'use strict'

const keywords = require('../keywords')
const deepEqual = require('../../utils/object').deepEqual
const hasOwnProperty = require('../../utils/object').hasOwnProperty

function factory (type, config, load, typed, math) {
  /**
   * Node
   */
  function Node () {
    if (!(this instanceof Node)) {
      throw new SyntaxError('Constructor must be called with the new operator')
    }
  }

  /**
   * Evaluate the node
   * @param {Object} [scope]  Scope to read/write variables
   * @return {*}              Returns the result
   */
  Node.prototype.eval = function (scope) {
    return this.compile().eval(scope)
  }

  Node.prototype.type = 'Node'

  Node.prototype.isNode = true

  Node.prototype.comment = ''

  /**
   * Compile the node into an optimized, evauatable JavaScript function
   * @return {{eval: function([Object])}} expr  Returns an object with a function 'eval',
   *                                  which can be invoked as expr.eval([scope: Object]),
   *                                  where scope is an optional object with
   *                                  variables.
   */
  Node.prototype.compile = function () {
    const expr = this._compile(math.expression.mathWithTransform, {})
    const args = {}
    const context = null
    return {
      eval: function evalNode (scope) {
        const s = scope || {}
        _validateScope(s)
        return expr(s, args, context)
      }
    }
  }

  /**
   * 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: *)
   */
  Node.prototype._compile = function (math, argNames) {
    throw new Error('Method _compile should be implemented by type ' + this.type)
  }

  /**
   * Execute a callback for each of the child nodes of this node
   * @param {function(child: Node, path: string, parent: Node)} callback
   */
  Node.prototype.forEach = function (callback) {
    // must be implemented by each of the Node implementations
    throw new Error('Cannot run forEach on a Node interface')
  }

  /**
   * Create a new Node 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 {OperatorNode} Returns a transformed copy of the node
   */
  Node.prototype.map = function (callback) {
    // must be implemented by each of the Node implementations
    throw new Error('Cannot run map on a Node interface')
  }

  /**
   * Validate whether an object is a Node, for use with map
   * @param {Node} node
   * @returns {Node} Returns the input if it's a node, else throws an Error
   * @protected
   */
  Node.prototype._ifNode = function (node) {
    if (!type.isNode(node)) {
      throw new TypeError('Callback function must return a Node')
    }

    return node
  }

  /**
   * Recursively traverse all nodes in a node tree. Executes given callback for
   * this node and each of its child nodes.
   * @param {function(node: Node, path: string, parent: Node)} callback
   *          A callback called for every node in the node tree.
   */
  Node.prototype.traverse = function (callback) {
    // execute callback for itself
    callback(this, null, null) // eslint-disable-line standard/no-callback-literal

    // recursively traverse over all childs of a node
    function _traverse (node, callback) {
      node.forEach(function (child, path, parent) {
        callback(child, path, parent)
        _traverse(child, callback)
      })
    }

    _traverse(this, callback)
  }

  /**
   * Recursively transform a node tree via a transform function.
   *
   * For example, to replace all nodes of type SymbolNode having name 'x' with a
   * ConstantNode with value 2:
   *
   *     const res = Node.transform(function (node, path, parent) {
   *       if (node && node.isSymbolNode) && (node.name === 'x')) {
   *         return new ConstantNode(2)
   *       }
   *       else {
   *         return node
   *       }
   *     })
   *
   * @param {function(node: Node, path: string, parent: Node) : Node} callback
   *          A mapping function accepting a node, and returning
   *          a replacement for the node or the original node.
   *          Signature: callback(node: Node, index: string, parent: Node) : Node
   * @return {Node} Returns the original node or its replacement
   */
  Node.prototype.transform = function (callback) {
    // traverse over all childs
    function _transform (node, callback) {
      return node.map(function (child, path, parent) {
        const replacement = callback(child, path, parent)
        return _transform(replacement, callback)
      })
    }

    const replacement = callback(this, null, null) // eslint-disable-line standard/no-callback-literal
    return _transform(replacement, callback)
  }

  /**
   * Find any node in the node tree matching given filter function. For example, to
   * find all nodes of type SymbolNode having name 'x':
   *
   *     const results = Node.filter(function (node) {
   *       return (node && node.isSymbolNode) && (node.name === 'x')
   *     })
   *
   * @param {function(node: Node, path: string, parent: Node) : Node} callback
   *            A test function returning true when a node matches, and false
   *            otherwise. Function signature:
   *            callback(node: Node, index: string, parent: Node) : boolean
   * @return {Node[]} nodes       An array with nodes matching given filter criteria
   */
  Node.prototype.filter = function (callback) {
    const nodes = []

    this.traverse(function (node, path, parent) {
      if (callback(node, path, parent)) {
        nodes.push(node)
      }
    })

    return nodes
  }

  // TODO: deprecated since version 1.1.0, remove this some day
  Node.prototype.find = function () {
    throw new Error('Function Node.find is deprecated. Use Node.filter instead.')
  }

  // TODO: deprecated since version 1.1.0, remove this some day
  Node.prototype.match = function () {
    throw new Error('Function Node.match is deprecated. See functions Node.filter, Node.transform, Node.traverse.')
  }

  /**
   * Create a shallow clone of this node
   * @return {Node}
   */
  Node.prototype.clone = function () {
    // must be implemented by each of the Node implementations
    throw new Error('Cannot clone a Node interface')
  }

  /**
   * Create a deep clone of this node
   * @return {Node}
   */
  Node.prototype.cloneDeep = function () {
    return this.map(function (node) {
      return node.cloneDeep()
    })
  }

  /**
   * Deep compare this node with another node.
   * @param {Node} other
   * @return {boolean} Returns true when both nodes are of the same type and
   *                   contain the same values (as do their childs)
   */
  Node.prototype.equals = function (other) {
    return other
      ? deepEqual(this, other)
      : false
  }

  /**
   * Get string representation. (wrapper function)
   *
   * This function can get an object of the following form:
   * {
   *    handler: //This can be a callback function of the form
   *             // "function callback(node, options)"or
   *             // a map that maps function names (used in FunctionNodes)
   *             // to callbacks
   *    parenthesis: "keep" //the parenthesis option (This is optional)
   * }
   *
   * @param {Object} [options]
   * @return {string}
   */
  Node.prototype.toString = function (options) {
    let customString
    if (options && typeof options === 'object') {
      switch (typeof options.handler) {
        case 'object':
        case 'undefined':
          break
        case 'function':
          customString = options.handler(this, options)
          break
        default:
          throw new TypeError('Object or function expected as callback')
      }
    }

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

    return this._toString(options)
  }

  /**
   * Get a JSON representation of the node
   * Both .toJSON() and the static .fromJSON(json) should be implemented by all
   * implementations of Node
   * @returns {Object}
   */
  Node.prototype.toJSON = function () {
    throw new Error('Cannot serialize object: toJSON not implemented by ' + this.type)
  }

  /**
   * Get HTML representation. (wrapper function)
   *
   * This function can get an object of the following form:
   * {
   *    handler: //This can be a callback function of the form
   *             // "function callback(node, options)" or
   *             // a map that maps function names (used in FunctionNodes)
   *             // to callbacks
   *    parenthesis: "keep" //the parenthesis option (This is optional)
   * }
   *
   * @param {Object} [options]
   * @return {string}
   */
  Node.prototype.toHTML = function (options) {
    let customString
    if (options && typeof options === 'object') {
      switch (typeof options.handler) {
        case 'object':
        case 'undefined':
          break
        case 'function':
          customString = options.handler(this, options)
          break
        default:
          throw new TypeError('Object or function expected as callback')
      }
    }

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

    return this.toHTML(options)
  }

  /**
   * Internal function to generate the string output.
   * This has to be implemented by every Node
   *
   * @throws {Error}
   */
  Node.prototype._toString = function () {
    // must be implemented by each of the Node implementations
    throw new Error('_toString not implemented for ' + this.type)
  }

  /**
   * Get LaTeX representation. (wrapper function)
   *
   * This function can get an object of the following form:
   * {
   *    handler: //This can be a callback function of the form
   *             // "function callback(node, options)"or
   *             // a map that maps function names (used in FunctionNodes)
   *             // to callbacks
   *    parenthesis: "keep" //the parenthesis option (This is optional)
   * }
   *
   * @param {Object} [options]
   * @return {string}
   */
  Node.prototype.toTex = function (options) {
    let customTex
    if (options && typeof options === 'object') {
      switch (typeof options.handler) {
        case 'object':
        case 'undefined':
          break
        case 'function':
          customTex = options.handler(this, options)
          break
        default:
          throw new TypeError('Object or function expected as callback')
      }
    }

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

    return this._toTex(options)
  }

  /**
   * Internal function to generate the LaTeX output.
   * This has to be implemented by every Node
   *
   * @param {Object} [options]
   * @throws {Error}
   */
  Node.prototype._toTex = function (options) {
    // must be implemented by each of the Node implementations
    throw new Error('_toTex not implemented for ' + this.type)
  }

  /**
   * Get identifier.
   * @return {string}
   */
  Node.prototype.getIdentifier = function () {
    return this.type
  }

  /**
   * Get the content of the current Node.
   * @return {Node} node
   **/
  Node.prototype.getContent = function () {
    return this
  }

  /**
   * Validate the symbol names of a scope.
   * Throws an error when the scope contains an illegal symbol.
   * @param {Object} scope
   */
  function _validateScope (scope) {
    for (const symbol in scope) {
      if (hasOwnProperty(scope, symbol)) {
        if (symbol in keywords) {
          throw new Error('Scope contains an illegal symbol, "' + symbol + '" is a reserved keyword')
        }
      }
    }
  }

  return Node
}

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