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

// Reads a Hot Tub app backup (an exported SQLite database) and turns the videos
// it has flagged as favorites into this client's favorites.
//
// The app and this client don't agree on identity: the app keys a video by a
// hash it computes locally, while the server -- and so this client -- keys it by
// something like "reddit-1rdudss". So an imported favorite is matched to an
// existing one by URL, and carries no id of its own; see App.favorites.mergeImported.
(function() {
    // The app stores a comma-separated set here ("favorite", "recent", ...).
    // It also keeps a `favoriteDate` on rows it no longer flags -- a leftover
    // from unfavoriting -- so the flag, not the date, is what counts.
    const FAVORITE_FLAG = 'favorite';

    // Only what a favorite needs. Skipping the rest matters: `allFormats` alone
    // is kilobytes of resolved-format JSON per row, and it is exactly the kind
    // of thing this client must not store -- those URLs are signed and expire
    // (see App.favorites.normalize).
    const COLUMNS = ['url', 'title', 'thumb', 'duration', 'uploader', 'flags', 'favoriteDate'];

    const hasFavoriteFlag = function(flags) {
        if (!flags) return false;
        return String(flags).split(',').some((flag) => flag.trim().toLowerCase() === FAVORITE_FLAG);
    };

    // Newest first, matching how favorites are ordered when added by hand.
    const byNewest = function(a, b) {
        return String(b.favoriteDate || '').localeCompare(String(a.favoriteDate || ''));
    };

    App.hottubBackup.readFavorites = function(buffer) {
        const db = App.sqlite.open(buffer);
        if (db.tableNames().indexOf('video_details') < 0) {
            throw new Error('This database has no video_details table -- is it a Hot Tub backup?');
        }
        const rows = db.readTable('video_details', { columns: COLUMNS });
        return rows
            .filter((row) => row.url && hasFavoriteFlag(row.flags))
            .sort(byNewest)
            .map((row) => ({
                // No id: the app's own is meaningless to this client, and the
                // URL is what both sides agree on.
                key: row.url,
                id: null,
                url: row.url,
                title: row.title || '',
                thumb: row.thumb || '',
                channel: '',
                uploader: row.uploader || '',
                duration: Number(row.duration) || 0,
                isLive: false
            }));
    };

    App.hottubBackup.readFile = function(file) {
        return file.arrayBuffer().then((buffer) => App.hottubBackup.readFavorites(buffer));
    };

    // Reads the file and merges what it finds. Resolves to the merge summary
    // ({found, added, skipped, total}) so the caller can report it.
    App.hottubBackup.importFile = function(file) {
        return App.hottubBackup.readFile(file).then((entries) => {
            const result = App.favorites.mergeImported(entries);
            return Object.assign({ found: entries.length }, result);
        });
    };
})();