'use strict';

var _require = require('chokidar');

const FSWatcher = _require.FSWatcher;

const Path = require('path');

/**
 * This watcher wraps chokidar so that we watch directories rather than individual files.
 * This prevents us from hitting EMFILE errors when running out of file descriptors.
 */
class Watcher {
  constructor() {
    // FS events on macOS are flakey in the tests, which write lots of files very quickly
    // See https://github.com/paulmillr/chokidar/issues/612
    this.shouldWatchDirs = process.env.NODE_ENV !== 'test';
    this.watcher = new FSWatcher({
      useFsEvents: this.shouldWatchDirs,
      ignoreInitial: true,
      ignored: /\.cache|\.git/
    });

    this.watchedDirectories = new Map();

    // Only close the watcher after the ready event is emitted
    this.ready = false;
    this.stopped = false;
    this.watcher.once('ready', () => {
      this.ready = true;
      if (this.stopped) {
        this.watcher.close();
      }
    });
  }

  /**
   * Find a parent directory of `path` which is already watched
   */
  getWatchedParent(path) {
    path = Path.dirname(path);

    let root = Path.parse(path).root;
    while (path !== root) {
      if (this.watchedDirectories.has(path)) {
        return path;
      }

      path = Path.dirname(path);
    }

    return null;
  }

  /**
   * Find a list of child directories of `path` which are already watched
   */
  getWatchedChildren(path) {
    path = Path.dirname(path) + Path.sep;

    let res = [];
    var _iteratorNormalCompletion = true;
    var _didIteratorError = false;
    var _iteratorError = undefined;

    try {
      for (var _iterator = this.watchedDirectories.keys()[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
        let dir = _step.value;

        if (dir.startsWith(path)) {
          res.push(dir);
        }
      }
    } catch (err) {
      _didIteratorError = true;
      _iteratorError = err;
    } finally {
      try {
        if (!_iteratorNormalCompletion && _iterator.return) {
          _iterator.return();
        }
      } finally {
        if (_didIteratorError) {
          throw _iteratorError;
        }
      }
    }

    return res;
  }

  /**
   * Add a path to the watcher
   */
  watch(path) {
    if (this.shouldWatchDirs) {
      // If there is no parent directory already watching this path, add a new watcher.
      let parent = this.getWatchedParent(path);
      if (!parent) {
        // Find watchers on child directories, and remove them. They will be handled by the new parent watcher.
        let children = this.getWatchedChildren(path);
        let count = 1;

        var _iteratorNormalCompletion2 = true;
        var _didIteratorError2 = false;
        var _iteratorError2 = undefined;

        try {
          for (var _iterator2 = children[Symbol.iterator](), _step2; !(_iteratorNormalCompletion2 = (_step2 = _iterator2.next()).done); _iteratorNormalCompletion2 = true) {
            let dir = _step2.value;

            count += this.watchedDirectories.get(dir);
            this.watcher._closePath(dir);
            this.watchedDirectories.delete(dir);
          }
        } catch (err) {
          _didIteratorError2 = true;
          _iteratorError2 = err;
        } finally {
          try {
            if (!_iteratorNormalCompletion2 && _iterator2.return) {
              _iterator2.return();
            }
          } finally {
            if (_didIteratorError2) {
              throw _iteratorError2;
            }
          }
        }

        let dir = Path.dirname(path);
        this.watcher.add(dir);
        this.watchedDirectories.set(dir, count);
      } else {
        // Otherwise, increment the reference count of the parent watcher.
        this.watchedDirectories.set(parent, this.watchedDirectories.get(parent) + 1);
      }
    } else {
      this.watcher.add(path);
    }
  }

  /**
   * Remove a path from the watcher
   */
  unwatch(path) {
    if (this.shouldWatchDirs) {
      let dir = this.getWatchedParent(path);
      if (dir) {
        // When the count of files watching a directory reaches zero, unwatch it.
        let count = this.watchedDirectories.get(dir) - 1;
        if (count === 0) {
          this.watchedDirectories.delete(dir);
          this.watcher.unwatch(dir);
        } else {
          this.watchedDirectories.set(dir, count);
        }
      }
    } else {
      this.watcher.unwatch(path);
    }
  }

  /**
   * Add an event handler
   */
  on(event, callback) {
    this.watcher.on(event, callback);
  }

  /**
   * Stop watching all paths
   */
  stop() {
    this.stopped = true;
    if (this.ready) {
      this.watcher.close();
    }
  }
}

module.exports = Watcher;