// UI management and event handlers

var UI = {
    elements: {},
    
    init: function() {
        // Cache DOM elements
        this.elements = {
            totalMass: document.getElementById('total-mass'),
            spendableMass: document.getElementById('spendable-mass'),
	    totalLevel: document.getElementById('total-level'),
            asteroidLevel: document.getElementById('asteroid-level'),
            cometLevel: document.getElementById('comet-level'),
            planetLevel: document.getElementById('planet-level'),
            giantLevel: document.getElementById('giant-level'),
            mtypeLevel: document.getElementById('mtype-level'),
	    ktypeLevel: document.getElementById('ktype-level'),
	    gtypeLevel: document.getElementById('gtype-level'),
            asteroidUpgradeBtn: document.getElementById('asteroid-upgrade-btn'),
            cometUpgradeBtn: document.getElementById('comet-upgrade-btn'),
            planetUpgradeBtn: document.getElementById('planet-upgrade-btn'),
            giantUpgradeBtn: document.getElementById('giant-upgrade-btn'),
            mtypeUpgradeBtn: document.getElementById('mtype-upgrade-btn'),
            ktypeUpgradeBtn: document.getElementById('ktype-upgrade-btn'),
            gtypeUpgradeBtn: document.getElementById('gtype-upgrade-btn'),
            gearIcon: document.getElementById('gear-icon'),
            settingsMenu: document.getElementById('settings-menu'),
            resetBtn: document.getElementById('reset-btn'),
	    leaderboardModal: document.getElementById('leaderboardModal'),
	    leaderboardToggle: document.getElementById('leaderboardToggle'),
	    leaderboardPanel: document.getElementById('leaderboardPanel'),
	    leaderboardList: document.getElementById('leaderboardList'),
	    sortMass: document.getElementById('sortMass'),
	    sortAge: document.getElementById('sortAge'),
	    massRate: document.getElementById('massRate')
        };

	// Sorting buttons
	this.elements.sortMass.addEventListener('click', () => this.openLeaderboard('mass'));
	this.elements.sortAge.addEventListener('click', () => this.openLeaderboard('age'));

        this.setupEventListeners();
    },

    setupEventListeners: function() {
        const self = this;
        const gear = self.elements.gearIcon;
        const settingsMenu = self.elements.settingsMenu;
        const leaderboardToggle = self.elements.leaderboardToggle;
        const leaderboardPanel = self.elements.leaderboardPanel;
	const resetBtn = self.elements.resetBtn;
	const holeIcon = document.getElementById('hole-icon');
        const upgradePanel = document.getElementById('upgrade-panel');

	// ---------- Upgrade Panel ----------
        if (holeIcon && upgradePanel) {
            // Toggle upgrade panel
            holeIcon.addEventListener('click', (e) => {
                e.stopPropagation();
		if (settingsMenu) settingsMenu.classList.remove('open');
                if (leaderboardPanel) leaderboardPanel.classList.remove('show');
                upgradePanel.classList.toggle('open');
            });
    
            // Prevent clicks inside panel from closing it
            upgradePanel.addEventListener('click', (e) => {
                e.stopPropagation();
            });
        }
    
   
        // ---------- Leaderboard ----------
        if (leaderboardToggle && leaderboardPanel) {
            // Toggle leaderboard panel
            leaderboardToggle.addEventListener('click', (e) => {
                e.stopPropagation(); // prevent document click
		if (settingsMenu) settingsMenu.classList.remove('open');
                if (upgradePanel) upgradePanel.classList.remove('open');
                leaderboardPanel.classList.toggle('show');
    
                if (leaderboardPanel.classList.contains('show')) {
                    self.openLeaderboard('mass'); // load leaderboard by mass immediately
                }
            });
    
            // Prevent clicks inside the panel from closing it
            leaderboardPanel.addEventListener('click', (e) => {
                e.stopPropagation();
            });
        }
	if (resetBtn) {
            resetBtn.addEventListener('click', function() {
                Storage.resetGame();
            });
        }

         // ---------- Settings Menu ----------
        if (gear && settingsMenu) {
            // Toggle settings menu
            gear.addEventListener('click', (e) => {
                e.stopPropagation(); // prevent document click from immediately closing
		if (upgradePanel) upgradePanel.classList.remove('open');
                if (leaderboardPanel) leaderboardPanel.classList.remove('show');
                settingsMenu.classList.toggle('open');
            });
    
            // Prevent clicks inside menu from closing it
            settingsMenu.addEventListener('click', (e) => {
                e.stopPropagation();
            });
        }

	// ---------- Session Transfer ----------
        var exportBtn = document.getElementById('export-session-btn');
        var claimBtn = document.getElementById('transfer-claim-btn');

        if (exportBtn) {
            exportBtn.addEventListener('click', function(e) {
                e.stopPropagation();
                self.exportSession();
            });
        }

	if (claimBtn) {
            claimBtn.addEventListener('click', async function(e) {
                e.stopPropagation();
                var input = document.getElementById('transfer-code-input');
                var isVisible = input.style.display !== 'none';

                if (!isVisible) {
                    input.style.display = 'block';
                    claimBtn.classList.add('active');
                    input.focus();
                    return;
                }

                var code = input.value.trim();

                if (!code) {
                    input.style.display = 'none';
                    claimBtn.classList.remove('active');
                    return;
                }

                if (!/^[0-9a-fA-F]{5}$/.test(code)) {
                    showErrorNotification('Invalid or expired code');
                    return;
                }

                try {
                    var result = await Server.claimTransferCode(code.toLowerCase());
                    if (!result || !result.playerId) throw new Error();

                    Storage.setCookie('playerId', result.playerId, 365);
                    Storage.setCookie('sessionToken', result.sessionToken, 365);

                    showSuccessNotification('Session imported — reloading...');
                    setTimeout(function() { location.reload(); }, 1500);

                } catch (err) {
                    showErrorNotification('Invalid or expired code');
                }
            });
        }

	var transferInput = document.getElementById('transfer-code-input');
        if (transferInput) {
            transferInput.addEventListener('keydown', function(e) {
                if (e.key === 'Enter') {
                    e.stopPropagation();
                    claimBtn.click();
                }
            });
        }

        // ---------- Click outside to close ----------
        document.addEventListener('click', () => {
            // Close settings menu
            if (settingsMenu) {
                settingsMenu.classList.remove('open');
            }
    
	    // Close leaderboard panel
	    if (leaderboardPanel) {
	        leaderboardPanel.classList.remove('show');
	        // Clear refresh intervals when closing
	        if (this._leaderboardRefreshInterval) {
	            clearInterval(this._leaderboardRefreshInterval);
	            this._leaderboardRefreshInterval = null;
	        }
	        if (this._leaderboardIndicatorInterval) {
	            clearInterval(this._leaderboardIndicatorInterval);
	            this._leaderboardIndicatorInterval = null;
	        }
	    }

            if (upgradePanel) {
                upgradePanel.classList.remove('open');
            }
        });
    },

    setUpgradeHandlers: function(handlers) {
        this.elements.asteroidUpgradeBtn.addEventListener('click', handlers.asteroid);
        this.elements.cometUpgradeBtn.addEventListener('click', handlers.comet);
        this.elements.planetUpgradeBtn.addEventListener('click', handlers.planet);
        this.elements.giantUpgradeBtn.addEventListener('click', handlers.giant);
        this.elements.mtypeUpgradeBtn.addEventListener('click', handlers.mtype);
	this.elements.ktypeUpgradeBtn.addEventListener('click', handlers.ktype);
	this.elements.gtypeUpgradeBtn.addEventListener('click', handlers.gtype);
    },
    
    update: function(gameState, config) {
	if (this.elements.spendableMass) {
            this.elements.spendableMass.textContent = 
                'Available to Spend: ' + this.formatMass(gameState.totalMassConsumed);
       }
        this.updateMassDisplay(gameState, config);
        this.updateRateDisplay(gameState, config);
        this.updateUpgradeDisplay(gameState);
	this.updateTotalLevel(gameState);
	this.updateActiveObjects();
    },

    updateMassDisplay: function(state, config) {
    
        const bhMassText = this.formatMass(state.blackHoleTotalMass, { forceSolarMass: true });
        const consumedText = this.formatMass(state.totalMassConsumedEver);
    
        this.elements.totalMass.innerHTML = `
            <span class="tooltip-trigger">
                Black Hole Mass: ${bhMassText}
                <span class="tooltip">
                    The mass of your black hole in solar masses.<br>
                    1 Solar Mass (M☉) ≈ 1.989 × 10³⁰ kg.<br><br>
                    Total mass absorbed:<br>
                    ${consumedText}
                </span>
        `;
    },
    
    updateRateDisplay: function(state, config) {
        const theoretical = calculateTheoreticalRate(state, config);
        const windowedTheoretical = calculateTheoreticalRate(state, config, 1000);
        const trend = state.rateShortTrend || 'same';
    
        const rateShortText  = this.formatMass(theoretical) + '/s';
        const rateMediumText = this.formatMass(theoretical * 3600) + '/h';
        const rateLongText   = this.formatMass(theoretical * 86400) + '/d';
    
        const delta = (state.rateShort || 0) - windowedTheoretical;
        const sign = delta >= 0 ? '+' : '-';
        const deltaText = sign + this.formatMass(Math.abs(delta)) + '/s';
        const deltaClass = trend === 'same' ? 'rate-same' : 'rate-' + trend;
    
        const rateText = `
            <span class="rate-same">${rateShortText}</span>
            <span class="${deltaClass}">&nbsp;${deltaText}</span>
            </br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;${rateMediumText}</span>
            </br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;${rateLongText}</span>
        `;
    
        this.elements.massRate.innerHTML = `
            <span>&nbsp;&nbsp;Rates: ${rateText}</span>
        `;
    },

    updateUpgradeDisplay: function(gameState) {
        this.updateAsteroidUpgrade(gameState);
        
        // Only show comet upgrade if unlocked
        if (gameState.cometUnlocked) {
            this.updateCometUpgrade(gameState);
            this.elements.cometLevel.parentElement.style.display = '';
        } else {
            this.elements.cometLevel.parentElement.style.display = 'none';
        }
        
        // Only show planet upgrade if unlocked
        if (gameState.planetUnlocked) {
            this.updatePlanetUpgrade(gameState);
            this.elements.planetLevel.parentElement.style.display = '';
        } else {
            this.elements.planetLevel.parentElement.style.display = 'none';
        }
        
        // Only show giant upgrade if unlocked
        if (gameState.giantUnlocked) {
            this.updateGiantUpgrade(gameState);
            this.elements.giantLevel.parentElement.style.display = '';
        } else {
            this.elements.giantLevel.parentElement.style.display = 'none';
        }

	// Only show mtype upgrade if unlocked
	if (gameState.mtypeUnlocked) {
            this.updateMtypeUpgrade(gameState);
            this.elements.mtypeLevel.parentElement.style.display = '';
        } else {
            this.elements.mtypeLevel.parentElement.style.display = 'none';
        }

	// Only show ktype upgrade if unlocked
        if (gameState.ktypeUnlocked) {
            this.updateKtypeUpgrade(gameState);
            this.elements.ktypeLevel.parentElement.style.display = '';
        } else {
            this.elements.ktypeLevel.parentElement.style.display = 'none';
        }

	// Only show gtype upgrade if unlocked
        if (gameState.gtypeUnlocked) {
            this.updateGtypeUpgrade(gameState);
            this.elements.gtypeLevel.parentElement.style.display = '';
        } else {
            this.elements.gtypeLevel.parentElement.style.display = 'none';
        }

	var canAffordAny = 
            gameState.totalMassConsumed >= gameState.asteroidUpgradeCost ||
            (gameState.cometUnlocked && gameState.totalMassConsumed >= gameState.cometUpgradeCost) ||
            (gameState.planetUnlocked && gameState.totalMassConsumed >= gameState.planetUpgradeCost) ||
            (gameState.giantUnlocked && gameState.totalMassConsumed >= gameState.giantUpgradeCost) ||
            (gameState.mtypeUnlocked && gameState.totalMassConsumed >= gameState.mtypeUpgradeCost) ||
            (gameState.ktypeUnlocked && gameState.totalMassConsumed >= gameState.ktypeUpgradeCost) ||
            (gameState.gtypeUnlocked && gameState.totalMassConsumed >= gameState.gtypeUpgradeCost);
        
        var holeIcon = document.getElementById('hole-icon');
        if (holeIcon) {
            if (canAffordAny) {
                holeIcon.classList.add('pulse');
            } else {
                holeIcon.classList.remove('pulse');
            }
        }
    },

    updateTotalLevel: function(gameState) {
        var el = this.elements.totalLevel;
        if (!el) return;
    
        var totalLevel =
            gameState.asteroidUpgradeLevel +
            gameState.cometUpgradeLevel +
            gameState.planetUpgradeLevel +
            gameState.giantUpgradeLevel +
            gameState.mtypeUpgradeLevel +
            gameState.ktypeUpgradeLevel +
            gameState.gtypeUpgradeLevel;
    
        el.innerHTML =
            '<span class="tooltip-trigger">' +
                'Total Level: ' + totalLevel +
                '<span class="tooltip">' +
                    'Sum of all upgrades.<br>' +
                '</span>' +
            '</span>';
    
        var starBonusEl = document.getElementById('star-bonus');
        if (!starBonusEl) return;
    
        var mBonus = gameState.mtypeUpgradeLevel * CONFIG.MTYPE_SPAWN_BOOST_PER_LEVEL * 100;
        var kBonus = gameState.ktypeUpgradeLevel * CONFIG.KTYPE_SPAWN_BOOST_PER_LEVEL * 100;
        var gBonus = gameState.gtypeUpgradeLevel * CONFIG.GTYPE_SPAWN_BOOST_PER_LEVEL * 100;
        var totalStarBonus = (mBonus + kBonus + gBonus).toFixed(0);
    
	var starTooltip =
            '*-Type upgrades boost the spawn rate of all objects.';
        
        if (mBonus > 1) {
            starTooltip += '<br><br>M-Type: +' + mBonus.toFixed(0) + '%<br>';
        }
        
        if (kBonus > 1) {
            starTooltip += 'K-Type: +' + kBonus.toFixed(0) + '%<br>';
        }
        
        if (gBonus > 1) {
            starTooltip += 'G-Type: +' + gBonus.toFixed(0) + '%';
        }

        starBonusEl.innerHTML =
            '<span class="tooltip-trigger">' +
                '<br><span style="color:#FC6;">Star Bonus: +' + totalStarBonus + '%</span>' +
                '<span class="tooltip">' + starTooltip + '</span>' +
            '</span>';
    },

    updateActiveObjects: function() {
        var el = document.getElementById('active-objects');
        if (!el) return;
        
        var count = window.gameAsteroids ? window.gameAsteroids.length : 0;
        var now = Date.now();
        
        // Initialize tracking
        if (this._lastObjectCount === undefined) {
            this._lastObjectCount = count;
            this._objectTrend = 'same';
            this._lastObjectCheck = now;
        }
        
        // Only update trend once per second to avoid flicker
        if (now - this._lastObjectCheck >= 1000) {
            if (count > this._lastObjectCount) {
                this._objectTrend = 'up';
            } else if (count < this._lastObjectCount) {
                this._objectTrend = 'down';
            } else {
                this._objectTrend = 'same';
            }
            this._lastObjectCount = count;
            this._lastObjectCheck = now;
        }
        
        // Apply trend color
        el.innerHTML = 'Objects: <span class="rate-' + this._objectTrend + '">' + count + '</span>';
    },
    
    updateAsteroidUpgrade: function(gameState) {
	var rate = (1000 / gameState.currentAsteroidSpawnInterval).toFixed(2);
        var bonusPercent = (gameState.asteroidUpgradeLevel * CONFIG.UPGRADE_BONUS_PER_LEVEL_ASTER * 100).toFixed(0);
	var tooltipText = 'Asteroids are rocky, airless bodies that range in size from tiny pebbles to hundreds of kilometers across. Some asteroids have moons or even binary companions.<br><br>Rate: ' + rate + '/sec<br>Bonus: ' + bonusPercent + '%';
	if (!gameState.cometUnlocked) tooltipText += '<br><span style="color:#0FF;">Unlocks Comets at level 20</span>';
        
        this.elements.asteroidLevel.innerHTML = '<span class="tooltip-trigger">Asteroids: Level ' + 
            gameState.asteroidUpgradeLevel + 
            '<span class="tooltip">' + tooltipText + '</span></span>';
        
	this.elements.asteroidUpgradeBtn.textContent =
            'Upgrade (Cost: ' + this.formatMass(gameState.asteroidUpgradeCost) + ')';

        this.elements.asteroidUpgradeBtn.disabled = 
            gameState.totalMassConsumed < gameState.asteroidUpgradeCost;
    },
    
    updateCometUpgrade: function(gameState) {
	var rate = (60000 / gameState.currentCometSpawnInterval).toFixed(2);
        var bonusPercent = (gameState.cometUpgradeLevel * CONFIG.UPGRADE_BONUS_PER_LEVEL_COMET * 100).toFixed(0);
        var tooltipText = 'Comets are small icy bodies that typically release gas and dust, forming a glowing coma and often a tail. They are composed mainly of ice, rock, and organic compounds.<br><br>Rate: ' + rate + '/min<br>Bonus: ' + bonusPercent + '%';
	if (!gameState.planetUnlocked) tooltipText += '<br><span style="color:#0FF;">Unlocks Planets at level 15</span>';
        
        this.elements.cometLevel.innerHTML = '<span class="tooltip-trigger">Comets: Level ' + 
            gameState.cometUpgradeLevel + 
            '<span class="tooltip">' + tooltipText + '</span></span>';
        
	this.elements.cometUpgradeBtn.textContent =
	    'Upgrade (Cost: ' + this.formatMass(gameState.cometUpgradeCost) + ')';

        this.elements.cometUpgradeBtn.disabled = 
            gameState.totalMassConsumed < gameState.cometUpgradeCost;
    },
    
    updatePlanetUpgrade: function(gameState) {
	var rate = (CONFIG.BASE_PLANET_SPAWN_INTERVAL / gameState.currentPlanetSpawnInterval).toFixed(2);
        var bonusPercent = (gameState.planetUpgradeLevel * CONFIG.UPGRADE_BONUS_PER_LEVEL_PLANT * 100).toFixed(0);
        var tooltipText = 'Planets are roughly spherical accumulations of rock and metal, with solid surfaces and relatively thin atmospheres. Local examples include Mercury, Earth, and Pluto. They may vary greatly in size.<br><br>Rate: ' + rate + '/hour<br>Bonus: ' + bonusPercent + '%';
	if (!gameState.giantUnlocked) tooltipText += '<br><span style="color:#0FF;">Unlocks Giants at level 10</span>';
        
        this.elements.planetLevel.innerHTML = '<span class="tooltip-trigger">Planets: Level ' + 
            gameState.planetUpgradeLevel + 
            '<span class="tooltip">' + tooltipText + '</span></span>';
        
	this.elements.planetUpgradeBtn.textContent =
	    'Upgrade (Cost: ' + this.formatMass(gameState.planetUpgradeCost) + ')';

        this.elements.planetUpgradeBtn.disabled = 
            gameState.totalMassConsumed < gameState.planetUpgradeCost;
    },
    
    updateGiantUpgrade: function(gameState) {
	var rate = (CONFIG.BASE_GIANT_SPAWN_INTERVAL / gameState.currentGiantSpawnInterval).toFixed(2);
        var bonusPercent = (gameState.giantUpgradeLevel * CONFIG.UPGRADE_BONUS_PER_LEVEL_GIANT * 100).toFixed(0);
        var tooltipText = 'Gas giants are large planets made mostly of hydrogen and helium, with thick atmospheres and no solid surface.<br>Ice giants are similar but contain higher amounts of frozen materials like water, ammonia, and methane in their atmospheres.<br>Local examples include Jupiter and Neptune.<br><br>Rate: ' + rate + '/6hours<br>Bonus: ' + bonusPercent + '%';
	if (!gameState.mtypeUnlocked) tooltipText += '<br><span style="color:#0FF;">Unlocks M-Type at level 5</span>';
        
        this.elements.giantLevel.innerHTML = '<span class="tooltip-trigger">Giants: Level ' + 
            gameState.giantUpgradeLevel + 
            '<span class="tooltip">' + tooltipText + '</span></span>';
        
	this.elements.giantUpgradeBtn.textContent =
	    'Upgrade (Cost: ' + this.formatMass(gameState.giantUpgradeCost) + ')';

        this.elements.giantUpgradeBtn.disabled = 
            gameState.totalMassConsumed < gameState.giantUpgradeCost;
    },

    updateMtypeUpgrade: function(gameState) {
	var rate = (CONFIG.BASE_MTYPE_SPAWN_INTERVAL / gameState.currentMtypeSpawnInterval).toFixed(2);
        var bonusPercent = (gameState.mtypeUpgradeLevel * CONFIG.UPGRADE_BONUS_PER_LEVEL_MTYPE * 100).toFixed(0);
        var tooltipText = 'M-types, also known as red  dwarfs, are the smallest and coolest stars with masses ranging from about 0.08 to 0.45 M☉.<br>They are the most common star in the universe, making up roughly three quarters of all main-sequence stars, but are not easily visible due to their low luminosity.<br><br>Rate: ' + rate + '/day<br>Bonus: ' + bonusPercent + '%';
	if (!gameState.ktypeUnlocked) tooltipText += '<br><span style="color:#0FF;">Unlocks K-Type at level 5</span>';

        this.elements.mtypeLevel.innerHTML = '<span class="tooltip-trigger">M-Type: Level ' +
            gameState.mtypeUpgradeLevel +
            '<span class="tooltip">' + tooltipText + '</span></span>';
        this.elements.mtypeUpgradeBtn.textContent =
            'Upgrade (Cost: ' + this.formatMass(gameState.mtypeUpgradeCost) + ')';
        this.elements.mtypeUpgradeBtn.disabled =
            gameState.totalMassConsumed < gameState.mtypeUpgradeCost;
    },

    updateKtypeUpgrade: function(gameState) {
	var rate = (CONFIG.BASE_KTYPE_SPAWN_INTERVAL / gameState.currentKtypeSpawnInterval).toFixed(2);
        var bonusPercent = (gameState.ktypeUpgradeLevel * CONFIG.UPGRADE_BONUS_PER_LEVEL_KTYPE * 100).toFixed(0);
        var tooltipText = 'K-types, also known as orange dwarfs, are medium-sized stars that are cooler than the Sun, with masses ranging from about 0.45 to 0.8 M☉. They are known for their stability and long lifespans (20 to 70 billion years), making them potential candidates for supporting inhabited planets.<br><br>Rate: ' + rate + '/2days<br>Bonus: ' + bonusPercent + '%';
	if (!gameState.gtypeUnlocked) tooltipText += '<br><span style="color:#0FF;">Unlocks G-Type at level 5</span>';
	
        this.elements.ktypeLevel.innerHTML = '<span class="tooltip-trigger">K-Type: Level ' +
            gameState.ktypeUpgradeLevel +
            '<span class="tooltip">' + tooltipText + '</span></span>';
        this.elements.ktypeUpgradeBtn.textContent =
            'Upgrade (Cost: ' + this.formatMass(gameState.ktypeUpgradeCost) + ')';
        this.elements.ktypeUpgradeBtn.disabled =
            gameState.totalMassConsumed < gameState.ktypeUpgradeCost;
    },

    updateGtypeUpgrade: function(gameState) {
	var rate = (CONFIG.BASE_GTYPE_SPAWN_INTERVAL / gameState.currentGtypeSpawnInterval).toFixed(2);
        var bonusPercent = (gameState.gtypeUpgradeLevel * CONFIG.UPGRADE_BONUS_PER_LEVEL_GTYPE * 100).toFixed(0);
	        var tooltipText = 'G-Types, also known as yellow dwarfs, are medium-sized stars that are about the size of our Sun (~1 M☉). The term yellow dwarf is a misnomer, as most G-Types (including the Sun) are in fact white. These stars are stable and long-lived, making them strong candidates for hosting habitable planets.<br><br>Rate: ' + rate + '/3days<br>Bonus: ' + bonusPercent + '%';
	
        this.elements.gtypeLevel.innerHTML = '<span class="tooltip-trigger">G-Type: Level ' +
            gameState.gtypeUpgradeLevel +
            '<span class="tooltip">' + tooltipText + '</span></span>';
        this.elements.gtypeUpgradeBtn.textContent =
            'Upgrade (Cost: ' + this.formatMass(gameState.gtypeUpgradeCost) + ')';
        this.elements.gtypeUpgradeBtn.disabled =
            gameState.totalMassConsumed < gameState.gtypeUpgradeCost;
    },

    formatMass: function(massKg, options = {}) {
	if (massKg == null) return '0'; // fallback
        const SOLAR_SWITCH_KG = CONFIG.SOLAR_MASS_KG * 0.01; // ~1% solar mass
    
        // Forced solar mass display (e.g. black holes)
        if (options.forceSolarMass || massKg >= SOLAR_SWITCH_KG) {
            var solarMasses = massKg / CONFIG.SOLAR_MASS_KG;
    
            // Precision scales nicely with magnitude
            if (solarMasses >= 1000) return solarMasses.toFixed(0) + ' M☉';
            if (solarMasses >= 1)    return solarMasses.toFixed(3) + ' M☉';
            return solarMasses.toFixed(5) + ' M☉';
        }
    
        // SI mass units (tonnes-based)
        if (massKg >= 1e30) return (massKg / 1e30).toFixed(2) + ' Qt'; // Quettatonnes
        if (massKg >= 1e27) return (massKg / 1e27).toFixed(2) + ' Rt'; // Ronnatonnes
        if (massKg >= 1e24) return (massKg / 1e24).toFixed(2) + ' Yt'; // Yottatonnes
        if (massKg >= 1e21) return (massKg / 1e21).toFixed(2) + ' Zt'; // Zettatonnes
        if (massKg >= 1e18) return (massKg / 1e18).toFixed(2) + ' Et'; // Exatonnes
        if (massKg >= 1e15) return (massKg / 1e15).toFixed(2) + ' Pt'; // Petatonnes
        if (massKg >= 1e12) return (massKg / 1e12).toFixed(2) + ' Tt'; // Teratonnes
        if (massKg >= 1e9)  return (massKg / 1e9).toFixed(2) + ' Gt'; // Gigatonnes
        if (massKg >= 1e6)  return (massKg / 1e6).toFixed(2) + ' Mt'; // Megatonnes
        if (massKg >= 1e3)  return (massKg / 1e3).toFixed(2) + ' tonnes'; // Tonnes
    
        return massKg.toFixed(0) + ' kg';
    },
    
    formatTime: function(ms) {
        var seconds = Math.floor(ms / 1000);
        var minutes = Math.floor(seconds / 60);
        var hours = Math.floor(minutes / 60);
        var days = Math.floor(hours / 24);
        
        if (days > 0) {
            return days + 'd ' + (hours % 24) + 'h';
        } else if (hours > 0) {
            return hours + 'h ' + (minutes % 60) + 'm';
        } else if (minutes > 0) {
            return minutes + 'm ' + (seconds % 60) + 's';
        } else {
            return seconds + 's';
        }
    },
    
    formatAge: function(ms) {
        var days = Math.floor(ms / (24 * 60 * 60 * 1000));
        var hours = Math.floor((ms % (24 * 60 * 60 * 1000)) / (60 * 60 * 1000));
        
        if (days > 0) {
            return days + 'd ' + hours + 'h';
        } else if (hours > 0) {
            return hours + 'h';
        } else {
            return 'New';
        }
    },
    

	openLeaderboard: async function(sortBy = 'mass') {
	    const container = this.elements.leaderboardList;
	    const localPlayerId = Server.playerId;
	
	    // Show loading only on first load
	    if (!this._cachedLeaderboardData) {
	        container.innerHTML = '<div style="text-align:center; padding:20px;">Loading...</div>';
	    }
	
	    // Fetch leaderboard
	    let data = await Server.getLeaderboard(sortBy);
	    if (!data.length) {
	        container.innerHTML = '<div style="text-align:center; padding:20px;">No entries yet</div>';
	        return;
	    }
	
	    this._cachedLeaderboardData = data;
	    this._currentSort = sortBy;
	
	    // Render function (can be called independently)
	    const render = () => {
	        const now = Date.now();
	        const fifteenMinutes = 15 * 60 * 1000;
	
	        let html = '';
	        data.forEach((entry, i) => {
	            const rank = i + 1;
	            const medal = rank===1?'🥇':rank===2?'🥈':rank===3?'🥉':rank+'.';
	            const isLocal = entry.id === localPlayerId;
	
	            // Calculate online status in real-time
	            const isOnline = (now - entry.lastSeen) < fifteenMinutes;
	            const onlineIndicator = isOnline ? '<span class="online-indicator"></span>' : '';
	            const nameSuffix = isLocal ? '💗' : '';
	
	            const displayName = entry.id ? entry.id.slice(-5) : 'Anon';
	
	            // Calculate time since last seen
		    const timeSinceLastSeen = now - entry.lastSeen;
		    const lastSeenText = formatTimeSince(timeSinceLastSeen);
		    
		    html += `<div class="leaderboard-entry${isLocal ? ' local-player' : ''}">
		        <span class="rank">${medal}</span>
		        <span class="name">${this.escapeHtml(displayName)}${onlineIndicator}${nameSuffix}</span>
		        <span class="value last-seen">${lastSeenText}</span>
		        <span class="value mass${sortBy==='mass'?' sorted':''}">${this.formatMass(entry.mass,{forceSolarMass:true})}</span>
		        <span class="value age${sortBy==='age'?' sorted':''}">${this.formatAge(entry.holeAge)}</span>
		    </div>`;
	        });
	        container.innerHTML = html;
	    };
	
	    render();
	
	    // Auto-refresh data every 30 seconds
	    if (this._leaderboardRefreshInterval) {
	        clearInterval(this._leaderboardRefreshInterval);
	    }
	
	    this._leaderboardRefreshInterval = setInterval(async () => {
	        if (this.elements.leaderboardPanel.classList.contains('show')) {
	            // Re-fetch data
	            data = await Server.getLeaderboard(sortBy);
	            this._cachedLeaderboardData = data;
	        } else {
	            clearInterval(this._leaderboardRefreshInterval);
	            this._leaderboardRefreshInterval = null;
	        }
	    }, 30000);
	
	    // Re-render indicators every 5 seconds (lightweight, no API call)
	    if (this._leaderboardIndicatorInterval) {
	        clearInterval(this._leaderboardIndicatorInterval);
	    }
	
	    this._leaderboardIndicatorInterval = setInterval(() => {
	        if (this.elements.leaderboardPanel.classList.contains('show')) {
	            render(); // Just re-render with updated time calculations
	        } else {
	            clearInterval(this._leaderboardIndicatorInterval);
	            this._leaderboardIndicatorInterval = null;
	        }
	    }, 5000);
	},

    escapeHtml: function(text) {
        if (!text) return '';
        return text
            .replace(/&/g, '&amp;')
            .replace(/</g, '&lt;')
            .replace(/>/g, '&gt;')
            .replace(/"/g, '&quot;')
            .replace(/'/g, '&#039;');
    },

    exportSession: async function() {
        var btn = document.getElementById('export-session-btn');
        var display = document.getElementById('export-code-display');
        var codeEl = document.getElementById('transfer-code-value');
        var expiryEl = document.getElementById('transfer-code-expiry');

        if (!btn || !display || !codeEl) return;

        btn.disabled = true;
        btn.textContent = 'Export';
        display.style.display = 'none';

        try {
            var result = await Server.createTransferCode();
	    if (!result || !result.code) {
                showErrorNotification(result && result.error ? result.error : 'Failed to generate transfer code');
                return;
            }
            codeEl.textContent = result.code.toUpperCase();
            display.style.display = 'block';
            btn.classList.add('menu-btn-export-active');

            var expiresAt = result.expiresAt;
            if (this._transferTimer) clearInterval(this._transferTimer);
            var self = this;

            var tick = function() {
                var remaining = Math.max(0, expiresAt - Date.now());
                var mins = Math.floor(remaining / 60000);
                var secs = Math.floor((remaining % 60000) / 1000);
                if (expiryEl) expiryEl.textContent = 'Expires in ' + mins + ':' + (secs < 10 ? '0' : '') + secs;
                if (remaining === 0) {
                    clearInterval(self._transferTimer);
                    if (codeEl) codeEl.textContent = 'EXPIRED';
                    if (expiryEl) expiryEl.textContent = '';
                    btn.classList.remove('menu-btn-export-active');
                }
            };

            tick(); // run immediately
            this._transferTimer = setInterval(tick, 1000);

        } catch (e) {
            showErrorNotification('Failed to generate transfer code');
        }

        btn.disabled = false;
        btn.textContent = 'Export';
    }
};