2 files changed, 75 insertions, 0 deletions

diff --git a/server/lib/cache/index.ts b/server/lib/cache/index.ts
new file mode 100644
index 000000000..7bf63790a
--- /dev/null
+++ b/server/lib/cache/index.ts
@@ -0,0 +1 @@
+export * from './videos-preview-cache'
diff --git a/server/lib/cache/videos-preview-cache.ts b/server/lib/cache/videos-preview-cache.ts
new file mode 100644
index 000000000..9d365e496
--- /dev/null
+++ b/server/lib/cache/videos-preview-cache.ts
@@ -0,0 +1,74 @@
+import * as request from 'request'
+import * as asyncLRU from 'async-lru'
+import { join } from 'path'
+import { createWriteStream } from 'fs'
+import * as Promise from 'bluebird'
+
+import { database as db, CONFIG, CACHE } from '../../initializers'
+import { logger, writeFilePromise, unlinkPromise } from '../../helpers'
+import { VideoInstance } from '../../models'
+import { fetchRemotePreview } from '../../lib'
+
+class VideosPreviewCache {
+
+  private static instance: VideosPreviewCache
+
+  private lru
+
+  private constructor () { }
+
+  static get Instance () {
+    return this.instance || (this.instance = new this())
+  }
+
+  init (max: number) {
+    this.lru = new asyncLRU({
+      max,
+      load: (key, cb) => {
+        this.loadPreviews(key)
+          .then(res => cb(null, res))
+          .catch(err => cb(err))
+      }
+    })
+
+    this.lru.on('evict', (obj: { key: string, value: string }) => {
+      unlinkPromise(obj.value).then(() => logger.debug('%s evicted from VideosPreviewCache', obj.value))
+    })
+  }
+
+  getPreviewPath (key: string) {
+    return new Promise<string>((res, rej) => {
+      this.lru.get(key, (err, value) => {
+        err ? rej(err) : res(value)
+      })
+    })
+  }
+
+  private loadPreviews (key: string) {
+    return db.Video.loadByUUIDAndPopulateAuthorAndPodAndTags(key)
+      .then(video => {
+        if (!video) return undefined
+
+        if (video.isOwned()) return join(CONFIG.STORAGE.PREVIEWS_DIR, video.getPreviewName())
+
+        return this.saveRemotePreviewAndReturnPath(video)
+      })
+  }
+
+  private saveRemotePreviewAndReturnPath (video: VideoInstance) {
+    const req = fetchRemotePreview(video.Author.Pod, video)
+
+    return new Promise<string>((res, rej) => {
+      const path = join(CACHE.DIRECTORIES.PREVIEWS, video.getPreviewName())
+      const stream = createWriteStream(path)
+
+      req.pipe(stream)
+         .on('finish', () => res(path))
+         .on('error', (err) => rej(err))
+    })
+  }
+}
+
+export {
+  VideosPreviewCache
+}