FunctionNode.js

import { isAccessorNode, isFunctionAssignmentNode, isIndexNode, isNode, isSymbolNode } from '../../utils/is.js'
import { escape, format } from '../../utils/string.js'
import { hasOwnProperty } from '../../utils/object.js'
import { getSafeProperty, getSafeMethod } from '../../utils/customs.js'
import { createSubScope } from '../../utils/scope.js'
import { factory } from '../../utils/factory.js'
import { defaultTemplate, latexFunctions } from '../../utils/latex.js'

const name = 'FunctionNode'
const dependencies = [
  'math',
  'Node',
  'SymbolNode'
]

export const createFunctionNode = /* #__PURE__ */ factory(name, dependencies, ({ math, Node, SymbolNode }) => {
  /* format to fixed length */
  const strin = entity => format(entity, { truncate: 78 })

  /*
   * 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 = /\$(?:\{([a-z_][a-z_0-9]*)(?:\[([0-9]+)\])?\}|\$)/gi

    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 (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 (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 (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
  }

  class FunctionNode extends Node {
    /**
     * @constructor FunctionNode
     * @extends {./Node}
     * invoke a list with arguments on a node
     * @param {./Node | string} fn
     *     Item resolving to a function on which to invoke
     *     the arguments, typically a SymbolNode or AccessorNode
     * @param {./Node[]} args
     */
    constructor (fn, args) {
      super()
      if (typeof fn === 'string') {
        fn = new SymbolNode(fn)
      }

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

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

    // readonly property name
    get name () {
      return this.fn.name || ''
    }

    static name = name
    get type () { return name }
    get isFunctionNode () { return 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: *)
     */
    _compile (math, argNames) {
      // compile arguments
      const evalArgs = this.args.map((arg) => arg._compile(math, argNames))

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

          const resolveFn = (scope) => {
            let value
            if (scope.has(name)) {
              value = scope.get(name)
            } else if (name in math) {
              value = getSafeProperty(math, name)
            } else {
              return FunctionNode.onUndefinedFunction(name)
            }
            if (typeof value === 'function') {
              return value
            }
            throw new TypeError(
              `'${name}' is not a function; its value is:\n  ${strin(value)}`
            )
          }

          if (isRaw) {
            // pass unevaluated parameters (nodes) to the function
            // "raw" evaluation
            const rawArgs = this.args
            return function evalFunctionNode (scope, args, context) {
              const fn = resolveFn(scope)

              // the original function can be overwritten in the scope with a non-rawArgs function
              if (fn.rawArgs === true) {
                return fn(rawArgs, math, createSubScope(scope, args))
              } else {
                // "regular" evaluation
                const values = evalArgs.map((evalArg) => evalArg(scope, args, context))
                return fn(...values)
              }
            }
          } else {
            // "regular" evaluation
            switch (evalArgs.length) {
              case 0: return function evalFunctionNode (scope, args, context) {
                const fn = resolveFn(scope)
                return fn()
              }
              case 1: return function evalFunctionNode (scope, args, context) {
                const fn = resolveFn(scope)
                const evalArg0 = evalArgs[0]
                return fn(
                  evalArg0(scope, args, context)
                )
              }
              case 2: return function evalFunctionNode (scope, args, context) {
                const fn = resolveFn(scope)
                const evalArg0 = evalArgs[0]
                const evalArg1 = evalArgs[1]
                return fn(
                  evalArg0(scope, args, context),
                  evalArg1(scope, args, context)
                )
              }
              default: return function evalFunctionNode (scope, args, context) {
                const fn = resolveFn(scope)
                const values = evalArgs.map((evalArg) => evalArg(scope, args, context))
                return fn(...values)
              }
            }
          }
        } else { // the function symbol is an argName
          const rawArgs = this.args
          return function evalFunctionNode (scope, args, context) {
            const fn = getSafeProperty(args, name)
            if (typeof fn !== 'function') {
              throw new TypeError(
                `Argument '${name}' was not a function; received: ${strin(fn)}`
              )
            }
            if (fn.rawArgs) {
              // "Raw" evaluation
              return fn(rawArgs, math, createSubScope(scope, args))
            } else {
              const values = evalArgs.map(
                (evalArg) => evalArg(scope, args, context))
              return fn.apply(fn, values)
            }
          }
        }
      } else if (
        isAccessorNode(this.fn) &&
          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)
          const fn = getSafeMethod(object, prop)

          if (fn?.rawArgs) {
            // "Raw" evaluation
            return fn(rawArgs, math, createSubScope(scope, args))
          } else {
            // "regular" evaluation
            const values = evalArgs.map((evalArg) => evalArg(scope, args, context))
            return fn.apply(object, values)
          }
        }
      } else {
        // node.fn.isAccessorNode && !node.fn.index.isObjectProperty()
        // we have to dynamically determine whether the function has the
        // rawArgs property
        const fnExpr = this.fn.toString()
        const evalFn = this.fn._compile(math, argNames)
        const rawArgs = this.args

        return function evalFunctionNode (scope, args, context) {
          const fn = evalFn(scope, args, context)
          if (typeof fn !== 'function') {
            throw new TypeError(
              `Expression '${fnExpr}' did not evaluate to a function; value is:` +
                `\n  ${strin(fn)}`
            )
          }
          if (fn.rawArgs) {
            // "Raw" evaluation
            return fn(rawArgs, math, createSubScope(scope, args))
          } else {
            // "regular" evaluation
            const values = evalArgs.map(
              (evalArg) => evalArg(scope, args, context))
            return fn.apply(fn, values)
          }
        }
      }
    }

    /**
     * Execute a callback for each of the child nodes of this node
     * @param {function(child: Node, path: string, parent: Node)} callback
     */
    forEach (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 whose children are the results of calling
     * the provided callback function for each child of the original node.
     * @param {function(child: Node, path: string, parent: Node): Node} callback
     * @returns {FunctionNode} Returns a transformed copy of the node
     */
    map (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}
     */
    clone () {
      return new FunctionNode(this.fn, this.args.slice(0))
    }

    /**
     * Throws an error 'Undefined function {name}'
     * @param {string} name
     */
    static onUndefinedFunction = function (name) {
      throw new Error('Undefined function ' + name)
    }

    /**
     * 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
     */
    toString (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 super.toString(options)
    }

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

      const fn = 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}
     */
    toJSON () {
      return {
        mathjs: name,
        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}
     */
    static fromJSON = function (json) {
      return new FunctionNode(json.fn, json.args)
    }

    /**
     * Get HTML representation
     * @param {Object} options
     * @return {string} str
     */
    _toHTML (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>'
    }

    /**
     * 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}
     */
    toTex (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 super.toTex(options)
    }

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

      let latexConverter

      if (latexFunctions[this.name]) {
        latexConverter = latexFunctions[this.name]
      }

      // toTex property on the function itself
      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(defaultTemplate, this, options)
    }

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

  return FunctionNode
}, { isClass: true, isNode: true })