anotherim-desktop/main/src/ui/conversation_summary/conversation_view.vala

using Gee;
using Gtk;
using Pango;

using Dino.Entities;

namespace Dino.Ui.ConversationSummary {

[GtkTemplate (ui = "/im/dino/conversation_summary/view.ui")]
public class ConversationView : Box, Plugins.ConversationItemCollection {

    public Conversation? conversation { get; private set; }

    [GtkChild] private ScrolledWindow scrolled;
    [GtkChild] private Box main;
    [GtkChild] private Stack stack;

    private StreamInteractor stream_interactor;
    private Gee.TreeSet<Plugins.MetaConversationItem> meta_items = new TreeSet<Plugins.MetaConversationItem>((a, b) => { return a.sort_time.compare(b.sort_time); });
    private Gee.Map<Plugins.MetaConversationItem, Gee.List<Plugins.MetaConversationItem>> meta_after_items = new Gee.HashMap<Plugins.MetaConversationItem, Gee.List<Plugins.MetaConversationItem>>();
    private Gee.HashMap<Plugins.MetaConversationItem, ConversationItemSkeleton> item_item_skeletons = new Gee.HashMap<Plugins.MetaConversationItem, ConversationItemSkeleton>();
    private Gee.HashMap<Plugins.MetaConversationItem, Widget> widgets = new Gee.HashMap<Plugins.MetaConversationItem, Widget>();
    private Gee.List<ConversationItemSkeleton> item_skeletons = new Gee.ArrayList<ConversationItemSkeleton>();
    private MessagePopulator message_item_populator;

    private double? was_value;
    private double? was_upper;
    private double? was_page_size;

    private Mutex reloading_mutex = new Mutex();
    private bool animate = false;

    public ConversationView(StreamInteractor stream_interactor) {
        this.stream_interactor = stream_interactor;
        scrolled.vadjustment.notify["upper"].connect_after(on_upper_notify);
        scrolled.vadjustment.notify["value"].connect(on_value_notify);

        message_item_populator = new MessagePopulator(stream_interactor);

        Application app = GLib.Application.get_default() as Application;
        app.plugin_registry.register_conversation_item_populator(new ChatStatePopulator(stream_interactor));

        Timeout.add_seconds(60, () => {
            foreach (ConversationItemSkeleton item_skeleton in item_skeletons) {
                item_skeleton.update_time();
            }
            return true;
        });

        Util.force_base_background(this);
    }

    public void initialize_for_conversation(Conversation? conversation) {
        this.conversation = conversation;
        stack.set_visible_child_name("void");
        clear();
        was_upper = null;
        was_page_size = null;
        animate = false;
        Timeout.add(20, () => { animate = true; return false; });

        message_item_populator.init(conversation, this);
        message_item_populator.populate_number(conversation, new DateTime.now_utc(), 50);

        Dino.Application app = Dino.Application.get_default();
        foreach (Plugins.ConversationItemPopulator populator in app.plugin_registry.conversation_item_populators) {
            populator.init(conversation, this, Plugins.WidgetType.GTK);
        }

        stack.set_visible_child_name("main");
    }

    public void insert_item(Plugins.MetaConversationItem item) {
        meta_items.add(item);
        if (!item.can_merge || !merge_back(item)) {
            insert_new(item);
        }
    }

    public void remove_item(Plugins.MetaConversationItem item) {
        main.remove(widgets[item]);
        widgets.unset(item);
        meta_items.remove(item);
        item_skeletons.remove(item_item_skeletons[item]);
        item_item_skeletons.unset(item);
    }

    private bool merge_back(Plugins.MetaConversationItem item) {
        Plugins.MetaConversationItem? lower_item = meta_items.lower(item);
        if (lower_item != null) {
            ConversationItemSkeleton lower_skeleton = item_item_skeletons[lower_item];
            Plugins.MetaConversationItem lower_start_item = lower_skeleton.items[0];
            if (lower_start_item.can_merge &&
                    item.display_time.difference(lower_start_item.display_time) < TimeSpan.MINUTE &&
                    lower_start_item.jid.equals(item.jid) &&
                    lower_start_item.encryption == item.encryption &&
                    item.mark != Message.Marked.WONTSEND) {
                lower_skeleton.add_meta_item(item);
                force_alloc_width(lower_skeleton, main.get_allocated_width());
                item_item_skeletons[item] = lower_skeleton;
                return true;
            }
        }
        return false;
    }

    private void insert_new(Plugins.MetaConversationItem item) {
        ConversationItemSkeleton item_skeleton = new ConversationItemSkeleton(stream_interactor, conversation);
        item_skeleton.add_meta_item(item);
        item_item_skeletons[item] = item_skeleton;
        Plugins.MetaConversationItem? lower_item = meta_items.lower(item);
        int index = lower_item != null ? item_skeletons.index_of(item_item_skeletons[lower_item]) + 1 : 0;
        item_skeletons.insert(index, item_skeleton);

        Widget insert = item_skeleton;
        if (animate) {
            Revealer revealer = new Revealer() {transition_duration = 200, transition_type = RevealerTransitionType.SLIDE_UP, visible = true};
            revealer.add(item_skeleton);
            insert = revealer;
            main.add(insert);
            revealer.reveal_child = true;
        } else {
            main.add(insert);
        }
        widgets[item] = insert;
        force_alloc_width(insert, main.get_allocated_width());
        main.reorder_child(insert, index);
    }

    private void on_upper_notify() {
        if (was_upper == null || scrolled.vadjustment.value >  was_upper - was_page_size - 1 ||
                scrolled.vadjustment.value >  was_upper - was_page_size - 1) { // scrolled down or content smaller than page size
            scrolled.vadjustment.value = scrolled.vadjustment.upper - scrolled.vadjustment.page_size; // scroll down
        } else if (scrolled.vadjustment.value < scrolled.vadjustment.upper - scrolled.vadjustment.page_size - 1) {
            scrolled.vadjustment.value = scrolled.vadjustment.upper - was_upper + scrolled.vadjustment.value; // stay at same content
        }
        was_upper = scrolled.vadjustment.upper;
        was_page_size = scrolled.vadjustment.page_size;
        reloading_mutex.trylock();
        reloading_mutex.unlock();
    }

    private void on_value_notify() {
        if (scrolled.vadjustment.value < 200) {
            load_earlier_messages();
        }
    }

    private void load_earlier_messages() {
        was_value = scrolled.vadjustment.value;
        if (!reloading_mutex.trylock()) return;
        if (meta_items.size > 0) message_item_populator.populate_number(conversation, meta_items.first().sort_time, 20);
    }

    // Workaround GTK TextView issues
    private void force_alloc_width(Widget widget, int width) {
        Allocation alloc = Allocation();
        widget.get_preferred_width(out alloc.width, null);
        widget.get_preferred_height(out alloc.height, null);
        alloc.width = width;
        widget.size_allocate(alloc);
    }

    private void clear() {
        meta_items.clear();
        meta_after_items.clear();
        item_skeletons.clear();
        item_item_skeletons.clear();
        main.@foreach((widget) => { main.remove(widget); });
    }
}

}