'use strict'

const latex = require('../../utils/latex')
const escape = require('../../utils/string').escape
const hasOwnProperty = require('../../utils/object').hasOwnProperty
const map = require('../../utils/array').map
const validateSafeMethod = require('../../utils/customs').validateSafeMethod
const getSafeProperty = require('../../utils/customs').getSafeProperty

function factory (type, config, load, typed, math) {
  const Node = load(require('./Node'))
  const SymbolNode = load(require('./SymbolNode'))

  /**
   * @constructor FunctionNode
   * @extends {./Node}
   * invoke a list with arguments on a node
   * @param {./Node | string} fn Node resolving with a function on which to invoke
   *                             the arguments, typically a SymboNode or AccessorNode
   * @param {./Node[]} args
   */
  function FunctionNode (fn, args) {
    if (!(this instanceof FunctionNode)) {
      throw new SyntaxError('Constructor must be called with the new operator')
    }

    if (typeof fn === 'string') {
      fn = new SymbolNode(fn)
    }

    // validate input
    if (!type.isNode(fn)) throw new TypeError('Node expected as parameter "fn"')
    if (!Array.isArray(args) || !args.every(type.isNode)) {
      throw new TypeError('Array containing Nodes expected for parameter "args"')
    }

    this.fn = fn
    this.args = args || []

    // readonly property name
    Object.defineProperty(this, 'name', {
      get: function () {
        return this.fn.name || ''
      }.bind(this),
      set: function () {
        throw new Error('Cannot assign a new name, name is read-only')
      }
    })

    // TODO: deprecated since v3, remove some day
    const deprecated = function () {
      throw new Error('Property `FunctionNode.object` is deprecated, use `FunctionNode.fn` instead')
    }
    Object.defineProperty(this, 'object', { get: deprecated, set: deprecated })
  }

  FunctionNode.prototype = new Node()

  FunctionNode.prototype.type = 'FunctionNode'

  FunctionNode.prototype.isFunctionNode = true

  /**
   * Compile a node into a JavaScript function.
   * This basically pre-calculates as much as possible and only leaves open
   * calculations which depend on a dynamic scope with variables.
   * @param {Object} math     Math.js namespace with functions and constants.
   * @param {Object} argNames An object with argument names as key and `true`
   *                          as value. Used in the SymbolNode to optimize
   *                          for arguments from user assigned functions
   *                          (see FunctionAssignmentNode) or special symbols
   *                          like `end` (see IndexNode).
   * @return {function} Returns a function which can be called like:
   *                        evalNode(scope: Object, args: Object, context: *)
   */
  FunctionNode.prototype._compile = function (math, argNames) {
    if (!(this instanceof FunctionNode)) {
      throw new TypeError('No valid FunctionNode')
    }

    // compile arguments
    const evalArgs = map(this.args, function (arg) {
      return arg._compile(math, argNames)
    })

    if (type.isSymbolNode(this.fn)) {
      // we can statically determine whether the function has an rawArgs property
      const name = this.fn.name
      const fn = name in math ? getSafeProperty(math, name) : undefined
      const isRaw = (typeof fn === 'function') && (fn.rawArgs === true)

      if (isRaw) {
        // pass unevaluated parameters (nodes) to the function
        // "raw" evaluation
        const rawArgs = this.args
        return function evalFunctionNode (scope, args, context) {
          return (name in scope ? getSafeProperty(scope, name) : fn)(rawArgs, math, Object.assign({}, scope, args))
        }
      } else {
        // "regular" evaluation
        if (evalArgs.length === 1) {
          const evalArg0 = evalArgs[0]
          return function evalFunctionNode (scope, args, context) {
            return (name in scope ? getSafeProperty(scope, name) : fn)(evalArg0(scope, args, context))
          }
        } else if (evalArgs.length === 2) {
          const evalArg0 = evalArgs[0]
          const evalArg1 = evalArgs[1]
          return function evalFunctionNode (scope, args, context) {
            return (name in scope ? getSafeProperty(scope, name) : fn)(evalArg0(scope, args, context), evalArg1(scope, args, context))
          }
        } else {
          return function evalFunctionNode (scope, args, context) {
            return (name in scope ? getSafeProperty(scope, name) : fn).apply(null, map(evalArgs, function (evalArg) {
              return evalArg(scope, args, context)
            }))
          }
        }
      }
    } else if (type.isAccessorNode(this.fn) &&
        type.isIndexNode(this.fn.index) && this.fn.index.isObjectProperty()) {
      // execute the function with the right context: the object of the AccessorNode

      const evalObject = this.fn.object._compile(math, argNames)
      const prop = this.fn.index.getObjectProperty()
      const rawArgs = this.args

      return function evalFunctionNode (scope, args, context) {
        const object = evalObject(scope, args, context)
        validateSafeMethod(object, prop)
        const isRaw = object[prop] && object[prop].rawArgs

        return isRaw
          ? object[prop](rawArgs, math, Object.assign({}, scope, args)) // "raw" evaluation
          : object[prop].apply(object, map(evalArgs, function (evalArg) { // "regular" evaluation
            return evalArg(scope, args, context)
          }))
      }
    } else { // node.fn.isAccessorNode && !node.fn.index.isObjectProperty()
      // we have to dynamically determine whether the function has a rawArgs property
      const evalFn = this.fn._compile(math, argNames)
      const rawArgs = this.args

      return function evalFunctionNode (scope, args, context) {
        const fn = evalFn(scope, args, context)
        const isRaw = fn && fn.rawArgs

        return isRaw
          ? fn(rawArgs, math, Object.assign({}, scope, args)) // "raw" evaluation
          : fn.apply(fn, map(evalArgs, function (evalArg) { // "regular" evaluation
            return evalArg(scope, args, context)
          }))
      }
    }
  }

  /**
   * Execute a callback for each of the child nodes of this node
   * @param {function(child: Node, path: string, parent: Node)} callback
   */
  FunctionNode.prototype.forEach = function (callback) {
    callback(this.fn, 'fn', this)

    for (let i = 0; i < this.args.length; i++) {
      callback(this.args[i], 'args[' + i + ']', this)
    }
  }

  /**
   * Create a new FunctionNode having it's childs be the results of calling
   * the provided callback function for each of the childs of the original node.
   * @param {function(child: Node, path: string, parent: Node): Node} callback
   * @returns {FunctionNode} Returns a transformed copy of the node
   */
  FunctionNode.prototype.map = function (callback) {
    const fn = this._ifNode(callback(this.fn, 'fn', this))
    const args = []
    for (let i = 0; i < this.args.length; i++) {
      args[i] = this._ifNode(callback(this.args[i], 'args[' + i + ']', this))
    }
    return new FunctionNode(fn, args)
  }

  /**
   * Create a clone of this node, a shallow copy
   * @return {FunctionNode}
   */
  FunctionNode.prototype.clone = function () {
    return new FunctionNode(this.fn, this.args.slice(0))
  }

  // backup Node's toString function
  // @private
  const nodeToString = FunctionNode.prototype.toString

  /**
   * Get string representation. (wrapper function)
   * This overrides parts of Node's toString function.
   * If callback is an object containing callbacks, it
   * calls the correct callback for the current node,
   * otherwise it falls back to calling Node's toString
   * function.
   *
   * @param {Object} options
   * @return {string} str
   * @override
   */
  FunctionNode.prototype.toString = function (options) {
    let customString
    const name = this.fn.toString(options)
    if (options && (typeof options.handler === 'object') && hasOwnProperty(options.handler, name)) {
      // callback is a map of callback functions
      customString = options.handler[name](this, options)
    }

    if (typeof customString !== 'undefined') {
      return customString
    }

    // fall back to Node's toString
    return nodeToString.call(this, options)
  }

  /**
   * Get string representation
   * @param {Object} options
   * @return {string} str
   */
  FunctionNode.prototype._toString = function (options) {
    const args = this.args.map(function (arg) {
      return arg.toString(options)
    })

    const fn = type.isFunctionAssignmentNode(this.fn)
      ? ('(' + this.fn.toString(options) + ')')
      : this.fn.toString(options)

    // format the arguments like "add(2, 4.2)"
    return fn + '(' + args.join(', ') + ')'
  }

  /**
   * Get a JSON representation of the node
   * @returns {Object}
   */
  FunctionNode.prototype.toJSON = function () {
    return {
      mathjs: 'FunctionNode',
      fn: this.fn,
      args: this.args
    }
  }

  /**
   * Instantiate an AssignmentNode from its JSON representation
   * @param {Object} json  An object structured like
   *                       `{"mathjs": "FunctionNode", fn: ..., args: ...}`,
   *                       where mathjs is optional
   * @returns {FunctionNode}
   */
  FunctionNode.fromJSON = function (json) {
    return new FunctionNode(json.fn, json.args)
  }

  /**
   * Get HTML representation
   * @param {Object} options
   * @return {string} str
   */
  FunctionNode.prototype.toHTML = function (options) {
    const args = this.args.map(function (arg) {
      return arg.toHTML(options)
    })

    // format the arguments like "add(2, 4.2)"
    return '<span class="math-function">' + escape(this.fn) + '</span><span class="math-paranthesis math-round-parenthesis">(</span>' + args.join('<span class="math-separator">,</span>') + '<span class="math-paranthesis math-round-parenthesis">)</span>'
  }

  /*
   * Expand a LaTeX template
   *
   * @param {string} template
   * @param {Node} node
   * @param {Object} options
   * @private
   **/
  function expandTemplate (template, node, options) {
    let latex = ''

    // Match everything of the form ${identifier} or ${identifier[2]} or $$
    // while submatching identifier and 2 (in the second case)
    const regex = new RegExp('\\$(?:\\{([a-z_][a-z_0-9]*)(?:\\[([0-9]+)\\])?\\}|\\$)', 'ig')

    let inputPos = 0 // position in the input string
    let match
    while ((match = regex.exec(template)) !== null) { // go through all matches
      // add everything in front of the match to the LaTeX string
      latex += template.substring(inputPos, match.index)
      inputPos = match.index

      if (match[0] === '$$') { // escaped dollar sign
        latex += '$'
        inputPos++
      } else { // template parameter
        inputPos += match[0].length
        const property = node[match[1]]
        if (!property) {
          throw new ReferenceError('Template: Property ' + match[1] + ' does not exist.')
        }
        if (match[2] === undefined) { // no square brackets
          switch (typeof property) {
            case 'string':
              latex += property
              break
            case 'object':
              if (type.isNode(property)) {
                latex += property.toTex(options)
              } else if (Array.isArray(property)) {
                // make array of Nodes into comma separated list
                latex += property.map(function (arg, index) {
                  if (type.isNode(arg)) {
                    return arg.toTex(options)
                  }
                  throw new TypeError('Template: ' + match[1] + '[' + index + '] is not a Node.')
                }).join(',')
              } else {
                throw new TypeError('Template: ' + match[1] + ' has to be a Node, String or array of Nodes')
              }
              break
            default:
              throw new TypeError('Template: ' + match[1] + ' has to be a Node, String or array of Nodes')
          }
        } else { // with square brackets
          if (type.isNode(property[match[2]] && property[match[2]])) {
            latex += property[match[2]].toTex(options)
          } else {
            throw new TypeError('Template: ' + match[1] + '[' + match[2] + '] is not a Node.')
          }
        }
      }
    }
    latex += template.slice(inputPos) // append rest of the template

    return latex
  }

  // backup Node's toTex function
  // @private
  const nodeToTex = FunctionNode.prototype.toTex

  /**
   * Get LaTeX representation. (wrapper function)
   * This overrides parts of Node's toTex function.
   * If callback is an object containing callbacks, it
   * calls the correct callback for the current node,
   * otherwise it falls back to calling Node's toTex
   * function.
   *
   * @param {Object} options
   * @return {string}
   */
  FunctionNode.prototype.toTex = function (options) {
    let customTex
    if (options && (typeof options.handler === 'object') && hasOwnProperty(options.handler, this.name)) {
      // callback is a map of callback functions
      customTex = options.handler[this.name](this, options)
    }

    if (typeof customTex !== 'undefined') {
      return customTex
    }

    // fall back to Node's toTex
    return nodeToTex.call(this, options)
  }

  /**
   * Get LaTeX representation
   * @param {Object} options
   * @return {string} str
   */
  FunctionNode.prototype._toTex = function (options) {
    const args = this.args.map(function (arg) { // get LaTeX of the arguments
      return arg.toTex(options)
    })

    let latexConverter

    if (math[this.name] && ((typeof math[this.name].toTex === 'function') || (typeof math[this.name].toTex === 'object') || (typeof math[this.name].toTex === 'string'))) {
      // .toTex is a callback function
      latexConverter = math[this.name].toTex
    }

    let customToTex
    switch (typeof latexConverter) {
      case 'function': // a callback function
        customToTex = latexConverter(this, options)
        break
      case 'string': // a template string
        customToTex = expandTemplate(latexConverter, this, options)
        break
      case 'object': // an object with different "converters" for different numbers of arguments
        switch (typeof latexConverter[args.length]) {
          case 'function':
            customToTex = latexConverter[args.length](this, options)
            break
          case 'string':
            customToTex = expandTemplate(latexConverter[args.length], this, options)
            break
        }
    }

    if (typeof customToTex !== 'undefined') {
      return customToTex
    }

    return expandTemplate(latex.defaultTemplate, this, options)
  }

  /**
   * Get identifier.
   * @return {string}
   */
  FunctionNode.prototype.getIdentifier = function () {
    return this.type + ':' + this.name
  }

  return FunctionNode
}

exports.name = 'FunctionNode'
exports.path = 'expression.node'
exports.math = true // request access to the math namespace as 5th argument of the factory function
exports.factory = factory