const {Emitter} = require('event-kit')
const Gutter = require('./gutter')

module.exports = class GutterContainer {
  constructor (textEditor) {
    this.gutters = []
    this.textEditor = textEditor
    this.emitter = new Emitter()
  }

  scheduleComponentUpdate () {
    this.textEditor.scheduleComponentUpdate()
  }

  destroy () {
    // Create a copy, because `Gutter::destroy` removes the gutter from
    // GutterContainer's @gutters.
    const guttersToDestroy = this.gutters.slice(0)
    for (let gutter of guttersToDestroy) {
      if (gutter.name !== 'line-number') { gutter.destroy() }
    }
    this.gutters = []
    this.emitter.dispose()
  }

  addGutter (options) {
    options = options || {}
    const gutterName = options.name
    if (gutterName === null) {
      throw new Error('A name is required to create a gutter.')
    }
    if (this.gutterWithName(gutterName)) {
      throw new Error('Tried to create a gutter with a name that is already in use.')
    }
    const newGutter = new Gutter(this, options)

    let inserted = false
    // Insert the gutter into the gutters array, sorted in ascending order by 'priority'.
    // This could be optimized, but there are unlikely to be many gutters.
    for (let i = 0; i < this.gutters.length; i++) {
      if (this.gutters[i].priority >= newGutter.priority) {
        this.gutters.splice(i, 0, newGutter)
        inserted = true
        break
      }
    }
    if (!inserted) {
      this.gutters.push(newGutter)
    }
    this.scheduleComponentUpdate()
    this.emitter.emit('did-add-gutter', newGutter)
    return newGutter
  }

  getGutters () {
    return this.gutters.slice()
  }

  gutterWithName (name) {
    for (let gutter of this.gutters) {
      if (gutter.name === name) { return gutter }
    }
    return null
  }

  observeGutters (callback) {
    for (let gutter of this.getGutters()) { callback(gutter) }
    return this.onDidAddGutter(callback)
  }

  onDidAddGutter (callback) {
    return this.emitter.on('did-add-gutter', callback)
  }

  onDidRemoveGutter (callback) {
    return this.emitter.on('did-remove-gutter', callback)
  }

  /*
  Section: Private Methods
  */

  // Processes the destruction of the gutter. Throws an error if this gutter is
  // not within this gutterContainer.
  removeGutter (gutter) {
    const index = this.gutters.indexOf(gutter)
    if (index > -1) {
      this.gutters.splice(index, 1)
      this.scheduleComponentUpdate()
      this.emitter.emit('did-remove-gutter', gutter.name)
    } else {
      throw new Error('The given gutter cannot be removed because it is not ' +
          'within this GutterContainer.'
      )
    }
  }

  // The public interface is Gutter::decorateMarker or TextEditor::decorateMarker.
  addGutterDecoration (gutter, marker, options) {
    if (gutter.type === 'line-number') {
      options.type = 'line-number'
    } else {
      options.type = 'gutter'
    }
    options.gutterName = gutter.name
    return this.textEditor.decorateMarker(marker, options)
  }
}
