const _ = require('underscore-plus')
const {Emitter, Disposable, CompositeDisposable} = require('event-kit')
const TextEditor = require('./text-editor')
const ScopeDescriptor = require('./scope-descriptor')

const EDITOR_PARAMS_BY_SETTING_KEY = [
  ['core.fileEncoding', 'encoding'],
  ['editor.atomicSoftTabs', 'atomicSoftTabs'],
  ['editor.showInvisibles', 'showInvisibles'],
  ['editor.tabLength', 'tabLength'],
  ['editor.invisibles', 'invisibles'],
  ['editor.showCursorOnSelection', 'showCursorOnSelection'],
  ['editor.showIndentGuide', 'showIndentGuide'],
  ['editor.showLineNumbers', 'showLineNumbers'],
  ['editor.softWrap', 'softWrapped'],
  ['editor.softWrapHangingIndent', 'softWrapHangingIndentLength'],
  ['editor.softWrapAtPreferredLineLength', 'softWrapAtPreferredLineLength'],
  ['editor.preferredLineLength', 'preferredLineLength'],
  ['editor.maxScreenLineLength', 'maxScreenLineLength'],
  ['editor.autoIndent', 'autoIndent'],
  ['editor.autoIndentOnPaste', 'autoIndentOnPaste'],
  ['editor.scrollPastEnd', 'scrollPastEnd'],
  ['editor.undoGroupingInterval', 'undoGroupingInterval'],
  ['editor.scrollSensitivity', 'scrollSensitivity']
]

// Experimental: This global registry tracks registered `TextEditors`.
//
// If you want to add functionality to a wider set of text editors than just
// those appearing within workspace panes, use `atom.textEditors.observe` to
// invoke a callback for all current and future registered text editors.
//
// If you want packages to be able to add functionality to your non-pane text
// editors (such as a search field in a custom user interface element), register
// them for observation via `atom.textEditors.add`. **Important:** When you're
// done using your editor, be sure to call `dispose` on the returned disposable
// to avoid leaking editors.
module.exports =
class TextEditorRegistry {
  constructor ({config, assert, packageManager}) {
    this.assert = assert
    this.config = config
    this.clear()

    this.initialPackageActivationPromise = new Promise((resolve) => {
      // TODO: Remove this usage of a private property of PackageManager.
      // Should PackageManager just expose a promise-based API like this?
      if (packageManager.deferredActivationHooks) {
        packageManager.onDidActivateInitialPackages(resolve)
      } else {
        resolve()
      }
    })
  }

  deserialize (state) {
    this.editorGrammarOverrides = state.editorGrammarOverrides
  }

  serialize () {
    return {
      editorGrammarOverrides: Object.assign({}, this.editorGrammarOverrides)
    }
  }

  clear () {
    if (this.subscriptions) {
      this.subscriptions.dispose()
    }

    this.subscriptions = new CompositeDisposable()
    this.editors = new Set()
    this.emitter = new Emitter()
    this.scopesWithConfigSubscriptions = new Set()
    this.editorsWithMaintainedConfig = new Set()
    this.editorsWithMaintainedGrammar = new Set()
    this.editorGrammarOverrides = {}
    this.editorGrammarScores = new WeakMap()
  }

  destroy () {
    this.subscriptions.dispose()
    this.editorsWithMaintainedConfig = null
  }

  // Register a `TextEditor`.
  //
  // * `editor` The editor to register.
  //
  // Returns a {Disposable} on which `.dispose()` can be called to remove the
  // added editor. To avoid any memory leaks this should be called when the
  // editor is destroyed.
  add (editor) {
    this.editors.add(editor)
    editor.registered = true
    this.emitter.emit('did-add-editor', editor)

    return new Disposable(() => this.remove(editor))
  }

  build (params) {
    params = Object.assign({assert: this.assert}, params)

    let scope = null
    if (params.buffer) {
      const {grammar} = params.buffer.getLanguageMode()
      if (grammar) {
        scope = new ScopeDescriptor({scopes: [grammar.scopeName]})
      }
    }

    Object.assign(params, this.textEditorParamsForScope(scope))

    return new TextEditor(params)
  }

  // Remove a `TextEditor`.
  //
  // * `editor` The editor to remove.
  //
  // Returns a {Boolean} indicating whether the editor was successfully removed.
  remove (editor) {
    var removed = this.editors.delete(editor)
    editor.registered = false
    return removed
  }

  // Invoke the given callback with all the current and future registered
  // `TextEditors`.
  //
  // * `callback` {Function} to be called with current and future text editors.
  //
  // Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
  observe (callback) {
    this.editors.forEach(callback)
    return this.emitter.on('did-add-editor', callback)
  }

  // Keep a {TextEditor}'s configuration in sync with Atom's settings.
  //
  // * `editor` The editor whose configuration will be maintained.
  //
  // Returns a {Disposable} that can be used to stop updating the editor's
  // configuration.
  maintainConfig (editor) {
    if (this.editorsWithMaintainedConfig.has(editor)) {
      return new Disposable(noop)
    }
    this.editorsWithMaintainedConfig.add(editor)

    this.updateAndMonitorEditorSettings(editor)
    const languageChangeSubscription = editor.buffer.onDidChangeLanguageMode((newLanguageMode, oldLanguageMode) => {
      this.updateAndMonitorEditorSettings(editor, oldLanguageMode)
    })
    this.subscriptions.add(languageChangeSubscription)

    const updateTabTypes = () => {
      const configOptions = {scope: editor.getRootScopeDescriptor()}
      editor.setSoftTabs(shouldEditorUseSoftTabs(
        editor,
        this.config.get('editor.tabType', configOptions),
        this.config.get('editor.softTabs', configOptions)
      ))
    }

    updateTabTypes()
    const tokenizeSubscription = editor.onDidTokenize(updateTabTypes)
    this.subscriptions.add(tokenizeSubscription)

    return new Disposable(() => {
      this.editorsWithMaintainedConfig.delete(editor)
      tokenizeSubscription.dispose()
      languageChangeSubscription.dispose()
      this.subscriptions.remove(languageChangeSubscription)
      this.subscriptions.remove(tokenizeSubscription)
    })
  }

  // Deprecated: set a {TextEditor}'s grammar based on its path and content,
  // and continue to update its grammar as grammars are added or updated, or
  // the editor's file path changes.
  //
  // * `editor` The editor whose grammar will be maintained.
  //
  // Returns a {Disposable} that can be used to stop updating the editor's
  // grammar.
  maintainGrammar (editor) {
    atom.grammars.maintainGrammar(editor.getBuffer())
  }

  // Deprecated: Force a {TextEditor} to use a different grammar than the
  // one that would otherwise be selected for it.
  //
  // * `editor` The editor whose gramamr will be set.
  // * `languageId` The {String} language ID for the desired {Grammar}.
  setGrammarOverride (editor, languageId) {
    atom.grammars.assignLanguageMode(editor.getBuffer(), languageId)
  }

  // Deprecated: Retrieve the grammar scope name that has been set as a
  // grammar override for the given {TextEditor}.
  //
  // * `editor` The editor.
  //
  // Returns a {String} scope name, or `null` if no override has been set
  // for the given editor.
  getGrammarOverride (editor) {
    return atom.grammars.getAssignedLanguageId(editor.getBuffer())
  }

  // Deprecated: Remove any grammar override that has been set for the given {TextEditor}.
  //
  // * `editor` The editor.
  clearGrammarOverride (editor) {
    atom.grammars.autoAssignLanguageMode(editor.getBuffer())
  }

  async updateAndMonitorEditorSettings (editor, oldLanguageMode) {
    await this.initialPackageActivationPromise
    this.updateEditorSettingsForLanguageMode(editor, oldLanguageMode)
    await this.subscribeToSettingsForEditorScope(editor)
  }

  updateEditorSettingsForLanguageMode (editor, oldLanguageMode) {
    const newLanguageMode = editor.buffer.getLanguageMode()

    if (oldLanguageMode) {
      const newSettings = this.textEditorParamsForScope(newLanguageMode.rootScopeDescriptor)
      const oldSettings = this.textEditorParamsForScope(oldLanguageMode.rootScopeDescriptor)

      const updatedSettings = {}
      for (const [, paramName] of EDITOR_PARAMS_BY_SETTING_KEY) {
        // Update the setting only if it has changed between the two language
        // modes.  This prevents user-modified settings in an editor (like
        // 'softWrapped') from being reset when the language mode changes.
        if (!_.isEqual(newSettings[paramName], oldSettings[paramName])) {
          updatedSettings[paramName] = newSettings[paramName]
        }
      }

      if (_.size(updatedSettings) > 0) {
        editor.update(updatedSettings)
      }
    } else {
      editor.update(this.textEditorParamsForScope(newLanguageMode.rootScopeDescriptor))
    }
  }

  async subscribeToSettingsForEditorScope (editor) {
    const scopeDescriptor = editor.getRootScopeDescriptor()
    const scopeChain = scopeDescriptor.getScopeChain()

    if (!this.scopesWithConfigSubscriptions.has(scopeChain)) {
      this.scopesWithConfigSubscriptions.add(scopeChain)
      const configOptions = {scope: scopeDescriptor}

      for (const [settingKey, paramName] of EDITOR_PARAMS_BY_SETTING_KEY) {
        this.subscriptions.add(
          this.config.onDidChange(settingKey, configOptions, ({newValue}) => {
            this.editorsWithMaintainedConfig.forEach((editor) => {
              if (editor.getRootScopeDescriptor().isEqual(scopeDescriptor)) {
                editor.update({[paramName]: newValue})
              }
            })
          })
        )
      }

      const updateTabTypes = () => {
        const tabType = this.config.get('editor.tabType', configOptions)
        const softTabs = this.config.get('editor.softTabs', configOptions)
        this.editorsWithMaintainedConfig.forEach((editor) => {
          if (editor.getRootScopeDescriptor().isEqual(scopeDescriptor)) {
            editor.setSoftTabs(shouldEditorUseSoftTabs(editor, tabType, softTabs))
          }
        })
      }

      this.subscriptions.add(
        this.config.onDidChange('editor.tabType', configOptions, updateTabTypes),
        this.config.onDidChange('editor.softTabs', configOptions, updateTabTypes)
      )
    }
  }

  textEditorParamsForScope (scopeDescriptor) {
    const result = {}
    const configOptions = {scope: scopeDescriptor}
    for (const [settingKey, paramName] of EDITOR_PARAMS_BY_SETTING_KEY) {
      result[paramName] = this.config.get(settingKey, configOptions)
    }
    return result
  }
}

function shouldEditorUseSoftTabs (editor, tabType, softTabs) {
  switch (tabType) {
    case 'hard':
      return false
    case 'soft':
      return true
    case 'auto':
      switch (editor.usesSoftTabs()) {
        case true:
          return true
        case false:
          return false
        default:
          return softTabs
      }
  }
}

function noop () {}
