var Storage = {
    setCookie: function(name, value, days) {
        var expires = "";
        if (days) {
            var date = new Date();
            date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
            expires = "; expires=" + date.toUTCString();
        }
        document.cookie = name + "=" + (value || "") + expires + "; path=/; SameSite=Strict";
    },

    getCookie: function(name) {
        var nameEQ = name + "=";
        var ca = document.cookie.split(';');
        for (var i = 0; i < ca.length; i++) {
            var c = ca[i];
            while (c.charAt(0) == ' ') c = c.substring(1, c.length);
            if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length, c.length);
        }
        return null;
    },

    deleteCookie: function(name) {
        document.cookie = name + '=; expires=Thu, 01 Jan 1970 00:00:00 UTC; path=/; SameSite=Strict';
    },

    // Simple checksum: sum of char codes
    checksum: function(str) {
        var sum = 0;
        for (var i = 0; i < str.length; i++) {
            sum = (sum + str.charCodeAt(i)) % 65536;
        }
        return sum.toString(16).padStart(4, '0');
    },

    saveGame: function(gameState) {
        var saveData = {
            blackHoleTotalMass: gameState.blackHoleTotalMass,
            totalMassConsumedEver: gameState.totalMassConsumedEver,
            totalMassConsumed: gameState.totalMassConsumed,
            asteroidUpgradeLevel: gameState.asteroidUpgradeLevel,
            asteroidUpgradeCost: gameState.asteroidUpgradeCost,
            cometUpgradeLevel: gameState.cometUpgradeLevel,
            cometUpgradeCost: gameState.cometUpgradeCost,
            planetUpgradeLevel: gameState.planetUpgradeLevel,
            planetUpgradeCost: gameState.planetUpgradeCost,
            giantUpgradeLevel: gameState.giantUpgradeLevel,
            giantUpgradeCost: gameState.giantUpgradeCost,
            asteroidSpawnCount: gameState.asteroidSpawnCount,
	    lastAsteroidSpawn: gameState.lastAsteroidSpawn,
            lastCometSpawn: gameState.lastCometSpawn,
            lastPlanetSpawn: gameState.lastPlanetSpawn,
            lastGiantSpawn: gameState.lastGiantSpawn,
	    sM: gameState.sM,
            sT: gameState.sT,
            mM: gameState.mM,
            mT: gameState.mT,
            lM: gameState.lM,
            lT: gameState.lT,
            rateShort: gameState.rateShort,
            rateMedium: gameState.rateMedium,
            rateLong: gameState.rateLong,
            savedAt: Date.now()
        };

        var json = JSON.stringify(saveData);
        var chksum = this.checksum(json);
        var packaged = btoa(chksum + json); // prepend checksum, then base64
        this.setCookie('blackHoleSave', packaged, 365);

        var saveStatus = document.getElementById('save-status');
        saveStatus.textContent = 'Game saved successfully!';
        setTimeout(function() { saveStatus.textContent = ''; }, 3000);
    },

    loadGame: function() {
        var savedData = this.getCookie('blackHoleSave');
        if (!savedData) return null;

        try {
            // try base64 decode
            var decoded = atob(savedData);

            // new format: first 4 chars = checksum
            var chksum = decoded.slice(0, 4);
            var json = decoded.slice(4);

            // verify checksum
            if (this.checksum(json) !== chksum) {
                console.warn('Save data integrity check failed.');
                return null;
            }

            return JSON.parse(json);
        } catch (e) {
            // old save format (plain JSON)
            try { return JSON.parse(savedData); }
            catch { return null; }
        }
    },

    resetGame: function() {
        this.deleteCookie('blackHoleSave');
        location.reload();
    }
};