Plugins divided into main and renderer processes.

src/renderer/plugins.js

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+const {resolve, basename} = require('path')
+const notifier = require('node-notifier')
+const crypto = require('crypto')
+
+const config = require('../config')
+
+module.exports = class Plugins {
+  constructor () {
+    // modules path
+    this.path = resolve(config.getConfigPath(), 'plugins')
+    log('Path: ', this.path)
+    this.availableExtensions = [
+      'onCheckForSubtitles'
+    ]
+
+    this.forceUpdate = false
+    this.updating = false
+    this.watchers = []
+    this.state = {}
+  }
+
+  init (params) {
+    this.state = params.state
+
+    // initialize state
+    this.state.saved = Object.assign(this.state.saved || {})
+
+    // caches
+    this.plugins = config.getPlugins()
+    this.paths = this.getPaths(this.plugins)
+    this.id = this.getId(this.plugins)
+    this.modules = this.requirePlugins()
+
+    // TODO: fire an event when plugins finish updating and listen to that.
+    // Listen to plugin changes on config.
+    // New plugins added, plugins removed or updated.
+    // The actual plugin update action will take place in the MAIN process.
+    config.subscribe(() => {
+      const plugins = config.getPlugins()
+      if (plugins !== this.plugins) {
+        const id = this.getId(plugins)
+        if (this.id !== id) {
+          log('UPDATING...')
+          this.id = id
+          this.plugins = plugins
+          this.paths = this.getPaths(this.plugins)
+        }
+      }
+    })
+
+    // Plugins will be updated on the MAIN process after 5s.
+    if (this.needsUpdate()) {
+      setTimeout(() => {
+        this.init(params)
+      }, 6000)
+      log('Plugins need update, init scheduled')
+      return
+    }
+
+    this.loadPlugins()
+    this.initPlugins(params)
+  }
+
+  initPlugins (params) {
+    this.modules.forEach(plugin => {
+      if (plugin.init) {
+        plugin.init(params)
+      }
+    })
+  }
+
+  on (action, params) {
+    log(`ON ${action}:`, params)
+    this.modules.forEach(plugin => {
+      const actionName = this.capitalizeFirstLetter(action)
+      const methodName = `on${actionName}`
+      if (typeof plugin[methodName] === 'function') {
+        plugin[methodName](params)
+      }
+    })
+  }
+
+  capitalizeFirstLetter (string) {
+    return string.charAt(0).toUpperCase() + string.slice(1)
+  }
+
+  didPluginsChange () {
+    return this.state.saved.installedPlugins !== this.id
+  }
+
+  hasPlugins () {
+    return !this.isEmptyObject(this.plugins)
+  }
+
+  isFirstInstall () {
+    return (!this.state.saved.installedPlugins && this.hasPlugins())
+  }
+
+  needsUpdate () {
+    return (this.didPluginsChange() || this.isFirstInstall())
+  }
+
+  getId (plugins) {
+    const hash = crypto.createHash('sha256')
+    hash.update(JSON.stringify(plugins))
+    return hash.digest('hex')
+  }
+
+  loadPlugins (err, localOnly = false) {
+    this.updating = false
+
+    // handle errors first
+    if (err) {
+      console.error(err.stack)
+      if (/not a recognized/.test(err.message) || /command not found/.test(err.message)) {
+        this.alert(
+          'Error updating plugins: We could not find the "npm" command. Make sure it\'s in $PATH'
+        )
+        return
+      }
+
+      this.alert(`Error updating plugins: Check '${this.path}/npm-debug.log' for more information.`)
+      return
+    }
+
+    // update state with latest plugins
+    this.state.saved.plugins = this.plugins
+
+    // cache modules
+    this.modules = this.requirePlugins()
+
+    // clear require cache
+    this.clearCache()
+  }
+
+  getPluginVersions () {
+    const paths_ = this.paths.plugins
+    return paths_.map(path => {
+      let version = null
+      try {
+        // eslint-disable-next-line import/no-dynamic-require
+        version = require(resolve(path, 'package.json')).version
+      } catch (err) { }
+      return [
+        basename(path),
+        version
+      ]
+    })
+  }
+
+  clearCache () {
+    // clear require cache
+    for (const entry in require.cache) {
+      if (entry.indexOf(this.path) === 0) {
+        delete require.cache[entry]
+      }
+    }
+  }
+
+  isEmptyObject (obj) {
+    return (Object.keys(obj).length === 0)
+  }
+
+  alert (message) {
+    notifier.notify({
+      title: 'WebTorrent Plugins',
+      // icon: config.icon, // TODO: save icon in webtorrent local folder and set config.icon
+      message: message
+    })
+  }
+
+  subscribe (fn) {
+    this.watchers.push(fn)
+    return () => {
+      this.watchers.splice(this.watchers.indexOf(fn), 1)
+    }
+  }
+
+  isLocalPath (string) {
+    // matches unix and windows local paths
+    return string.match(/^(\/|[a-z]:\/)/i)
+  }
+
+  getPaths (plugins) {
+    const pluginNames = Object.keys(plugins)
+
+    return {
+      plugins: pluginNames.map(name => {
+        let url = plugins[name]
+
+        // plugin is already on a local folder
+        // directly load it from its current location
+        if (this.isLocalPath(url)) return url
+
+        // plugin will be installed with npm install from a remote url
+        return resolve(this.path, 'node_modules', name.split('#')[0])
+      })
+    }
+  }
+
+  exposesSupportedApi (plugin) {
+    if (!plugin) return false
+
+    return this.availableExtensions.some((methodName) => {
+      return (typeof plugin[methodName] === 'function')
+    })
+  }
+
+  requirePlugins () {
+    const {plugins} = this.paths
+    let installNeeded = false
+
+    const load = (path) => {
+      if (!path.match(/\/$/)) {
+        path += '/'
+      }
+
+      const rendererPath = `${path}renderer.js`
+
+      try {
+        const Plugin = require(rendererPath) // eslint-disable import/no-dynamic-require
+        const plugin = new Plugin()
+
+        const exposed = this.exposesSupportedApi(plugin)
+        if (!exposed) {
+          log('Plugin not exposing any available extensions.', rendererPath, Object.keys(plugin))
+          return
+        }
+
+        // populate the name for internal errors here
+        plugin._name = basename(rendererPath)
+
+        return plugin
+      } catch (err) {
+        log('Require plugins ERROR:', err)
+        this.alert(`Error loading plugin: ${rendererPath}`)
+        // plugin not installed
+        // node_modules removed? did a manual plugin uninstall?
+        // try installing and then loading if successfull
+        installNeeded = true
+      }
+    }
+
+    // Plugin installation happens on the MAIN process.
+    // If plugins haven't finished installing, wait for them.
+    if (installNeeded) {
+      log('Plugins install needed, wait...')
+      setTimeout(() => {
+        this.requirePlugins()
+      }, 3000)
+    }
+    return plugins.map(load).filter(v => Boolean(v))
+  }
+
+  // decorates the base object by calling plugin[key]
+  // for all the available plugins
+  decorateObject (base, key) {
+    let decorated = base
+    this.modules.forEach(plugin => {
+      if (plugin[key]) {
+        const res = plugin[key](decorated)
+        if (res && typeof res === 'object') {
+          decorated = res
+        } else {
+          this.alert(`Plugin error: "${plugin._name}": invalid return type for \`${key}\``)
+        }
+      }
+    })
+
+    return decorated
+  }
+}
+
+/**
+ * Logs passed arguments to console using a prefix.
+ *
+ */
+function log () {
+  const prefix = '[ PLUGINS.Renderer ]-->'
+  const args = [prefix]
+
+  for (var i = 0; i < arguments.length; ++i) {
+    args.push(arguments[i])
+  }
+
+  console.log.apply(console, args)
+}