'use strict';
var EventEmitter = require('events').EventEmitter;
var fs = require('fs');
var sysPath = require('path');
var asyncEach = require('async-each');
var anymatch = require('anymatch');
var globParent = require('glob-parent');
var isGlob = require('is-glob');
var isAbsolute = require('path-is-absolute');
var inherits = require('inherits');

var NodeFsHandler = require('./lib/nodefs-handler');
var FsEventsHandler = require('./lib/fsevents-handler');

var arrify = function (value) {
    if (value == null) return [];
    return Array.isArray(value) ? value : [value];
};

var flatten = function (list, result) {
    if (result == null) result = [];
    list.forEach(function (item) {
        if (Array.isArray(item)) {
            flatten(item, result);
        } else {
            result.push(item);
        }
    });
    return result;
};

// Little isString util for use in Array#every.
var isString = function (thing) {
    return typeof thing === 'string';
};

// Public: Main class.
// Watches files & directories for changes.
//
// * _opts - object, chokidar options hash
//
// Emitted events:
// `add`, `addDir`, `change`, `unlink`, `unlinkDir`, `all`, `error`
//
// Examples
//
//  var watcher = new FSWatcher()
//    .add(directories)
//    .on('add', path => console.log('File', path, 'was added'))
//    .on('change', path => console.log('File', path, 'was changed'))
//    .on('unlink', path => console.log('File', path, 'was removed'))
//    .on('all', (event, path) => console.log(path, ' emitted ', event))
//
function FSWatcher(_opts) {
    EventEmitter.call(this);
    var opts = {};
    // in case _opts that is passed in is a frozen object
    if (_opts) for (var opt in _opts) opts[opt] = _opts[opt];
    this._watched = Object.create(null);
    this._closers = Object.create(null);
    this._ignoredPaths = Object.create(null);
    Object.defineProperty(this, '_globIgnored', {
        get: function () {
            return Object.keys(this._ignoredPaths);
        }
    });
    this.closed = false;
    this._throttled = Object.create(null);
    this._symlinkPaths = Object.create(null);

    function undef(key) {
        return opts[key] === undefined;
    }

    // Set up default options.
    if (undef('persistent')) opts.persistent = true;
    if (undef('ignoreInitial')) opts.ignoreInitial = false;
    if (undef('ignorePermissionErrors')) opts.ignorePermissionErrors = false;
    if (undef('interval')) opts.interval = 100;
    if (undef('binaryInterval')) opts.binaryInterval = 300;
    this.enableBinaryInterval = opts.binaryInterval !== opts.interval;

    // Enable fsevents on OS X when polling isn't explicitly enabled.
    if (undef('useFsEvents')) opts.useFsEvents = !opts.usePolling;

    // If we can't use fsevents, ensure the options reflect it's disabled.
    if (!FsEventsHandler.canUse()) opts.useFsEvents = false;

    // Use polling on Mac if not using fsevents.
    // Other platforms use non-polling fs.watch.
    if (undef('usePolling') && !opts.useFsEvents) {
        opts.usePolling = process.platform === 'darwin';
    }

    // Global override (useful for end-developers that need to force polling for all
    // instances of chokidar, regardless of usage/dependency depth)
    var envPoll = process.env.CHOKIDAR_USEPOLLING;
    if (envPoll !== undefined) {
        var envLower = envPoll.toLowerCase();

        if (envLower === 'false' || envLower === '0') {
            opts.usePolling = false;
        } else if (envLower === 'true' || envLower === '1') {
            opts.usePolling = true;
        } else {
            opts.usePolling = !!envLower
        }
    }

    // Editor atomic write normalization enabled by default with fs.watch
    if (undef('atomic')) opts.atomic = !opts.usePolling && !opts.useFsEvents;
    if (opts.atomic) this._pendingUnlinks = Object.create(null);

    if (undef('followSymlinks')) opts.followSymlinks = true;

    if (undef('awaitWriteFinish')) opts.awaitWriteFinish = false;
    if (opts.awaitWriteFinish === true) opts.awaitWriteFinish = {};
    var awf = opts.awaitWriteFinish;
    if (awf) {
        if (!awf.stabilityThreshold) awf.stabilityThreshold = 2000;
        if (!awf.pollInterval) awf.pollInterval = 100;

        this._pendingWrites = Object.create(null);
    }
    if (opts.ignored) opts.ignored = arrify(opts.ignored);

    this._isntIgnored = function (path, stat) {
        return !this._isIgnored(path, stat);
    }.bind(this);

    var readyCalls = 0;
    this._emitReady = function () {
        if (++readyCalls >= this._readyCount) {
            this._emitReady = Function.prototype;
            this._readyEmitted = true;
            // use process.nextTick to allow time for listener to be bound
            process.nextTick(this.emit.bind(this, 'ready'));
        }
    }.bind(this);

    this.options = opts;

    // You’re frozen when your heart’s not open.
    Object.freeze(opts);
}

inherits(FSWatcher, EventEmitter);

// Common helpers
// --------------

// Private method: Normalize and emit events
//
// * event     - string, type of event
// * path      - string, file or directory path
// * val[1..3] - arguments to be passed with event
//
// Returns the error if defined, otherwise the value of the
// FSWatcher instance's `closed` flag
FSWatcher.prototype._emit = function (event, path, val1, val2, val3) {
    if (this.options.cwd) path = sysPath.relative(this.options.cwd, path);
    var args = [event, path];
    if (val3 !== undefined) args.push(val1, val2, val3);
    else if (val2 !== undefined) args.push(val1, val2);
    else if (val1 !== undefined) args.push(val1);

    var awf = this.options.awaitWriteFinish;
    if (awf && this._pendingWrites[path]) {
        this._pendingWrites[path].lastChange = new Date();
        return this;
    }

    if (this.options.atomic) {
        if (event === 'unlink') {
            this._pendingUnlinks[path] = args;
            setTimeout(function () {
                Object.keys(this._pendingUnlinks).forEach(function (path) {
                    this.emit.apply(this, this._pendingUnlinks[path]);
                    this.emit.apply(this, ['all'].concat(this._pendingUnlinks[path]));
                    delete this._pendingUnlinks[path];
                }.bind(this));
            }.bind(this), typeof this.options.atomic === "number"
                ? this.options.atomic
                : 100);
            return this;
        } else if (event === 'add' && this._pendingUnlinks[path]) {
            event = args[0] = 'change';
            delete this._pendingUnlinks[path];
        }
    }

    var emitEvent = function () {
        this.emit.apply(this, args);
        if (event !== 'error') this.emit.apply(this, ['all'].concat(args));
    }.bind(this);

    if (awf && (event === 'add' || event === 'change') && this._readyEmitted) {
        var awfEmit = function (err, stats) {
            if (err) {
                event = args[0] = 'error';
                args[1] = err;
                emitEvent();
            } else if (stats) {
                // if stats doesn't exist the file must have been deleted
                if (args.length > 2) {
                    args[2] = stats;
                } else {
                    args.push(stats);
                }
                emitEvent();
            }
        };

        this._awaitWriteFinish(path, awf.stabilityThreshold, event, awfEmit);
        return this;
    }

    if (event === 'change') {
        if (!this._throttle('change', path, 50)) return this;
    }

    if (
        this.options.alwaysStat && val1 === undefined &&
        (event === 'add' || event === 'addDir' || event === 'change')
    ) {
        var fullPath = this.options.cwd ? sysPath.join(this.options.cwd, path) : path;
        fs.stat(fullPath, function (error, stats) {
            // Suppress event when fs.stat fails, to avoid sending undefined 'stat'
            if (error || !stats) return;

            args.push(stats);
            emitEvent();
        });
    } else {
        emitEvent();
    }

    return this;
};

// Private method: Common handler for errors
//
// * error  - object, Error instance
//
// Returns the error if defined, otherwise the value of the
// FSWatcher instance's `closed` flag
FSWatcher.prototype._handleError = function (error) {
    var code = error && error.code;
    var ipe = this.options.ignorePermissionErrors;
    if (error &&
        code !== 'ENOENT' &&
        code !== 'ENOTDIR' &&
        (!ipe || (code !== 'EPERM' && code !== 'EACCES'))
    ) this.emit('error', error);
    return error || this.closed;
};

// Private method: Helper utility for throttling
//
// * action  - string, type of action being throttled
// * path    - string, path being acted upon
// * timeout - int, duration of time to suppress duplicate actions
//
// Returns throttle tracking object or false if action should be suppressed
FSWatcher.prototype._throttle = function (action, path, timeout) {
    if (!(action in this._throttled)) {
        this._throttled[action] = Object.create(null);
    }
    var throttled = this._throttled[action];
    if (path in throttled) return false;
    function clear() {
        delete throttled[path];
        clearTimeout(timeoutObject);
    }

    var timeoutObject = setTimeout(clear, timeout);
    throttled[path] = {timeoutObject: timeoutObject, clear: clear};
    return throttled[path];
};

// Private method: Awaits write operation to finish
//
// * path    - string, path being acted upon
// * threshold - int, time in milliseconds a file size must be fixed before
//                    acknowledgeing write operation is finished
// * awfEmit - function, to be called when ready for event to be emitted
// Polls a newly created file for size variations. When files size does not
// change for 'threshold' milliseconds calls callback.
FSWatcher.prototype._awaitWriteFinish = function (path, threshold, event, awfEmit) {
    var timeoutHandler;

    var fullPath = path;
    if (this.options.cwd && !isAbsolute(path)) {
        fullPath = sysPath.join(this.options.cwd, path);
    }

    var now = new Date();

    var awaitWriteFinish = (function (prevStat) {
        fs.stat(fullPath, function (err, curStat) {
            if (err) {
                if (err.code !== 'ENOENT') awfEmit(err);
                return;
            }

            var now = new Date();

            if (prevStat && curStat.size != prevStat.size) {
                this._pendingWrites[path].lastChange = now;
            }

            if (now - this._pendingWrites[path].lastChange >= threshold) {
                delete this._pendingWrites[path];
                awfEmit(null, curStat);
            } else {
                timeoutHandler = setTimeout(
                    awaitWriteFinish.bind(this, curStat),
                    this.options.awaitWriteFinish.pollInterval
                );
            }
        }.bind(this));
    }.bind(this));

    if (!(path in this._pendingWrites)) {
        this._pendingWrites[path] = {
            lastChange: now,
            cancelWait: function () {
                delete this._pendingWrites[path];
                clearTimeout(timeoutHandler);
                return event;
            }.bind(this)
        };
        timeoutHandler = setTimeout(
            awaitWriteFinish.bind(this),
            this.options.awaitWriteFinish.pollInterval
        );
    }
};

// Private method: Determines whether user has asked to ignore this path
//
// * path  - string, path to file or directory
// * stats - object, result of fs.stat
//
// Returns boolean
var dotRe = /\..*\.(sw[px])$|\~$|\.subl.*\.tmp/;
FSWatcher.prototype._isIgnored = function (path, stats) {
    if (this.options.atomic && dotRe.test(path)) return true;

    if (!this._userIgnored) {
        var cwd = this.options.cwd;
        var ignored = this.options.ignored;
        if (cwd && ignored) {
            ignored = ignored.map(function (path) {
                if (typeof path !== 'string') return path;
                return isAbsolute(path) ? path : sysPath.join(cwd, path);
            });
        }
        var paths = arrify(ignored)
            .filter(function (path) {
                return typeof path === 'string' && !isGlob(path);
            }).map(function (path) {
                return path + '/**';
            });
        this._userIgnored = anymatch(
            this._globIgnored.concat(ignored).concat(paths)
        );
    }

    return this._userIgnored([path, stats]);
};

// Private method: Provides a set of common helpers and properties relating to
// symlink and glob handling
//
// * path - string, file, directory, or glob pattern being watched
// * depth - int, at any depth > 0, this isn't a glob
//
// Returns object containing helpers for this path
var replacerRe = /^\.[\/\\]/;
FSWatcher.prototype._getWatchHelpers = function (path, depth) {
    path = path.replace(replacerRe, '');
    var watchPath = depth || !isGlob(path) ? path : globParent(path);
    var fullWatchPath = sysPath.resolve(watchPath);
    var hasGlob = watchPath !== path;
    var globFilter = hasGlob ? anymatch(path) : false;
    var follow = this.options.followSymlinks;
    var globSymlink = hasGlob && follow ? null : false;

    var checkGlobSymlink = function (entry) {
        // only need to resolve once
        // first entry should always have entry.parentDir === ''
        if (globSymlink == null) {
            globSymlink = entry.fullParentDir === fullWatchPath ? false : {
                realPath: entry.fullParentDir,
                linkPath: fullWatchPath
            };
        }

        if (globSymlink) {
            return entry.fullPath.replace(globSymlink.realPath, globSymlink.linkPath);
        }

        return entry.fullPath;
    };

    var entryPath = function (entry) {
        return sysPath.join(watchPath,
            sysPath.relative(watchPath, checkGlobSymlink(entry))
        );
    };

    var filterPath = function (entry) {
        if (entry.stat && entry.stat.isSymbolicLink()) return filterDir(entry);
        var resolvedPath = entryPath(entry);
        return (!hasGlob || globFilter(resolvedPath)) &&
            this._isntIgnored(resolvedPath, entry.stat) &&
            (this.options.ignorePermissionErrors ||
            this._hasReadPermissions(entry.stat));
    }.bind(this);

    var getDirParts = function (path) {
        if (!hasGlob) return false;
        var parts = sysPath.relative(watchPath, path).split(/[\/\\]/);
        return parts;
    };

    var dirParts = getDirParts(path);
    if (dirParts && dirParts.length > 1) dirParts.pop();
    var unmatchedGlob;

    var filterDir = function (entry) {
        if (hasGlob) {
            var entryParts = getDirParts(checkGlobSymlink(entry));
            var globstar = false;
            unmatchedGlob = !dirParts.every(function (part, i) {
                if (part === '**') globstar = true;
                return globstar || !entryParts[i] || anymatch(part, entryParts[i]);
            });
        }
        return !unmatchedGlob && this._isntIgnored(entryPath(entry), entry.stat);
    }.bind(this);

    return {
        followSymlinks: follow,
        statMethod: follow ? 'stat' : 'lstat',
        path: path,
        watchPath: watchPath,
        entryPath: entryPath,
        hasGlob: hasGlob,
        globFilter: globFilter,
        filterPath: filterPath,
        filterDir: filterDir
    };
};

// Directory helpers
// -----------------

// Private method: Provides directory tracking objects
//
// * directory - string, path of the directory
//
// Returns the directory's tracking object
FSWatcher.prototype._getWatchedDir = function (directory) {
    var dir = sysPath.resolve(directory);
    var watcherRemove = this._remove.bind(this);
    if (!(dir in this._watched)) this._watched[dir] = {
        _items: Object.create(null),
        add: function (item) {
            if (item !== '.') this._items[item] = true;
        },
        remove: function (item) {
            delete this._items[item];
            if (!this.children().length) {
                fs.readdir(dir, function (err) {
                    if (err) watcherRemove(sysPath.dirname(dir), sysPath.basename(dir));
                });
            }
        },
        has: function (item) {
            return item in this._items;
        },
        children: function () {
            return Object.keys(this._items);
        }
    };
    return this._watched[dir];
};

// File helpers
// ------------

// Private method: Check for read permissions
// Based on this answer on SO: http://stackoverflow.com/a/11781404/1358405
//
// * stats - object, result of fs.stat
//
// Returns boolean
FSWatcher.prototype._hasReadPermissions = function (stats) {
    return Boolean(4 & parseInt(((stats && stats.mode) & 0x1ff).toString(8)[0], 10));
};

// Private method: Handles emitting unlink events for
// files and directories, and via recursion, for
// files and directories within directories that are unlinked
//
// * directory - string, directory within which the following item is located
// * item      - string, base path of item/directory
//
// Returns nothing
FSWatcher.prototype._remove = function (directory, item) {
    // if what is being deleted is a directory, get that directory's paths
    // for recursive deleting and cleaning of watched object
    // if it is not a directory, nestedDirectoryChildren will be empty array
    var path = sysPath.join(directory, item);
    var fullPath = sysPath.resolve(path);
    var isDirectory = this._watched[path] || this._watched[fullPath];

    // prevent duplicate handling in case of arriving here nearly simultaneously
    // via multiple paths (such as _handleFile and _handleDir)
    if (!this._throttle('remove', path, 100)) return;

    // if the only watched file is removed, watch for its return
    var watchedDirs = Object.keys(this._watched);
    if (!isDirectory && !this.options.useFsEvents && watchedDirs.length === 1) {
        this.add(directory, item, true);
    }

    // This will create a new entry in the watched object in either case
    // so we got to do the directory check beforehand
    var nestedDirectoryChildren = this._getWatchedDir(path).children();

    // Recursively remove children directories / files.
    nestedDirectoryChildren.forEach(function (nestedItem) {
        this._remove(path, nestedItem);
    }, this);

    // Check if item was on the watched list and remove it
    var parent = this._getWatchedDir(directory);
    var wasTracked = parent.has(item);
    parent.remove(item);

    // If we wait for this file to be fully written, cancel the wait.
    var relPath = path;
    if (this.options.cwd) relPath = sysPath.relative(this.options.cwd, path);
    if (this.options.awaitWriteFinish && this._pendingWrites[relPath]) {
        var event = this._pendingWrites[relPath].cancelWait();
        if (event === 'add') return;
    }

    // The Entry will either be a directory that just got removed
    // or a bogus entry to a file, in either case we have to remove it
    delete this._watched[path];
    delete this._watched[fullPath];
    var eventName = isDirectory ? 'unlinkDir' : 'unlink';
    if (wasTracked && !this._isIgnored(path)) this._emit(eventName, path);

    // Avoid conflicts if we later create another file with the same name
    if (!this.options.useFsEvents) {
        this._closePath(path);
    }
};

FSWatcher.prototype._closePath = function (path) {
    if (!this._closers[path]) return;
    this._closers[path]();
    delete this._closers[path];
    this._getWatchedDir(sysPath.dirname(path)).remove(sysPath.basename(path));
}

// Public method: Adds paths to be watched on an existing FSWatcher instance

// * paths     - string or array of strings, file/directory paths and/or globs
// * _origAdd  - private boolean, for handling non-existent paths to be watched
// * _internal - private boolean, indicates a non-user add

// Returns an instance of FSWatcher for chaining.
FSWatcher.prototype.add = function (paths, _origAdd, _internal) {
    var cwd = this.options.cwd;
    this.closed = false;
    paths = flatten(arrify(paths));

    if (!paths.every(isString)) {
        throw new TypeError('Non-string provided as watch path: ' + paths);
    }

    if (cwd) paths = paths.map(function (path) {
        if (isAbsolute(path)) {
            return path;
        } else if (path[0] === '!') {
            return '!' + sysPath.join(cwd, path.substring(1));
        } else {
            return sysPath.join(cwd, path);
        }
    });

    // set aside negated glob strings
    paths = paths.filter(function (path) {
        if (path[0] === '!') {
            this._ignoredPaths[path.substring(1)] = true;
        } else {
            // if a path is being added that was previously ignored, stop ignoring it
            delete this._ignoredPaths[path];
            delete this._ignoredPaths[path + '/**'];

            // reset the cached userIgnored anymatch fn
            // to make ignoredPaths changes effective
            this._userIgnored = null;

            return true;
        }
    }, this);

    if (this.options.useFsEvents && FsEventsHandler.canUse()) {
        if (!this._readyCount) this._readyCount = paths.length;
        if (this.options.persistent) this._readyCount *= 2;
        paths.forEach(this._addToFsEvents, this);
    } else {
        if (!this._readyCount) this._readyCount = 0;
        this._readyCount += paths.length;
        asyncEach(paths, function (path, next) {
            this._addToNodeFs(path, !_internal, 0, 0, _origAdd, function (err, res) {
                if (res) this._emitReady();
                next(err, res);
            }.bind(this));
        }.bind(this), function (error, results) {
            results.forEach(function (item) {
                if (!item) return;
                this.add(sysPath.dirname(item), sysPath.basename(_origAdd || item));
            }, this);
        }.bind(this));
    }

    return this;
};

// Public method: Close watchers or start ignoring events from specified paths.

// * paths     - string or array of strings, file/directory paths and/or globs

// Returns instance of FSWatcher for chaining.
FSWatcher.prototype.unwatch = function (paths) {
    if (this.closed) return this;
    paths = flatten(arrify(paths));

    paths.forEach(function (path) {
        // convert to absolute path unless relative path already matches
        if (!isAbsolute(path) && !this._closers[path]) {
            if (this.options.cwd) path = sysPath.join(this.options.cwd, path);
            path = sysPath.resolve(path);
        }

        this._closePath(path);

        this._ignoredPaths[path] = true;
        if (path in this._watched) {
            this._ignoredPaths[path + '/**'] = true;
        }

        // reset the cached userIgnored anymatch fn
        // to make ignoredPaths changes effective
        this._userIgnored = null;
    }, this);

    return this;
};

// Public method: Close watchers and remove all listeners from watched paths.

// Returns instance of FSWatcher for chaining.
FSWatcher.prototype.close = function () {
    if (this.closed) return this;

    this.closed = true;
    Object.keys(this._closers).forEach(function (watchPath) {
        this._closers[watchPath]();
        delete this._closers[watchPath];
    }, this);
    this._watched = Object.create(null);

    this.removeAllListeners();
    return this;
};

// Public method: Expose list of watched paths

// Returns object w/ dir paths as keys and arrays of contained paths as values.
FSWatcher.prototype.getWatched = function () {
    var watchList = {};
    Object.keys(this._watched).forEach(function (dir) {
        var key = this.options.cwd ? sysPath.relative(this.options.cwd, dir) : dir;
        watchList[key || '.'] = Object.keys(this._watched[dir]._items).sort();
    }.bind(this));
    return watchList;
};

// Attach watch handler prototype methods
function importHandler(handler) {
    Object.keys(handler.prototype).forEach(function (method) {
        FSWatcher.prototype[method] = handler.prototype[method];
    });
}
importHandler(NodeFsHandler);
if (FsEventsHandler.canUse()) importHandler(FsEventsHandler);

// Export FSWatcher class
exports.FSWatcher = FSWatcher;

// Public function: Instantiates watcher with paths to be tracked.

// * paths     - string or array of strings, file/directory paths and/or globs
// * options   - object, chokidar options

// Returns an instance of FSWatcher for chaining.
exports.watch = function (paths, options) {
    return new FSWatcher(options).add(paths);
};
