var chokidar = require('chokidar');
var mm = require('minimatch');
var expandBraces = require('expand-braces');

var helper = require('./helper');
var log = require('./logger').create('watcher');

var DIR_SEP = require('path').sep;

// Get parent folder, that be watched (does not contain any special globbing character)
var baseDirFromPattern = function(pattern) {
  return pattern.replace(/[\/\\][^\/\\]*\*.*$/, '')           // remove parts with *
                .replace(/[\/\\][^\/\\]*[\!\+]\(.*$/, '')     // remove parts with !(...) and +(...)
                .replace(/[\/\\][^\/\\]*\)\?.*$/, '') || DIR_SEP; // remove parts with (...)?
};

var watchPatterns = function(patterns, watcher) {
  // filter only unique non url patterns paths
  var pathsToWatch = [];
  var uniqueMap = {};
  var path;

  // expand ['a/{b,c}'] to ['a/b', 'a/c']
  patterns = expandBraces(patterns);

  patterns.forEach(function(pattern) {
    path = baseDirFromPattern(pattern);
    if (!uniqueMap[path]) {
      uniqueMap[path] = true;
      pathsToWatch.push(path);
    }
  });

  // watch only common parents, no sub paths
  pathsToWatch.forEach(function(path) {
    if (!pathsToWatch.some(function(p) {
      return p !== path && path.substr(0, p.length + 1) === p + DIR_SEP;
    })) {
      watcher.add(path);
      log.debug('Watching "%s"', path);
    }
  });
};

// Function to test if a path should be ignored by chokidar.
var createIgnore = function(patterns, excludes) {
  return function(path, stat) {
    if (!stat || stat.isDirectory()) {
      return false;
    }

    // Check if the path matches any of the watched patterns.
    if (!patterns.some(function(pattern) {
      return mm(path, pattern, {dot: true});
    })) {
      return true;
    }

    // Check if the path matches any of the exclude patterns.
    if (excludes.some(function(pattern) {
      return mm(path, pattern, {dot: true});
    })) {
      return true;
    }

    return false;
  };
};

var onlyWatchedTrue = function(pattern) {
  return pattern.watched;
};

var getWatchedPatterns = function(patternObjects) {
  return patternObjects.filter(onlyWatchedTrue).map(function(patternObject) {
    return patternObject.pattern;
  });
};

exports.watch = function(patterns, excludes, fileList, usePolling, emitter) {
  var watchedPatterns = getWatchedPatterns(patterns);
  var options = {
    usePolling: usePolling,
    ignorePermissionErrors: true,
    ignoreInitial: true,
    ignored: createIgnore(watchedPatterns, excludes)
  };
  var chokidarWatcher = new chokidar.FSWatcher(options);

  watchPatterns(watchedPatterns, chokidarWatcher);

  var bind = function(fn) {
    return function(path) {
      return fn.call(fileList, helper.normalizeWinPath(path));
    };
  };

  // register events
  chokidarWatcher.on('add', bind(fileList.addFile))
                 .on('change', bind(fileList.changeFile))
                 .on('unlink', bind(fileList.removeFile))
                 // If we don't subscribe; unhandled errors from Chokidar will bring Karma down
                 // (see GH Issue #959)
                 .on('error', function(e) {
                    log.debug(e);
                  });

  emitter.on('exit', function(done) {
    chokidarWatcher.close();
    done();
  });

  return chokidarWatcher;
};

exports.watch.$inject = ['config.files', 'config.exclude', 'fileList', 'config.usePolling',
  'emitter'];
