Add client.cacheUser method (#548)

* Add client.cacheUser method

* Fixed ESLint issues

* Added existence check first

src/client/Client.js

@@ -135,6 +135,16 @@ class Client extends EventEmitter {
     return this.rest.methods.loginToken(email);
   }
 
+  /**
+   * Forces a user to be cached.
+   * @param {String} id The ID of the user to cache
+   * @return {Promise<User>}
+   */
+  cacheUser(id) {
+    if (this.users.has(id)) return Promise.resolve(this.users.get(id));
+    return this.rest.methods.getUser(id);
+  }
+
   /**
    * Returns a Collection, mapping Guild ID to Voice Connections.
    * @readonly

src/client/actions/ActionsManager.js

@@ -17,6 +17,7 @@ class ActionsManager {
     this.register('GuildRoleCreate');
     this.register('GuildRoleDelete');
     this.register('GuildRoleUpdate');
+    this.register('UserGet');
     this.register('UserUpdate');
   }
 

src/client/actions/UserGet.js

@@ -0,0 +1,15 @@
+const Action = require('./Action');
+
+class UserGetAction extends Action {
+
+  handle(data) {
+    const client = this.client;
+    const user = client.dataManager.newUser(data);
+
+    return {
+      user,
+    };
+  }
+}
+
+module.exports = UserGetAction;

src/client/rest/RESTMethods.js

@@ -193,6 +193,16 @@ class RESTMethods {
     });
   }
 
+  getUser(userID) {
+    return new Promise((resolve, reject) => {
+      this.rest.makeRequest('get', Constants.Endpoints.user(userID), true)
+        .then((data) => {
+          resolve(this.rest.client.actions.UserGet.handle(data).user);
+        })
+        .catch(reject);
+    });
+  }
+
   updateCurrentUser(_data) {
     return new Promise((resolve, reject) => {
       const user = this.rest.client.user;

src/util/Constants.js

@@ -75,12 +75,15 @@ const Endpoints = exports.Endpoints = {
   // general endpoints
   login: `${API}/auth/login`,
   logout: `${API}/auth/logout`,
+  gateway: `${API}/gateway`,
+  invite: (id) => `${API}/invite/${id}`,
+
+  // users
+  user: (userID) => `${API}/users/${userID}`,
+  userChannels: (userID) => `${Endpoints.user(userID)}/channels`,
+  avatar: (userID, avatar) => `${Endpoints.user(userID)}/avatars/${avatar}.jpg`,
   me: `${API}/users/@me`,
   meGuild: (guildID) => `${Endpoints.me}/guilds/${guildID}`,
-  gateway: `${API}/gateway`,
-  userChannels: (userID) => `${API}/users/${userID}/channels`,
-  avatar: (userID, avatar) => `${API}/users/${userID}/avatars/${avatar}.jpg`,
-  invite: (id) => `${API}/invite/${id}`,
 
   // guilds
   guilds: `${API}/guilds`,