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/* Copyright 2009-2011 Yorba Foundation
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 *
 * This software is licensed under the GNU LGPL (version 2.1 or later).
 * See the COPYING file in this distribution. 
 */

//
// DirectoryMonitor will monitor an entire directory for changes to all files and directories
// within it.  It uses FileMonitor to monitor all directories it discovers at initialization
// and reports changes to the files and directories just as FileMonitor reports them.  Subclasses
// can override the notify_* methods to filter or monitor events before the signal is fired,
// or can override the signals themselves to be notified afterwards.
//
// start_discovery() must be called to initiate monitoring.  Directories and files will be reported
// as they're discovered.  Directories will be monitored as they're discovered as well.  Discovery
// can only be initiated once.
//
// All signals are virtual and have a corresponding notify_* protected virtual function.
// Subclasses can either override the notify or the signal to decide when they want to process
// the event.
//
// DirectoryMonitor also adds a level of intelligence to GLib's monitoring API.Because certain
// file/directory events are decomposed by FileMonitor into more atomic events, it's difficult
// to know when these "composed" events have occurred.  (For example, a file move is reported
// as a DELETED event followed by a CREATED event, with no clue that the two are related.)  Later
// versions added the MOVE event, but we can't rely on those being installed.  Also, documentation
// suggests it's only available with certain back-ends.
//
// DirectoryMonitor attempts to solve this by deducing when a set of events actually equals
// a composite event.  It requires more memory in order to do this (i.e. it stores all files and
// their information), but the trade-off is easier file/directory monitoring via familiar
// semantics.
//
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// DirectoryMonitor also will synthesize events when normal monitor events don't produce expected
// results.  For example, if a directory is moved out of DirectoryMonitor's root, it is reported
// as a delete event, but none of its children are reported as deleted.  Similarly, a directory
// rename can be captured as a move, but notifications for all its children are not fired and
// are synthesized by DirectoryMonitor.  DirectoryMonitor will fire delete and move notifications
// for all the directory's children in depth-first order.
//
// In general, DirectoryMonitor attempts to preserve ordering of events, so that (for example) a
// file-altered event doesn't fire before a file-created, and so on.
//
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// Because of these requirements, DirectoryMonitor maintains a FileInfo struct on all directories 
// and files being monitored.  (It maintains the attributes gather during the discovery phase, i.e. 
// SUPPLIED_ATTRIBUTES.)  This information can be retrieved via get_info(), get_file_id(), and
// get_etag().  These calls can be made at any time; the information is stored before any signal
// is fired.
//
// Note that DirectoryMonitor currently only supports files and directories.  Other file types
// (special, symbolic links, shortcuts, and mount points) are not supported.  It has been seen
// when a temporary file is created for its file type to be reported as "unknown" and when it's
// altered/deleted to be reported as a regular file.  This means it's possible for a file not to
// be reported as discovered or created but to be reported as altered and/or deleted.
//
// DirectoryMonitor can be configured to not recurse (in which case it only discovers/monitors
// the root directory) and to not monitor (in which case only discovery occurs).
//

public class DirectoryMonitor : Object {
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    public const int DEFAULT_PRIORITY = Priority.LOW;
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    public const FileQueryInfoFlags DIR_INFO_FLAGS = FileQueryInfoFlags.NONE;
    public const FileQueryInfoFlags FILE_INFO_FLAGS = FileQueryInfoFlags.NOFOLLOW_SYMLINKS;
    
    // when using UNKNOWN_FILE_FLAGS, check if the resulting FileInfo's symlink status matches
    // symlink support for files and directories by calling is_file_symlink_supported().
    public const FileQueryInfoFlags UNKNOWN_INFO_FLAGS = FileQueryInfoFlags.NONE;
    public const bool SUPPORT_DIR_SYMLINKS = true;
    public const bool SUPPORT_FILE_SYMLINKS = false;
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    public const string SUPPLIED_ATTRIBUTES = Util.FILE_ATTRIBUTES;
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    private const FileMonitorFlags FILE_MONITOR_FLAGS = FileMonitorFlags.SEND_MOVED;
    private const uint DELETED_EXPIRATION_MSEC = 500;
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    private const int MAX_EXPLORATION_DIRS = 5;
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    private enum FType {
        FILE,
        DIRECTORY,
        UNSUPPORTED
    }
    
    private class QueryInfoQueueElement {
        private static uint current = 0;
        
        public DirectoryMonitor owner;
        public File file;
        public File? other_file;
        public FileMonitorEvent event;
        public uint position;
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        public ulong time_created_msec;
        public FileInfo? info = null;
        public Error? err = null;
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        public bool completed = false;
        
        public QueryInfoQueueElement(DirectoryMonitor owner, File file, File? other_file, 
            FileMonitorEvent event) {
            this.owner = owner;
            this.file = file;
            this.other_file = other_file;
            this.event = event;
            this.position = current++;
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            this.time_created_msec = now_ms();
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        }
        
        public void on_completed(Object? source, AsyncResult aresult) {
            File source_file = (File) source;
            
            // finish the async operation to get the result
            try {
                info = source_file.query_info_async.end(aresult);
            } catch (Error err) {
                this.err = err;
            }
            
            // mark as completed
            completed = true;
            
            // notify owner this job is finished, to process the queue
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            owner.process_query_queue(this);
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        }
    }
    
    // The FileInfoMap solves several related problems while maintaining FileInfo's in memory
    // so they're available to users of DirectoryMonitor as well as DirectoryMonitor itself,
    // which uses them to detect certain conditions.  FileInfoMap uses a File ID to maintain
    // only unique references to each File (and thus can be used to detect symlinked files).
    private class FileInfoMap {
        private Gee.HashMap<File, FileInfo> map = new Gee.HashMap<File, FileInfo>(file_hash,
            file_equal);
        private Gee.HashMap<string, File> id_map = new Gee.HashMap<string, File>(str_hash,
            str_equal, file_equal);
        
        public FileInfoMap() {
        }
        
        protected bool normalize_file(File file, FileInfo? info, out File normalized, out string id) {
            // if no info is supplied, see if file straight-up corresponds .. if not, we're out of
            // luck
            FileInfo? local_info = info;
            if (local_info == null) {
                local_info = map.get(file);
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                if (local_info == null) {
                    normalized = null;
                    id = null;
                    
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                    return false;
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                }
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            }
            
            string? file_id = get_file_info_id(local_info);
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            if (file_id == null) {
                normalized = null;
                id = null;
                
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                return false;
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            }
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            File? known_file = id_map.get(file_id);
            
            id = (string) file_id;
            normalized = (known_file != null) ? known_file : file;
            
            return true;
        }
        
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        public bool update(File file, FileInfo info) {
            // if the file out-and-out exists, remove it now
            if (map.has_key(file)) {
                bool removed = map.unset(file);
                assert(removed);
            }
            
            // if the id exists, remove it too
            string? existing_id = get_file_info_id(info);
            if (existing_id != null && id_map.has_key(existing_id)) {
                bool removed = id_map.unset(existing_id);
                assert(removed);
            }
            
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            string id;
            File normalized;
            if (!normalize_file(file, info, out normalized, out id))
                return false;
            
            map.set(normalized, info);
            id_map.set(id, normalized);
            
            return true;
        }
        
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        public bool remove(File file, FileInfo? info) {
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            string id;
            File normalized;
            if (!normalize_file(file, info, out normalized, out id))
                return false;
            
            map.unset(normalized);
            id_map.unset(id);
            
            return true;
        }
        
        // This calls the virtual function remove() for all files, so overriding it is sufficient
        // (but not necessarily most efficient)
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        public void remove_all(Gee.Collection<File> files) {
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            foreach (File file in files)
                remove(file, null);
        }
        
        public bool contains(File file, FileInfo? info) {
            string id;
            File normalized;
            if (!normalize_file(file, info, out normalized, out id))
                return false;
            
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            return id_map.has_key(id);
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        }
        
        public string? get_id(File file, FileInfo? info) {
            // if FileInfo is valid, easy pickings
            if (info != null)
                return get_file_info_id(info);
            
            string id;
            File normalized;
            if (!normalize_file(file, null, out normalized, out id))
                return null;
            
            return id;
        }
        
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        public Gee.Collection<File> get_all() {
            return map.keys;
        }
        
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        public FileInfo? get_info(File file) {
            // if file is known as-is, use that
            FileInfo? info = map.get(file);
            if (info != null)
                return info;
            
            string id;
            File normalized;
            if (!normalize_file(file, null, out normalized, out id))
                return null;
            
            return map.get(normalized);
        }
        
        public FileInfo? query_info(File file, Cancellable? cancellable) {
            FileInfo? info = get_info(file);
            if (info != null)
                return info;
            
            // This *only* retrieves the file ID, which is then used to obtain the in-memory file
            // information.
            try {
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                info = file.query_info(FILE_ATTRIBUTE_ID_FILE, UNKNOWN_INFO_FLAGS, cancellable);
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            } catch (Error err) {
                warning("Unable to query file ID of %s: %s", file.get_path(), err.message);
                
                return null;
            }
            
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            if (!is_file_symlink_supported(info))
                return null;
            
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            string? id = info.get_attribute_string(FILE_ATTRIBUTE_ID_FILE);
            if (id == null)
                return null;
            
            File? normalized = id_map.get(id);
            if (normalized == null)
                return null;
            
            return map.get(file);
        }
        
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        public File? find_match(FileInfo match) {
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            string? match_id = get_file_info_id(match);
            if (match_id == null)
                return null;
            
            // get all the interesting matchable items from the supplied FileInfo
            int64 match_size = match.get_size();
            TimeVal match_time;
            match.get_modification_time(out match_time);
            
            foreach (File file in map.keys) {
                FileInfo info = map.get(file);
                
                // file id match is instant match
                if (get_file_info_id(info) == match_id)
                    return file;
                
                // if file size *and* modification time match, stop
                if (match_size != info.get_size())
                    continue;
                
                TimeVal time;
                info.get_modification_time(out time);
                
                if (time.tv_sec != match_time.tv_sec)
                    continue;
                
                return file;
            }
            
            return null;
        }
        
        public void remove_descendents(File root, FileInfoMap descendents) {
            Gee.ArrayList<File> pruned = null;
            foreach (File file in map.keys) {
                File? parent = file.get_parent();
                while (parent != null) {
                    if (parent.equal(root)) {
                        if (pruned == null)
                            pruned = new Gee.ArrayList<File>();
                        
                        pruned.add(file);
                        descendents.update(file, map.get(file));
                        
                        break;
                    }
                    
                    parent = parent.get_parent();
                }
            }
            
            if (pruned != null)
                remove_all(pruned);
        }
        
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        // This returns only the immediate descendents of the root sorted by type.  Returns the
        // total number of children located.
        public int get_children(File root, Gee.Collection<File> files, Gee.Collection<File> dirs) {
            int count = 0;
            foreach (File file in map.keys) {
                File? parent = file.get_parent();
                if (parent == null || !parent.equal(root))
                    continue;
                
                FType ftype = get_ftype(map.get(file));
                switch (ftype) {
                    case FType.FILE:
                        files.add(file);
                        count++;
                    break;
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                    case FType.DIRECTORY:
                        dirs.add(file);
                        count++;
                    break;
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                    default:
                        assert(ftype == FType.UNSUPPORTED);
                    break;
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                }
            }
            
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            return count;
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        }
    }
    
    private File root;
    private bool recurse;
    private bool monitoring;
    private Gee.HashMap<string, FileMonitor> monitors = new Gee.HashMap<string, FileMonitor>();
    private Gee.Queue<QueryInfoQueueElement> query_info_queue = new Gee.LinkedList<
        QueryInfoQueueElement>();
    private FileInfoMap files = new FileInfoMap();
    private FileInfoMap parent_moved = new FileInfoMap();
    private Cancellable cancellable = new Cancellable();
    private int outstanding_exploration_dirs = 0;
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    private bool started = false;
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    private bool has_discovery_started = false;
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    private uint delete_timer_id = 0;
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    // This signal will be fired *after* directory-moved has been fired.
    public virtual signal void root_moved(File old_root, File new_root, FileInfo new_root_info) {
    }
    
    // If the root is deleted, then the DirectoryMonitor is essentially dead; it has no monitor
    // to wait for the root to be re-created, and everything beneath the root is obviously blown
    // away as well.
    //
    // This signal will be fired *after* directory-deleted has been fired.
    public virtual signal void root_deleted(File root) {
    }
    
    public virtual signal void discovery_started() {
    }
    
    public virtual signal void file_discovered(File file, FileInfo info) {
    }
    
    public virtual signal void directory_discovered(File file, FileInfo info) {
    }
    
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    // reason is a user-visible string.  May be called more than once during discovery.
    // Discovery always completes with discovery-completed.
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    public virtual signal void discovery_failed(string reason) {
    }
    
    public virtual signal void discovery_completed() {
        has_discovery_started = false;
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        mdbg("discovery completed");
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    }
    
    public virtual signal void file_created(File file, FileInfo info) {
    }
    
    public virtual signal void file_moved(File old_file, File new_file, FileInfo new_file_info) {
    }
    
    // FileInfo is not updated for each file-altered signal.
    public virtual signal void file_altered(File file) {
    }
    
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    // This is called when the monitor detects that alteration (attributes or otherwise) to the
    // file has completed.
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    public virtual signal void file_alteration_completed(File file, FileInfo info) {
    }
    
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    public virtual signal void file_attributes_altered(File file) {
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    }
    
    public virtual signal void file_deleted(File file) {
    }
    
    // This implies that the directory is now being monitored.
    public virtual signal void directory_created(File dir, FileInfo info) {
    }
    
    // This implies that the old directory is no longer being monitored and the new one is.
    public virtual signal void directory_moved(File old_dir, File new_dir, FileInfo new_dir_info) {
    }
    
    // FileInfo is not updated for each directory-altered signal.
    public virtual signal void directory_altered(File dir) {
    }
    
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    // This is called when the monitor detects that alteration (attributes or otherwise) to the
    // directory has completed.
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    public virtual signal void directory_alteration_completed(File dir, FileInfo info) {
    }
    
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    public virtual signal void directory_attributes_altered(File dir) {
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    }
    
    // This implies that the directory is now no longer be monitored (unsurprisingly).
    public virtual signal void directory_deleted(File dir) {
    }
    
    public virtual signal void closed() {
    }
    
    public DirectoryMonitor(File root, bool recurse, bool monitoring) {
        this.root = root;
        this.recurse = recurse;
        this.monitoring = monitoring;
    }
    
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    protected static void mdbg(string msg) {
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#if TRACE_MONITORING
        debug("%s", msg);
#endif
    }
    
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    public bool is_recursive() {
        return recurse;
    }
    
    public bool is_monitoring() {
        return monitoring;
    }
    
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    protected virtual void notify_root_deleted(File root) {
        assert(this.root.equal(root));
        
        mdbg("root deleted");
        root_deleted(root);
    }
    
    private void internal_notify_root_moved(File old_root, File new_root, FileInfo new_root_info) {
        bool removed = files.remove(old_root, null);
        assert(removed);
        
        bool updated = files.update(new_root, new_root_info);
        assert(updated);
        
        root = new_root;
        
        notify_root_moved(old_root, new_root, new_root_info);
    }
    
    protected virtual void notify_root_moved(File old_root, File new_root, FileInfo new_root_info) {
        assert(this.root.equal(old_root));
        
        mdbg("root moved: %s -> %s".printf(old_root.get_path(), new_root.get_path()));
        root_moved(old_root, new_root, new_root_info);
    }
    
    protected virtual void notify_discovery_started() {
        mdbg("discovery started");
        discovery_started();
    }
    
    protected virtual void internal_notify_file_discovered(File file, FileInfo info) {
        bool updated = files.update(file, info);
        assert(updated);
        
        notify_file_discovered(file, info);
    }
    
    protected virtual void notify_file_discovered(File file, FileInfo info) {
        mdbg("file discovered: %s".printf(file.get_path()));
        file_discovered(file, info);
    }
    
    protected virtual void internal_notify_directory_discovered(File dir, FileInfo info) {
        bool updated = files.update(dir, info);
        assert(updated);
        
        notify_directory_discovered(dir, info);
    }
    
    protected virtual void notify_directory_discovered(File dir, FileInfo info) {
        mdbg("directory discovered: %s".printf(dir.get_path()));
        directory_discovered(dir, info);
    }
    
    protected virtual void notify_discovery_failed(string reason) {
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        warning("discovery failed: %s", reason);
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        discovery_failed(reason);
    }
    
    protected virtual void notify_discovery_completed() {
        discovery_completed();
    }
    
    private void internal_notify_file_created(File file, FileInfo info) {
        File old_file;
        FileInfo old_file_info;
        if (is_file_create_move(file, info, out old_file, out old_file_info)) {
            internal_notify_file_moved(old_file, file, info);
        } else {
            bool updated = files.update(file, info);
            assert(updated);
            
            notify_file_created(file, info);
        }
    }
    
    protected virtual void notify_file_created(File file, FileInfo info) {
        mdbg("file created: %s".printf(file.get_path()));
        file_created(file, info);
    }
    
    private void internal_notify_file_moved(File old_file, File new_file, FileInfo new_file_info) {
        // don't assert because it's possible this call was generated via a deleted-created
        // sequence, in which case the old_file won't be in files
        files.remove(old_file, null);
        
        bool updated = files.update(new_file, new_file_info);
        assert(updated);
        
        notify_file_moved(old_file, new_file, new_file_info);
    }
    
    protected virtual void notify_file_moved(File old_file, File new_file, FileInfo new_file_info) {
        mdbg("file moved: %s -> %s".printf(old_file.get_path(), new_file.get_path()));
        file_moved(old_file, new_file, new_file_info);
    }
    
    protected virtual void notify_file_altered(File file) {
        mdbg("file altered: %s".printf(file.get_path()));
        file_altered(file);
    }
    
    private void internal_notify_file_alteration_completed(File file, FileInfo info) {
        bool updated = files.update(file, info);
        assert(updated);
        
        notify_file_alteration_completed(file, info);
    }
    
    protected virtual void notify_file_alteration_completed(File file, FileInfo info) {
        mdbg("file alteration completed: %s".printf(file.get_path()));
        file_alteration_completed(file, info);
    }
    
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    protected virtual void notify_file_attributes_altered(File file) {
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        mdbg("file attributes altered: %s".printf(file.get_path()));
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        file_attributes_altered(file);
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    }
    
    private void internal_notify_file_deleted(File file) {
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        bool removed = files.remove(file, null);
        assert(removed);
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        notify_file_deleted(file);
    }
    
    protected virtual void notify_file_deleted(File file) {
        mdbg("file deleted: %s".printf(file.get_path()));
        file_deleted(file);
    }
    
    private void internal_notify_directory_created(File dir, FileInfo info) {
        File old_dir;
        FileInfo old_dir_info;
        if (is_file_create_move(dir, info, out old_dir, out old_dir_info)) {
            // A directory move, like a file move, is actually a directory-deleted followed
            // by a directory-created.  Unlike a file move, what follows directory-created
            // is a file/directory-created for each file and directory inside the folder
            // (although the matching deletes are never fired).  We want to issue moves for 
            // all those files as well and suppress the create calls.
            files.remove_descendents(old_dir, parent_moved);
            
            internal_notify_directory_moved(old_dir, old_dir_info, dir, info);
        } else {
            bool updated = files.update(dir, info);
            assert(updated);
            
            notify_directory_created(dir, info);
        }
    }
    
    protected virtual void notify_directory_created(File dir, FileInfo info) {
        mdbg("directory created: %s".printf(dir.get_path()));
        directory_created(dir, info);
    }
    
    private void internal_notify_directory_moved(File old_dir, FileInfo old_dir_info, File new_dir,
        FileInfo new_dir_info) {
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        async_internal_notify_directory_moved.begin(old_dir, old_dir_info, new_dir, new_dir_info);
    }
    
    private async void async_internal_notify_directory_moved(File old_dir, FileInfo old_dir_info,
        File new_dir, FileInfo new_dir_info) {
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        Gee.ArrayList<File> file_children = new Gee.ArrayList<File>(file_equal);
        Gee.ArrayList<File> dir_children = new Gee.ArrayList<File>(file_equal);
        int count = files.get_children(old_dir, file_children, dir_children);
        if (count > 0) {
            // descend into directories and let them notify their children on the way up
            // (if files.get_info() returns null, that indicates the directory/file was already
            // deleted in recurse)
            foreach (File dir_child in dir_children) {
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                FileInfo? dir_info = files.get_info(dir_child);
                if (dir_info == null) {
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                    warning("Unable to retrieve directory-moved info for %s", dir_child.get_path());
                    
                    continue;
                }
                
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                yield async_internal_notify_directory_moved(dir_child, dir_info,
                    new_dir.get_child(dir_child.get_basename()), dir_info);
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            }
            
            // then move the children
            foreach (File file_child in file_children) {
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                FileInfo? file_info = files.get_info(file_child);
                if (file_info == null) {
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                    warning("Unable to retrieve directory-moved info for %s", file_child.get_path());
                    
                    continue;
                }
                
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                internal_notify_file_moved(file_child, new_dir.get_child(file_child.get_basename()),
                    file_info);
                
                Idle.add(async_internal_notify_directory_moved.callback, DEFAULT_PRIORITY);
                yield;
677 678 679
            }
        }
        
680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718
        // Don't assert here because it's possible this call was made due to a deleted-created
        // sequence, in which case the directory has already been removed from files
        files.remove(old_dir, null);
        
        bool updated = files.update(new_dir, new_dir_info);
        assert(updated);
        
        // remove the old monitor and add the new one
        remove_monitor(old_dir, old_dir_info);
        add_monitor(new_dir, new_dir_info);
        
        notify_directory_moved(old_dir, new_dir, new_dir_info);
    }
    
    protected virtual void notify_directory_moved(File old_dir, File new_dir, FileInfo new_dir_info) {
        mdbg("directory moved: %s -> %s".printf(old_dir.get_path(), new_dir.get_path()));
        directory_moved(old_dir, new_dir, new_dir_info);
        
        if (old_dir.equal(root))
            internal_notify_root_moved(old_dir, new_dir, new_dir_info);
    }
    
    protected virtual void notify_directory_altered(File dir) {
        mdbg("directory altered: %s".printf(dir.get_path()));
        directory_altered(dir);
    }
    
    private void internal_notify_directory_alteration_completed(File dir, FileInfo info) {
        bool updated = files.update(dir, info);
        assert(updated);
        
        notify_directory_alteration_completed(dir, info);
    }
    
    protected virtual void notify_directory_alteration_completed(File dir, FileInfo info) {
        mdbg("directory alteration completed: %s".printf(dir.get_path()));
        directory_alteration_completed(dir, info);
    }
    
719
    protected virtual void notify_directory_attributes_altered(File dir) {
720
        mdbg("directory attributes altered: %s".printf(dir.get_path()));
721
        directory_attributes_altered(dir);
722 723 724 725 726 727 728 729 730
    }
    
    private void internal_notify_directory_deleted(File dir) {
        FileInfo? info = files.get_info(dir);
        assert(info != null);
        
        // stop monitoring this directory
        remove_monitor(dir, info);
        
731
        async_notify_directory_deleted.begin(dir, false);
732 733
    }
    
734
    private async void async_notify_directory_deleted(File dir, bool already_removed) {
735 736 737 738
        // Note that in this function no assertion checking is done ... there are many
        // reasons a deleted file may not be known to the internal bookkeeping; if
        // the file is gone and we didn't know about it, then it's no problem.
        
739 740 741 742 743 744 745 746 747 748 749 750 751 752 753
        // because a directory can be deleted without its children being deleted first (probably
        // means it has been moved to a location outside of the monitored root), need to
        // synthesize notifications for all its children
        Gee.ArrayList<File> file_children = new Gee.ArrayList<File>(file_equal);
        Gee.ArrayList<File> dir_children = new Gee.ArrayList<File>(file_equal);
        int count = files.get_children(dir, file_children, dir_children);
        if (count > 0) {
            // don't use  internal_* variants as they deal with "real" and not synthesized
            // notifications.  also note that files.get_info() can return null because items are
            // being deleted on the way back up the tree ... when files.get_info() returns null,
            // it means the file/directory was already deleted in a recursed method, and so no
            // assertions on them
            
            // descend first into directories, deleting files and directories on the way up
            foreach (File dir_child in dir_children)
754
                yield async_notify_directory_deleted(dir_child, false);
755 756 757 758
            
            // now notify deletions on all immediate children files ... don't notify directory
            // deletion because that's handled right before exiting this method
            foreach (File file_child in file_children) {
759
                files.remove(file_child, null);
760 761
                
                notify_file_deleted(file_child);
762 763 764
                
                Idle.add(async_notify_directory_deleted.callback, DEFAULT_PRIORITY);
                yield;
765 766 767
            }
        }
        
768 769
        if (!already_removed)
            files.remove(dir, null);
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        notify_directory_deleted(dir);
    }
    
    protected virtual void notify_directory_deleted(File dir) {
        mdbg("directory deleted: %s".printf(dir.get_path()));
        directory_deleted(dir);
        
        if (dir.equal(root))
            notify_root_deleted(dir);
    }
    
    protected virtual void notify_closed() {
        mdbg("monitoring of %s closed".printf(root.get_path()));
        closed();
    }
    
    public File get_root() {
        return root;
    }
    
    public bool is_in_root(File file) {
792
        return file.has_prefix(root);
793 794
    }
    
795 796 797 798
    public bool has_started() {
        return started;
    }
    
799
    public void start_discovery() {
800
        assert(!started);
801 802
        
        has_discovery_started = true;
803 804
        started = true;
        
805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826
        notify_discovery_started();
        
        // start exploring the directory, adding monitors as the directories are discovered
        outstanding_exploration_dirs = 1;
        explore_async.begin(root, null, true);
    }
    
    // This should be called when a DirectoryMonitor needs to be destroyed or released.  This
    // will halt background exploration and close all resources.
    public virtual void close() {
        // cancel any outstanding async I/O
        cancellable.cancel();
        
        // cancel all monitors
        foreach (FileMonitor monitor in monitors.values)
            cancel_monitor(monitor);
        
        monitors.clear();
        
        notify_closed();
    }
    
827
    private static FType get_ftype(FileInfo info) {
828 829 830 831 832 833 834 835 836 837 838 839 840 841 842
        FileType file_type = info.get_file_type();
        switch (file_type) {
            case FileType.REGULAR:
                return FType.FILE;
            
            case FileType.DIRECTORY:
                return FType.DIRECTORY;
            
            default:
                mdbg("query_ftype: Unknown file type %s".printf(file_type.to_string()));
                return FType.UNSUPPORTED;
        }
    }
    
    private async void explore_async(File dir, FileInfo? dir_info, bool in_discovery) {
843 844 845 846 847 848 849 850
        if (files.contains(dir, dir_info)) {
            warning("Directory loop detected at %s, not exploring", dir.get_path());
            
            explore_directory_completed(in_discovery);
            
            return;
        }
        
851 852 853 854
        // if FileInfo wasn't supplied by caller, fetch it now
        FileInfo? local_dir_info = dir_info;
        if (local_dir_info == null) {
            try {
855 856
                local_dir_info = yield dir.query_info_async(SUPPLIED_ATTRIBUTES, DIR_INFO_FLAGS,
                    DEFAULT_PRIORITY, cancellable);
857 858 859
            } catch (Error err) {
                warning("Unable to retrieve info on %s: %s", dir.get_path(), err.message);
                
860 861
                explore_directory_completed(in_discovery);
                
862 863 864 865
                return;
            }
        }
        
866 867 868 869 870 871 872 873
        if (local_dir_info.get_is_hidden()) {
            warning("Ignoring hidden directory %s", dir.get_path());
            
            explore_directory_completed(in_discovery);
            
            return;
        }
        
874 875 876 877 878 879 880 881 882 883 884
        // File ID is required for directory monitoring.  No ID, no ride!
        // TODO: Replace the warning with notify_discovery_failed() and provide a user-visible
        // string.
        if (get_file_info_id(local_dir_info) == null) {
            warning("Unable to retrieve file ID on %s: skipping", dir.get_path());
            
            explore_directory_completed(in_discovery);
            
            return;
        }
        
885 886
        // verify this is a directory
        if (local_dir_info.get_file_type() != FileType.DIRECTORY) {
887 888
            notify_discovery_failed(_("Unable to monitor %s: Not a directory (%s)").printf(
                dir.get_path(), local_dir_info.get_file_type().to_string()));
889
            
890 891
            explore_directory_completed(in_discovery);
            
892 893 894 895 896 897 898 899 900 901 902 903
            return;
        }
        
        // collect all directories and files in the directory, to consolidate reporting them as
        // well as traversing the subdirectories -- but to avoid a lot of unnecessary resource
        // allocations (think empty directories, or leaf nodes with only files), only allocate
        // the maps when necessary
        Gee.HashMap<File, FileInfo> dir_map = null;
        Gee.HashMap<File, FileInfo> file_map = null;
        
        try {
            FileEnumerator enumerator = yield dir.enumerate_children_async(SUPPLIED_ATTRIBUTES,
904
                UNKNOWN_INFO_FLAGS, DEFAULT_PRIORITY, cancellable);
905
            for (;;) {
906
                List<FileInfo>? infos = yield enumerator.next_files_async(10, DEFAULT_PRIORITY,
907 908 909 910 911
                    cancellable);
                if (infos == null)
                    break;
                
                foreach (FileInfo info in infos) {
912 913 914 915 916 917 918 919
                    // we don't deal with hidden files or directories
                    if (info.get_is_hidden()) {
                        warning("Skipping hidden file/directory %s",
                            dir.get_child(info.get_name()).get_path());
                        
                        continue;
                    }
                    
920 921 922 923
                    // check for symlink support
                    if (!is_file_symlink_supported(info))
                        continue;
                    
924 925 926 927 928
                    switch (info.get_file_type()) {
                        case FileType.REGULAR:
                            if (file_map == null)
                                file_map = new Gee.HashMap<File, FileInfo>(file_hash, file_equal);
                            
929
                            file_map.set(dir.get_child(info.get_name()), info);
930 931 932 933 934 935
                        break;
                        
                        case FileType.DIRECTORY:
                            if (dir_map == null)
                                dir_map = new Gee.HashMap<File, FileInfo>(file_hash, file_equal);
                            
936
                            dir_map.set(dir.get_child(info.get_name()), info);
937 938 939 940 941 942 943 944 945 946 947
                        break;
                        
                        default:
                            // ignored
                        break;
                    }
                }
            }
        } catch (Error err2) {
            warning("Aborted directory traversal of %s: %s", dir.get_path(), err2.message);
            
948 949
            explore_directory_completed(in_discovery);
            
950 951 952 953 954 955 956 957 958 959 960 961 962 963
            return;
        }
        
        // report the local (caller-supplied) directory as discovered *before* reporting its files
        if (in_discovery)
            internal_notify_directory_discovered(dir, local_dir_info);
        else
            internal_notify_directory_created(dir, local_dir_info);
        
        // now with everything snarfed up and the directory reported as discovered, begin 
        // monitoring the directory
        add_monitor(dir, local_dir_info);
        
        // report files in local directory
964 965
        if (file_map != null)
            yield notify_directory_files(file_map, in_discovery);
966 967 968 969
        
        // post all the subdirectory traversals, allowing them to report themselves as discovered
        if (recurse && dir_map != null) {
            foreach (File subdir in dir_map.keys) {
970 971 972 973
                if (++outstanding_exploration_dirs > MAX_EXPLORATION_DIRS)
                    yield explore_async(subdir, dir_map.get(subdir), in_discovery);
                else
                    explore_async.begin(subdir, dir_map.get(subdir), in_discovery);
974 975 976
            }
        }
        
977 978 979
        explore_directory_completed(in_discovery);
    }
    
980 981 982 983 984 985 986 987 988 989 990 991 992
    private async void notify_directory_files(Gee.Map<File, FileInfo> map, bool in_discovery) {
        Gee.MapIterator<File, FileInfo> iter = map.map_iterator();
        while (iter.next()) {
            if (in_discovery)
                internal_notify_file_discovered(iter.get_key(), iter.get_value());
            else
                internal_notify_file_created(iter.get_key(), iter.get_value());
            
            Idle.add(notify_directory_files.callback, DEFAULT_PRIORITY);
            yield;
        }
    }
    
993 994 995
    // called whenever exploration of a directory is completed, to know when to signal that
    // discovery has ended
    private void explore_directory_completed(bool in_discovery) {
996 997 998 999 1000
        assert(outstanding_exploration_dirs > 0);
        outstanding_exploration_dirs--;
        
        if (in_discovery && outstanding_exploration_dirs == 0)
            notify_discovery_completed();
1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014
    }
    
    // Only submit directories ... file monitoring is wasteful when a single directory monitor can
    // do all the work.  Returns true if monitor added, false if already monitored (or not
    // monitoring, or unable to  monitor due to error).
    private bool add_monitor(File dir, FileInfo info) {
        if (!monitoring)
            return false;
        
        string? id = files.get_id(dir, info);
        if (id == null)
            return false;
        
        // if one already exists, nop
1015
        if (monitors.has_key(id))
1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063
            return false;
        
        FileMonitor monitor = null;
        try {
            monitor = dir.monitor_directory(FILE_MONITOR_FLAGS, null);
        } catch (Error err) {
            warning("Unable to monitor %s: %s", dir.get_path(), err.message);
            
            return false;
        }
        
        monitors.set(id, monitor);
        monitor.changed.connect(on_monitor_notification);
        
        mdbg("Added monitor for %s".printf(dir.get_path()));
        
        return true;
    }
    
    // Returns true if the directory is removed (i.e. was being monitored).
    private bool remove_monitor(File dir, FileInfo info) {
        if (!monitoring)
            return false;
        
        string? id = files.get_id(dir, info);
        if (id == null)
            return false;
        
        FileMonitor? monitor = monitors.get(id);
        if (monitor == null)
            return false;
        
        bool removed = monitors.unset(id);
        assert(removed);
        
        cancel_monitor(monitor);
        
        mdbg("Removed monitor for %s".printf(dir.get_path()));
        
        return true;
    }
    
    private void cancel_monitor(FileMonitor monitor) {
        monitor.changed.disconnect(on_monitor_notification);
        monitor.cancel();
    }
    
    private void on_monitor_notification(File file, File? other_file, FileMonitorEvent event) {
1064
        mdbg("NOTIFY %s: file=%s other_file=%s".printf(event.to_string(), file.get_path(),
1065 1066 1067 1068 1069 1070 1071 1072 1073
            other_file != null ? other_file.get_path() : "(none)"));
        
        // The problem: Having basic file information about each file is valuable (and necessary
        // in certain situations), but it is a blocking operation, no matter how "quick" it
        // may seem.  Async I/O is perfect to handle this, but it can complete out of order, and
        // it's highly desirous to report events in the same order they're received.  FileInfo
        // queries are queued up then and processed in order as they're completed.
        
        // Every event needs to be queued, but not all events generates query I/O
1074 1075
        QueryInfoQueueElement query_info = new QueryInfoQueueElement(this, file, other_file, event);
        query_info_queue.offer(query_info);
1076 1077 1078 1079
        
        switch (event) {
            case FileMonitorEvent.CREATED:
            case FileMonitorEvent.CHANGES_DONE_HINT:
1080
                file.query_info_async.begin(SUPPLIED_ATTRIBUTES, UNKNOWN_INFO_FLAGS,
1081 1082 1083 1084 1085 1086 1087 1088 1089
                    DEFAULT_PRIORITY, cancellable, query_info.on_completed);
            break;
            
            case FileMonitorEvent.DELETED:
                // don't complete it yet, it might be followed by a CREATED event indicating a
                // move ... instead, let it sit on the queue and allow the timer (or a coming
                // CREATED event) complete it
                if (delete_timer_id == 0)
                    delete_timer_id = Timeout.add(DELETED_EXPIRATION_MSEC / 2, check_for_expired_delete_events);
1090 1091 1092 1093 1094 1095
            break;
            
            case FileMonitorEvent.MOVED:
                // unlike the others, other_file is the destination of the move, and therefore the
                // one we need to get info on
                if (other_file != null) {
1096
                    other_file.query_info_async.begin(SUPPLIED_ATTRIBUTES, UNKNOWN_INFO_FLAGS,
1097
                        DEFAULT_PRIORITY, cancellable, query_info.on_completed);
1098 1099
                } else {
                    warning("Unable to process MOVED event: no other_file");
1100
                    query_info_queue.remove(query_info);
1101 1102 1103 1104 1105
                }
            break;
            
            default:
                // artifically complete it
1106 1107
                query_info.completed = true;
                process_query_queue(query_info);
1108 1109 1110 1111
            break;
        }
    }
    
1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145
    private void process_query_queue(QueryInfoQueueElement? query_info) {
        // if the completed element was a CREATE event, attempt to match it to a DELETE (which
        // then converts into a MOVED) and remove the CREATE event
        if (query_info != null && query_info.info != null && query_info.event == FileMonitorEvent.CREATED) {
            // if there's no match in the files table for this created file, then it can't be
            // matched to a previously deleted file
            File? match = files.find_match(query_info.info);
            if (match != null) {
                bool matched = false;
                foreach (QueryInfoQueueElement enqueued in query_info_queue) {
                    if (enqueued.event != FileMonitorEvent.DELETED
                        || enqueued.completed
                        || !match.equal(enqueued.file)) {
                        continue;
                    }
                    
                    mdbg("Matching CREATED %s to DELETED %s for MOVED".printf(query_info.file.get_path(),
                        enqueued.file.get_path()));
                    
                    enqueued.event = FileMonitorEvent.MOVED;
                    enqueued.other_file = query_info.file;
                    enqueued.info = query_info.info;
                    enqueued.completed = true;
                    
                    matched = true;
                    
                    break;
                }
                
                if (matched)
                    query_info_queue.remove(query_info);
            }
        }
        
1146 1147 1148 1149 1150 1151 1152 1153
        // peel off completed events from the queue in order
        for (;;) {
            // check if empty or waiting for completion on the next event
            QueryInfoQueueElement? next = query_info_queue.peek();
            if (next == null || !next.completed)
                break;
            
            // remove
1154 1155
            QueryInfoQueueElement? n = query_info_queue.poll();
            assert(next == n);
1156 1157 1158 1159 1160
            
            mdbg("Completed info query %u for %s on %s".printf(next.position, next.event.to_string(),
                next.file.get_path()));
            
            if (next.err != null) {
1161 1162
                mdbg("Unable to retrieve file information for %s, dropping %s: %s".printf(
                    next.file.get_path(), next.event.to_string(), next.err.message));
1163 1164 1165 1166
                
                continue;
            }
            
1167 1168 1169 1170 1171 1172 1173 1174
            // Directory monitoring requires file ID.  No ID, no ride!
            if (next.info != null && get_file_info_id(next.info) == null) {
                mdbg("Unable to retrieve file ID for %s, dropping %s".printf(next.file.get_path(),
                    next.event.to_string()));
                
                continue;
            }
            
1175 1176 1177 1178 1179 1180 1181 1182
            // watch for symlink support
            if (next.info != null && !is_file_symlink_supported(next.info)) {
                mdbg("No symlink support for %s, dropping %s".printf(next.file.get_path(),
                    next.event.to_string()));
                
                continue;
            }
            
1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205
            on_monitor_notification_ready(next.file, next.other_file, next.info, next.event);
        }
    }
    
    private void on_monitor_notification_ready(File file, File? other_file, FileInfo? info,
        FileMonitorEvent event) {
        mdbg("READY %s: file=%s other_file=%s".printf(event.to_string(), file.get_path(),
            other_file != null ? other_file.get_path() : "(null)"));
        
        // Nasty, nasty switches-in-a-switch construct, but this demuxes the possibilities into
        // easily digestible upcalls and signals
        switch (event) {
            case FileMonitorEvent.CREATED:
                assert(info != null);
                
                FType ftype = get_ftype(info);
                switch (ftype) {
                    case FType.FILE:
                        internal_notify_file_created(file, info);
                    break;
                    
                    case FType.DIRECTORY:
                        // other files may have been created under this new directory before we have
1206
                        // a chance to register a monitor, so scan it now looking for new additions
1207 1208
                        // (this call will notify of creation and monitor this new directory once 
                        // it's been scanned)
1209
                        outstanding_exploration_dirs++;
1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224
                        explore_async.begin(file, info, false);
                    break;
                    
                    default:
                        assert(ftype == FType.UNSUPPORTED);
                    break;
                }
            break;
            
            case FileMonitorEvent.CHANGED:
                // don't query info for each change, but only when done hint comes down the pipe
                assert(info == null);
                
                FileInfo local_info = get_file_info(file);
                if (local_info == null) {
1225
                    mdbg("Changed event for unknown file %s".printf(file.get_path()));
1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321
                    
                    break;
                }
                
                FType ftype = get_ftype(local_info);
                switch (ftype) {
                    case FType.FILE:
                        notify_file_altered(file);
                    break;
                    
                    case FType.DIRECTORY:
                        notify_directory_altered(file);
                    break;
                    
                    default:
                        assert(ftype == FType.UNSUPPORTED);
                    break;
                }
            break;
            
            case FileMonitorEvent.CHANGES_DONE_HINT:
                assert(info != null);
                
                FType ftype = get_ftype(info);
                switch (ftype) {
                    case FType.FILE:
                        internal_notify_file_alteration_completed(file, info);
                    break;
                    
                    case FType.DIRECTORY:
                        internal_notify_directory_alteration_completed(file, info);
                    break;
                    
                    default:
                        assert(ftype == FType.UNSUPPORTED);
                    break;
                }
            break;
            
            case FileMonitorEvent.MOVED:
                assert(info != null);
                assert(other_file != null);
                
                // in the moved case, file info is for other file (the destination in the move
                // operation)
                FType ftype = get_ftype(info);
                switch (ftype) {
                    case FType.FILE:
                        internal_notify_file_moved(file, other_file, info);
                    break;
                    
                    case FType.DIRECTORY:
                        // get the old FileInfo (contained in files)
                        FileInfo? old_dir_info = files.get_info(file);
                        if (old_dir_info == null) {
                            warning("Directory moved event for unknown file %s", file.get_path());
                            
                            break;
                        }
                        
                        internal_notify_directory_moved(file, old_dir_info, other_file, info);
                    break;
                    
                    default:
                        assert(ftype == FType.UNSUPPORTED);
                    break;
                }
            break;
            
            case FileMonitorEvent.DELETED:
                assert(info == null);
                
                FileInfo local_info = get_file_info(file);
                if (local_info == null) {
                    warning("Deleted event for unknown file %s", file.get_path());
                    
                    break;
                }
                
                FType ftype = get_ftype(local_info);
                switch (ftype) {
                    case FType.FILE:
                        internal_notify_file_deleted(file);
                    break;
                    
                    case FType.DIRECTORY:
                        internal_notify_directory_deleted(file);
                    break;
                    
                    default:
                        assert(ftype == FType.UNSUPPORTED);
                    break;
                }
            break;
            
            case FileMonitorEvent.ATTRIBUTE_CHANGED:
1322 1323
                // doesn't fetch attributes until CHANGES_DONE_HINT comes down the pipe
                assert(info == null);
1324
                
1325 1326 1327 1328 1329 1330 1331 1332
                FileInfo local_info = get_file_info(file);
                if (local_info == null) {
                    warning("Attribute changed event for unknown file %s", file.get_path());
                    
                    break;
                }
                
                FType ftype = get_ftype(local_info);
1333 1334
                switch (ftype) {
                    case FType.FILE:
1335
                        notify_file_attributes_altered(file);
1336 1337 1338
                    break;
                    
                    case FType.DIRECTORY:
1339
                        notify_directory_attributes_altered(file);
1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373
                    break;
                    
                    default:
                        assert(ftype == FType.UNSUPPORTED);
                    break;
                }
            break;
            
            case FileMonitorEvent.PRE_UNMOUNT:
            case FileMonitorEvent.UNMOUNTED:
                // not currently handling these events
            break;
            
            default:
                warning("Unknown directory monitor event %s", event.to_string());
            break;
        }
    }
    
    // Returns true if a move occurred.  Internal state is modified to recognize the
    // situation (i.e. the move should be reported).
    private bool is_file_create_move(File file, FileInfo info, out File old_file,
        out FileInfo old_file_info) {
        // look for created file whose parent was actually moved
        File? match = parent_moved.find_match(info);
        if (match != null) {
            old_file = match;
            old_file_info = parent_moved.get_info(match);
            
            parent_moved.remove(match, info);
            
            return true;
        }
        
1374 1375 1376
        old_file = null;
        old_file_info = null;
        
1377 1378 1379
        return false;
    }
    
1380 1381 1382 1383 1384 1385 1386 1387
    private bool check_for_expired_delete_events() {
        ulong expiration = now_ms() - DELETED_EXPIRATION_MSEC;
        
        bool any_deleted = false;
        bool any_expired = false;
        foreach (QueryInfoQueueElement element in query_info_queue) {
            if (element.event != FileMonitorEvent.DELETED)
                continue;
1388
            
1389
            any_deleted = true;
1390
            
1391 1392 1393 1394 1395 1396
            if (element.time_created_msec > expiration)
                continue;
            
            // synthesize the completion
            element.completed = true;
            any_expired = true;
1397 1398
        }
        
1399 1400
        if (any_expired)
            process_query_queue(null);
1401
        
1402 1403
        if (!any_deleted)
            delete_timer_id = 0;
1404
        
1405
        return any_deleted;
1406 1407 1408 1409 1410 1411 1412
    }
    
    // This method does its best to return FileInfo for the file.  It performs no I/O.
    public FileInfo? get_file_info(File file) {
        return files.get_info(file);
    }
    
1413 1414 1415 1416 1417 1418
    // This method returns all files and directories that the DirectoryMonitor knows of.  This
    // call is only useful when runtime monitoring is enabled.  It performs no I/O.
    public Gee.Collection<File> get_files() {
        return files.get_all();
    }
    
1419 1420 1421 1422 1423 1424
    // This method will attempt to find the in-memory FileInfo for the file, but if it cannot
    // be found it will query the file for it's ID and obtain in-memory file information from
    // there.
    public FileInfo? query_file_info(File file) {
        return files.query_info(file, cancellable);
    }
1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450
    
    // This checks if the FileInfo is for a symlinked file/directory and if symlinks for the file
    // type are supported by DirectoryMonitor.  Note that this requires the FileInfo have support
    // for the "standard::is-symlink" and "standard::type" file attributes, which SUPPLIED_ATTRIBUTES
    // provides.
    //
    // Returns true if the file is not a symlink or if symlinks are supported for the file type,
    // false otherwise.  If an unsupported file type, returns false.
    public static bool is_file_symlink_supported(FileInfo info) {
        if (!info.get_is_symlink())
            return true;
        
        FType ftype = get_ftype(info);
        switch (ftype) {
            case FType.DIRECTORY:
                return SUPPORT_DIR_SYMLINKS;
            
            case FType.FILE:
                return SUPPORT_FILE_SYMLINKS;
            
            default:
                assert(ftype == FType.UNSUPPORTED);
                
                return false;
        }
    }
1451 1452
}