'use strict';
const fs = require('fs');
const path = require('path');
const os = require('os');
const EventEmitter = require('events');
const assert = require('assert');
const _ = require('lodash');
const findUp = require('find-up');
const readPkgUp = require('read-pkg-up');
const chalk = require('chalk');
const makeDir = require('make-dir');
const minimist = require('minimist');
const runAsync = require('run-async');
const through = require('through2');
const FileEditor = require('mem-fs-editor');
const debug = require('debug')('yeoman:generator');
const Conflicter = require('./util/conflicter');
const Storage = require('./util/storage');
const promptSuggestion = require('./util/prompt-suggestion');

const EMPTY = '@@_YEOMAN_EMPTY_MARKER_@@';

/**
 * The `Generator` class provides the common API shared by all generators.
 * It define options, arguments, file, prompt, log, API, etc.
 *
 * It mixes into its prototype all the methods found in the `actions/` mixins.
 *
 * Every generator should extend this base class.
 *
 * @constructor
 * @mixes actions/help
 * @mixes actions/install
 * @mixes actions/spawn-command
 * @mixes actions/user
 * @mixes nodejs/EventEmitter
 *
 * @param {String|Array} args
 * @param {Object} options
 *
 * @property {Object}   env         - the current Environment being run
 * @property {Object}   args        - Provide arguments at initialization
 * @property {String}   resolved    - the path to the current generator
 * @property {String}   description - Used in `--help` output
 * @property {String}   appname     - The application name
 * @property {Storage}  config      - `.yo-rc` config file manager
 * @property {Object}   fs          - An instance of {@link https://github.com/SBoudrias/mem-fs-editor Mem-fs-editor}
 * @property {Function} log         - Output content through Interface Adapter
 *
 * @example
 * const Generator = require('yeoman-generator');
 * module.exports = class extends Generator {
 *   writing() {
 *     this.fs.write(this.destinationPath('index.js'), 'const foo = 1;');
 *   }
 * };
 */
class Generator extends EventEmitter {
  constructor(args, options) {
    super();

    if (!Array.isArray(args)) {
      options = args;
      args = [];
    }

    this.options = options || {};
    this._initOptions = _.clone(options);
    this._args = args || [];
    this._options = {};
    this._arguments = [];
    this._composedWith = [];
    this._transformStreams = [];

    this.option('help', {
      type: Boolean,
      alias: 'h',
      description: 'Print the generator\'s options and usage'
    });

    this.option('skip-cache', {
      type: Boolean,
      description: 'Do not remember prompt answers',
      default: false
    });

    this.option('skip-install', {
      type: Boolean,
      description: 'Do not automatically install dependencies',
      default: false
    });

    // Checks required parameters
    assert(this.options.env, 'You must provide the environment object. Use env#create() to create a new generator.');
    assert(this.options.resolved, 'You must provide the resolved path value. Use env#create() to create a new generator.');
    this.env = this.options.env;
    this.resolved = this.options.resolved;

    // Ensure the environment support features this yeoman-generator version require.
    require('yeoman-environment').enforceUpdate(this.env);

    this.description = this.description || '';

    this.async = () => () => {};

    this.fs = FileEditor.create(this.env.sharedFs);
    this.conflicter = new Conflicter(this.env.adapter, this.options.force);

    // Mirror the adapter log method on the generator.
    //
    // example:
    // this.log('foo');
    // this.log.error('bar');
    this.log = this.env.adapter.log;

    // Determine the app root
    this.contextRoot = this.env.cwd;

    let rootPath = findUp.sync('.yo-rc.json', {
      cwd: this.env.cwd
    });
    rootPath = rootPath ? path.dirname(rootPath) : this.env.cwd;

    if (rootPath !== this.env.cwd) {
      this.log([
        '',
        'Just found a `.yo-rc.json` in a parent directory.',
        'Setting the project root at: ' + rootPath
      ].join('\n'));
      this.destinationRoot(rootPath);
    }

    this.appname = this.determineAppname();
    this.config = this._getStorage();
    this._globalConfig = this._getGlobalStorage();

    // Ensure source/destination path, can be configured from subclasses
    this.sourceRoot(path.join(path.dirname(this.resolved), 'templates'));
  }

  /*
   * Prompt user to answer questions. The signature of this method is the same as {@link https://github.com/SBoudrias/Inquirer.js Inquirer.js}
   *
   * On top of the Inquirer.js API, you can provide a `{cache: true}` property for
   * every question descriptor. When set to true, Yeoman will store/fetch the
   * user's answers as defaults.
   *
   * @param  {array} questions  Array of question descriptor objects. See {@link https://github.com/SBoudrias/Inquirer.js/blob/master/README.md Documentation}
   * @return {Promise}
   */
  prompt(questions) {
    questions = promptSuggestion.prefillQuestions(this._globalConfig, questions);
    questions = promptSuggestion.prefillQuestions(this.config, questions);

    return this.env.adapter.prompt(questions).then(answers => {
      if (!this.options['skip-cache']) {
        promptSuggestion.storeAnswers(this._globalConfig, questions, answers, false);
        promptSuggestion.storeAnswers(this.config, questions, answers, true);
      }

      return answers;
    });
  }

  /**
   * Adds an option to the set of generator expected options, only used to
   * generate generator usage. By default, generators get all the cli options
   * parsed by nopt as a `this.options` hash object.
   *
   * ### Options:
   *
   *   - `description` Description for the option
   *   - `type` Either Boolean, String or Number
   *   - `alias` Option name alias (example `-h` and --help`)
   *   - `default` Default value
   *   - `hide` Boolean whether to hide from help
   *
   * @param {String} name
   * @param {Object} config
   */
  option(name, config) {
    config = config || {};

    // Alias default to defaults for backward compatibility.
    if ('defaults' in config) {
      config.default = config.defaults;
    }
    config.description = config.description || config.desc;

    _.defaults(config, {
      name,
      description: 'Description for ' + name,
      type: Boolean,
      hide: false
    });

    // Check whether boolean option is invalid (starts with no-)
    const boolOptionRegex = /^no-/;
    if (config.type === Boolean && name.match(boolOptionRegex)) {
      const simpleName = name.replace(boolOptionRegex, '');
      return this.emit('error', new Error([
        `Option name ${chalk.yellow(name)} cannot start with ${chalk.red('no-')}\n`,
        `Option name prefixed by ${chalk.yellow('--no')} are parsed as implicit`,
        ` boolean. To use ${chalk.yellow('--' + name)} as an option, use\n`,
        chalk.cyan(`  this.option('${simpleName}', {type: Boolean})`)
      ].join('')));
    }

    if (this._options[name] === null || this._options[name] === undefined) {
      this._options[name] = config;
    }

    this.parseOptions();
    return this;
  }

  /**
   * Adds an argument to the class and creates an attribute getter for it.
   *
   * Arguments are different from options in several aspects. The first one
   * is how they are parsed from the command line, arguments are retrieved
   * based on their position.
   *
   * Besides, arguments are used inside your code as a property (`this.argument`),
   * while options are all kept in a hash (`this.options`).
   *
   * ### Options:
   *
   *   - `description` Description for the argument
   *   - `required` Boolean whether it is required
   *   - `optional` Boolean whether it is optional
   *   - `type` String, Number, Array, or Object
   *   - `default` Default value for this argument
   *
   * @param {String} name
   * @param {Object} config
   */
  argument(name, config) {
    config = config || {};

    // Alias default to defaults for backward compatibility.
    if ('defaults' in config) {
      config.default = config.defaults;
    }
    config.description = config.description || config.desc;

    _.defaults(config, {
      name,
      required: config.default === null || config.default === undefined,
      type: String
    });

    this._arguments.push(config);

    this.parseOptions();
    return this;
  }

  parseOptions() {
    const minimistDef = {
      string: [],
      boolean: [],
      alias: {},
      default: {}
    };

    _.each(this._options, option => {
      if (option.type === Boolean) {
        minimistDef.boolean.push(option.name);
        if (!('default' in option) && !option.required) {
          minimistDef.default[option.name] = EMPTY;
        }
      } else {
        minimistDef.string.push(option.name);
      }

      if (option.alias) {
        minimistDef.alias[option.alias] = option.name;
      }

      // Only apply default values if we don't already have a value injected from
      // the runner
      if (option.name in this._initOptions) {
        minimistDef.default[option.name] = this._initOptions[option.name];
      } else if (option.alias && option.alias in this._initOptions) {
        minimistDef.default[option.name] = this._initOptions[option.alias];
      } else if ('default' in option) {
        minimistDef.default[option.name] = option.default;
      }
    });

    const parsedOpts = minimist(this._args, minimistDef);

    // Parse options to the desired type
    _.each(parsedOpts, (option, name) => {
      // Manually set value as undefined if it should be.
      if (option === EMPTY) {
        parsedOpts[name] = undefined;
        return;
      }
      if (this._options[name] && option !== undefined) {
        parsedOpts[name] = this._options[name].type(option);
      }
    });

    // Parse positional arguments to valid options
    this._arguments.forEach((config, index) => {
      let value;
      if (index >= parsedOpts._.length) {
        if (config.name in this._initOptions) {
          value = this._initOptions[config.name];
        } else if ('default' in config) {
          value = config.default;
        } else {
          return;
        }
      } else if (config.type === Array) {
        value = parsedOpts._.slice(index, parsedOpts._.length);
      } else {
        value = config.type(parsedOpts._[index]);
      }

      parsedOpts[config.name] = value;
    });

    // Make the parsed options available to the instance
    Object.assign(this.options, parsedOpts);
    this.args = parsedOpts._;
    this.arguments = parsedOpts._;

    // Make sure required args are all present
    this.checkRequiredArgs();
  }

  checkRequiredArgs() {
    // If the help option was provided, we don't want to check for required
    // arguments, since we're only going to print the help message anyway.
    if (this.options.help) {
      return;
    }

    // Bail early if it's not possible to have a missing required arg
    if (this.args.length > this._arguments.length) {
      return;
    }

    this._arguments.forEach((config, position) => {
      // If the help option was not provided, check whether the argument was
      // required, and whether a value was provided.
      if (config.required && position >= this.args.length) {
        return this.emit('error', new Error(`Did not provide required argument ${chalk.bold(config.name)}!`));
      }
    });
  }

  /**
   * Runs the generator, scheduling prototype methods on a run queue. Method names
   * will determine the order each method is run. Methods without special names
   * will run in the default queue.
   *
   * Any method named `constructor` and any methods prefixed by a `_` won't be scheduled.
   *
   * You can also supply the arguments for the method to be invoked. If none are
   * provided, the same values used to initialize the invoker are used to
   * initialize the invoked.
   *
   * @param {Function} [cb]
   */
  run(cb) {
    cb = cb || (() => {});

    const self = this;
    this._running = true;
    this.emit('run');

    const methods = Object.getOwnPropertyNames(Object.getPrototypeOf(this));
    const validMethods = methods.filter(methodIsValid);
    assert(validMethods.length, 'This Generator is empty. Add at least one method for it to run.');

    this.env.runLoop.once('end', () => {
      this.emit('end');
      cb();
    });

    // Ensure a prototype method is a candidate run by default
    function methodIsValid(name) {
      return name.charAt(0) !== '_' && name !== 'constructor';
    }

    function addMethod(method, methodName, queueName) {
      queueName = queueName || 'default';
      debug(`Queueing ${methodName} in ${queueName}`);
      self.env.runLoop.add(queueName, completed => {
        debug(`Running ${methodName}`);
        self.emit(`method:${methodName}`);

        runAsync(function () {
          self.async = () => this.async();
          return method.apply(self, self.args);
        })().then(completed).catch(err => {
          debug(`An error occured while running ${methodName}`, err);

          // Ensure we emit the error event outside the promise context so it won't be
          // swallowed when there's no listeners.
          setImmediate(() => {
            self.emit('error', err);
            cb(err);
          });
        });
      });
    }

    function addInQueue(name) {
      const item = Object.getPrototypeOf(self)[name];
      const queueName = self.env.runLoop.queueNames.indexOf(name) === -1 ? null : name;

      // Name points to a function; run it!
      if (typeof item === 'function') {
        return addMethod(item, name, queueName);
      }

      // Not a queue hash; stop
      if (!queueName) {
        return;
      }

      // Run each queue items
      _.each(item, (method, methodName) => {
        if (!_.isFunction(method) || !methodIsValid(methodName)) {
          return;
        }

        addMethod(method, methodName, queueName);
      });
    }

    validMethods.forEach(addInQueue);

    const writeFiles = () => {
      this.env.runLoop.add('conflicts', this._writeFiles.bind(this), {
        once: 'write memory fs to disk'
      });
    };

    this.env.sharedFs.on('change', writeFiles);
    writeFiles();

    // Add the default conflicts handling
    this.env.runLoop.add('conflicts', done => {
      this.conflicter.resolve(err => {
        if (err) {
          this.emit('error', err);
        }

        done();
      });
    });

    _.invokeMap(this._composedWith, 'run');
    return this;
  }

  /**
   * Compose this generator with another one.
   * @param  {String} namespace  The generator namespace to compose with
   * @param  {Object} options    The options passed to the Generator
   * @param  {Object} [settings] Settings hash on the composition relation
   * @param  {string} [settings.local]        Path to a locally stored generator
   * @param  {String} [settings.link="weak"]  If "strong", the composition will occured
   *                                          even when the composition is initialized by
   *                                          the end user
   * @return {this}
   *
   * @example <caption>Using a peerDependency generator</caption>
   * this.composeWith('bootstrap', { sass: true });
   *
   * @example <caption>Using a direct dependency generator</caption>
   * this.composeWith(require.resolve('generator-bootstrap/app/main.js'), { sass: true });
   */
  composeWith(modulePath, options) {
    let generator;
    options = options || {};

    // Pass down the default options so they're correctly mirrored down the chain.
    options = _.extend({
      skipInstall: this.options.skipInstall,
      'skip-install': this.options.skipInstall,
      skipCache: this.options.skipCache,
      'skip-cache': this.options.skipCache
    }, options);

    try {
      const Generator = require(modulePath); // eslint-disable-line import/no-dynamic-require
      Generator.resolved = require.resolve(modulePath);
      Generator.namespace = this.env.namespace(modulePath);
      generator = this.env.instantiate(Generator, {
        options,
        arguments: options.arguments
      });
    } catch (err) {
      if (err.code === 'MODULE_NOT_FOUND') {
        generator = this.env.create(modulePath, {
          options,
          arguments: options.arguments
        });
      } else {
        throw err;
      }
    }

    if (this._running) {
      generator.run();
    } else {
      this._composedWith.push(generator);
    }

    return this;
  }

  /**
   * Determine the root generator name (the one who's extending Generator).
   * @return {String} The name of the root generator
   */
  rootGeneratorName() {
    const pkg = readPkgUp.sync({cwd: this.resolved}).pkg;
    return pkg ? pkg.name : '*';
  }

  /**
   * Determine the root generator version (the one who's extending Generator).
   * @return {String} The version of the root generator
   */
  rootGeneratorVersion() {
    const pkg = readPkgUp.sync({cwd: this.resolved}).pkg;
    return pkg ? pkg.version : '0.0.0';
  }

  /**
   * Return a storage instance.
   * @return {Storage} Generator storage
   * @private
   */
  _getStorage() {
    const storePath = path.join(this.destinationRoot(), '.yo-rc.json');
    return new Storage(this.rootGeneratorName(), this.fs, storePath);
  }

  /**
   * Setup a globalConfig storage instance.
   * @return {Storage} Global config storage
   * @private
   */
  _getGlobalStorage() {
    const storePath = path.join(os.homedir(), '.yo-rc-global.json');
    const storeName = `${this.rootGeneratorName()}:${this.rootGeneratorVersion()}`;
    return new Storage(storeName, this.fs, storePath);
  }

  /**
   * Change the generator destination root directory.
   * This path is used to find storage, when using a file system helper method (like
   * `this.write` and `this.copy`)
   * @param  {String} rootPath new destination root path
   * @return {String}          destination root path
   */
  destinationRoot(rootPath) {
    if (typeof rootPath === 'string') {
      this._destinationRoot = path.resolve(rootPath);

      if (!fs.existsSync(rootPath)) {
        makeDir.sync(rootPath);
      }

      process.chdir(rootPath);
      this.env.cwd = rootPath;

      // Reset the storage
      this.config = this._getStorage();
    }

    return this._destinationRoot || this.env.cwd;
  }

  /**
   * Change the generator source root directory.
   * This path is used by multiples file system methods like (`this.read` and `this.copy`)
   * @param  {String} rootPath new source root path
   * @return {String}          source root path
   */
  sourceRoot(rootPath) {
    if (typeof rootPath === 'string') {
      this._sourceRoot = path.resolve(rootPath);
    }

    return this._sourceRoot;
  }

  /**
   * Join a path to the source root.
   * @param  {...String} path
   * @return {String}    joined path
   */
  templatePath() {
    let filepath = path.join.apply(path, arguments);

    if (!path.isAbsolute(filepath)) {
      filepath = path.join(this.sourceRoot(), filepath);
    }

    return filepath;
  }

  /**
   * Join a path to the destination root.
   * @param  {...String} path
   * @return {String}    joined path
   */
  destinationPath() {
    let filepath = path.join.apply(path, arguments);

    if (!path.isAbsolute(filepath)) {
      filepath = path.join(this.destinationRoot(), filepath);
    }

    return filepath;
  }

  /**
   * Determines the name of the application.
   *
   * First checks for name in bower.json.
   * Then checks for name in package.json.
   * Finally defaults to the name of the current directory.
   * @return {String} The name of the application
   */
  determineAppname() {
    let appname = this.fs.readJSON(this.destinationPath('bower.json'), {}).name;

    if (!appname) {
      appname = this.fs.readJSON(this.destinationPath('package.json'), {}).name;
    }

    if (!appname) {
      appname = path.basename(this.destinationRoot());
    }

    return appname.replace(/[^\w\s]+?/g, ' ');
  }

  /**
   * Add a transform stream to the commit stream.
   *
   * Most usually, these transform stream will be Gulp plugins.
   *
   * @param  {stream.Transform|stream.Transform[]} stream An array of Transform stream
   * or a single one.
   * @return {this}
   */
  registerTransformStream(streams) {
    assert(streams, 'expected to receive a transform stream as parameter');
    if (!Array.isArray(streams)) {
      streams = [streams];
    }
    this._transformStreams = this._transformStreams.concat(streams);
    return this;
  }

  /**
   * Write memory fs file to disk and logging results
   * @param {Function} done - callback once files are written
   * @private
   */
  _writeFiles(done) {
    const self = this;

    const conflictChecker = through.obj(function (file, enc, cb) {
      const stream = this;

      // If the file has no state requiring action, move on
      if (file.state === null) {
        return cb();
      }

      // Config file should not be processed by the conflicter. Just pass through
      const filename = path.basename(file.path);

      if (filename === '.yo-rc.json' || filename === '.yo-rc-global.json') {
        this.push(file);
        return cb();
      }

      self.conflicter.checkForCollision(file.path, file.contents, (err, status) => {
        if (err) {
          cb(err);
          return;
        }

        if (status === 'skip') {
          delete file.state;
        } else {
          stream.push(file);
        }

        cb();
      });
      self.conflicter.resolve();
    });

    const transformStreams = this._transformStreams.concat([conflictChecker]);
    this.fs.commit(transformStreams, () => {
      done();
    });
  }
}

// Mixin the actions modules
_.extend(Generator.prototype, require('./actions/install'));
_.extend(Generator.prototype, require('./actions/help'));
_.extend(Generator.prototype, require('./actions/spawn-command'));
Generator.prototype.user = require('./actions/user');

module.exports = Generator;