/* Copyright 2016 Software Freedom Conservancy Inc.
 *
 * This software is licensed under the GNU Lesser General Public License
 * (version 2.1 or later).  See the COPYING file in this distribution.
 */

public class Sidebar.Tree : Gtk.TreeView {
    public const int ICON_SIZE = 16;
    
    // Only one ExternalDropHandler can be registered with the Tree; it's responsible for completing
    // the "drag-data-received" signal properly.
    public delegate void ExternalDropHandler(Gdk.DragContext context, Sidebar.Entry? entry,
        Gtk.SelectionData data, uint info, uint time);
    
    private class EntryWrapper : Object {
        public Sidebar.Entry entry;
        public Gtk.TreeRowReference row;
        
        public EntryWrapper(Gtk.TreeModel model, Sidebar.Entry entry, Gtk.TreePath path) {
            this.entry = entry;
            this.row = new Gtk.TreeRowReference(model, path);
        }
        
        public Gtk.TreePath get_path() {
            return row.get_path();
        }
        
        public Gtk.TreeIter get_iter() {
            Gtk.TreeIter iter;
            bool valid = row.get_model().get_iter(out iter, get_path());
            assert(valid);
            
            return iter;
        }
    }
    
    private class RootWrapper : EntryWrapper {
        public int root_position;
        
        public RootWrapper(Gtk.TreeModel model, Sidebar.Entry entry, Gtk.TreePath path, int root_position) {
            base (model, entry, path);
            
            this.root_position = root_position;
        }
    }
    
    private enum Columns {
        NAME,
        TOOLTIP,
        WRAPPER,
        ICON,
        N_COLUMNS
    }
    
    private Gtk.TreeStore store = new Gtk.TreeStore(Columns.N_COLUMNS,
        typeof (string),            // NAME
        typeof (string?),           // TOOLTIP
        typeof (EntryWrapper),      // WRAPPER
        typeof (string?)            // ICON
    );
    
    private Gtk.UIManager ui = new Gtk.UIManager();
    private Gtk.CellRendererText text_renderer;
    private unowned ExternalDropHandler drop_handler;
    private Gtk.Entry? text_entry = null;
    private Gee.HashMap<Sidebar.Entry, EntryWrapper> entry_map =
        new Gee.HashMap<Sidebar.Entry, EntryWrapper>();
    private Gee.HashMap<Sidebar.Branch, int> branches = new Gee.HashMap<Sidebar.Branch, int>();
    private int editing_disabled = 0;
    private bool mask_entry_selected_signal = false;
    private weak EntryWrapper? selected_wrapper = null;
    private Gtk.Menu? default_context_menu = null;
    private bool expander_called_manually = false;
    private int expander_special_count = 0;
    private bool is_internal_drag_in_progress = false;
    private Sidebar.Entry? internal_drag_source_entry = null;
    private Gtk.TreeRowReference? old_path_ref = null;
    
    public signal void entry_selected(Sidebar.SelectableEntry selectable);
    
    public signal void selected_entry_removed(Sidebar.SelectableEntry removed);
    
    public signal void branch_added(Sidebar.Branch branch);
    
    public signal void branch_removed(Sidebar.Branch branch);
    
    public signal void branch_shown(Sidebar.Branch branch, bool shown);
    
    public signal void page_created(Sidebar.PageRepresentative entry, Page page);
    
    public signal void destroying_page(Sidebar.PageRepresentative entry, Page page);
    
    public Tree(Gtk.TargetEntry[] target_entries, Gdk.DragAction actions,
        ExternalDropHandler drop_handler) {
        set_model(store);
        get_style_context().add_class("sidebar");
        
        Gtk.TreeViewColumn text_column = new Gtk.TreeViewColumn();
        text_column.set_expand(true);
        Gtk.CellRendererPixbuf icon_renderer = new Gtk.CellRendererPixbuf();
        icon_renderer.follow_state = true;
        text_column.pack_start(icon_renderer, false);
        text_column.add_attribute(icon_renderer, "icon_name", Columns.ICON);
        text_column.set_cell_data_func(icon_renderer, icon_renderer_function);
        text_renderer = new Gtk.CellRendererText();
        text_renderer.ellipsize = Pango.EllipsizeMode.END;
        text_renderer.editing_canceled.connect(on_editing_canceled);
        text_renderer.editing_started.connect(on_editing_started);
        text_column.pack_start(text_renderer, true);
        text_column.add_attribute(text_renderer, "markup", Columns.NAME);
        append_column(text_column);
        
        Gtk.CellRendererText invisitext = new Gtk.CellRendererText();
        Gtk.TreeViewColumn page_holder = new Gtk.TreeViewColumn();
        page_holder.pack_start(invisitext, true);
        page_holder.visible = false;
        append_column(page_holder);
        
        set_headers_visible(false);
        set_enable_search(false);
        set_rules_hint(false);
        set_show_expanders(true);
        set_reorderable(false);
        set_enable_tree_lines(false);
        set_grid_lines(Gtk.TreeViewGridLines.NONE);
        set_tooltip_column(Columns.TOOLTIP);
        
        Gtk.TreeSelection selection = get_selection();
        selection.set_mode(Gtk.SelectionMode.BROWSE);
        selection.set_select_function(on_selection);
        
        test_expand_row.connect(on_toggle_row);
        test_collapse_row.connect(on_toggle_row);
        
        // It Would Be Nice if the target entries and actions were gleaned by querying each 
        // Sidebar.Entry as it was added, but that's a tad too complicated for our needs
        // currently
        enable_model_drag_dest(target_entries, actions);

        Gtk.TargetEntry[] source_entries = new Gtk.TargetEntry[0];
        source_entries += target_entries[LibraryWindow.TargetType.TAG_PATH];
        enable_model_drag_source(Gdk.ModifierType.BUTTON1_MASK, source_entries,
            Gdk.DragAction.COPY);

        this.drop_handler = drop_handler;
        
        popup_menu.connect(on_context_menu_keypress);
        
        setup_default_context_menu();
        
        drag_begin.connect(on_drag_begin);
        drag_end.connect(on_drag_end);
        drag_motion.connect(on_drag_motion);
    }
    
    ~Tree() {
        text_renderer.editing_canceled.disconnect(on_editing_canceled);
        text_renderer.editing_started.disconnect(on_editing_started);
    }
    
    public void icon_renderer_function(Gtk.CellLayout layout, Gtk.CellRenderer renderer, Gtk.TreeModel model, Gtk.TreeIter iter) {
        EntryWrapper? wrapper = get_wrapper_at_iter(iter);
        if (wrapper == null) {
            return;
        }
        renderer.visible = !(wrapper.entry is Sidebar.Header);
    }
    
    private void on_drag_begin(Gdk.DragContext ctx) {
        is_internal_drag_in_progress = true;
    }
    
    private void on_drag_end(Gdk.DragContext ctx) {
        is_internal_drag_in_progress = false;
        internal_drag_source_entry = null;
    }
    
    private bool on_drag_motion (Gdk.DragContext context, int x, int y, uint time_) {
        if (is_internal_drag_in_progress && internal_drag_source_entry == null) {
            Gtk.TreePath? path;
            Gtk.TreeViewDropPosition position;
            get_dest_row_at_pos(x, y, out path, out position);
            
            if (path != null) {
                EntryWrapper wrapper = get_wrapper_at_path(path);
                if (wrapper != null)
                    internal_drag_source_entry = wrapper.entry;
            }
        }
        
        return false;
    }
    
    private void setup_default_context_menu() {
        Gtk.ActionGroup group = new Gtk.ActionGroup("SidebarDefault");
        Gtk.ActionEntry[] actions = new Gtk.ActionEntry[0];
        
        Gtk.ActionEntry new_search = { "CommonNewSearch", null, TRANSLATABLE, null, null, on_new_search };
        new_search.label = _("Ne_w Saved Search...");
        actions += new_search;

        Gtk.ActionEntry new_tag = { "CommonNewTag", null, TRANSLATABLE, null, null, on_new_tag };
        new_tag.label = _("New _Tag...");
        actions += new_tag;
        
        group.add_actions(actions, this);
        ui.insert_action_group(group, 0);
        
        File ui_file = Resources.get_ui("sidebar_default_context.ui");
        try {
            ui.add_ui_from_file(ui_file.get_path());
        } catch (Error err) {
            AppWindow.error_message("Error loading UI file %s: %s".printf(
                ui_file.get_path(), err.message));
            Application.get_instance().panic();
        }
        default_context_menu = (Gtk.Menu) ui.get_widget("/SidebarDefaultContextMenu");
        
        ui.ensure_update();
    }
    
    private bool has_wrapper(Sidebar.Entry entry) {
        return entry_map.has_key(entry);
    }
    
    private EntryWrapper? get_wrapper(Sidebar.Entry entry) {
        EntryWrapper? wrapper = entry_map.get(entry);
        if (wrapper == null)
            warning("Entry %s not found in sidebar", entry.to_string());
        
        return wrapper;
    }
    
    private EntryWrapper? get_wrapper_at_iter(Gtk.TreeIter iter) {
        Value val;
        store.get_value(iter, Columns.WRAPPER, out val);
        
        EntryWrapper? wrapper = (EntryWrapper?) val;
        if (wrapper == null)
            message("No entry found in sidebar at %s", store.get_path(iter).to_string());
        
        return wrapper;
    }
    
    private EntryWrapper? get_wrapper_at_path(Gtk.TreePath path) {
        Gtk.TreeIter iter;
        if (!store.get_iter(out iter, path)) {
            message("No entry found in sidebar at %s", path.to_string());
            
            return null;
        }
        
        return get_wrapper_at_iter(iter);
    }
    
    // Note that this method will result in the "entry-selected" signal to fire if mask_signal
    // is set to false.
    public bool place_cursor(Sidebar.Entry entry, bool mask_signal) {
        if (!expand_to_entry(entry))
            return false;
        
        EntryWrapper? wrapper = get_wrapper(entry);
        if (wrapper == null)
            return false;
        
        get_selection().select_path(wrapper.get_path());
        
        mask_entry_selected_signal = mask_signal;
        set_cursor(wrapper.get_path(), null, false);
        mask_entry_selected_signal = false;
        
        return scroll_to_entry(entry);
    }
    
    public bool is_selected(Sidebar.Entry entry) {
        EntryWrapper? wrapper = get_wrapper(entry);
        
        // Even though get_selection() does not report its return type as nullable, it can be null
        // if the window has been destroyed.
        Gtk.TreeSelection selection = get_selection();
        if (selection == null)
            return false;
        
        return (wrapper != null) ? selection.path_is_selected(wrapper.get_path()) : false;
    }
    
    public bool is_any_selected() {
        return get_selection().count_selected_rows() != 0;
    }

    private Gtk.TreePath? get_selected_path() {
        Gtk.TreeModel model;
        Gtk.TreeSelection? selection = get_selection();
        if (selection == null){
            return null;
        }
        GLib.List<Gtk.TreePath> rows = selection.get_selected_rows(out model);
        assert(rows.length() == 0 || rows.length() == 1);

        return rows.length() != 0 ? rows.nth_data(0) : null;
    }

    private string get_name_for_entry(Sidebar.Entry entry) {
        string name = guarded_markup_escape_text(entry.get_sidebar_name());
        
        Sidebar.EmphasizableEntry? emphasizable_entry = entry as Sidebar.EmphasizableEntry;
        if (emphasizable_entry != null && emphasizable_entry.is_emphasized())
            name = "<b>%s</b>".printf(name);
        
        return name;
    }
    
    public virtual bool accept_cursor_changed() {
        return true;
    }
    
    public override void cursor_changed() {
        Gtk.TreePath? path = get_selected_path();
        if (path == null) {
            if (base.cursor_changed != null)
                base.cursor_changed();
            return;
        }
        
        EntryWrapper? wrapper = get_wrapper_at_path(path);
        
        if (selected_wrapper != wrapper) {
            EntryWrapper old_wrapper = selected_wrapper;
            selected_wrapper = wrapper;
            
            if (editing_disabled == 0 && wrapper != null && wrapper.entry is Sidebar.RenameableEntry)
                text_renderer.editable = ((Sidebar.RenameableEntry) wrapper.entry).is_user_renameable();
            
            if (wrapper != null && !mask_entry_selected_signal) {
                Sidebar.SelectableEntry? selectable = wrapper.entry as Sidebar.SelectableEntry;
                if (selectable != null) {
                    if (accept_cursor_changed()) {
                        entry_selected(selectable);
                    } else {
                        place_cursor(old_wrapper.entry, true);
                    }
                }
            }
        }
        
        if (base.cursor_changed != null)
            base.cursor_changed();
    }
    
    public void disable_editing() {
        if (editing_disabled++ == 0)
            text_renderer.editable = false;
    }
    
    public void enable_editing() {
        Gtk.TreePath? path = get_selected_path();
        if (path != null && editing_disabled > 0 && --editing_disabled == 0) {
            EntryWrapper? wrapper = get_wrapper_at_path(path);
            if (wrapper != null && (wrapper.entry is Sidebar.RenameableEntry))
                text_renderer.editable = ((Sidebar.RenameableEntry) wrapper.entry).
                    is_user_renameable();
        }
    }
    
    public void toggle_branch_expansion(Gtk.TreePath path, bool expand_all) {
        expander_called_manually = true;
        if (is_row_expanded(path))
            collapse_row(path);
        else
            expand_row(path, expand_all);
    }
    
    public bool expand_to_entry(Sidebar.Entry entry) {
        expander_called_manually = true;
        EntryWrapper? wrapper = get_wrapper(entry);
        if (wrapper == null)
            return false;
        
        expand_to_path(wrapper.get_path());
        
        return true;
    }
    
    public void expand_to_first_child(Sidebar.Entry entry) {
        expander_called_manually = true;
        EntryWrapper? wrapper = get_wrapper(entry);
        if (wrapper == null)
            return;
        
        Gtk.TreePath path = wrapper.get_path();
        
        Gtk.TreeIter iter;
        while (store.get_iter(out iter, path)) {
            if (!store.iter_has_child(iter))
                break;
            
            path.down();
        }
        
        expand_to_path(path);
    }
    
    public void graft(Sidebar.Branch branch, int position) requires (position >= 0) {
        assert(!branches.has_key(branch));
        
        branches.set(branch, position);
        
        if (branch.get_show_branch()) {
            associate_branch(branch);
            
            if (branch.is_startup_expand_to_first_child())
                expand_to_first_child(branch.get_root());

            if (branch.is_startup_open_grouping())
                expand_to_entry(branch.get_root());
        }
        
        branch.entry_added.connect(on_branch_entry_added);
        branch.entry_removed.connect(on_branch_entry_removed);
        branch.entry_moved.connect(on_branch_entry_moved);
        branch.entry_reparented.connect(on_branch_entry_reparented);
        branch.children_reordered.connect(on_branch_children_reordered);
        branch.show_branch.connect(on_show_branch);
        
        branch_added(branch);
    }
    
    // This is used to associate a known branch with the TreeView.
    private void associate_branch(Sidebar.Branch branch) {
        assert(branches.has_key(branch));
        
        int position = branches.get(branch);
        
        Gtk.TreeIter? insertion_iter = null;
        
        // search current roots for insertion point
        Gtk.TreeIter iter;
        bool found = store.get_iter_first(out iter);
        while (found) {
            RootWrapper? root_wrapper = get_wrapper_at_iter(iter) as RootWrapper;
            assert(root_wrapper != null);
            
            if (position < root_wrapper.root_position) {
                store.insert_before(out insertion_iter, null, iter);
                
                break;
            }
            
            found = store.iter_next(ref iter);
        }
        
        // if not found, append
        if (insertion_iter == null)
            store.append(out insertion_iter, null);
        
        associate_wrapper(insertion_iter,
            new RootWrapper(store, branch.get_root(), store.get_path(insertion_iter), position));
        
        // mirror the branch's initial contents from below the root down, let the signals handle
        // future work
        associate_children(branch, branch.get_root(), insertion_iter);
    }
    
    private void associate_children(Sidebar.Branch branch, Sidebar.Entry parent,
        Gtk.TreeIter parent_iter) {
        Gee.List<Sidebar.Entry>? children = branch.get_children(parent);
        if (children == null)
            return;
        
        foreach (Sidebar.Entry child in children) {
            Gtk.TreeIter append_iter;
            store.append(out append_iter, parent_iter);
            
            associate_entry(append_iter, child);
            associate_children(branch, child, append_iter);
        }
    }
    
    private void associate_entry(Gtk.TreeIter assoc_iter, Sidebar.Entry entry) {
        associate_wrapper(assoc_iter, new EntryWrapper(store, entry, store.get_path(assoc_iter)));
    }
    
    private void associate_wrapper(Gtk.TreeIter assoc_iter, EntryWrapper wrapper) {
        Sidebar.Entry entry = wrapper.entry;
        
        assert(!entry_map.has_key(entry));
        entry_map.set(entry, wrapper);
        
        store.set(assoc_iter, Columns.NAME, get_name_for_entry(entry));
        store.set(assoc_iter, Columns.TOOLTIP, guarded_markup_escape_text(entry.get_sidebar_tooltip()));
        store.set(assoc_iter, Columns.WRAPPER, wrapper);
        load_entry_icons(assoc_iter);
        
        entry.sidebar_tooltip_changed.connect(on_sidebar_tooltip_changed);
        entry.sidebar_icon_changed.connect(on_sidebar_icon_changed);
        
        Sidebar.PageRepresentative? pageable = entry as Sidebar.PageRepresentative;
        if (pageable != null) {
            pageable.page_created.connect(on_sidebar_page_created);
            pageable.destroying_page.connect(on_sidebar_destroying_page);
        }

        Sidebar.EmphasizableEntry? emphasizable = entry as Sidebar.EmphasizableEntry;
        if (emphasizable != null)
            emphasizable.is_emphasized_changed.connect(on_is_emphasized_changed);
        
        Sidebar.RenameableEntry? renameable = entry as Sidebar.RenameableEntry;
        if (renameable != null)
            renameable.sidebar_name_changed.connect(on_sidebar_name_changed);
                
        entry.grafted(this);
    }
    
    private EntryWrapper reparent_wrapper(Gtk.TreeIter new_iter, EntryWrapper current_wrapper) {
        Sidebar.Entry entry = current_wrapper.entry;
        
        bool removed = entry_map.unset(entry);
        assert(removed);
        
        EntryWrapper new_wrapper = new EntryWrapper(store, entry, store.get_path(new_iter));
        entry_map.set(entry, new_wrapper);
        
        store.set(new_iter, Columns.NAME, get_name_for_entry(entry));
        store.set(new_iter, Columns.TOOLTIP, guarded_markup_escape_text(entry.get_sidebar_tooltip()));
        store.set(new_iter, Columns.WRAPPER, new_wrapper);
        load_entry_icons(new_iter);
        
        return new_wrapper;
    }
    
    public void prune(Sidebar.Branch branch) {
        assert(branches.has_key(branch));
        
        if (has_wrapper(branch.get_root()))
            disassociate_branch(branch);
        
        branch.entry_added.disconnect(on_branch_entry_added);
        branch.entry_removed.disconnect(on_branch_entry_removed);
        branch.entry_moved.disconnect(on_branch_entry_moved);
        branch.entry_reparented.disconnect(on_branch_entry_reparented);
        branch.children_reordered.disconnect(on_branch_children_reordered);
        branch.show_branch.disconnect(on_show_branch);
        
        bool removed = branches.unset(branch);
        assert(removed);
        
        branch_removed(branch);
    }
    
    private void disassociate_branch(Sidebar.Branch branch) {
        RootWrapper? root_wrapper = get_wrapper(branch.get_root()) as RootWrapper;
        assert(root_wrapper != null);
        
        disassociate_wrapper_and_signal(root_wrapper, false);
    }
    
    // A wrapper for disassociate_wrapper() (?!?) that fires the "selected-entry-removed" signal if
    // condition exists
    private void disassociate_wrapper_and_signal(EntryWrapper wrapper, bool only_children) {
        bool selected = is_selected(wrapper.entry);
        
        disassociate_wrapper(wrapper, only_children);
        
        if (selected) {
            Sidebar.SelectableEntry? selectable = wrapper.entry as Sidebar.SelectableEntry;
            assert(selectable != null);
            
            selected_entry_removed(selectable);
        }
    }
    
    private void disassociate_wrapper(EntryWrapper wrapper, bool only_children) {
        Gee.ArrayList<EntryWrapper> children = new Gee.ArrayList<EntryWrapper>();
        
        Gtk.TreeIter child_iter;
        bool found = store.iter_children(out child_iter, wrapper.get_iter());
        while (found) {
            EntryWrapper? child_wrapper = get_wrapper_at_iter(child_iter);
            assert(child_wrapper != null);
            
            children.add(child_wrapper);
            
            found = store.iter_next(ref child_iter);
        }
        
        foreach (EntryWrapper child_wrapper in children)
            disassociate_wrapper(child_wrapper, false);
        
        if (only_children)
            return;
        
        Gtk.TreeIter iter = wrapper.get_iter();
        store.remove(ref iter);
        
        if (selected_wrapper == wrapper)
            selected_wrapper = null;
        
        Sidebar.Entry entry = wrapper.entry;
        
        entry.pruned(this);
        
        entry.sidebar_tooltip_changed.disconnect(on_sidebar_tooltip_changed);
        entry.sidebar_icon_changed.disconnect(on_sidebar_icon_changed);
        
        Sidebar.PageRepresentative? pageable = entry as Sidebar.PageRepresentative;
        if (pageable != null) {
            pageable.page_created.disconnect(on_sidebar_page_created);
            pageable.destroying_page.disconnect(on_sidebar_destroying_page);
        }
        
        Sidebar.RenameableEntry? renameable = entry as Sidebar.RenameableEntry;
        if (renameable != null)
            renameable.sidebar_name_changed.disconnect(on_sidebar_name_changed);
        
        Sidebar.EmphasizableEntry? emphasizable = entry as Sidebar.EmphasizableEntry;
        if (emphasizable != null)
            emphasizable.is_emphasized_changed.disconnect(on_is_emphasized_changed);
        
        bool removed = entry_map.unset(entry);
        assert(removed);
    }
    
    private void on_branch_entry_added(Sidebar.Branch branch, Sidebar.Entry entry) {
        Sidebar.Entry? parent = branch.get_parent(entry);
        assert(parent != null);
        
        EntryWrapper? parent_wrapper = get_wrapper(parent);
        assert(parent_wrapper != null);
        
        Gtk.TreeIter insertion_iter;
        Sidebar.Entry? next = branch.get_next_sibling(entry);
        if (next != null) {
            EntryWrapper next_wrapper = get_wrapper(next);
            
            // insert before the next sibling in this branch level
            store.insert_before(out insertion_iter, parent_wrapper.get_iter(), next_wrapper.get_iter());
        } else {
            // append to the bottom of this branch level
            store.append(out insertion_iter, parent_wrapper.get_iter());
        }
        
        associate_entry(insertion_iter, entry);
        associate_children(branch, entry, insertion_iter);
        
        if (branch.is_auto_open_on_new_child())
            expand_to_entry(entry);
    }
    
    private void on_branch_entry_removed(Sidebar.Branch branch, Sidebar.Entry entry) {
        EntryWrapper? wrapper = get_wrapper(entry);
        assert(wrapper != null);
        assert(!(wrapper is RootWrapper));
        
        disassociate_wrapper_and_signal(wrapper, false);
    }
    
    private void on_branch_entry_moved(Sidebar.Branch branch, Sidebar.Entry entry) {
        EntryWrapper? wrapper = get_wrapper(entry);
        assert(wrapper != null);
        assert(!(wrapper is RootWrapper));
        
        // null means entry is now at the top of the sibling list
        Gtk.TreeIter? prev_iter = null;
        Sidebar.Entry? prev = branch.get_previous_sibling(entry);
        if (prev != null) {
            EntryWrapper? prev_wrapper = get_wrapper(prev);
            assert(prev_wrapper != null);
            
            prev_iter = prev_wrapper.get_iter();
        }
        
        Gtk.TreeIter entry_iter = wrapper.get_iter();
        store.move_after(ref entry_iter, prev_iter);
    }
    
    private void on_branch_entry_reparented(Sidebar.Branch branch, Sidebar.Entry entry,
        Sidebar.Entry old_parent) {
        EntryWrapper? wrapper = get_wrapper(entry);
        assert(wrapper != null);
        assert(!(wrapper is RootWrapper));
        
        bool selected = (get_current_path().compare(wrapper.get_path()) == 0);
        
        // remove from current position in tree
        Gtk.TreeIter iter = wrapper.get_iter();
        store.remove(ref iter);
        
        Sidebar.Entry? parent = branch.get_parent(entry);
        assert(parent != null);
        
        EntryWrapper? parent_wrapper = get_wrapper(parent);
        assert(parent_wrapper != null);
        
        // null means entry is now at the top of the sibling list
        Gtk.TreeIter? prev_iter = null;
        Sidebar.Entry? prev = branch.get_previous_sibling(entry);
        if (prev != null) {
            EntryWrapper? prev_wrapper = get_wrapper(prev);
            assert(prev_wrapper != null);
            
            prev_iter = prev_wrapper.get_iter();
        }
        
        Gtk.TreeIter new_iter;
        store.insert_after(out new_iter, parent_wrapper.get_iter(), prev_iter);
        
        EntryWrapper new_wrapper = reparent_wrapper(new_iter, wrapper);
        
        if (selected) {
            expand_to_entry(new_wrapper.entry);
            place_cursor(new_wrapper.entry, false);
        }
    }
    
    private void on_branch_children_reordered(Sidebar.Branch branch, Sidebar.Entry entry) {
        Gee.List<Sidebar.Entry>? children = branch.get_children(entry);
        if (children == null)
            return;
        
        // This works by moving the entries to the bottom of the tree's list in the order they
        // are presented in the Sidebar.Branch list.
        foreach (Sidebar.Entry child in children) {
            EntryWrapper? child_wrapper = get_wrapper(child);
            assert(child_wrapper != null);
            
            Gtk.TreeIter child_iter = child_wrapper.get_iter();
            store.move_before(ref child_iter, null);
        }
    }
    
    private void on_show_branch(Sidebar.Branch branch, bool shown) {
        if (shown)
            associate_branch(branch);
        else
            disassociate_branch(branch);
        
        branch_shown(branch, shown);
    }
    
    private void on_sidebar_tooltip_changed(Sidebar.Entry entry, string? tooltip) {
        EntryWrapper? wrapper = get_wrapper(entry);
        assert(wrapper != null);
        
        store.set(wrapper.get_iter(), Columns.TOOLTIP, guarded_markup_escape_text(tooltip));
    }
    
    private void on_sidebar_icon_changed(Sidebar.Entry entry, string? icon) {
        EntryWrapper? wrapper = get_wrapper(entry);
        assert(wrapper != null);
        
        store.set(wrapper.get_iter(), Columns.ICON, icon);
    }

    private void rename_entry(Sidebar.Entry entry) {
        EntryWrapper? wrapper = get_wrapper(entry);
        assert(wrapper != null);
        
        store.set(wrapper.get_iter(), Columns.NAME, get_name_for_entry(entry));
    }
    
    private void on_sidebar_name_changed(Sidebar.Entry entry, string name) {
        rename_entry(entry);
    }
    
    private void on_sidebar_page_created(Sidebar.PageRepresentative entry, Page page) {
        page_created(entry, page);
    }
    
    private void on_is_emphasized_changed(Sidebar.EmphasizableEntry entry, bool is_emphasized) {
        rename_entry(entry);
    }
    
    private void on_sidebar_destroying_page(Sidebar.PageRepresentative entry, Page page) {
        destroying_page(entry, page);
    }
    
    private void load_entry_icons(Gtk.TreeIter iter) {
        EntryWrapper? wrapper = get_wrapper_at_iter(iter);
        if (wrapper == null)
            return;
        string? icon = wrapper.entry.get_sidebar_icon();
        store.set(iter, Columns.ICON, icon);
    }
    
    private void load_branch_icons(Gtk.TreeIter iter) {
        load_entry_icons(iter);
        
        Gtk.TreeIter child_iter;
        if (store.iter_children(out child_iter, iter)) {
            do {
                load_branch_icons(child_iter);
            } while (store.iter_next(ref child_iter));
        }
    }
    
    private bool on_selection(Gtk.TreeSelection selection, Gtk.TreeModel model, Gtk.TreePath path,
        bool path_currently_selected) {
        // only allow selection if a page is selectable
        EntryWrapper? wrapper = get_wrapper_at_path(path);
        
        return (wrapper != null) ? (wrapper.entry is Sidebar.SelectableEntry) : false;
    }
    
    private Gtk.TreePath? get_path_from_event(Gdk.EventButton event) {
        int x, y;
        Gdk.ModifierType mask;
        event.window.get_device_position(Gdk.Display.get_default().get_device_manager().
            get_client_pointer(), out x, out y, out mask);
        
        int cell_x, cell_y;
        Gtk.TreePath path;
        return get_path_at_pos(x, y, out path, null, out cell_x, out cell_y) ? path : null;
    }
    
    private Gtk.TreePath? get_current_path() {
        Gtk.TreeModel model;
        GLib.List<Gtk.TreePath> rows = get_selection().get_selected_rows(out model);
        assert(rows.length() == 0 || rows.length() == 1);
        
        return rows.length() != 0 ? rows.nth_data(0) : null;
    }
    
    private bool on_context_menu_keypress() {
        GLib.List<Gtk.TreePath> rows = get_selection().get_selected_rows(null);
        if (rows == null)
            return false;
        
        Gtk.TreePath? path = rows.data;
        if (path == null)
            return false;
        
        scroll_to_cell(path, null, false, 0, 0);
        
        return popup_context_menu(path);
    }
    
    private bool popup_context_menu(Gtk.TreePath path, Gdk.EventButton? event = null) {
        EntryWrapper? wrapper = get_wrapper_at_path(path);
        if (wrapper == null)
            return false;
        
        Sidebar.Contextable? contextable = wrapper.entry as Sidebar.Contextable;
        if (contextable == null)
            return false;
        
        // First select the sidebar item so that its context menu will be available.        
        Sidebar.SelectableEntry? selectable = wrapper.entry as Sidebar.SelectableEntry;
        if (selectable != null)
            entry_selected(selectable);
                
        Gtk.Menu? context_menu = contextable.get_sidebar_context_menu(event);
        if (context_menu == null)
            return false;

        if (event != null)
            context_menu.popup(null, null, null, event.button, event.time);
        else
            context_menu.popup(null, null, null, 0, Gtk.get_current_event_time());
        
        return true;
    }
    
    private bool popup_default_context_menu(Gdk.EventButton event) {
        default_context_menu.popup(null, null, null, event.button, event.time);
        return true;
    }
    
    public bool on_toggle_row(Gtk.TreeIter iter, Gtk.TreePath path) {
        // Determine whether to allow the row to toggle
        EntryWrapper? wrapper = get_wrapper_at_iter(iter);
        if (wrapper == null) {
            return false; // don't affect things
        }
        
        // Most of the time, only allow manual toggles
        bool should_allow_toggle = expander_called_manually;
        
        // Cancel out the manual flag
        expander_called_manually = false;
        
        // If we are an expanded parent entry with content
        if (is_row_expanded(path) && store.iter_has_child(iter) && wrapper.entry is Sidebar.SelectableEntry) {
            // We are taking a special action
            expander_special_count++;
            if (expander_special_count == 1) {
                // Workaround that prevents arrows from double-toggling
                return true;
            } else {
                // Toggle only if non-manual, as opposed to the usual behavior
                should_allow_toggle = !should_allow_toggle;
            }
        } else {
            // Reset the special behavior count
            expander_special_count = 0;
        }
        
        if (should_allow_toggle) {
            return false;
        }
        // Prevent branch expansion toggle
        return true;
    }
    
    public override bool button_press_event(Gdk.EventButton event) {
        Gtk.TreePath? path = get_path_from_event(event);

        // user clicked on empty area, but isn't trying to spawn a context menu?
        if ((path == null) && (event.button != 3)) {
            return true;
        }

        if (event.button == 3 && event.type == Gdk.EventType.BUTTON_PRESS) {
            // single right click
            if (path != null)
                popup_context_menu(path, event);
            else
                popup_default_context_menu(event);
        } else if (event.button == 1 && event.type == Gdk.EventType.BUTTON_PRESS) {
            if (path == null) {
                old_path_ref = null;
                return base.button_press_event(event);
            }
            
            EntryWrapper? wrapper = get_wrapper_at_path(path);
            
            if (wrapper == null) {
                old_path_ref = null;
                return base.button_press_event(event);
            }
            
            // Enable single click to toggle tree entries (bug 4985)
            if (wrapper.entry is Sidebar.ExpandableEntry
                || wrapper.entry is Sidebar.InternalDropTargetEntry) {
                // all labels are InternalDropTargetEntries
                toggle_branch_expansion(path, false);
            }
            
            // Is this a click on an already-highlighted tree item?
            if ((old_path_ref != null) && (old_path_ref.get_path() != null)
                && (old_path_ref.get_path().compare(path) == 0)) {
                // yes, don't allow single-click editing, but 
                // pass the event on for dragging.
                text_renderer.editable = false;
                return base.button_press_event(event);
            }
            
            // Got click on different tree item, make sure it is editable
            // if it needs to be.
            if (wrapper.entry is Sidebar.RenameableEntry &&
                ((Sidebar.RenameableEntry) wrapper.entry).is_user_renameable()) {
                text_renderer.editable = true;
            }
            
            // Remember what tree item is highlighted for next time.
            old_path_ref = new Gtk.TreeRowReference(store, path);
        }

        return base.button_press_event(event);
    }
    
    public bool is_keypress_interpreted(Gdk.EventKey event) {
        switch (Gdk.keyval_name(event.keyval)) {
            case "F2":
            case "Delete":
            case "Return":
            case "KP_Enter":
                return true;
            
            default:
                return false;
        }
    }
    
    public override bool key_press_event(Gdk.EventKey event) {
        switch (Gdk.keyval_name(event.keyval)) {
            case "Return":
            case "KP_Enter":
                Gtk.TreePath? path = get_current_path();
                if (path != null)
                    toggle_branch_expansion(path, false);
                
                return true;
            
            case "F2":
                return rename_in_place();
            
            case "Delete":
                Gtk.TreePath? path = get_current_path();
                
                return (path != null) ? destroy_path(path) : false;
        }
        
        return base.key_press_event(event);
    }
    
    public bool rename_entry_in_place(Sidebar.Entry entry) {
        if (!expand_to_entry(entry))
            return false;
        
        if (!place_cursor(entry, false))
            return false;
        
        return rename_in_place();
    }
    
    private bool rename_in_place() {
        Gtk.TreePath? cursor_path;
        Gtk.TreeViewColumn? cursor_column;
        get_cursor(out cursor_path, out cursor_column);
        
        if (can_rename_path(cursor_path)) {
            set_cursor_on_cell (cursor_path, cursor_column, text_renderer, true);
            
            return true;
        }
        
        return false;
    }
    
    public bool scroll_to_entry(Sidebar.Entry entry) {
        EntryWrapper? wrapper = get_wrapper(entry);
        if (wrapper == null)
            return false;
        
        scroll_to_cell(wrapper.get_path(), null, false, 0, 0);
        
        return true;
    }

    public override void drag_data_get(Gdk.DragContext context, Gtk.SelectionData selection_data,
        uint info, uint time) {
        InternalDragSourceEntry? drag_source = null;
        
        if (internal_drag_source_entry != null) {
            Sidebar.SelectableEntry selectable =
                internal_drag_source_entry as Sidebar.SelectableEntry;
            if (selectable == null) {
                drag_source = internal_drag_source_entry as InternalDragSourceEntry;
            }
        }
        
        if (drag_source == null) {
            Gtk.TreePath? selected_path = get_selected_path();
            if (selected_path == null)
                return;

            EntryWrapper? wrapper = get_wrapper_at_path(selected_path);
            if (wrapper == null)
                return;
            
            drag_source = wrapper.entry as InternalDragSourceEntry;
            if (drag_source == null)
                return;
        }
        
        drag_source.prepare_selection_data(selection_data);
    }
    
    public override void drag_data_received(Gdk.DragContext context, int x, int y,
        Gtk.SelectionData selection_data, uint info, uint time) {
        
        Gtk.TreePath path;
        Gtk.TreeViewDropPosition pos;
        if (!get_dest_row_at_pos(x, y, out path, out pos)) {
            // If an external drop, hand it off to the handler
            if (Gtk.drag_get_source_widget(context) == null)
                drop_handler(context, null, selection_data, info, time);
            else
                Gtk.drag_finish(context, false, false, time);
            
            return;
        }
        
        // Note that a drop outside a sidebar entry is legal if an external drop.
        EntryWrapper? wrapper = get_wrapper_at_path(path);
        
        // If an external drop, hand it off to the handler
        if (Gtk.drag_get_source_widget(context) == null) {
            drop_handler(context, (wrapper != null) ? wrapper.entry : null, selection_data,
                info, time);
            
            return;
        }
        
        // An internal drop only applies to DropTargetEntry's
        if (wrapper == null) {
            Gtk.drag_finish(context, false, false, time);
            
            return;
        }
        
        Sidebar.InternalDropTargetEntry? targetable = wrapper.entry as Sidebar.InternalDropTargetEntry;
        if (targetable == null) {
            Gtk.drag_finish(context, false, false, time);
            
            return;
        }
        
        bool success = false;
        
        if (selection_data.get_data_type().name() == LibraryWindow.TAG_PATH_MIME_TYPE) {
            success = targetable.internal_drop_received_arbitrary(selection_data);
        } else {
            Gee.List<MediaSource>? media = unserialize_media_sources(selection_data.get_data(),
                selection_data.get_length());
            if (media != null && media.size > 0)
                success = targetable.internal_drop_received(media);
        }
        
        Gtk.drag_finish(context, success, false, time);
    }

    public override bool drag_motion(Gdk.DragContext context, int x, int y, uint time) {
        // call the base signal to get rows with children to spring open
        base.drag_motion(context, x, y, time);

        Gtk.TreePath path;
        Gtk.TreeViewDropPosition pos;
        bool has_dest = get_dest_row_at_pos(x, y, out path, out pos);
        
        // we don't want to insert between rows, only select the rows themselves
        if (!has_dest || pos == Gtk.TreeViewDropPosition.BEFORE)
            set_drag_dest_row(path, Gtk.TreeViewDropPosition.INTO_OR_BEFORE);
        else if (pos == Gtk.TreeViewDropPosition.AFTER)
            set_drag_dest_row(path, Gtk.TreeViewDropPosition.INTO_OR_AFTER);
        
        Gdk.drag_status(context, context.get_suggested_action(), time);
        
        return has_dest;
    }
    
    // Returns true if path is renameable, and selects the path as well.
    private bool can_rename_path(Gtk.TreePath path) {
        if (editing_disabled > 0)
            return false;
        
        EntryWrapper? wrapper = get_wrapper_at_path(path);
        if (wrapper == null)
            return false;
        
        Sidebar.RenameableEntry? renameable = wrapper.entry as Sidebar.RenameableEntry;
        if (renameable == null)
            return false;
        
        if (wrapper.entry is Sidebar.Header)
            return false;
        
        get_selection().select_path(path);
        
        return true;
    }

    private bool destroy_path(Gtk.TreePath path) {
        EntryWrapper? wrapper = get_wrapper_at_path(path);
        if (wrapper == null)
            return false;
        
        Sidebar.DestroyableEntry? destroyable = wrapper.entry as Sidebar.DestroyableEntry;
        if (destroyable == null)
            return false;
        
        destroyable.destroy_source();
        
        return true;
    }

    private void on_editing_started(Gtk.CellEditable editable, string path) {
        if (editable is Gtk.Entry) {
            text_entry = (Gtk.Entry) editable;
            text_entry.editing_done.connect(on_editing_done);
            text_entry.focus_out_event.connect(on_editing_focus_out);
            text_entry.editable = true;
        }
    }
    
    private void on_editing_canceled() {
        text_entry.editable = false;
        
        text_entry.editing_done.disconnect(on_editing_done);
        text_entry.focus_out_event.disconnect(on_editing_focus_out);
    }
    
    private void on_editing_done() {
        text_entry.editable = false;
        
        EntryWrapper? wrapper = get_wrapper_at_path(get_current_path());
        if (wrapper != null) {
            Sidebar.RenameableEntry? renameable = wrapper.entry as Sidebar.RenameableEntry;
            if (renameable != null)
                renameable.rename(text_entry.get_text());
        }
        
        text_entry.editing_done.disconnect(on_editing_done);
        text_entry.focus_out_event.disconnect(on_editing_focus_out);
    }

    private bool on_editing_focus_out(Gdk.EventFocus event) {
        // We'll return false here, in case other parts of the app
        // want to know if the button press event that caused
        // us to lose focus have been fully handled.
        return false;
    }
    
    private void on_new_search() {
        (new SavedSearchDialog()).show();
    }

    private void on_new_tag() {
        NewRootTagCommand creation_command = new NewRootTagCommand();
        AppWindow.get_command_manager().execute(creation_command);
        LibraryWindow.get_app().rename_tag_in_sidebar(creation_command.get_created_tag());
    }    
}