Bookmark
     {
         if (! isset($this->bookmarks[$id])) {
             throw new BookmarkNotFoundException();
@@ -156,7 +166,8 @@ class BookmarkFileService implements BookmarkServiceInterface
         }
 
         $bookmark = $this->bookmarks[$id];
-        if (($bookmark->isPrivate() && $visibility != 'all' && $visibility != 'private')
+        if (
+            ($bookmark->isPrivate() && $visibility != 'all' && $visibility != 'private')
             || (! $bookmark->isPrivate() && $visibility != 'all' && $visibility != 'public')
         ) {
             throw new Exception('Unauthorized');
@@ -168,20 +179,17 @@ class BookmarkFileService implements BookmarkServiceInterface
     /**
      * @inheritDoc
      */
-    public function set($bookmark, $save = true)
+    public function set(Bookmark $bookmark, bool $save = true): Bookmark
     {
         if (true !== $this->isLoggedIn) {
             throw new Exception(t('You\'re not authorized to alter the datastore'));
         }
-        if (! $bookmark instanceof Bookmark) {
-            throw new Exception(t('Provided data is invalid'));
-        }
         if (! isset($this->bookmarks[$bookmark->getId()])) {
             throw new BookmarkNotFoundException();
         }
         $bookmark->validate();
 
-        $bookmark->setUpdated(new \DateTime());
+        $bookmark->setUpdated(new DateTime());
         $this->bookmarks[$bookmark->getId()] = $bookmark;
         if ($save === true) {
             $this->save();
@@ -193,15 +201,12 @@ class BookmarkFileService implements BookmarkServiceInterface
     /**
      * @inheritDoc
      */
-    public function add($bookmark, $save = true)
+    public function add(Bookmark $bookmark, bool $save = true): Bookmark
     {
         if (true !== $this->isLoggedIn) {
             throw new Exception(t('You\'re not authorized to alter the datastore'));
         }
-        if (! $bookmark instanceof Bookmark) {
-            throw new Exception(t('Provided data is invalid'));
-        }
-        if (! empty($bookmark->getId())) {
+        if (!empty($bookmark->getId())) {
             throw new Exception(t('This bookmarks already exists'));
         }
         $bookmark->setId($this->bookmarks->getNextId());
@@ -218,14 +223,11 @@ class BookmarkFileService implements BookmarkServiceInterface
     /**
      * @inheritDoc
      */
-    public function addOrSet($bookmark, $save = true)
+    public function addOrSet(Bookmark $bookmark, bool $save = true): Bookmark
     {
         if (true !== $this->isLoggedIn) {
             throw new Exception(t('You\'re not authorized to alter the datastore'));
         }
-        if (! $bookmark instanceof Bookmark) {
-            throw new Exception('Provided data is invalid');
-        }
         if ($bookmark->getId() === null) {
             return $this->add($bookmark, $save);
         }
@@ -235,14 +237,11 @@ class BookmarkFileService implements BookmarkServiceInterface
     /**
      * @inheritDoc
      */
-    public function remove($bookmark, $save = true)
+    public function remove(Bookmark $bookmark, bool $save = true): void
     {
         if (true !== $this->isLoggedIn) {
             throw new Exception(t('You\'re not authorized to alter the datastore'));
         }
-        if (! $bookmark instanceof Bookmark) {
-            throw new Exception(t('Provided data is invalid'));
-        }
         if (! isset($this->bookmarks[$bookmark->getId()])) {
             throw new BookmarkNotFoundException();
         }
@@ -257,7 +256,7 @@ class BookmarkFileService implements BookmarkServiceInterface
     /**
      * @inheritDoc
      */
-    public function exists($id, $visibility = null)
+    public function exists(int $id, string $visibility = null): bool
     {
         if (! isset($this->bookmarks[$id])) {
             return false;
@@ -268,7 +267,8 @@ class BookmarkFileService implements BookmarkServiceInterface
         }
 
         $bookmark = $this->bookmarks[$id];
-        if (($bookmark->isPrivate() && $visibility != 'all' && $visibility != 'private')
+        if (
+            ($bookmark->isPrivate() && $visibility != 'all' && $visibility != 'private')
             || (! $bookmark->isPrivate() && $visibility != 'all' && $visibility != 'public')
         ) {
             return false;
@@ -280,7 +280,7 @@ class BookmarkFileService implements BookmarkServiceInterface
     /**
      * @inheritDoc
      */
-    public function count($visibility = null)
+    public function count(string $visibility = null): int
     {
         return count($this->search([], $visibility));
     }
@@ -288,7 +288,7 @@ class BookmarkFileService implements BookmarkServiceInterface
     /**
      * @inheritDoc
      */
-    public function save()
+    public function save(): void
     {
         if (true !== $this->isLoggedIn) {
             // TODO: raise an Exception instead
@@ -303,14 +303,15 @@ class BookmarkFileService implements BookmarkServiceInterface
     /**
      * @inheritDoc
      */
-    public function bookmarksCountPerTag($filteringTags = [], $visibility = null)
+    public function bookmarksCountPerTag(array $filteringTags = [], string $visibility = null): array
     {
         $bookmarks = $this->search(['searchtags' => $filteringTags], $visibility);
         $tags = [];
         $caseMapping = [];
         foreach ($bookmarks as $bookmark) {
             foreach ($bookmark->getTags() as $tag) {
-                if (empty($tag)
+                if (
+                    empty($tag)
                     || (! $this->isLoggedIn && startsWith($tag, '.'))
                     || $tag === BookmarkMarkdownFormatter::NO_MD_TAG
                     || in_array($tag, $filteringTags, true)
@@ -339,38 +340,55 @@ class BookmarkFileService implements BookmarkServiceInterface
         $keys = array_keys($tags);
         $tmpTags = array_combine($keys, $keys);
         array_multisort($tags, SORT_DESC, $tmpTags, SORT_ASC, $tags);
+
         return $tags;
     }
 
     /**
      * @inheritDoc
      */
-    public function days()
-    {
-        $bookmarkDays = [];
-        foreach ($this->search() as $bookmark) {
-            $bookmarkDays[$bookmark->getCreated()->format('Ymd')] = 0;
+    public function findByDate(
+        \DateTimeInterface $from,
+        \DateTimeInterface $to,
+        ?\DateTimeInterface &$previous,
+        ?\DateTimeInterface &$next
+    ): array {
+        $out = [];
+        $previous = null;
+        $next = null;
+
+        foreach ($this->search([], null, false, false, true) as $bookmark) {
+            if ($to < $bookmark->getCreated()) {
+                $next = $bookmark->getCreated();
+            } elseif ($from < $bookmark->getCreated() && $to > $bookmark->getCreated()) {
+                $out[] = $bookmark;
+            } else {
+                if ($previous !== null) {
+                    break;
+                }
+                $previous = $bookmark->getCreated();
+            }
         }
-        $bookmarkDays = array_keys($bookmarkDays);
-        sort($bookmarkDays);
 
-        return $bookmarkDays;
+        return $out;
     }
 
     /**
      * @inheritDoc
      */
-    public function filterDay($request)
+    public function getLatest(): ?Bookmark
     {
-        $visibility = $this->isLoggedIn ? BookmarkFilter::$ALL : BookmarkFilter::$PUBLIC;
+        foreach ($this->search([], null, false, false, true) as $bookmark) {
+            return $bookmark;
+        }
 
-        return $this->bookmarkFilter->filter(BookmarkFilter::$FILTER_DAY, $request, false, $visibility);
+        return null;
     }
 
     /**
      * @inheritDoc
      */
-    public function initialize()
+    public function initialize(): void
     {
         $initializer = new BookmarkInitializer($this);
         $initializer->initialize();
@@ -383,7 +401,7 @@ class BookmarkFileService implements BookmarkServiceInterface
     /**
      * Handles migration to the new database format (BookmarksArray).
      */
-    protected function migrate()
+    protected function migrate(): void
     {
         $bookmarkDb = new LegacyLinkDB(
             $this->conf->get('resource.datastore'),
@@ -391,14 +409,14 @@ class BookmarkFileService implements BookmarkServiceInterface
             false
         );
         $updater = new LegacyUpdater(
-            UpdaterUtils::read_updates_file($this->conf->get('resource.updates')),
+            UpdaterUtils::readUpdatesFile($this->conf->get('resource.updates')),
             $bookmarkDb,
             $this->conf,
             true
         );
         $newUpdates = $updater->update();
         if (! empty($newUpdates)) {
-            UpdaterUtils::write_updates_file(
+            UpdaterUtils::writeUpdatesFile(
                 $this->conf->get('resource.updates'),
                 $updater->getDoneUpdates()
             );
diff --git a/application/bookmark/BookmarkFilter.php b/application/bookmark/BookmarkFilter.php
index 6636bbfe..db83c51c 100644
--- a/application/bookmark/BookmarkFilter.php
+++ b/application/bookmark/BookmarkFilter.php
@@ -1,9 +1,12 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Shaarli\Bookmark;
 
 use Exception;
 use Shaarli\Bookmark\Exception\BookmarkNotFoundException;
+use Shaarli\Config\ConfigManager;
 
 /**
  * Class LinkFilter.
@@ -56,12 +59,16 @@ class BookmarkFilter
      */
     private $bookmarks;
 
+    /** @var ConfigManager */
+    protected $conf;
+
     /**
      * @param Bookmark[] $bookmarks initialization.
      */
-    public function __construct($bookmarks)
+    public function __construct($bookmarks, ConfigManager $conf)
     {
         $this->bookmarks = $bookmarks;
+        $this->conf = $conf;
     }
 
     /**
@@ -77,8 +84,13 @@ class BookmarkFilter
      *
      * @throws BookmarkNotFoundException
      */
-    public function filter($type, $request, $casesensitive = false, $visibility = 'all', $untaggedonly = false)
-    {
+    public function filter(
+        string $type,
+        $request,
+        bool $casesensitive = false,
+        string $visibility = 'all',
+        bool $untaggedonly = false
+    ) {
         if (!in_array($visibility, ['all', 'public', 'private'])) {
             $visibility = 'all';
         }
@@ -100,10 +112,14 @@ class BookmarkFilter
                     $filtered = $this->bookmarks;
                 }
                 if (!empty($request[0])) {
-                    $filtered = (new BookmarkFilter($filtered))->filterTags($request[0], $casesensitive, $visibility);
+                    $filtered = (new BookmarkFilter($filtered, $this->conf))
+                        ->filterTags($request[0], $casesensitive, $visibility)
+                    ;
                 }
                 if (!empty($request[1])) {
-                    $filtered = (new BookmarkFilter($filtered))->filterFulltext($request[1], $visibility);
+                    $filtered = (new BookmarkFilter($filtered, $this->conf))
+                        ->filterFulltext($request[1], $visibility)
+                    ;
                 }
                 return $filtered;
             case self::$FILTER_TEXT:
@@ -128,13 +144,13 @@ class BookmarkFilter
      *
      * @return Bookmark[] filtered bookmarks.
      */
-    private function noFilter($visibility = 'all')
+    private function noFilter(string $visibility = 'all')
     {
         if ($visibility === 'all') {
             return $this->bookmarks;
         }
 
-        $out = array();
+        $out = [];
         foreach ($this->bookmarks as $key => $value) {
             if ($value->isPrivate() && $visibility === 'private') {
                 $out[$key] = $value;
@@ -151,11 +167,11 @@ class BookmarkFilter
      *
      * @param string $smallHash permalink hash.
      *
-     * @return array $filtered array containing permalink data.
+     * @return Bookmark[] $filtered array containing permalink data.
      *
-     * @throws \Shaarli\Bookmark\Exception\BookmarkNotFoundException if the smallhash doesn't match any link.
+     * @throws BookmarkNotFoundException if the smallhash doesn't match any link.
      */
-    private function filterSmallHash($smallHash)
+    private function filterSmallHash(string $smallHash)
     {
         foreach ($this->bookmarks as $key => $l) {
             if ($smallHash == $l->getShortUrl()) {
@@ -186,15 +202,15 @@ class BookmarkFilter
      * @param string $searchterms search query.
      * @param string $visibility  Optional: return only all/private/public bookmarks.
      *
-     * @return array search results.
+     * @return Bookmark[] search results.
      */
-    private function filterFulltext($searchterms, $visibility = 'all')
+    private function filterFulltext(string $searchterms, string $visibility = 'all')
     {
         if (empty($searchterms)) {
             return $this->noFilter($visibility);
         }
 
-        $filtered = array();
+        $filtered = [];
         $search = mb_convert_case(html_entity_decode($searchterms), MB_CASE_LOWER, 'UTF-8');
         $exactRegex = '/"([^"]+)"/';
         // Retrieve exact search terms.
@@ -206,8 +222,8 @@ class BookmarkFilter
         $explodedSearchAnd = array_values(array_filter($explodedSearchAnd));
 
         // Filter excluding terms and update andSearch.
-        $excludeSearch = array();
-        $andSearch = array();
+        $excludeSearch = [];
+        $andSearch = [];
         foreach ($explodedSearchAnd as $needle) {
             if ($needle[0] == '-' && strlen($needle) > 1) {
                 $excludeSearch[] = substr($needle, 1);
@@ -227,33 +243,38 @@ class BookmarkFilter
                 }
             }
 
-            // Concatenate link fields to search across fields.
-            // Adds a '\' separator for exact search terms.
-            $content  = mb_convert_case($link->getTitle(), MB_CASE_LOWER, 'UTF-8') .'\\';
-            $content .= mb_convert_case($link->getDescription(), MB_CASE_LOWER, 'UTF-8') .'\\';
-            $content .= mb_convert_case($link->getUrl(), MB_CASE_LOWER, 'UTF-8') .'\\';
-            $content .= mb_convert_case($link->getTagsString(), MB_CASE_LOWER, 'UTF-8') .'\\';
+            $lengths = [];
+            $content = $this->buildFullTextSearchableLink($link, $lengths);
 
             // Be optimistic
             $found = true;
+            $foundPositions = [];
 
             // First, we look for exact term search
-            for ($i = 0; $i < count($exactSearch) && $found; $i++) {
-                $found = strpos($content, $exactSearch[$i]) !== false;
-            }
-
-            // Iterate over keywords, if keyword is not found,
+            // Then iterate over keywords, if keyword is not found,
             // no need to check for the others. We want all or nothing.
-            for ($i = 0; $i < count($andSearch) && $found; $i++) {
-                $found = strpos($content, $andSearch[$i]) !== false;
+            foreach ([$exactSearch, $andSearch] as $search) {
+                for ($i = 0; $i < count($search) && $found !== false; $i++) {
+                    $found = mb_strpos($content, $search[$i]);
+                    if ($found === false) {
+                        break;
+                    }
+
+                    $foundPositions[] = ['start' => $found, 'end' => $found + mb_strlen($search[$i])];
+                }
             }
 
             // Exclude terms.
-            for ($i = 0; $i < count($excludeSearch) && $found; $i++) {
+            for ($i = 0; $i < count($excludeSearch) && $found !== false; $i++) {
                 $found = strpos($content, $excludeSearch[$i]) === false;
             }
 
-            if ($found) {
+            if ($found !== false) {
+                $link->addAdditionalContentEntry(
+                    'search_highlight',
+                    $this->postProcessFoundPositions($lengths, $foundPositions)
+                );
+
                 $filtered[$id] = $link;
             }
         }
@@ -268,8 +289,9 @@ class BookmarkFilter
      *
      * @return string generated regex fragment
      */
-    private static function tag2regex($tag)
+    protected function tag2regex(string $tag): string
     {
+        $tagsSeparator = $this->conf->get('general.tags_separator', ' ');
         $len = strlen($tag);
         if (!$len || $tag === "-" || $tag === "*") {
             // nothing to search, return empty regex
@@ -283,12 +305,13 @@ class BookmarkFilter
             $i = 0; // start at first character
             $regex = '(?='; // use positive lookahead
         }
-        $regex .= '.*(?:^| )'; // before tag may only be a space or the beginning
+        // before tag may only be the separator or the beginning
+        $regex .= '.*(?:^|' . $tagsSeparator . ')';
         // iterate over string, separating it into placeholder and content
         for (; $i < $len; $i++) {
             if ($tag[$i] === '*') {
                 // placeholder found
-                $regex .= '[^ ]*?';
+                $regex .= '[^' . $tagsSeparator . ']*?';
             } else {
                 // regular characters
                 $offset = strpos($tag, '*', $i);
@@ -304,7 +327,8 @@ class BookmarkFilter
                 $i = $offset;
             }
         }
-        $regex .= '(?:$| ))'; // after the tag may only be a space or the end
+        // after the tag may only be the separator or the end
+        $regex .= '(?:$|' . $tagsSeparator . '))';
         return $regex;
     }
 
@@ -314,22 +338,23 @@ class BookmarkFilter
      * You can specify one or more tags, separated by space or a comma, e.g.
      *  print_r($mydb->filterTags('linux programming'));
      *
-     * @param string $tags          list of tags separated by commas or blank spaces.
-     * @param bool   $casesensitive ignore case if false.
-     * @param string $visibility    Optional: return only all/private/public bookmarks.
+     * @param string|array $tags          list of tags, separated by commas or blank spaces if passed as string.
+     * @param bool         $casesensitive ignore case if false.
+     * @param string       $visibility    Optional: return only all/private/public bookmarks.
      *
-     * @return array filtered bookmarks.
+     * @return Bookmark[] filtered bookmarks.
      */
-    public function filterTags($tags, $casesensitive = false, $visibility = 'all')
+    public function filterTags($tags, bool $casesensitive = false, string $visibility = 'all')
     {
+        $tagsSeparator = $this->conf->get('general.tags_separator', ' ');
         // get single tags (we may get passed an array, even though the docs say different)
         $inputTags = $tags;
         if (!is_array($tags)) {
             // we got an input string, split tags
-            $inputTags = preg_split('/(?:\s+)|,/', $inputTags, -1, PREG_SPLIT_NO_EMPTY);
+            $inputTags = tags_str2array($inputTags, $tagsSeparator);
         }
 
-        if (!count($inputTags)) {
+        if (count($inputTags) === 0) {
             // no input tags
             return $this->noFilter($visibility);
         }
@@ -346,7 +371,7 @@ class BookmarkFilter
         }
 
         // build regex from all tags
-        $re = '/^' . implode(array_map("self::tag2regex", $inputTags)) . '.*$/';
+        $re = '/^' . implode(array_map([$this, 'tag2regex'], $inputTags)) . '.*$/';
         if (!$casesensitive) {
             // make regex case insensitive
             $re .= 'i';
@@ -366,10 +391,11 @@ class BookmarkFilter
                     continue;
                 }
             }
-            $search = $link->getTagsString(); // build search string, start with tags of current link
+            // build search string, start with tags of current link
+            $search = $link->getTagsString($tagsSeparator);
             if (strlen(trim($link->getDescription())) && strpos($link->getDescription(), '#') !== false) {
                 // description given and at least one possible tag found
-                $descTags = array();
+                $descTags = [];
                 // find all tags in the form of #tag in the description
                 preg_match_all(
                     '/(?<![' . self::$HASHTAG_CHARS . '])#([' . self::$HASHTAG_CHARS . ']+?)\b/sm',
@@ -378,9 +404,9 @@ class BookmarkFilter
                 );
                 if (count($descTags[1])) {
                     // there were some tags in the description, add them to the search string
-                    $search .= ' ' . implode(' ', $descTags[1]);
+                    $search .= $tagsSeparator . tags_array2str($descTags[1], $tagsSeparator);
                 }
-            };
+            }
             // match regular expression with search string
             if (!preg_match($re, $search)) {
                 // this entry does _not_ match our regex
@@ -396,9 +422,9 @@ class BookmarkFilter
      *
      * @param string $visibility return only all/private/public bookmarks.
      *
-     * @return array filtered bookmarks.
+     * @return Bookmark[] filtered bookmarks.
      */
-    public function filterUntagged($visibility)
+    public function filterUntagged(string $visibility)
     {
         $filtered = [];
         foreach ($this->bookmarks as $key => $link) {
@@ -410,7 +436,7 @@ class BookmarkFilter
                 }
             }
 
-            if (empty(trim($link->getTagsString()))) {
+            if (empty($link->getTags())) {
                 $filtered[$key] = $link;
             }
         }
@@ -427,11 +453,11 @@ class BookmarkFilter
      * @param string $day day to filter.
      * @param string $visibility return only all/private/public bookmarks.
 
-     * @return array all link matching given day.
+     * @return Bookmark[] all link matching given day.
      *
      * @throws Exception if date format is invalid.
      */
-    public function filterDay($day, $visibility)
+    public function filterDay(string $day, string $visibility)
     {
         if (!checkDateFormat('Ymd', $day)) {
             throw new Exception('Invalid date format');
@@ -460,9 +486,9 @@ class BookmarkFilter
      * @param string $tags          string containing a list of tags.
      * @param bool   $casesensitive will convert everything to lowercase if false.
      *
-     * @return array filtered tags string.
+     * @return string[] filtered tags string.
      */
-    public static function tagsStrToArray($tags, $casesensitive)
+    public static function tagsStrToArray(string $tags, bool $casesensitive): array
     {
         // We use UTF-8 conversion to handle various graphemes (i.e. cyrillic, or greek)
         $tagsOut = $casesensitive ? $tags : mb_convert_case($tags, MB_CASE_LOWER, 'UTF-8');
@@ -470,4 +496,75 @@ class BookmarkFilter
 
         return preg_split('/\s+/', $tagsOut, -1, PREG_SPLIT_NO_EMPTY);
     }
+
+    /**
+     * This method finalize the content of the foundPositions array,
+     * by associated all search results to their associated bookmark field,
+     * making sure that there is no overlapping results, etc.
+     *
+     * @param array $fieldLengths   Start and end positions of every bookmark fields in the aggregated bookmark content.
+     * @param array $foundPositions Positions where the search results were found in the aggregated content.
+     *
+     * @return array Updated $foundPositions, by bookmark field.
+     */
+    protected function postProcessFoundPositions(array $fieldLengths, array $foundPositions): array
+    {
+        // Sort results by starting position ASC.
+        usort($foundPositions, function (array $entryA, array $entryB): int {
+            return $entryA['start'] > $entryB['start'] ? 1 : -1;
+        });
+
+        $out = [];
+        $currentMax = -1;
+        foreach ($foundPositions as $foundPosition) {
+            // we do not allow overlapping highlights
+            if ($foundPosition['start'] < $currentMax) {
+                continue;
+            }
+
+            $currentMax = $foundPosition['end'];
+            foreach ($fieldLengths as $part => $length) {
+                if ($foundPosition['start'] < $length['start'] || $foundPosition['start'] > $length['end']) {
+                    continue;
+                }
+
+                $out[$part][] = [
+                    'start' => $foundPosition['start'] - $length['start'],
+                    'end' => $foundPosition['end'] - $length['start'],
+                ];
+                break;
+            }
+        }
+
+        return $out;
+    }
+
+    /**
+     * Concatenate link fields to search across fields. Adds a '\' separator for exact search terms.
+     * Also populate $length array with starting and ending positions of every bookmark field
+     * inside concatenated content.
+     *
+     * @param Bookmark $link
+     * @param array    $lengths (by reference)
+     *
+     * @return string Lowercase concatenated fields content.
+     */
+    protected function buildFullTextSearchableLink(Bookmark $link, array &$lengths): string
+    {
+        $tagString = $link->getTagsString($this->conf->get('general.tags_separator', ' '));
+        $content  = mb_convert_case($link->getTitle(), MB_CASE_LOWER, 'UTF-8') . '\\';
+        $content .= mb_convert_case($link->getDescription(), MB_CASE_LOWER, 'UTF-8') . '\\';
+        $content .= mb_convert_case($link->getUrl(), MB_CASE_LOWER, 'UTF-8') . '\\';
+        $content .= mb_convert_case($tagString, MB_CASE_LOWER, 'UTF-8') . '\\';
+
+        $lengths['title'] = ['start' => 0, 'end' => mb_strlen($link->getTitle())];
+        $nextField = $lengths['title']['end'] + 1;
+        $lengths['description'] = ['start' => $nextField, 'end' => $nextField + mb_strlen($link->getDescription())];
+        $nextField = $lengths['description']['end'] + 1;
+        $lengths['url'] = ['start' => $nextField, 'end' => $nextField + mb_strlen($link->getUrl())];
+        $nextField = $lengths['url']['end'] + 1;
+        $lengths['tags'] = ['start' => $nextField, 'end' => $nextField + mb_strlen($tagString)];
+
+        return $content;
+    }
 }
diff --git a/application/bookmark/BookmarkIO.php b/application/bookmark/BookmarkIO.php
index 6bf7f365..c78dbe41 100644
--- a/application/bookmark/BookmarkIO.php
+++ b/application/bookmark/BookmarkIO.php
@@ -1,7 +1,11 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Shaarli\Bookmark;
 
+use malkusch\lock\mutex\Mutex;
+use malkusch\lock\mutex\NoMutex;
 use Shaarli\Bookmark\Exception\DatastoreNotInitializedException;
 use Shaarli\Bookmark\Exception\EmptyDataStoreException;
 use Shaarli\Bookmark\Exception\NotWritableDataStoreException;
@@ -27,11 +31,14 @@ class BookmarkIO
      */
     protected $conf;
 
+
+    /** @var Mutex */
+    protected $mutex;
+
     /**
      * string Datastore PHP prefix
      */
     protected static $phpPrefix = '<?php /* ';
-
     /**
      * string Datastore PHP suffix
      */
@@ -42,16 +49,21 @@ class BookmarkIO
      *
      * @param ConfigManager $conf instance
      */
-    public function __construct($conf)
+    public function __construct(ConfigManager $conf, Mutex $mutex = null)
     {
+        if ($mutex === null) {
+            // This should only happen with legacy classes
+            $mutex = new NoMutex();
+        }
         $this->conf = $conf;
         $this->datastore = $conf->get('resource.datastore');
+        $this->mutex = $mutex;
     }
 
     /**
      * Reads database from disk to memory
      *
-     * @return BookmarkArray instance
+     * @return Bookmark[]
      *
      * @throws NotWritableDataStoreException    Data couldn't be loaded
      * @throws EmptyDataStoreException          Datastore file exists but does not contain any bookmark
@@ -67,11 +79,16 @@ class BookmarkIO
             throw new NotWritableDataStoreException($this->datastore);
         }
 
+        $content = null;
+        $this->mutex->synchronized(function () use (&$content) {
+            $content = file_get_contents($this->datastore);
+        });
+
         // Note that gzinflate is faster than gzuncompress.
         // See: http://www.php.net/manual/en/function.gzdeflate.php#96439
         $links = unserialize(gzinflate(base64_decode(
-            substr(file_get_contents($this->datastore),
-                strlen(self::$phpPrefix), -strlen(self::$phpSuffix)))));
+            substr($content, strlen(self::$phpPrefix), -strlen(self::$phpSuffix))
+        )));
 
         if (empty($links)) {
             if (filesize($this->datastore) > 100) {
@@ -86,7 +103,7 @@ class BookmarkIO
     /**
      * Saves the database from memory to disk
      *
-     * @param BookmarkArray $links instance.
+     * @param Bookmark[] $links
      *
      * @throws NotWritableDataStoreException the datastore is not writable
      */
@@ -95,14 +112,18 @@ class BookmarkIO
         if (is_file($this->datastore) && !is_writeable($this->datastore)) {
             // The datastore exists but is not writeable
             throw new NotWritableDataStoreException($this->datastore);
-        } else if (!is_file($this->datastore) && !is_writeable(dirname($this->datastore))) {
+        } elseif (!is_file($this->datastore) && !is_writeable(dirname($this->datastore))) {
             // The datastore does not exist and its parent directory is not writeable
             throw new NotWritableDataStoreException(dirname($this->datastore));
         }
 
-        file_put_contents(
-            $this->datastore,
-            self::$phpPrefix.base64_encode(gzdeflate(serialize($links))).self::$phpSuffix
-        );
+        $data = self::$phpPrefix . base64_encode(gzdeflate(serialize($links))) . self::$phpSuffix;
+
+        $this->mutex->synchronized(function () use ($data) {
+            file_put_contents(
+                $this->datastore,
+                $data
+            );
+        });
     }
 }
diff --git a/application/bookmark/BookmarkInitializer.php b/application/bookmark/BookmarkInitializer.php
index 815047e3..8ab5c441 100644
--- a/application/bookmark/BookmarkInitializer.php
+++ b/application/bookmark/BookmarkInitializer.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Shaarli\Bookmark;
 
 /**
@@ -11,6 +13,9 @@ namespace Shaarli\Bookmark;
  * To prevent data corruption, it does not overwrite existing bookmarks,
  * even though there should not be any.
  *
+ * We disable this because otherwise it creates indentation issues, and heredoc is not supported by PHP gettext.
+ * @phpcs:disable Generic.Files.LineLength.TooLong
+ *
  * @package Shaarli\Bookmark
  */
 class BookmarkInitializer
@@ -23,7 +28,7 @@ class BookmarkInitializer
      *
      * @param BookmarkServiceInterface $bookmarkService
      */
-    public function __construct($bookmarkService)
+    public function __construct(BookmarkServiceInterface $bookmarkService)
     {
         $this->bookmarkService = $bookmarkService;
     }
@@ -31,13 +36,13 @@ class BookmarkInitializer
     /**
      * Initialize the data store with default bookmarks
      */
-    public function initialize()
+    public function initialize(): void
     {
         $bookmark = new Bookmark();
-        $bookmark->setTitle('quicksilver (loop) on Vimeo ' . t('(private bookmark with thumbnail demo)'));
-        $bookmark->setUrl('https://vimeo.com/153493904');
+        $bookmark->setTitle('Calm Jazz Music - YouTube ' . t('(private bookmark with thumbnail demo)'));
+        $bookmark->setUrl('https://www.youtube.com/watch?v=DVEUcbPkb-c');
         $bookmark->setDescription(t(
-'Shaarli will automatically pick up the thumbnail for links to a variety of websites.
+            'Shaarli will automatically pick up the thumbnail for links to a variety of websites.
 
 Explore your new Shaarli instance by trying out controls and menus.
 Visit the project on [Github](https://github.com/shaarli/Shaarli) or [the documentation](https://shaarli.readthedocs.io/en/master/) to learn more about Shaarli.
@@ -52,7 +57,7 @@ Now you can edit or delete the default shaares.
         $bookmark = new Bookmark();
         $bookmark->setTitle(t('Note: Shaare descriptions'));
         $bookmark->setDescription(t(
-'Adding a shaare without entering a URL creates a text-only "note" post such as this one.
+            'Adding a shaare without entering a URL creates a text-only "note" post such as this one.
 This note is private, so you are the only one able to see it while logged in.
 
 You can use this to keep notes, post articles, code snippets, and much more.
@@ -89,7 +94,7 @@ Markdown also supports tables:
             'Shaarli - ' . t('The personal, minimalist, super-fast, database free, bookmarking service')
         );
         $bookmark->setDescription(t(
-'Welcome to Shaarli!
+            'Welcome to Shaarli!
 
 Shaarli allows you to bookmark your favorite pages, and share them with others or store them privately.
 You can add a description to your bookmarks, such as this one, and tag them.
diff --git a/application/bookmark/BookmarkServiceInterface.php b/application/bookmark/BookmarkServiceInterface.php
index b9b483eb..08cdbb4e 100644
--- a/application/bookmark/BookmarkServiceInterface.php
+++ b/application/bookmark/BookmarkServiceInterface.php
@@ -1,79 +1,73 @@
 <?php
 
-namespace Shaarli\Bookmark;
+declare(strict_types=1);
 
+namespace Shaarli\Bookmark;
 
 use Shaarli\Bookmark\Exception\BookmarkNotFoundException;
 use Shaarli\Bookmark\Exception\NotWritableDataStoreException;
-use Shaarli\Config\ConfigManager;
-use Shaarli\History;
 
 /**
  * Class BookmarksService
  *
  * This is the entry point to manipulate the bookmark DB.
+ *
+ * Regarding return types of a list of bookmarks, it can either be an array or an ArrayAccess implementation,
+ * so until PHP 8.0 is the minimal supported version with union return types it cannot be explicitly added.
  */
 interface BookmarkServiceInterface
 {
     /**
-     * BookmarksService constructor.
-     *
-     * @param ConfigManager $conf       instance
-     * @param History       $history    instance
-     * @param bool          $isLoggedIn true if the current user is logged in
-     */
-    public function __construct(ConfigManager $conf, History $history, $isLoggedIn);
-
-    /**
      * Find a bookmark by hash
      *
-     * @param string $hash
+     * @param string      $hash       Bookmark's hash
+     * @param string|null $privateKey Optional key used to access private links while logged out
      *
-     * @return mixed
+     * @return Bookmark
      *
      * @throws \Exception
      */
-    public function findByHash($hash);
+    public function findByHash(string $hash, string $privateKey = null);
 
     /**
      * @param $url
      *
      * @return Bookmark|null
      */
-    public function findByUrl($url);
+    public function findByUrl(string $url): ?Bookmark;
 
     /**
      * Search bookmarks
      *
-     * @param mixed  $request
-     * @param string $visibility
-     * @param bool   $caseSensitive
-     * @param bool   $untaggedOnly
-     * @param bool   $ignoreSticky
+     * @param array   $request
+     * @param ?string $visibility
+     * @param bool    $caseSensitive
+     * @param bool    $untaggedOnly
+     * @param bool    $ignoreSticky
      *
      * @return Bookmark[]
      */
     public function search(
-        $request = [],
-        $visibility = null,
-        $caseSensitive = false,
-        $untaggedOnly = false,
+        array $request = [],
+        string $visibility = null,
+        bool $caseSensitive = false,
+        bool $untaggedOnly = false,
         bool $ignoreSticky = false
     );
 
     /**
      * Get a single bookmark by its ID.
      *
-     * @param int    $id         Bookmark ID
-     * @param string $visibility all|public|private e.g. with public, accessing a private bookmark will throw an
-     *                           exception
+     * @param int    $id          Bookmark ID
+     * @param ?string $visibility all|public|private e.g. with public, accessing a private bookmark will throw an
+     *                            exception
      *
      * @return Bookmark
      *
      * @throws BookmarkNotFoundException
      * @throws \Exception
      */
-    public function get($id, $visibility = null);
+    public function get(int $id, string $visibility = null);
 
     /**
      * Updates an existing bookmark (depending on its ID).
@@ -86,7 +80,7 @@ interface BookmarkServiceInterface
      * @throws BookmarkNotFoundException
      * @throws \Exception
      */
-    public function set($bookmark, $save = true);
+    public function set(Bookmark $bookmark, bool $save = true): Bookmark;
 
     /**
      * Adds a new bookmark (the ID must be empty).
@@ -98,7 +92,7 @@ interface BookmarkServiceInterface
      *
      * @throws \Exception
      */
-    public function add($bookmark, $save = true);
+    public function add(Bookmark $bookmark, bool $save = true): Bookmark;
 
     /**
      * Adds or updates a bookmark depending on its ID:
@@ -112,7 +106,7 @@ interface BookmarkServiceInterface
      *
      * @throws \Exception
      */
-    public function addOrSet($bookmark, $save = true);
+    public function addOrSet(Bookmark $bookmark, bool $save = true): Bookmark;
 
     /**
      * Deletes a bookmark.
@@ -122,65 +116,72 @@ interface BookmarkServiceInterface
      *
      * @throws \Exception
      */
-    public function remove($bookmark, $save = true);
+    public function remove(Bookmark $bookmark, bool $save = true): void;
 
     /**
      * Get a single bookmark by its ID.
      *
-     * @param int    $id         Bookmark ID
-     * @param string $visibility all|public|private e.g. with public, accessing a private bookmark will throw an
-     *                           exception
+     * @param int     $id         Bookmark ID
+     * @param ?string $visibility all|public|private e.g. with public, accessing a private bookmark will throw an
+     *                            exception
      *
      * @return bool
      */
-    public function exists($id, $visibility = null);
+    public function exists(int $id, string $visibility = null): bool;
 
     /**
      * Return the number of available bookmarks for given visibility.
      *
-     * @param string $visibility public|private|all
+     * @param ?string $visibility public|private|all
      *
      * @return int Number of bookmarks
      */
-    public function count($visibility = null);
+    public function count(string $visibility = null): int;
 
     /**
      * Write the datastore.
      *
      * @throws NotWritableDataStoreException
      */
-    public function save();
+    public function save(): void;
 
     /**
      * Returns the list tags appearing in the bookmarks with the given tags
      *
-     * @param array  $filteringTags tags selecting the bookmarks to consider
-     * @param string $visibility    process only all/private/public bookmarks
+     * @param array|null  $filteringTags tags selecting the bookmarks to consider
+     * @param string|null $visibility    process only all/private/public bookmarks
      *
      * @return array tag => bookmarksCount
      */
-    public function bookmarksCountPerTag($filteringTags = [], $visibility = 'all');
+    public function bookmarksCountPerTag(array $filteringTags = [], ?string $visibility = null): array;
 
     /**
-     * Returns the list of days containing articles (oldest first)
+     * Return a list of bookmark matching provided period of time.
+     * It also update directly previous and next date outside of given period found in the datastore.
+     *
+     * @param \DateTimeInterface      $from     Starting date.
+     * @param \DateTimeInterface      $to       Ending date.
+     * @param \DateTimeInterface|null $previous (by reference) updated with first created date found before $from.
+     * @param \DateTimeInterface|null $next     (by reference) updated with first created date found after $to.
      *
-     * @return array containing days (in format YYYYMMDD).
+     * @return array List of bookmarks matching provided period of time.
      */
-    public function days();
+    public function findByDate(
+        \DateTimeInterface $from,
+        \DateTimeInterface $to,
+        ?\DateTimeInterface &$previous,
+        ?\DateTimeInterface &$next
+    ): array;
 
     /**
-     * Returns the list of articles for a given day.
+     * Returns the latest bookmark by creation date.
      *
-     * @param string $request day to filter. Format: YYYYMMDD.
-     *
-     * @return Bookmark[] list of shaare found.
-     *
-     * @throws BookmarkNotFoundException
+     * @return Bookmark|null Found Bookmark or null if the datastore is empty.
      */
-    public function filterDay($request);
+    public function getLatest(): ?Bookmark;
 
     /**
      * Creates the default database after a fresh install.
      */
-    public function initialize();
+    public function initialize(): void;
 }
diff --git a/application/bookmark/LinkUtils.php b/application/bookmark/LinkUtils.php
index e7af4d55..d65e97ed 100644
--- a/application/bookmark/LinkUtils.php
+++ b/application/bookmark/LinkUtils.php
@@ -66,16 +66,19 @@ function html_extract_tag($tag, $html)
 {
     $propertiesKey = ['property', 'name', 'itemprop'];
     $properties = implode('|', $propertiesKey);
-    // Try to retrieve OpenGraph image.
-    $ogRegex = '#<meta[^>]+(?:'. $properties .')=["\']?(?:og:)?'. $tag .'["\'\s][^>]*content=["\']?(.*?)["\'/>]#';
+    // We need a OR here to accept either 'property=og:noquote' or 'property="og:unrelated og:my-tag"'
+    $orCondition  = '["\']?(?:og:)?' . $tag . '["\']?|["\'][^\'"]*?(?:og:)?' . $tag . '[^\'"]*?[\'"]';
+    // Try to retrieve OpenGraph tag.
+    $ogRegex = '#<meta[^>]+(?:' . $properties . ')=(?:' . $orCondition . ')[^>]*content=(["\'])([^\1]*?)\1.*?>#';
     // If the attributes are not in the order property => content (e.g. Github)
     // New regex to keep this readable... more or less.
-    $ogRegexReverse = '#<meta[^>]+content=["\']([^"\']+)[^>]+(?:'. $properties .')=["\']?(?:og)?:'. $tag .'["\'\s/>]#';
+    $ogRegexReverse = '#<meta[^>]+content=(["\'])([^\1]*?)\1[^>]+(?:' . $properties . ')=(?:' . $orCondition . ').*?>#';
 
-    if (preg_match($ogRegex, $html, $matches) > 0
+    if (
+        preg_match($ogRegex, $html, $matches) > 0
         || preg_match($ogRegexReverse, $html, $matches) > 0
     ) {
-        return $matches[1];
+        return $matches[2];
     }
 
     return false;
@@ -114,7 +117,7 @@ function hashtag_autolink($description, $indexUrl = '')
      * \p{Mn} - any non marking space (accents, umlauts, etc)
      */
     $regex = '/(^|\s)#([\p{Pc}\p{N}\p{L}\p{Mn}]+)/mui';
-    $replacement = '$1<a href="'. $indexUrl .'./add-tag/$2" title="Hashtag $2">#$2</a>';
+    $replacement = '$1<a href="' . $indexUrl . './add-tag/$2" title="Hashtag $2">#$2</a>';
     return preg_replace($regex, $replacement, $description);
 }
 
@@ -136,12 +139,17 @@ function space2nbsp($text)
  *
  * @param string $description shaare's description.
  * @param string $indexUrl    URL to Shaarli's index.
-
+ * @param bool   $autolink    Turn on/off automatic linkifications of URLs and hashtags
+ *
  * @return string formatted description.
  */
-function format_description($description, $indexUrl = '')
+function format_description($description, $indexUrl = '', $autolink = true)
 {
-    return nl2br(space2nbsp(hashtag_autolink(text2clickable($description), $indexUrl)));
+    if ($autolink) {
+        $description = hashtag_autolink(text2clickable($description), $indexUrl);
+    }
+
+    return nl2br(space2nbsp($description));
 }
 
 /**
@@ -169,3 +177,49 @@ function is_note($linkUrl)
 {
     return isset($linkUrl[0]) && $linkUrl[0] === '?';
 }
+
+/**
+ * Extract an array of tags from a given tag string, with provided separator.
+ *
+ * @param string|null $tags      String containing a list of tags separated by $separator.
+ * @param string      $separator Shaarli's default: ' ' (whitespace)
+ *
+ * @return array List of tags
+ */
+function tags_str2array(?string $tags, string $separator): array
+{
+    // For whitespaces, we use the special \s regex character
+    $separator = $separator === ' ' ? '\s' : $separator;
+
+    return preg_split('/\s*' . $separator . '+\s*/', trim($tags) ?? '', -1, PREG_SPLIT_NO_EMPTY);
+}
+
+/**
+ * Return a tag string with provided separator from a list of tags.
+ * Note that given array is clean up by tags_filter().
+ *
+ * @param array|null $tags      List of tags
+ * @param string     $separator
+ *
+ * @return string
+ */
+function tags_array2str(?array $tags, string $separator): string
+{
+    return implode($separator, tags_filter($tags, $separator));
+}
+
+/**
+ * Clean an array of tags: trim + remove empty entries
+ *
+ * @param array|null $tags List of tags
+ * @param string     $separator
+ *
+ * @return array
+ */
+function tags_filter(?array $tags, string $separator): array
+{
+    $trimDefault = " \t\n\r\0\x0B";
+    return array_values(array_filter(array_map(function (string $entry) use ($separator, $trimDefault): string {
+        return trim($entry, $trimDefault . $separator);
+    }, $tags ?? [])));
+}
diff --git a/application/bookmark/exception/BookmarkNotFoundException.php b/application/bookmark/exception/BookmarkNotFoundException.php
index 827a3d35..a91d1efa 100644
--- a/application/bookmark/exception/BookmarkNotFoundException.php
+++ b/application/bookmark/exception/BookmarkNotFoundException.php
@@ -1,4 +1,5 @@
 <?php
+
 namespace Shaarli\Bookmark\Exception;
 
 use Exception;
diff --git a/application/bookmark/exception/EmptyDataStoreException.php b/application/bookmark/exception/EmptyDataStoreException.php
index cd48c1e6..16a98470 100644
--- a/application/bookmark/exception/EmptyDataStoreException.php
+++ b/application/bookmark/exception/EmptyDataStoreException.php
@@ -1,7 +1,7 @@
 <?php
 
-
 namespace Shaarli\Bookmark\Exception;
 
-
-class EmptyDataStoreException extends \Exception {}
+class EmptyDataStoreException extends \Exception
+{
+}
diff --git a/application/bookmark/exception/InvalidBookmarkException.php b/application/bookmark/exception/InvalidBookmarkException.php
index 10c84a6d..fe184f8c 100644
--- a/application/bookmark/exception/InvalidBookmarkException.php
+++ b/application/bookmark/exception/InvalidBookmarkException.php
@@ -16,14 +16,14 @@ class InvalidBookmarkException extends \Exception
             } else {
                 $created = 'Not a DateTime object';
             }
-            $this->message = 'This bookmark is not valid'. PHP_EOL;
-            $this->message .= ' - ID: '. $bookmark->getId() . PHP_EOL;
-            $this->message .= ' - Title: '. $bookmark->getTitle() . PHP_EOL;
-            $this->message .= ' - Url: '. $bookmark->getUrl() . PHP_EOL;
-            $this->message .= ' - ShortUrl: '. $bookmark->getShortUrl() . PHP_EOL;
-            $this->message .= ' - Created: '. $created . PHP_EOL;
+            $this->message = 'This bookmark is not valid' . PHP_EOL;
+            $this->message .= ' - ID: ' . $bookmark->getId() . PHP_EOL;
+            $this->message .= ' - Title: ' . $bookmark->getTitle() . PHP_EOL;
+            $this->message .= ' - Url: ' . $bookmark->getUrl() . PHP_EOL;
+            $this->message .= ' - ShortUrl: ' . $bookmark->getShortUrl() . PHP_EOL;
+            $this->message .= ' - Created: ' . $created . PHP_EOL;
         } else {
-            $this->message = 'The provided data is not a bookmark'. PHP_EOL;
+            $this->message = 'The provided data is not a bookmark' . PHP_EOL;
             $this->message .= var_export($bookmark, true);
         }
     }
diff --git a/application/bookmark/exception/NotWritableDataStoreException.php b/application/bookmark/exception/NotWritableDataStoreException.php
index 95f34b50..df91f3bc 100644
--- a/application/bookmark/exception/NotWritableDataStoreException.php
+++ b/application/bookmark/exception/NotWritableDataStoreException.php
@@ -1,9 +1,7 @@
 <?php
 
-
 namespace Shaarli\Bookmark\Exception;
 
-
 class NotWritableDataStoreException extends \Exception
 {
     /**
@@ -13,7 +11,7 @@ class NotWritableDataStoreException extends \Exception
      */
     public function __construct($dataStore)
     {
-        $this->message = 'Couldn\'t load data from the data store file "'. $dataStore .'". '.
+        $this->message = 'Couldn\'t load data from the data store file "' . $dataStore . '". ' .
             'Your data might be corrupted, or your file isn\'t readable.';
     }
 }