window.App = window.App || {};
App.favoritesView = App.favoritesView || {};

// Browsing favorites as a full grid, the same way the channel listing is
// browsed: same cards, same virtualized masonry, same infinite scroll, same
// reels mode. The only difference is where the pages come from -- localStorage
// instead of the server -- so App.videos.loadVideos routes here while this view
// is active and every page hands its slice to App.videos.renderVideos.
(function() {
    const state = App.state;

    // A page of a local list can be bigger than a page from the server: there's
    // no request behind it, only the cost of building cards, which the
    // virtualizer already keeps to what's on screen.
    const PAGE_SIZE = 24;

    const view = {
        active: false,
        queue: [],   // the sorted favorites still to be handed to the grid
        offset: 0
    };

    // A favorite as the grid expects a video: `id` has to be unique per card
    // (the virtualizer and renderedVideoIds key on it), and an imported
    // favorite has no server id -- its key, which is the URL, stands in.
    const toVideo = function(entry) {
        return Object.assign({}, entry, { id: entry.key, tags: [] });
    };

    App.favoritesView.isActive = function() {
        return view.active;
    };

    App.favoritesView.loadNext = function() {
        if (!view.active) return false;
        const slice = view.queue.slice(view.offset, view.offset + PAGE_SIZE);
        view.offset += slice.length;
        state.hasNextPage = view.offset < view.queue.length;
        if (!slice.length) {
            App.videos.updateLoadMoreState();
            return false;
        }
        App.videos.renderVideos({ items: slice.map(toVideo) });
        App.videos.updateLoadMoreState();
        return true;
    };

    // Starts (or restarts, after a sort change) the favorites grid.
    App.favoritesView.open = function(options) {
        const sort = (options && options.sort) || App.favorites.getSort();
        const favorites = App.favorites.sorted(sort);
        if (!favorites.length) {
            App.ui.showError('No favorites yet. Tap the heart on a video to save one.');
            return false;
        }
        App.videos.resetGrid();
        view.active = true;
        view.queue = favorites;
        view.offset = 0;
        state.hasNextPage = true;
        document.body.classList.add('favorites-view-open');
        // Re-render the bar so it re-decides whether to be mounted: hidden in
        // settings or not, its header has to be on screen now, since that's
        // where the way back out lives (the palette can open this view too).
        App.favorites.renderBar();
        App.favoritesView.syncControls();
        App.favoritesView.loadNext();
        window.scrollTo({ top: 0, behavior: 'auto' });
        return true;
    };

    App.favoritesView.close = function(options) {
        if (!view.active) return;
        view.active = false;
        view.queue = [];
        view.offset = 0;
        document.body.classList.remove('favorites-view-open');
        // Back to whatever the settings say, and with its cards built again.
        App.favorites.renderBar();
        App.favoritesView.syncControls();
        // Back to the channel listing, unless the caller is about to load
        // something itself (a search, a channel switch).
        if (!(options && options.silent)) App.videos.resetAndReload();
    };

    App.favoritesView.toggle = function() {
        if (view.active) App.favoritesView.close();
        else App.favoritesView.open();
    };

    // Re-pages the grid under a new order, and re-renders the bar so both show
    // favorites the same way round.
    App.favoritesView.applySort = function(sort) {
        App.favorites.setSort(sort);
        App.favorites.renderBar();
        if (view.active) App.favoritesView.open({ sort });
    };

    App.favoritesView.syncControls = function() {
        const button = document.getElementById('favorites-browse-btn');
        if (button) {
            button.textContent = view.active ? 'Back to videos' : 'Browse all';
            button.setAttribute('aria-pressed', view.active ? 'true' : 'false');
        }
        const select = document.getElementById('favorites-sort');
        if (select && select.value !== App.favorites.getSort()) {
            select.value = App.favorites.getSort();
        }
    };
})();