document.addEventListener('DOMContentLoaded', function() {
    // DOM Elements
    const timerDisplay = document.getElementById('timer-display');
    const startBtn = document.getElementById('start-btn');
    const pauseBtn = document.getElementById('pause-btn');
    const resetBtn = document.getElementById('reset-btn');
    const hoursInput = document.getElementById('hours-input');
    const minutesInput = document.getElementById('minutes-input');
    const secondsInput = document.getElementById('seconds-input');
    const alarmSelect = document.getElementById('alarm-select');
    const volumeControl = document.getElementById('volume-control');
    const testAlarmBtn = document.getElementById('test-alarm');
    const alarmSound = document.getElementById('alarm-sound');
    const themeToggle = document.getElementById('theme-toggle');

    // Timer variables
    let timer;
    let totalSeconds = 0;
    let remainingSeconds = 0;
    let isRunning = false;

    // Theme toggle
    themeToggle.addEventListener('click', () => {
        document.documentElement.classList.toggle('dark');
        feather.replace();
    });

    // Initialize timer display
    updateTimerDisplay(0);

    // Start button click handler
    startBtn.addEventListener('click', () => {
        if (!isRunning) {
            if (remainingSeconds === 0) {
                const hours = parseInt(hoursInput.value) || 0;
                const minutes = parseInt(minutesInput.value) || 0;
                const seconds = parseInt(secondsInput.value) || 0;
                totalSeconds = (hours * 3600) + (minutes * 60) + seconds;
                remainingSeconds = totalSeconds;
            }

            if (remainingSeconds > 0) {
                isRunning = true;
                startBtn.disabled = true;
                pauseBtn.disabled = false;
                toggleInputs(true);

                timer = setInterval(() => {
                    remainingSeconds--;
                    updateTimerDisplay(remainingSeconds);

                    if (remainingSeconds <= 0) {
                        clearInterval(timer);
                        isRunning = false;
                        startBtn.disabled = false;
                        pauseBtn.disabled = true;
                        playAlarm();
                    }
                }, 1000);
            }
        }
    });

    // Pause button click handler
    pauseBtn.addEventListener('click', () => {
        if (isRunning) {
            clearInterval(timer);
            isRunning = false;
            startBtn.disabled = false;
            pauseBtn.disabled = true;
        }
    });

    // Reset button click handler
    resetBtn.addEventListener('click', () => {
        clearInterval(timer);
        isRunning = false;
        remainingSeconds = 0;
        updateTimerDisplay(0);
        startBtn.disabled = false;
        pauseBtn.disabled = true;
        toggleInputs(false);
    });

    // Test alarm button click handler
    testAlarmBtn.addEventListener('click', () => {
        playAlarm();
    });

    // Volume control change handler
    volumeControl.addEventListener('input', () => {
        alarmSound.volume = volumeControl.value;
    });

    // Update timer display
    function updateTimerDisplay(seconds) {
        const hours = Math.floor(seconds / 3600);
        const minutes = Math.floor((seconds % 3600) / 60);
        const secs = seconds % 60;

        timerDisplay.textContent = 
            `${String(hours).padStart(2, '0')}:${String(minutes).padStart(2, '0')}:${String(secs).padStart(2, '0')}`;
    }

    // Play alarm sound
    function playAlarm() {
        const soundFile = {
            'beep': 'https://assets.mixkit.co/sfx/preview/mixkit-alarm-digital-clock-beep-989.mp3',
            'bell': 'https://assets.mixkit.co/sfx/preview/mixkit-digital-clock-digital-alarm-buzzer-992.mp3',
            'digital': 'https://assets.mixkit.co/sfx/preview/mixkit-simple-digital-clock-alarm-995.mp3'
        }[alarmSelect.value];

        alarmSound.src = soundFile;
        alarmSound.volume = volumeControl.value;
        alarmSound.play();
    }

    // Toggle input fields disabled state
    function toggleInputs(disabled) {
        hoursInput.disabled = disabled;
        minutesInput.disabled = disabled;
        secondsInput.disabled = disabled;
    }

    // Input validation
    function validateInput(input, max) {
        if (input.value > max) {
            input.value = max;
        } else if (input.value < 0) {
            input.value = 0;
        }
    }

    hoursInput.addEventListener('change', () => validateInput(hoursInput, 23));
    minutesInput.addEventListener('change', () => validateInput(minutesInput, 59));
    secondsInput.addEventListener('change', () => validateInput(secondsInput, 59));
});