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

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

module.exports = {

  /**
   * Setup.
   */

  bind: function () {
    // uid as a cache identifier
    this.id = '__v_repeat_' + (++uid)
    // we need to insert the objToArray converter
    // as the first read filter, because it has to be invoked
    // before any user filters. (can't do it in `update`)
    if (!this.filters) {
      this.filters = {}
    }
    // add the object -> array convert filter
    var objectConverter = _.bind(objToArray, this)
    if (!this.filters.read) {
      this.filters.read = [objectConverter]
    } else {
      this.filters.read.unshift(objectConverter)
    }
    // setup anchor node
    this.anchor = _.createAnchor('v-repeat')
    _.replace(this.el, this.anchor)
    // check if this is a block repeat
    this.template = this.el.tagName === 'TEMPLATE'
      ? templateParser.parse(this.el, true)
      : this.el
    // check other directives that need to be handled
    // at v-repeat level
    this.checkIf()
    this.checkRef()
    this.checkComponent()
    // check for trackby param
    this.idKey =
      this._checkParam('track-by') ||
      this._checkParam('trackby') // 0.11.0 compat
    this.cache = Object.create(null)
  },

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

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

  /**
   * Check if v-ref/ v-el is also present.
   */

  checkRef: function () {
    var refID = _.attr(this.el, 'ref')
    this.refID = refID
      ? this.vm.$interpolate(refID)
      : null
    var elId = _.attr(this.el, 'el')
    this.elId = elId
      ? this.vm.$interpolate(elId)
      : null
  },

  /**
   * 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.Ctor = _.Vue
      // inline repeats should inherit
      this.inherit = true
      // important: transclude with no options, just
      // to ensure block start and block end
      this.template = transclude(this.template)
      var copy = _.extend({}, options)
      copy._asComponent = false
      this._linkFn = compile(this.template, copy)
    } else {
      this.Ctor = null
      this.asComponent = true
      // check inline-template
      if (this._checkParam('inline-template') !== null) {
        // extract inline template as a DocumentFragment
        this.inlineTempalte = _.extractContent(this.el, true)
      }
      var tokens = textParser.parse(id)
      if (tokens) {
        // dynamic component to be resolved later
        var ctorExp = textParser.tokensToExp(tokens)
        this.ctorGetter = expParser.parse(ctorExp).get
      } else {
        // static
        this.componentId = id
        this.pendingData = null
      }
    }
  },

  resolveComponent: function () {
    this.componentState = PENDING
    this.vm._resolveComponent(this.componentId, _.bind(function (Ctor) {
      if (this.componentState === ABORTED) {
        return
      }
      this.Ctor = Ctor
      var merged = _.mergeOptions(Ctor.options, {}, {
        $parent: this.vm
      })
      merged.template = this.inlineTempalte || merged.template
      merged._asComponent = true
      merged._parent = this.vm
      this.template = transclude(this.template, merged)
      // Important: mark the template as a root node so that
      // custom element components don't get compiled twice.
      // fixes #822
      this.template.__vue__ = true
      this._linkFn = compile(this.template, merged)
      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.ctorGetter.call(context, context)
    var Ctor = _.resolveAsset(this.vm.$options, 'components', id)
    _.assertAsset(Ctor, 'component', id)
    if (!Ctor.options) {
      _.warn(
        'Async resolution is not supported for v-repeat ' +
        '+ dynamic component. (component: ' + id + ')'
      )
      return _.Vue
    }
    return Ctor
  },

  /**
   * 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 (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) {
    data = data || []
    var type = typeof data
    if (type === 'number') {
      data = range(data)
    } else if (type === 'string') {
      data = _.toArray(data)
    }
    this.vms = this.diff(data, this.vms)
    // update v-ref
    if (this.refID) {
      this.vm.$[this.refID] = 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 anchor = this.anchor
    var alias = this.arg
    var init = !oldVms
    var vms = new Array(data.length)
    var obj, raw, vm, i, l
    // 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.$value : obj
      vm = !init && this.getVm(raw, converted ? obj.$key : null)
      if (vm) { // reusable instance
        vm._reused = true
        vm.$index = i // update $index
        // update data for track-by or object repeat,
        // since in these two cases the data is replaced
        // rather than mutated.
        if (idKey || converted) {
          if (alias) {
            vm[alias] = raw
          } else if (_.isPlainObject(raw)) {
            vm.$data = raw
          } else {
            vm.$value = raw
          }
        }
      } else { // new instance
        vm = this.build(obj, i, true)
        // the _new flag is used in the second pass for
        // vm cache retrival, but if this is the init phase
        // the flag can just be set to false directly.
        vm._new = !init
        vm._reused = false
      }
      vms[i] = vm
      // insert if this is first run
      if (init) {
        vm.$before(anchor)
      }
    }
    // 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)
    for (i = 0, l = oldVms.length; i < l; i++) {
      vm = oldVms[i]
      if (!vm._reused) {
        this.uncacheVm(vm)
        vm.$destroy(true)
      }
    }
    // final pass, move/insert new instances into the
    // right place. We're going in reverse here because
    // insertBefore relies on the next sibling to be
    // resolved.
    var targetNext, currentNext
    i = vms.length
    while (i--) {
      vm = vms[i]
      // this is the vm that we should be in front of
      targetNext = vms[i + 1]
      if (!targetNext) {
        // This is the last item. If it's reused then
        // everything else will eventually be in the right
        // place, so no need to touch it. Otherwise, insert
        // it.
        if (!vm._reused) {
          vm.$before(anchor)
        }
      } else {
        var nextEl = targetNext.$el
        if (vm._reused) {
          // this is the vm we are actually in front of
          currentNext = findNextVm(vm, anchor)
          // we only need to move if we are not in the right
          // place already.
          if (currentNext !== targetNext) {
            vm.$before(nextEl, null, false)
          }
        } else {
          // new instance, insert to existing next
          vm.$before(nextEl)
        }
      }
      vm._new = false
      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.$value = raw
    } else {
      // default
      data = raw
    }
    // resolve constructor
    var Ctor = this.Ctor || this.resolveDynamicComponent(data, meta)
    var vm = this.vm.$addChild({
      el: templateParser.clone(this.template),
      _asComponent: this.asComponent,
      _host: this._host,
      _linkFn: this._linkFn,
      _meta: meta,
      data: data,
      inherit: this.inherit,
      template: this.inlineTempalte
    }, Ctor)
    // flag this instance as a repeat instance
    // so that we can skip it in vm._digest
    vm._repeat = true
    // cache instance
    if (needCache) {
      this.cacheVm(raw, vm, this.converted ? meta.$key : null)
    }
    // sync back changes for two-way bindings of primitive values
    var type = typeof raw
    if (type === 'string' || type === 'number') {
      var dir = this
      vm.$watch(alias || '$value', function (val) {
        dir._withLock(function () {
          if (dir.converted) {
            dir.rawValue[vm.$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 {String} [key]
   */

  cacheVm: function (data, vm, key) {
    var idKey = this.idKey
    var cache = this.cache
    var id
    if (key || idKey) {
      id = idKey ? data[idKey] : key
      if (!cache[id]) {
        cache[id] = vm
      } else {
        _.warn('Duplicate track-by key in v-repeat: ' + id)
      }
    } else if (isObject(data)) {
      id = this.id
      if (data.hasOwnProperty(id)) {
        if (data[id] === null) {
          data[id] = vm
        } else {
          _.warn(
            'Duplicate objects are not supported in v-repeat ' +
            'when using components or transitions.'
          )
        }
      } else {
        _.define(data, id, vm)
      }
    } else {
      if (!cache[data]) {
        cache[data] = [vm]
      } else {
        cache[data].push(vm)
      }
    }
    vm._raw = data
  },

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

  getVm: function (data, key) {
    var idKey = this.idKey
    if (key || idKey) {
      var id = idKey ? data[idKey] : key
      return this.cache[id]
    } else if (isObject(data)) {
      return data[this.id]
    } else {
      var cached = this.cache[data]
      if (cached) {
        var i = 0
        var vm = cached[i]
        // since duplicated vm instances might be a reused
        // one OR a newly created one, we need to return the
        // first instance that is neither of these.
        while (vm && (vm._reused || vm._new)) {
          vm = cached[++i]
        }
        return vm
      }
    }
  },

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

  uncacheVm: function (vm) {
    var data = vm._raw
    var idKey = this.idKey
    if (idKey || this.converted) {
      var id = idKey ? data[idKey] : vm.$key
      this.cache[id] = null
    } else if (isObject(data)) {
      data[this.id] = null
      vm._raw = null
    } else {
      this.cache[data].pop()
    }
  }

}

/**
 * Helper to find the next 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.
 *
 * @param {Vue} vm
 * @param {Comment|Text} anchor
 * @return {Vue}
 */

function findNextVm (vm, anchor) {
  var el = (vm._blockEnd || vm.$el).nextSibling
  while (!el.__vue__ && el !== anchor) {
    el = el.nextSibling
  }
  return el.__vue__
}

/**
 * Attempt to convert non-Array objects to array.
 * This is the default filter installed to every v-repeat
 * directive.
 *
 * It will be called with **the directive** as `this`
 * context so that we can mark the repeat array as converted
 * from an object.
 *
 * @param {*} obj
 * @return {Array}
 * @private
 */

function objToArray (obj) {
  // regardless of type, store the un-filtered raw value.
  this.rawValue = obj
  if (!isPlainObject(obj)) {
    return obj
  }
  var keys = Object.keys(obj)
  var i = keys.length
  var res = new Array(i)
  var key
  while (i--) {
    key = keys[i]
    res[i] = {
      $key: key,
      $value: obj[key]
    }
  }
  // `this` points to the repeat directive instance
  this.converted = true
  return res
}

/**
 * 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
}