mathjs/src/expression/node/IndexNode.js

'use strict'

const map = require('../../utils/array').map
const escape = require('../../utils/string').escape

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

  const isArray = Array.isArray

  /**
   * @constructor IndexNode
   * @extends Node
   *
   * Describes a subset of a matrix or an object property.
   * Cannot be used on its own, needs to be used within an AccessorNode or
   * AssignmentNode.
   *
   * @param {Node[]} dimensions
   * @param {boolean} [dotNotation=false]  Optional property describing whether
   *                                       this index was written using dot
   *                                       notation like `a.b`, or using bracket
   *                                       notation like `a["b"]` (default).
   *                                       Used to stringify an IndexNode.
   */
  function IndexNode (dimensions, dotNotation) {
    if (!(this instanceof IndexNode)) {
      throw new SyntaxError('Constructor must be called with the new operator')
    }

    this.dimensions = dimensions
    this.dotNotation = dotNotation || false

    // validate input
    if (!isArray(dimensions) || !dimensions.every(type.isNode)) {
      throw new TypeError('Array containing Nodes expected for parameter "dimensions"')
    }
    if (this.dotNotation && !this.isObjectProperty()) {
      throw new Error('dotNotation only applicable for object properties')
    }

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

  IndexNode.prototype = new Node()

  IndexNode.prototype.type = 'IndexNode'

  IndexNode.prototype.isIndexNode = 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: *)
   */
  IndexNode.prototype._compile = function (math, argNames) {
    // TODO: implement support for bignumber (currently bignumbers are silently
    //       reduced to numbers when changing the value to zero-based)

    // TODO: Optimization: when the range values are ConstantNodes,
    //       we can beforehand resolve the zero-based value

    // optimization for a simple object property
    const evalDimensions = map(this.dimensions, function (range, i) {
      if (type.isRangeNode(range)) {
        if (range.needsEnd()) {
          // create a range containing end (like '4:end')
          const childArgNames = Object.create(argNames)
          childArgNames['end'] = true

          const evalStart = range.start._compile(math, childArgNames)
          const evalEnd = range.end._compile(math, childArgNames)
          const evalStep = range.step
            ? range.step._compile(math, childArgNames)
            : function () { return 1 }

          return function evalDimension (scope, args, context) {
            const size = math.size(context).valueOf()
            const childArgs = Object.create(args)
            childArgs['end'] = size[i]

            return createRange(
              evalStart(scope, childArgs, context),
              evalEnd(scope, childArgs, context),
              evalStep(scope, childArgs, context)
            )
          }
        } else {
          // create range
          const evalStart = range.start._compile(math, argNames)
          const evalEnd = range.end._compile(math, argNames)
          const evalStep = range.step
            ? range.step._compile(math, argNames)
            : function () { return 1 }

          return function evalDimension (scope, args, context) {
            return createRange(
              evalStart(scope, args, context),
              evalEnd(scope, args, context),
              evalStep(scope, args, context)
            )
          }
        }
      } else if (type.isSymbolNode(range) && range.name === 'end') {
        // SymbolNode 'end'
        const childArgNames = Object.create(argNames)
        childArgNames['end'] = true

        const evalRange = range._compile(math, childArgNames)

        return function evalDimension (scope, args, context) {
          const size = math.size(context).valueOf()
          const childArgs = Object.create(args)
          childArgs['end'] = size[i]

          return evalRange(scope, childArgs, context)
        }
      } else {
        // ConstantNode
        const evalRange = range._compile(math, argNames)
        return function evalDimension (scope, args, context) {
          return evalRange(scope, args, context)
        }
      }
    })

    return function evalIndexNode (scope, args, context) {
      const dimensions = map(evalDimensions, function (evalDimension) {
        return evalDimension(scope, args, context)
      })
      return math.index.apply(math, dimensions)
    }
  }

  /**
   * Execute a callback for each of the child nodes of this node
   * @param {function(child: Node, path: string, parent: Node)} callback
   */
  IndexNode.prototype.forEach = function (callback) {
    for (let i = 0; i < this.dimensions.length; i++) {
      callback(this.dimensions[i], 'dimensions[' + i + ']', this)
    }
  }

  /**
   * Create a new IndexNode 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 {IndexNode} Returns a transformed copy of the node
   */
  IndexNode.prototype.map = function (callback) {
    const dimensions = []
    for (let i = 0; i < this.dimensions.length; i++) {
      dimensions[i] = this._ifNode(callback(this.dimensions[i], 'dimensions[' + i + ']', this))
    }

    return new IndexNode(dimensions)
  }

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

  /**
   * Test whether this IndexNode contains a single property name
   * @return {boolean}
   */
  IndexNode.prototype.isObjectProperty = function () {
    return this.dimensions.length === 1 &&
        type.isConstantNode(this.dimensions[0]) &&
        typeof this.dimensions[0].value === 'string'
  }

  /**
   * Returns the property name if IndexNode contains a property.
   * If not, returns null.
   * @return {string | null}
   */
  IndexNode.prototype.getObjectProperty = function () {
    return this.isObjectProperty() ? this.dimensions[0].value : null
  }

  /**
   * Get string representation
   * @param {Object} options
   * @return {string} str
   */
  IndexNode.prototype._toString = function (options) {
    // format the parameters like "[1, 0:5]"
    return this.dotNotation
      ? ('.' + this.getObjectProperty())
      : ('[' + this.dimensions.join(', ') + ']')
  }

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

  /**
   * Instantiate an IndexNode from its JSON representation
   * @param {Object} json  An object structured like
   *                       `{"mathjs": "IndexNode", dimensions: [...], dotNotation: false}`,
   *                       where mathjs is optional
   * @returns {IndexNode}
   */
  IndexNode.fromJSON = function (json) {
    return new IndexNode(json.dimensions, json.dotNotation)
  }

  /**
   * Get HTML representation
   * @param {Object} options
   * @return {string} str
   */
  IndexNode.prototype.toHTML = function (options) {
    // format the parameters like "[1, 0:5]"
    const dimensions = []
    for (let i = 0; i < this.dimensions.length; i++) {
      dimensions[i] = this.dimensions[i].toHTML()
    }
    if (this.dotNotation) {
      return '<span class="math-operator math-accessor-operator">.</span>' + '<span class="math-symbol math-property">' + escape(this.getObjectProperty()) + '</span>'
    } else {
      return '<span class="math-parenthesis math-square-parenthesis">[</span>' + dimensions.join('<span class="math-separator">,</span>') + '<span class="math-parenthesis math-square-parenthesis">]</span>'
    }
  }

  /**
   * Get LaTeX representation
   * @param {Object} options
   * @return {string} str
   */
  IndexNode.prototype._toTex = function (options) {
    const dimensions = this.dimensions.map(function (range) {
      return range.toTex(options)
    })

    return this.dotNotation
      ? ('.' + this.getObjectProperty() + '')
      : ('_{' + dimensions.join(',') + '}')
  }

  // helper function to create a Range from start, step and end
  function createRange (start, end, step) {
    return new Range(
      type.isBigNumber(start) ? start.toNumber() : start,
      type.isBigNumber(end) ? end.toNumber() : end,
      type.isBigNumber(step) ? step.toNumber() : step
    )
  }

  return IndexNode
}

exports.name = 'IndexNode'
exports.path = 'expression.node'
exports.factory = factory