var _ = require('../util')
var compileProps = require('./compile-props')
var config = require('../config')
var textParser = require('../parsers/text')
var dirParser = require('../parsers/directive')
var templateParser = require('../parsers/template')
var resolveAsset = _.resolveAsset
var componentDef = require('../directives/component')

// terminal directives
var terminalDirectives = [
  'repeat',
  'if'
]

/**
 * Compile a template and return a reusable composite link
 * function, which recursively contains more link functions
 * inside. This top level compile function would normally
 * be called on instance root nodes, but can also be used
 * for partial compilation if the partial argument is true.
 *
 * The returned composite link function, when called, will
 * return an unlink function that tearsdown all directives
 * created during the linking phase.
 *
 * @param {Element|DocumentFragment} el
 * @param {Object} options
 * @param {Boolean} partial
 * @param {Vue} [host] - host vm of transcluded content
 * @return {Function}
 */

exports.compile = function (el, options, partial, host) {
  // link function for the node itself.
  var nodeLinkFn = partial || !options._asComponent
    ? compileNode(el, options)
    : null
  // link function for the childNodes
  var childLinkFn =
    !(nodeLinkFn && nodeLinkFn.terminal) &&
    el.tagName !== 'SCRIPT' &&
    el.hasChildNodes()
      ? compileNodeList(el.childNodes, options)
      : null

  /**
   * A composite linker function to be called on a already
   * compiled piece of DOM, which instantiates all directive
   * instances.
   *
   * @param {Vue} vm
   * @param {Element|DocumentFragment} el
   * @return {Function|undefined}
   */

  return function compositeLinkFn (vm, el) {
    // cache childNodes before linking parent, fix #657
    var childNodes = _.toArray(el.childNodes)
    // link
    var dirs = linkAndCapture(function () {
      if (nodeLinkFn) nodeLinkFn(vm, el, host)
      if (childLinkFn) childLinkFn(vm, childNodes, host)
    }, vm)
    return makeUnlinkFn(vm, dirs)
  }
}

/**
 * Apply a linker to a vm/element pair and capture the
 * directives created during the process.
 *
 * @param {Function} linker
 * @param {Vue} vm
 */

function linkAndCapture (linker, vm) {
  var originalDirCount = vm._directives.length
  linker()
  return vm._directives.slice(originalDirCount)
}

/**
 * Linker functions return an unlink function that
 * tearsdown all directives instances generated during
 * the process.
 *
 * We create unlink functions with only the necessary
 * information to avoid retaining additional closures.
 *
 * @param {Vue} vm
 * @param {Array} dirs
 * @param {Vue} [context]
 * @param {Array} [contextDirs]
 * @return {Function}
 */

function makeUnlinkFn (vm, dirs, context, contextDirs) {
  return function unlink (destroying) {
    teardownDirs(vm, dirs, destroying)
    if (context && contextDirs) {
      teardownDirs(context, contextDirs)
    }
  }
}

/**
 * Teardown partial linked directives.
 *
 * @param {Vue} vm
 * @param {Array} dirs
 * @param {Boolean} destroying
 */

function teardownDirs (vm, dirs, destroying) {
  var i = dirs.length
  while (i--) {
    dirs[i]._teardown()
    if (!destroying) {
      vm._directives.$remove(dirs[i])
    }
  }
}

/**
 * Compile link props on an instance.
 *
 * @param {Vue} vm
 * @param {Element} el
 * @param {Object} options
 * @return {Function}
 */

exports.compileAndLinkProps = function (vm, el, props) {
  var propsLinkFn = compileProps(el, props)
  var propDirs = linkAndCapture(function () {
    propsLinkFn(vm, null)
  }, vm)
  return makeUnlinkFn(vm, propDirs)
}

/**
 * Compile the root element of an instance.
 *
 * 1. attrs on context container (context scope)
 * 2. attrs on the component template root node, if
 *    replace:true (child scope)
 *
 * If this is a fragment instance, we only need to compile 1.
 *
 * This function does compile and link at the same time,
 * since root linkers can not be reused. It returns the
 * unlink function for potential context directives on the
 * container.
 *
 * @param {Vue} vm
 * @param {Element} el
 * @param {Object} options
 * @return {Function}
 */

exports.compileAndLinkRoot = function (vm, el, options) {
  var containerAttrs = options._containerAttrs
  var replacerAttrs = options._replacerAttrs
  var contextLinkFn, replacerLinkFn

  // only need to compile other attributes for
  // non-fragment instances
  if (el.nodeType !== 11) {
    // for components, container and replacer need to be
    // compiled separately and linked in different scopes.
    if (options._asComponent) {
      // 2. container attributes
      if (containerAttrs) {
        contextLinkFn = compileDirectives(containerAttrs, options)
      }
      if (replacerAttrs) {
        // 3. replacer attributes
        replacerLinkFn = compileDirectives(replacerAttrs, options)
      }
    } else {
      // non-component, just compile as a normal element.
      replacerLinkFn = compileDirectives(el.attributes, options)
    }
  }

  // link context scope dirs
  var context = vm._context
  var contextDirs
  if (context && contextLinkFn) {
    contextDirs = linkAndCapture(function () {
      contextLinkFn(context, el)
    }, context)
  }

  // link self
  var selfDirs = linkAndCapture(function () {
    if (replacerLinkFn) replacerLinkFn(vm, el)
  }, vm)

  // return the unlink function that tearsdown context
  // container directives.
  return makeUnlinkFn(vm, selfDirs, context, contextDirs)
}

/**
 * Compile a node and return a nodeLinkFn based on the
 * node type.
 *
 * @param {Node} node
 * @param {Object} options
 * @return {Function|null}
 */

function compileNode (node, options) {
  var type = node.nodeType
  if (type === 1 && node.tagName !== 'SCRIPT') {
    return compileElement(node, options)
  } else if (type === 3 && config.interpolate && node.data.trim()) {
    return compileTextNode(node, options)
  } else {
    return null
  }
}

/**
 * Compile an element and return a nodeLinkFn.
 *
 * @param {Element} el
 * @param {Object} options
 * @return {Function|null}
 */

function compileElement (el, options) {
  var linkFn
  var hasAttrs = el.hasAttributes()
  // check terminal directives (repeat & if)
  if (hasAttrs) {
    linkFn = checkTerminalDirectives(el, options)
  }
  // check element directives
  if (!linkFn) {
    linkFn = checkElementDirectives(el, options)
  }
  // check component
  if (!linkFn) {
    linkFn = checkComponent(el, options)
  }
  // normal directives
  if (!linkFn && hasAttrs) {
    linkFn = compileDirectives(el.attributes, options)
  }
  // if the element is a textarea, we need to interpolate
  // its content on initial render.
  if (el.tagName === 'TEXTAREA') {
    var realLinkFn = linkFn
    linkFn = function (vm, el) {
      el.value = vm.$interpolate(el.value)
      if (realLinkFn) realLinkFn(vm, el)
    }
    linkFn.terminal = true
  }
  return linkFn
}

/**
 * Compile a textNode and return a nodeLinkFn.
 *
 * @param {TextNode} node
 * @param {Object} options
 * @return {Function|null} textNodeLinkFn
 */

function compileTextNode (node, options) {
  var tokens = textParser.parse(node.data)
  if (!tokens) {
    return null
  }
  var frag = document.createDocumentFragment()
  var el, token
  for (var i = 0, l = tokens.length; i < l; i++) {
    token = tokens[i]
    el = token.tag
      ? processTextToken(token, options)
      : document.createTextNode(token.value)
    frag.appendChild(el)
  }
  return makeTextNodeLinkFn(tokens, frag, options)
}

/**
 * Process a single text token.
 *
 * @param {Object} token
 * @param {Object} options
 * @return {Node}
 */

function processTextToken (token, options) {
  var el
  if (token.oneTime) {
    el = document.createTextNode(token.value)
  } else {
    if (token.html) {
      el = document.createComment('v-html')
      setTokenType('html')
    } else {
      // IE will clean up empty textNodes during
      // frag.cloneNode(true), so we have to give it
      // something here...
      el = document.createTextNode(' ')
      setTokenType('text')
    }
  }
  function setTokenType (type) {
    token.type = type
    token.def = resolveAsset(options, 'directives', type)
    token.descriptor = dirParser.parse(token.value)[0]
  }
  return el
}

/**
 * Build a function that processes a textNode.
 *
 * @param {Array<Object>} tokens
 * @param {DocumentFragment} frag
 */

function makeTextNodeLinkFn (tokens, frag) {
  return function textNodeLinkFn (vm, el) {
    var fragClone = frag.cloneNode(true)
    var childNodes = _.toArray(fragClone.childNodes)
    var token, value, node
    for (var i = 0, l = tokens.length; i < l; i++) {
      token = tokens[i]
      value = token.value
      if (token.tag) {
        node = childNodes[i]
        if (token.oneTime) {
          value = vm.$eval(value)
          if (token.html) {
            _.replace(node, templateParser.parse(value, true))
          } else {
            node.data = value
          }
        } else {
          vm._bindDir(token.type, node,
                      token.descriptor, token.def)
        }
      }
    }
    _.replace(el, fragClone)
  }
}

/**
 * Compile a node list and return a childLinkFn.
 *
 * @param {NodeList} nodeList
 * @param {Object} options
 * @return {Function|undefined}
 */

function compileNodeList (nodeList, options) {
  var linkFns = []
  var nodeLinkFn, childLinkFn, node
  for (var i = 0, l = nodeList.length; i < l; i++) {
    node = nodeList[i]
    nodeLinkFn = compileNode(node, options)
    childLinkFn =
      !(nodeLinkFn && nodeLinkFn.terminal) &&
      node.tagName !== 'SCRIPT' &&
      node.hasChildNodes()
        ? compileNodeList(node.childNodes, options)
        : null
    linkFns.push(nodeLinkFn, childLinkFn)
  }
  return linkFns.length
    ? makeChildLinkFn(linkFns)
    : null
}

/**
 * Make a child link function for a node's childNodes.
 *
 * @param {Array<Function>} linkFns
 * @return {Function} childLinkFn
 */

function makeChildLinkFn (linkFns) {
  return function childLinkFn (vm, nodes, host) {
    var node, nodeLinkFn, childrenLinkFn
    for (var i = 0, n = 0, l = linkFns.length; i < l; n++) {
      node = nodes[n]
      nodeLinkFn = linkFns[i++]
      childrenLinkFn = linkFns[i++]
      // cache childNodes before linking parent, fix #657
      var childNodes = _.toArray(node.childNodes)
      if (nodeLinkFn) {
        nodeLinkFn(vm, node, host)
      }
      if (childrenLinkFn) {
        childrenLinkFn(vm, childNodes, host)
      }
    }
  }
}

/**
 * Check for element directives (custom elements that should
 * be resovled as terminal directives).
 *
 * @param {Element} el
 * @param {Object} options
 */

function checkElementDirectives (el, options) {
  var tag = el.tagName.toLowerCase()
  if (_.commonTagRE.test(tag)) return
  var def = resolveAsset(options, 'elementDirectives', tag)
  if (def) {
    return makeTerminalNodeLinkFn(el, tag, '', options, def)
  }
}

/**
 * Check if an element is a component. If yes, return
 * a component link function.
 *
 * @param {Element} el
 * @param {Object} options
 * @param {Boolean} hasAttrs
 * @return {Function|undefined}
 */

function checkComponent (el, options, hasAttrs) {
  var componentId = _.checkComponent(el, options, hasAttrs)
  if (componentId) {
    var componentLinkFn = function (vm, el, host) {
      vm._bindDir('component', el, {
        expression: componentId
      }, componentDef, host)
    }
    componentLinkFn.terminal = true
    return componentLinkFn
  }
}

/**
 * Check an element for terminal directives in fixed order.
 * If it finds one, return a terminal link function.
 *
 * @param {Element} el
 * @param {Object} options
 * @return {Function} terminalLinkFn
 */

function checkTerminalDirectives (el, options) {
  if (_.attr(el, 'pre') !== null) {
    return skip
  }
  var value, dirName
  for (var i = 0, l = terminalDirectives.length; i < l; i++) {
    dirName = terminalDirectives[i]
    if ((value = _.attr(el, dirName)) !== null) {
      return makeTerminalNodeLinkFn(el, dirName, value, options)
    }
  }
}

function skip () {}
skip.terminal = true

/**
 * Build a node link function for a terminal directive.
 * A terminal link function terminates the current
 * compilation recursion and handles compilation of the
 * subtree in the directive.
 *
 * @param {Element} el
 * @param {String} dirName
 * @param {String} value
 * @param {Object} options
 * @param {Object} [def]
 * @return {Function} terminalLinkFn
 */

function makeTerminalNodeLinkFn (el, dirName, value, options, def) {
  var descriptor = dirParser.parse(value)[0]
  // no need to call resolveAsset since terminal directives
  // are always internal
  def = def || options.directives[dirName]
  var fn = function terminalNodeLinkFn (vm, el, host) {
    vm._bindDir(dirName, el, descriptor, def, host)
  }
  fn.terminal = true
  return fn
}

/**
 * Compile the directives on an element and return a linker.
 *
 * @param {Array|NamedNodeMap} attrs
 * @param {Object} options
 * @return {Function}
 */

function compileDirectives (attrs, options) {
  var i = attrs.length
  var dirs = []
  var attr, name, value, dir, dirName, dirDef
  while (i--) {
    attr = attrs[i]
    name = attr.name
    value = attr.value
    if (name.indexOf(config.prefix) === 0) {
      dirName = name.slice(config.prefix.length)
      dirDef = resolveAsset(options, 'directives', dirName)
      if (process.env.NODE_ENV !== 'production') {
        _.assertAsset(dirDef, 'directive', dirName)
      }
      if (dirDef) {
        dirs.push({
          name: dirName,
          descriptors: dirParser.parse(value),
          def: dirDef
        })
      }
    } else if (config.interpolate) {
      dir = collectAttrDirective(name, value, options)
      if (dir) {
        dirs.push(dir)
      }
    }
  }
  // sort by priority, LOW to HIGH
  if (dirs.length) {
    dirs.sort(directiveComparator)
    return makeNodeLinkFn(dirs)
  }
}

/**
 * Build a link function for all directives on a single node.
 *
 * @param {Array} directives
 * @return {Function} directivesLinkFn
 */

function makeNodeLinkFn (directives) {
  return function nodeLinkFn (vm, el, host) {
    // reverse apply because it's sorted low to high
    var i = directives.length
    var dir, j, k
    while (i--) {
      dir = directives[i]
      if (dir._link) {
        // custom link fn
        dir._link(vm, el)
      } else {
        k = dir.descriptors.length
        for (j = 0; j < k; j++) {
          vm._bindDir(dir.name, el,
            dir.descriptors[j], dir.def, host)
        }
      }
    }
  }
}

/**
 * Check an attribute for potential dynamic bindings,
 * and return a directive object.
 *
 * Special case: class interpolations are translated into
 * v-class instead v-attr, so that it can work with user
 * provided v-class bindings.
 *
 * @param {String} name
 * @param {String} value
 * @param {Object} options
 * @return {Object}
 */

function collectAttrDirective (name, value, options) {
  var tokens = textParser.parse(value)
  var isClass = name === 'class'
  if (tokens) {
    var dirName = isClass ? 'class' : 'attr'
    var def = options.directives[dirName]
    var i = tokens.length
    var allOneTime = true
    while (i--) {
      var token = tokens[i]
      if (token.tag && !token.oneTime) {
        allOneTime = false
      }
    }
    return {
      def: def,
      _link: allOneTime
        ? function (vm, el) {
            el.setAttribute(name, vm.$interpolate(value))
          }
        : function (vm, el) {
            var exp = textParser.tokensToExp(tokens, vm)
            var desc = isClass
              ? dirParser.parse(exp)[0]
              : dirParser.parse(name + ':' + exp)[0]
            if (isClass) {
              desc._rawClass = value
            }
            vm._bindDir(dirName, el, desc, def)
          }
    }
  }
}

/**
 * Directive priority sort comparator
 *
 * @param {Object} a
 * @param {Object} b
 */

function directiveComparator (a, b) {
  a = a.def.priority || 0
  b = b.def.priority || 0
  return a > b ? 1 : -1
}