convo/lib/index.js

Easily create conversations (for more natural bots)

/**
 * Module Dependencies
 */

var strip_indent = require('strip-indent')
var assign = require('object-assign')
var is_regexp = require('is-regexp')
var find = require('array-find')
var parse = require('./parser')
var lexer = require('./lexer')
var clone = require('clone')

/**
 * Export `convo`
 *
 * @param {String} language
 * @return {Function}
 */

module.exports = function convo (language) {
  language = strip_indent(language)
  var tokens = lexer(language)
  var ast = parse(tokens)
  return Convo(ast)
}

/**
 * Initialize a `Convo`
 *
 * @param {Array} ast
 * @return {Function} Say
 */

function Convo (ast) {
  return function Say (context) {
    var response = null
    var choices = []

    switch (typeof context) {
      case 'string':
        var outgoing = goto_id(clone(ast), context)
        choices = outgoing ? outgoing.choices : null
        response = outgoing
        break
      case 'object':
        choices = clone(ast);
        response = null
        break
      default:
        choices = clone(ast)
        response = null
        break
    }

    var ids = {}

    function say (incoming) {
      var is_params = typeof incoming === 'object'
      if (!arguments.length || is_params) {
        return Question(response)(incoming)
      }

      // Find the choice that matches the incoming statement
      var choice = find(choices, function (choice) {
        return is_regexp(choice.incoming)
          ? choice.incoming.test(incoming)
          : choice.incoming === incoming
      })

      // ignore the choice if it doesn't match
      if (!choice) return Noop()

      // cache ref for later
      if (choice.outgoing.id) {
        ids[choice.outgoing.id] = choice
      }

      // Update the set of choices
      if (choice.outgoing.goto) {
        var next_choice = ids[choice.outgoing.goto]
          || (ids[choice.outgoing.goto] = find_id(ast, choice.outgoing.goto) || {})
        choices = next_choice.outgoing.choices
        response = next_choice.outgoing
      } else if (choice.outgoing.reset) {
        choices = clone(ast)
        response = null
      } else {
        choices = choice.outgoing.choices || []
        response = choice.outgoing || null
      }

      // Create a response function
      if (choice.outgoing.response) {
        return Template(choice, incoming)
      } else if (choice.outgoing.goto) {
        return Template(ids[choice.outgoing.goto], incoming)
      } else {
        return Noop()
      }
    }

    say.toJSON = function () {
      return clone(choices)
    }

    say.toString = function () {
      return response ? response.id : null
    }

    return say
  }
}

/**
 * Create a template
 *
 * @param {Object} choice
 * @param {String} incoming
 * @return {Function}
 */

function Template (choice, incoming) {
  var response = choice.outgoing.response
  var alias = choice.alias || choice.outgoing.response
  var params = {}

  if (is_regexp(choice.incoming)) {
    var m = incoming.match(choice.incoming)
    for (var i = 0, len = m.length; i < len; i++) {
      params[i] = m[i]
    }
  }

  function template (obj) {
    obj = assign(params, obj || {})
    return new Function('_', 'return `' + response + '`')(obj || {})
  }

  // return the alias
  template.toString = function () {
    return alias
  }

  // attach the params in case we need them
  template.params = params

  return template
}

/**
 * Create a Question
 *
 * @param {Object} outgoing
 * @return {Function}
 */

function Question (outgoing) {
  function template (obj) {
    return new Function('_', 'return `' + outgoing.response + '`')(obj || {})
  }

  // return the id
  template.toString = function () {
    return outgoing.id
  }

  return template
}

/**
 * Noop
 */

function Noop () {
  function noop () {}

  noop.toString = function () {
    return null
  }

  return noop
}

/**
 * Find an ID in the AST
 *
 * @param {Array} choices
 * @param {String} id
 * @return {Object}
 */

function find_id (choices, id) {
  for (var i = 0, choice; choice = choices[i]; i++) {
    if (choice.outgoing.id && choice.outgoing.id === id) {
      return choice
    } else if (choice.outgoing.choices && choice.outgoing.choices.length) {
      var res = find_id(choice.outgoing.choices, id)
      if (res) return res
    }
  }
  return null
}

/**
 * Go to a particular ID
 *
 * @param {Array} choices
 * @param {String} id
 * @return {Array}
 */

function goto_id (choices, id) {
  var choice = find_id(choices, id)
  if (!choice || !choice.outgoing) return null
  return choice.outgoing
}