var _ = require('./util')
var config = require('./config')
var Watcher = require('./watcher')
var textParser = require('./parsers/text')
var expParser = require('./parsers/expression')

/**
 * A directive links a DOM element with a piece of data,
 * which is the result of evaluating an expression.
 * It registers a watcher with the expression and calls
 * the DOM update function when a change is triggered.
 *
 * @param {String} name
 * @param {Node} el
 * @param {Vue} vm
 * @param {Object} descriptor
 *                 - {String} expression
 *                 - {String} [arg]
 *                 - {Array<Object>} [filters]
 * @param {Object} def - directive definition object
 * @param {Function} [linker] - pre-compiled linker function
 * @constructor
 */

function Directive (name, el, vm, descriptor, def, linker) {
  // public
  this.name = name
  this.el = el
  this.vm = vm
  // copy descriptor props
  this.raw = descriptor.raw
  this.expression = descriptor.expression
  this.arg = descriptor.arg
  this.filters = _.resolveFilters(vm, descriptor.filters)
  // private
  this._linker = linker
  this._locked = false
  this._bound = false
  // init
  this._bind(def)
}

var p = Directive.prototype

/**
 * Initialize the directive, mixin definition properties,
 * setup the watcher, call definition bind() and update()
 * if present.
 *
 * @param {Object} def
 */

p._bind = function (def) {
  if (this.name !== 'cloak' && this.el.removeAttribute) {
    this.el.removeAttribute(config.prefix + this.name)
  }
  if (typeof def === 'function') {
    this.update = def
  } else {
    _.extend(this, def)
  }
  this._watcherExp = this.expression
  this._checkDynamicLiteral()
  if (this.bind) {
    this.bind()
  }
  if (
    this.update && this._watcherExp &&
    (!this.isLiteral || this._isDynamicLiteral) &&
    !this._checkStatement()
  ) {
    // use raw expression as identifier because filters
    // make them different watchers
    var watcher = this.vm._watchers[this.raw]
    // wrapped updater for context
    var dir = this
    var update = this._update = function (val, oldVal) {
      if (!dir._locked) {
        dir.update(val, oldVal)
      }
    }
    if (!watcher) {
      watcher = this.vm._watchers[this.raw] = new Watcher(
        this.vm,
        this._watcherExp,
        update, // callback
        this.filters,
        this.twoWay, // need setter,
        this.deep
      )
    } else {
      watcher.addCb(update)
    }
    this._watcher = watcher
    if (this._initValue != null) {
      watcher.set(this._initValue)
    } else {
      this.update(watcher.value)
    }
  }
  this._bound = true
}

/**
 * check if this is a dynamic literal binding.
 *
 * e.g. v-component="{{currentView}}"
 */

p._checkDynamicLiteral = function () {
  var expression = this.expression
  if (expression && this.isLiteral) {
    var tokens = textParser.parse(expression)
    if (tokens) {
      var exp = textParser.tokensToExp(tokens)
      this.expression = this.vm.$get(exp)
      this._watcherExp = exp
      this._isDynamicLiteral = true
    }
  }
}

/**
 * Check if the directive is a function caller
 * and if the expression is a callable one. If both true,
 * we wrap up the expression and use it as the event
 * handler.
 *
 * e.g. v-on="click: a++"
 *
 * @return {Boolean}
 */

p._checkStatement = function () {
  var expression = this.expression
  if (
    expression && this.acceptStatement &&
    !expParser.pathTestRE.test(expression)
  ) {
    var fn = expParser.parse(expression).get
    var vm = this.vm
    var handler = function () {
      fn.call(vm, vm)
    }
    if (this.filters) {
      handler = _.applyFilters(
        handler,
        this.filters.read,
        vm
      )
    }
    this.update(handler)
    return true
  }
}

/**
 * Check for an attribute directive param, e.g. lazy
 *
 * @param {String} name
 * @return {String}
 */

p._checkParam = function (name) {
  var param = this.el.getAttribute(name)
  if (param !== null) {
    this.el.removeAttribute(name)
  }
  return param
}

/**
 * Teardown the watcher and call unbind.
 */

p._teardown = function () {
  if (this._bound) {
    if (this.unbind) {
      this.unbind()
    }
    var watcher = this._watcher
    if (watcher && watcher.active) {
      watcher.removeCb(this._update)
      if (!watcher.active) {
        this.vm._watchers[this.raw] = null
      }
    }
    this._bound = false
    this.vm = this.el = this._watcher = null
  }
}

/**
 * Set the corresponding value with the setter.
 * This should only be used in two-way directives
 * e.g. v-model.
 *
 * @param {*} value
 * @param {Boolean} lock - prevent wrtie triggering update.
 * @public
 */

p.set = function (value, lock) {
  if (this.twoWay) {
    if (lock) {
      this._locked = true
    }
    this._watcher.set(value)
    if (lock) {
      var self = this
      _.nextTick(function () {
        self._locked = false
      })
    }
  }
}

module.exports = Directive