var _ = require('../util')
var config = require('../config')
var isObject = _.isObject
var isPlainObject = _.isPlainObject
var textParser = require('../parsers/text')
var expParser = require('../parsers/expression')
var templateParser = require('../parsers/template')
var compiler = require('../compiler')
var uid = 0

// async component resolution states
var UNRESOLVED = 0
var PENDING = 1
var RESOLVED = 2
var ABORTED = 3

module.exports = {

  /**
   * Setup.
   */

  bind: function () {

    // some helpful tips...
    /* istanbul ignore if */
    if (
      process.env.NODE_ENV !== 'production' &&
      this.el.tagName === 'OPTION' &&
      this.el.parentNode && this.el.parentNode.__v_model
    ) {
      _.warn(
        'Don\'t use v-repeat for v-model options; ' +
        'use the `options` param instead: ' +
        'http://vuejs.org/guide/forms.html#Dynamic_Select_Options'
      )
    }

    // support for item in array syntax
    var inMatch = this.expression.match(/(.*) in (.*)/)
    if (inMatch) {
      this.arg = inMatch[1]
      this._watcherExp = inMatch[2]
    }
    // uid as a cache identifier
    this.id = '__v_repeat_' + (++uid)

    // setup anchor nodes
    this.start = _.createAnchor('v-repeat-start')
    this.end = _.createAnchor('v-repeat-end')
    _.replace(this.el, this.end)
    _.before(this.start, this.end)

    // check if this is a block repeat
    this.template = _.isTemplate(this.el)
      ? templateParser.parse(this.el, true)
      : this.el

    // check for trackby param
    this.idKey = this._checkParam('track-by')
    // check for transition stagger
    var stagger = +this._checkParam('stagger')
    this.enterStagger = +this._checkParam('enter-stagger') || stagger
    this.leaveStagger = +this._checkParam('leave-stagger') || stagger

    // check for v-ref/v-el
    this.refID = this._checkParam(config.prefix + 'ref')
    this.elID = this._checkParam(config.prefix + 'el')

    // check other directives that need to be handled
    // at v-repeat level
    this.checkIf()
    this.checkComponent()

    // create cache object
    this.cache = Object.create(null)
  },

  /**
   * Warn against v-if usage.
   */

  checkIf: function () {
    if (_.attr(this.el, 'if') !== null) {
      process.env.NODE_ENV !== 'production' && _.warn(
        'Don\'t use v-if with v-repeat. ' +
        'Use v-show or the "filterBy" filter instead.'
      )
    }
  },

  /**
   * Check the component constructor to use for repeated
   * instances. If static we resolve it now, otherwise it
   * needs to be resolved at build time with actual data.
   */

  checkComponent: function () {
    this.componentState = UNRESOLVED
    var options = this.vm.$options
    var id = _.checkComponent(this.el, options)
    if (!id) {
      // default constructor
      this.Component = _.Vue
      // inline repeats should inherit
      this.inline = true
      // important: transclude with no options, just
      // to ensure block start and block end
      this.template = compiler.transclude(this.template)
      var copy = _.extend({}, options)
      copy._asComponent = false
      this._linkFn = compiler.compile(this.template, copy)
    } else {
      this.Component = null
      this.asComponent = true
      // check inline-template
      if (this._checkParam('inline-template') !== null) {
        // extract inline template as a DocumentFragment
        this.inlineTemplate = _.extractContent(this.el, true)
      }
      var tokens = textParser.parse(id)
      if (tokens) {
        // dynamic component to be resolved later
        var componentExp = textParser.tokensToExp(tokens)
        this.componentGetter = expParser.parse(componentExp).get
      } else {
        // static
        this.componentId = id
        this.pendingData = null
      }
    }
  },

  resolveComponent: function () {
    this.componentState = PENDING
    this.vm._resolveComponent(this.componentId, _.bind(function (Component) {
      if (this.componentState === ABORTED) {
        return
      }
      this.Component = Component
      this.componentState = RESOLVED
      this.realUpdate(this.pendingData)
      this.pendingData = null
    }, this))
  },

  /**
   * Resolve a dynamic component to use for an instance.
   * The tricky part here is that there could be dynamic
   * components depending on instance data.
   *
   * @param {Object} data
   * @param {Object} meta
   * @return {Function}
   */

  resolveDynamicComponent: function (data, meta) {
    // create a temporary context object and copy data
    // and meta properties onto it.
    // use _.define to avoid accidentally overwriting scope
    // properties.
    var context = Object.create(this.vm)
    var key
    for (key in data) {
      _.define(context, key, data[key])
    }
    for (key in meta) {
      _.define(context, key, meta[key])
    }
    var id = this.componentGetter.call(context, context)
    var Component = _.resolveAsset(this.vm.$options, 'components', id)
    if (process.env.NODE_ENV !== 'production') {
      _.assertAsset(Component, 'component', id)
    }
    if (!Component.options) {
      process.env.NODE_ENV !== 'production' && _.warn(
        'Async resolution is not supported for v-repeat ' +
        '+ dynamic component. (component: ' + id + ')'
      )
      return _.Vue
    }
    return Component
  },

  /**
   * Update.
   * This is called whenever the Array mutates. If we have
   * a component, we might need to wait for it to resolve
   * asynchronously.
   *
   * @param {Array|Number|String} data
   */

  update: function (data) {
    if (process.env.NODE_ENV !== 'production' && !_.isArray(data)) {
      _.warn(
        'v-repeat pre-converts Objects into Arrays, and ' +
        'v-repeat filters should always return Arrays.'
      )
    }
    if (this.componentId) {
      var state = this.componentState
      if (state === UNRESOLVED) {
        this.pendingData = data
        // once resolved, it will call realUpdate
        this.resolveComponent()
      } else if (state === PENDING) {
        this.pendingData = data
      } else if (state === RESOLVED) {
        this.realUpdate(data)
      }
    } else {
      this.realUpdate(data)
    }
  },

  /**
   * The real update that actually modifies the DOM.
   *
   * @param {Array|Number|String} data
   */

  realUpdate: function (data) {
    this.vms = this.diff(data, this.vms)
    // update v-ref
    if (this.refID) {
      this.vm.$[this.refID] = this.converted
        ? toRefObject(this.vms)
        : this.vms
    }
    if (this.elID) {
      this.vm.$$[this.elID] = this.vms.map(function (vm) {
        return vm.$el
      })
    }
  },

  /**
   * Diff, based on new data and old data, determine the
   * minimum amount of DOM manipulations needed to make the
   * DOM reflect the new data Array.
   *
   * The algorithm diffs the new data Array by storing a
   * hidden reference to an owner vm instance on previously
   * seen data. This allows us to achieve O(n) which is
   * better than a levenshtein distance based algorithm,
   * which is O(m * n).
   *
   * @param {Array} data
   * @param {Array} oldVms
   * @return {Array}
   */

  diff: function (data, oldVms) {
    var idKey = this.idKey
    var converted = this.converted
    var start = this.start
    var end = this.end
    var inDoc = _.inDoc(start)
    var alias = this.arg
    var init = !oldVms
    var vms = new Array(data.length)
    var obj, raw, vm, i, l, primitive
    // First pass, go through the new Array and fill up
    // the new vms array. If a piece of data has a cached
    // instance for it, we reuse it. Otherwise build a new
    // instance.
    for (i = 0, l = data.length; i < l; i++) {
      obj = data[i]
      raw = converted ? obj.$value : obj
      primitive = !isObject(raw)
      vm = !init && this.getVm(raw, i, converted ? obj.$key : null)
      if (vm) { // reusable instance

        if (process.env.NODE_ENV !== 'production' && vm._reused) {
          _.warn(
            'Duplicate objects found in v-repeat="' + this.expression + '": ' +
            JSON.stringify(raw)
          )
        }

        vm._reused = true
        vm.$index = i // update $index
        // update data for track-by or object repeat,
        // since in these two cases the data is replaced
        // rather than mutated.
        if (idKey || converted || primitive) {
          if (alias) {
            vm[alias] = raw
          } else if (_.isPlainObject(raw)) {
            vm.$data = raw
          } else {
            vm.$value = raw
          }
        }
      } else { // new instance
        vm = this.build(obj, i, true)
        vm._reused = false
      }
      vms[i] = vm
      // insert if this is first run
      if (init) {
        vm.$before(end)
      }
    }
    // if this is the first run, we're done.
    if (init) {
      return vms
    }
    // Second pass, go through the old vm instances and
    // destroy those who are not reused (and remove them
    // from cache)
    var removalIndex = 0
    var totalRemoved = oldVms.length - vms.length
    for (i = 0, l = oldVms.length; i < l; i++) {
      vm = oldVms[i]
      if (!vm._reused) {
        this.uncacheVm(vm)
        vm.$destroy(false, true) // defer cleanup until removal
        this.remove(vm, removalIndex++, totalRemoved, inDoc)
      }
    }
    // final pass, move/insert new instances into the
    // right place.
    var targetPrev, prevEl, currentPrev
    var insertionIndex = 0
    for (i = 0, l = vms.length; i < l; i++) {
      vm = vms[i]
      // this is the vm that we should be after
      targetPrev = vms[i - 1]
      prevEl = targetPrev
        ? targetPrev._staggerCb
          ? targetPrev._staggerAnchor
          : targetPrev._fragmentEnd || targetPrev.$el
        : start
      if (vm._reused && !vm._staggerCb) {
        currentPrev = findPrevVm(vm, start, this.id)
        if (currentPrev !== targetPrev) {
          this.move(vm, prevEl)
        }
      } else {
        // new instance, or still in stagger.
        // insert with updated stagger index.
        this.insert(vm, insertionIndex++, prevEl, inDoc)
      }
      vm._reused = false
    }
    return vms
  },

  /**
   * Build a new instance and cache it.
   *
   * @param {Object} data
   * @param {Number} index
   * @param {Boolean} needCache
   */

  build: function (data, index, needCache) {
    var meta = { $index: index }
    if (this.converted) {
      meta.$key = data.$key
    }
    var raw = this.converted ? data.$value : data
    var alias = this.arg
    if (alias) {
      data = {}
      data[alias] = raw
    } else if (!isPlainObject(raw)) {
      // non-object values
      data = {}
      meta.$value = raw
    } else {
      // default
      data = raw
    }
    // resolve constructor
    var Component = this.Component || this.resolveDynamicComponent(data, meta)
    var parent = this._host || this.vm
    var vm = parent.$addChild({
      el: templateParser.clone(this.template),
      data: data,
      inherit: this.inline,
      template: this.inlineTemplate,
      // repeater meta, e.g. $index, $key
      _meta: meta,
      // mark this as an inline-repeat instance
      _repeat: this.inline,
      // is this a component?
      _asComponent: this.asComponent,
      // linker cachable if no inline-template
      _linkerCachable: !this.inlineTemplate && Component !== _.Vue,
      // pre-compiled linker for simple repeats
      _linkFn: this._linkFn,
      // identifier, shows that this vm belongs to this collection
      _repeatId: this.id,
      // transclusion content owner
      _context: this.vm
    }, Component)
    // cache instance
    if (needCache) {
      this.cacheVm(raw, vm, index, this.converted ? meta.$key : null)
    }
    // sync back changes for two-way bindings of primitive values
    var dir = this
    if (this.rawType === 'object' && isPrimitive(raw)) {
      vm.$watch(alias || '$value', function (val) {
        if (dir.filters) {
          process.env.NODE_ENV !== 'production' && _.warn(
            'You seem to be mutating the $value reference of ' +
            'a v-repeat instance (likely through v-model) ' +
            'and filtering the v-repeat at the same time. ' +
            'This will not work properly with an Array of ' +
            'primitive values. Please use an Array of ' +
            'Objects instead.'
          )
        }
        dir._withLock(function () {
          if (dir.converted) {
            dir.rawValue[vm.$key] = val
          } else {
            dir.rawValue.$set(vm.$index, val)
          }
        })
      })
    }
    return vm
  },

  /**
   * Unbind, teardown everything
   */

  unbind: function () {
    this.componentState = ABORTED
    if (this.refID) {
      this.vm.$[this.refID] = null
    }
    if (this.vms) {
      var i = this.vms.length
      var vm
      while (i--) {
        vm = this.vms[i]
        this.uncacheVm(vm)
        vm.$destroy()
      }
    }
  },

  /**
   * Cache a vm instance based on its data.
   *
   * If the data is an object, we save the vm's reference on
   * the data object as a hidden property. Otherwise we
   * cache them in an object and for each primitive value
   * there is an array in case there are duplicates.
   *
   * @param {Object} data
   * @param {Vue} vm
   * @param {Number} index
   * @param {String} [key]
   */

  cacheVm: function (data, vm, index, key) {
    var idKey = this.idKey
    var cache = this.cache
    var primitive = !isObject(data)
    var id
    if (key || idKey || primitive) {
      id = idKey
        ? idKey === '$index'
          ? index
          : data[idKey]
        : (key || index)
      if (!cache[id]) {
        cache[id] = vm
      } else if (!primitive && idKey !== '$index') {
        process.env.NODE_ENV !== 'production' && _.warn(
          'Duplicate objects with the same track-by key in v-repeat: ' + id
        )
      }
    } else {
      id = this.id
      if (data.hasOwnProperty(id)) {
        if (data[id] === null) {
          data[id] = vm
        } else {
          process.env.NODE_ENV !== 'production' && _.warn(
            'Duplicate objects found in v-repeat="' + this.expression + '": ' +
            JSON.stringify(data)
          )
        }
      } else {
        _.define(data, id, vm)
      }
    }
    vm._raw = data
  },

  /**
   * Try to get a cached instance from a piece of data.
   *
   * @param {Object} data
   * @param {Number} index
   * @param {String} [key]
   * @return {Vue|undefined}
   */

  getVm: function (data, index, key) {
    var idKey = this.idKey
    var primitive = !isObject(data)
    if (key || idKey || primitive) {
      var id = idKey
        ? idKey === '$index'
          ? index
          : data[idKey]
        : (key || index)
      return this.cache[id]
    } else {
      return data[this.id]
    }
  },

  /**
   * Delete a cached vm instance.
   *
   * @param {Vue} vm
   */

  uncacheVm: function (vm) {
    var data = vm._raw
    var idKey = this.idKey
    var index = vm.$index
    // fix #948: avoid accidentally fall through to
    // a parent repeater which happens to have $key.
    var key = vm.hasOwnProperty('$key') && vm.$key
    var primitive = !isObject(data)
    if (idKey || key || primitive) {
      var id = idKey
        ? idKey === '$index'
          ? index
          : data[idKey]
        : (key || index)
      this.cache[id] = null
    } else {
      data[this.id] = null
      vm._raw = null
    }
  },

  /**
   * Insert an instance.
   *
   * @param {Vue} vm
   * @param {Number} index
   * @param {Node} prevEl
   * @param {Boolean} inDoc
   */

  insert: function (vm, index, prevEl, inDoc) {
    if (vm._staggerCb) {
      vm._staggerCb.cancel()
      vm._staggerCb = null
    }
    var staggerAmount = this.getStagger(vm, index, null, 'enter')
    if (inDoc && staggerAmount) {
      // create an anchor and insert it synchronously,
      // so that we can resolve the correct order without
      // worrying about some elements not inserted yet
      var anchor = vm._staggerAnchor
      if (!anchor) {
        anchor = vm._staggerAnchor = _.createAnchor('stagger-anchor')
        anchor.__vue__ = vm
      }
      _.after(anchor, prevEl)
      var op = vm._staggerCb = _.cancellable(function () {
        vm._staggerCb = null
        vm.$before(anchor)
        _.remove(anchor)
      })
      setTimeout(op, staggerAmount)
    } else {
      vm.$after(prevEl)
    }
  },

  /**
   * Move an already inserted instance.
   *
   * @param {Vue} vm
   * @param {Node} prevEl
   */

  move: function (vm, prevEl) {
    vm.$after(prevEl, null, false)
  },

  /**
   * Remove an instance.
   *
   * @param {Vue} vm
   * @param {Number} index
   * @param {Boolean} inDoc
   */

  remove: function (vm, index, total, inDoc) {
    if (vm._staggerCb) {
      vm._staggerCb.cancel()
      vm._staggerCb = null
      // it's not possible for the same vm to be removed
      // twice, so if we have a pending stagger callback,
      // it means this vm is queued for enter but removed
      // before its transition started. Since it is already
      // destroyed, we can just leave it in detached state.
      return
    }
    var staggerAmount = this.getStagger(vm, index, total, 'leave')
    if (inDoc && staggerAmount) {
      var op = vm._staggerCb = _.cancellable(function () {
        vm._staggerCb = null
        remove()
      })
      setTimeout(op, staggerAmount)
    } else {
      remove()
    }
    function remove () {
      vm.$remove(function () {
        vm._cleanup()
      })
    }
  },

  /**
   * Get the stagger amount for an insertion/removal.
   *
   * @param {Vue} vm
   * @param {Number} index
   * @param {String} type
   * @param {Number} total
   */

  getStagger: function (vm, index, total, type) {
    type = type + 'Stagger'
    var transition = vm.$el.__v_trans
    var hooks = transition && transition.hooks
    var hook = hooks && (hooks[type] || hooks.stagger)
    return hook
      ? hook.call(vm, index, total)
      : index * this[type]
  },

  /**
   * Pre-process the value before piping it through the
   * filters, and convert non-Array objects to arrays.
   *
   * This function will be bound to this directive instance
   * and passed into the watcher.
   *
   * @param {*} value
   * @return {Array}
   * @private
   */

  _preProcess: function (value) {
    // regardless of type, store the un-filtered raw value.
    this.rawValue = value
    var type = this.rawType = typeof value
    if (!isPlainObject(value)) {
      this.converted = false
      if (type === 'number') {
        value = range(value)
      } else if (type === 'string') {
        value = _.toArray(value)
      }
      return value || []
    } else {
      // convert plain object to array.
      var keys = Object.keys(value)
      var i = keys.length
      var res = new Array(i)
      var key
      while (i--) {
        key = keys[i]
        res[i] = {
          $key: key,
          $value: value[key]
        }
      }
      this.converted = true
      return res
    }
  }
}

/**
 * Helper to find the previous element that is an instance
 * root node. This is necessary because a destroyed vm's
 * element could still be lingering in the DOM before its
 * leaving transition finishes, but its __vue__ reference
 * should have been removed so we can skip them.
 *
 * If this is a block repeat, we want to make sure we only
 * return vm that is bound to this v-repeat. (see #929)
 *
 * @param {Vue} vm
 * @param {Comment|Text} anchor
 * @return {Vue}
 */

function findPrevVm (vm, anchor, id) {
  var el = vm.$el.previousSibling
  /* istanbul ignore if */
  if (!el) return
  while (
    (!el.__vue__ || el.__vue__.$options._repeatId !== id) &&
    el !== anchor
  ) {
    el = el.previousSibling
  }
  return el.__vue__
}

/**
 * Create a range array from given number.
 *
 * @param {Number} n
 * @return {Array}
 */

function range (n) {
  var i = -1
  var ret = new Array(n)
  while (++i < n) {
    ret[i] = i
  }
  return ret
}

/**
 * Convert a vms array to an object ref for v-ref on an
 * Object value.
 *
 * @param {Array} vms
 * @return {Object}
 */

function toRefObject (vms) {
  var ref = {}
  for (var i = 0, l = vms.length; i < l; i++) {
    ref[vms[i].$key] = vms[i]
  }
  return ref
}

/**
 * Check if a value is a primitive one:
 * String, Number, Boolean, null or undefined.
 *
 * @param {*} value
 * @return {Boolean}
 */

function isPrimitive (value) {
  var type = typeof value
  return value == null ||
    type === 'string' ||
    type === 'number' ||
    type === 'boolean'
}