Add server code new feature walkthrough

2 files changed, 82 insertions, 6 deletions

diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index 4b62a7a30..56c3b65d1 100644
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -138,8 +138,6 @@ You can get a complete PeerTube development setup with Gitpod, a free one-click
 
 ### Server side
 
-You can find a documentation of the server code/architecture [here](https://docs.joinpeertube.org/contribute/architecture#server).
-
 To develop on the server-side:
 
 ```
@@ -150,11 +148,11 @@ Then, the server will listen on `localhost:9000`. When server source files
 change, these are automatically recompiled and the server will automatically
 restart.
 
-### Client side
-
-You can find a documentation of the client code/architecture
-[here](https://docs.joinpeertube.org/contribute/architecture#client).
+More detailed documentation is available:
+  * [Server code/architecture](https://docs.joinpeertube.org/contribute/architecture#server)
+  * [Server development (adding a new feature...)](/support/doc/development/server.md)
 
+### Client side
 
 To develop on the client side:
 
@@ -166,6 +164,10 @@ The API will listen on `localhost:9000` and the frontend on `localhost:3000`.
 Client files are automatically compiled on change, and the web browser will
 reload them automatically thanks to hot module replacement.
 
+More detailed documentation is available:
+  * [Client code/architecture](https://docs.joinpeertube.org/contribute/architecture#client)
+
+
 ### Client and server side
 
 The API will listen on `localhost:9000` and the frontend on `localhost:3000`.
diff --git a/support/doc/development/server.md b/support/doc/development/server.md
new file mode 100644
index 000000000..4647f2b4f
--- /dev/null
+++ b/support/doc/development/server.md
@@ -0,0 +1,74 @@
+# Server code
+
+## Add a new feature walkthrough
+
+Here's a list of all the parts of the server to update if you want to add a new feature (new API REST endpoints for example) to the PeerTube server.
+Some of these may be optional (for example your new endpoint may not need to send notifications) but this guide tries to be exhaustive.
+
+ * Configuration:
+   - Add you new configuration key in `config/default.yaml` and `config/production.yaml`
+   - If you configuration needs to be different in dev or tests environments, also update `config/dev.yaml` and `config/test.yaml`
+   - Load your configuration in `server/initializers/config.ts`
+   - Check new configuration keys are set in `server/initializers/checker-before-init.ts`
+   - You can also ensure configuration consistency in `server/initializers/checker-after-init.ts`
+   - If you want your configuration to be available in the client:
+     + Add your field in `shared/models/server/server-config.model.ts`
+     + Update `server/lib/server-config-manager.ts` to include your new configuration
+   - If you want your configuration to be updatable by the web admin in the client:
+     + Add your field in `shared/models/server/custom-config.model.ts`
+     + Add the configuration to the config object in the `server/controllers/api/config.ts` controller
+ * Controllers:
+   - Create the controller file and fill it with your REST API routes
+   - Import and use your controller in the parent controller
+ * Middlewares:
+   - Create your validator middleware in `server/middlewares/validators` that will be used by your controllers
+   - Add your new middleware file `server/middlewares/validators/index.ts` so it's easier to import
+   - Create the entry in `server/types/express.d.ts` to attach the database model loaded by your middleware to the express response
+ * Validators:
+   - Create your validators that will be used by your middlewares in `server/helpers/custom-validators`
+ * Typescript models:
+   - Create the API models (request parameters or response) in `shared/models`
+   - Add your models in `index.ts` of current directory to facilitate the imports
+ * Sequelize model (BDD):
+   - If you need to create a new table:
+     + Create the Sequelize model in `server/models/`:
+       * Create the `@Column`
+       * Add some indexes if you need
+       * Create static methods to load a specific from the database `loadBy...`
+       * Create static methods to load a list of models from the database `listBy...`
+       * Create the instance method `toFormattedJSON` that creates the JSON to send to the REST API from the model
+     + Add your new Sequelize model to `server/initializers/database.ts`
+     + Create a new file in `server/types` to define multiple versions of your Sequelize model depending on database associations
+     + Add this new file to `server/types/*/index.ts` to facilitate the imports
+     + Create database migrations:
+       * Create the migration file in `server/initializers/migrations` using raw SQL (copy the same SQL query as at PeerTube startup)
+       * Update `LAST_MIGRATION_VERSION` in `server/initializers/constants.ts`
+   - If updating database schema (adding/removing/renaming a column):
+     + Update the sequelize models in `server/models/`
+     + Add migrations:
+       * Create the migration file in `initializers/migrations` using Sequelize Query Interface (`.addColumn`, `.dropTable`, `.changeColumn`)
+       * Update `LAST_MIGRATION_VERSION` in `server/initializers/constants.ts`
+ * Notifications:
+   - Create the new notification model in `shared/models/users/user-notification.model.ts`
+   - Create the notification logic in `server/lib/notifier/shared`:
+     + Email subject has a common prefix (defined by the admin in PeerTube configuration)
+   - Add your notification to `server/lib/notifier/notifier.ts`
+   - Create the email template in `server/lib/emails`:
+     + A text version is automatically generated from the HTML
+     + The template usually extends `../common/grettings` that already says "Hi" and "Cheers". You just have to write the title and the content blocks that will be inserted in the appropriate places in the HTML template
+   - If you need to associate a new table with `userNotification`:
+     + Associate the new table in `UserNotificationModel` (don't forget the index)
+     + Add the object property in the API model definition (`shared/models/users/user-notification.model.ts`)
+     + Add the object in `UserNotificationModel.toFormattedJSON`
+     + Handle this new notification type in client (`UserNotificationsComponent`)
+     + Handle the new object property in client model (`UserNotification`)
+ * Tests:
+   - Create your command class in `shared/server-commands/` that will wrap HTTP requests to your new endpoint
+   - Add your command file in `index.ts` of current directory
+   - Instantiate your command class in `shared/server-commands/server/server.ts`
+   - Create your test file in `server/tests/api/check-params` to test middleware validators/authentification/user rights (offensive tests)
+   - Add it to `server/tests/api/check-params/index.ts`
+   - Create your test file in `server/tests/api` to test your new endpoints
+   - Add it to `index.ts` of current directory
+   - Add your notification test in `server/tests/api/notifications`
+ * Update REST API documentation in `support/doc/api/openapi.yaml`