'use strict'

const object = require('../utils/object')
const string = require('../utils/string')

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

  /**
   * Documentation object
   * @param {Object} doc  Object containing properties:
   *                      {string} name
   *                      {string} category
   *                      {string} description
   *                      {string[]} syntax
   *                      {string[]} examples
   *                      {string[]} seealso
   * @constructor
   */
  function Help (doc) {
    if (!(this instanceof Help)) {
      throw new SyntaxError('Constructor must be called with the new operator')
    }

    if (!doc) throw new Error('Argument "doc" missing')

    this.doc = doc
  }

  /**
   * Attach type information
   */
  Help.prototype.type = 'Help'
  Help.prototype.isHelp = true

  /**
   * Generate a string representation of the Help object
   * @return {string} Returns a string
   * @private
   */
  Help.prototype.toString = function () {
    const doc = this.doc || {}
    let desc = '\n'

    if (doc.name) {
      desc += 'Name: ' + doc.name + '\n\n'
    }
    if (doc.category) {
      desc += 'Category: ' + doc.category + '\n\n'
    }
    if (doc.description) {
      desc += 'Description:\n    ' + doc.description + '\n\n'
    }
    if (doc.syntax) {
      desc += 'Syntax:\n    ' + doc.syntax.join('\n    ') + '\n\n'
    }
    if (doc.examples) {
      desc += 'Examples:\n'
      for (let i = 0; i < doc.examples.length; i++) {
        const expr = doc.examples[i]
        desc += '    ' + expr + '\n'

        let res
        try {
          // note: res can be undefined when `expr` is an empty string
          res = parser.eval(expr)
        } catch (e) {
          res = e
        }
        if (res !== undefined && !type.isHelp(res)) {
          desc += '        ' + string.format(res, { precision: 14 }) + '\n'
        }
      }
      desc += '\n'
    }
    if (doc.seealso && doc.seealso.length) {
      desc += 'See also: ' + doc.seealso.join(', ') + '\n'
    }

    return desc
  }

  /**
   * Export the help object to JSON
   */
  Help.prototype.toJSON = function () {
    const obj = object.clone(this.doc)
    obj.mathjs = 'Help'
    return obj
  }

  /**
   * Instantiate a Help object from a JSON object
   * @param {Object} json
   * @returns {Help} Returns a new Help object
   */
  Help.fromJSON = function (json) {
    const doc = {}
    for (const prop in json) {
      if (prop !== 'mathjs') { // ignore mathjs field
        doc[prop] = json[prop]
      }
    }
    return new Help(doc)
  }

  /**
   * Returns a string representation of the Help object
   */
  Help.prototype.valueOf = Help.prototype.toString

  return Help
}

exports.name = 'Help'
exports.path = 'type'
exports.factory = factory