using Invercargill;
using Invercargill.DataStructures;
using Invercargill.Expressions;
using InvercargillSql;
using InvercargillSql.Orm;
using Inversion;
using ClankerSaddle.Data;

namespace ClankerSaddle.Services {

    /** The user_preferences key of the Spry theme slug ("" = core default). */
    public const string PREF_THEME = "theme";

    /** The user_preferences key of the colour mode (auto|light|dark). */
    public const string PREF_MODE = "mode";

    /** The default colour mode when no preference is stored. */
    public const string MODE_DEFAULT = "auto";

    /**
     * Per-user preferences (goal 41 task 2): the account settings'
     * key/value store behind the Spry theme picker. Reads go through
     * the ORM query API; writes are raw UPSERTs — the table's
     * composite primary key (user_id, key) defeats the ORM's
     * single-column update_async, so INSERT ... ON CONFLICT replaces
     * both halves of the pair.
     *
     * The theme helpers ({@link get_theme}, {@link set_theme}, {@link
     * get_mode}, {@link set_mode}) are thin sugar over the generic
     * string accessors; validation lives with the action that owns
     * the form, not here — storage accepts any string.
     */
    public class UserPreferenceService : Object {

        private OrmSession db = inject<OrmSession>();
        private Connection connection = inject<Connection>();

        /**
         * The stored value of `key` for `user_id`, or "" when the
         * user never set it.
         */
        public async string get_string(int64 user_id, string key) throws Error {
            var row = yield db.query<UserPreference>()
                .where(expr("user_id == $0 && key == $1",
                    elem<int64?>(user_id), elem(key)))
                .first_async();
            return row != null ? ((!)row).value : "";
        }

        /**
         * Upserts `value` under `key` for `user_id`: one row per
         * (user, key), replaced on conflict.
         */
        public async void set_string(int64 user_id, string key, string value) throws Error {
            yield connection.create_command(
                "INSERT INTO user_preferences (user_id, key, value)"
                + " VALUES (:user_id, :key, :value)"
                + " ON CONFLICT(user_id, key) DO UPDATE SET value = excluded.value")
                .with_parameter<Invercargill.Element>("user_id", elem<int64?>(user_id))
                .with_parameter<Invercargill.Element>("key", elem(key))
                .with_parameter<Invercargill.Element>("value", elem(value))
                .execute_non_query_async();
        }

        /** The stored theme slug ("" = the Spry core default). */
        public async string get_theme(int64 user_id) throws Error {
            return yield get_string(user_id, PREF_THEME);
        }

        /** Stores the theme slug ("" = the Spry core default). */
        public async void set_theme(int64 user_id, string theme) throws Error {
            yield set_string(user_id, PREF_THEME, theme);
        }

        /** The stored colour mode (auto when never set). */
        public async string get_mode(int64 user_id) throws Error {
            var mode = yield get_string(user_id, PREF_MODE);
            return mode.length > 0 ? mode : MODE_DEFAULT;
        }

        /** Stores the colour mode. */
        public async void set_mode(int64 user_id, string mode) throws Error {
            yield set_string(user_id, PREF_MODE, mode);
        }
    }
}