/**
 * Stay Fresh in AI — Presentation Engine
 * Pure JavaScript — No Dependencies
 */

(function () {
    'use strict';

    // ─── State ───
    let currentSlide = 1;
    const totalSlides = 10;
    let isAnimating = false;

    // ─── DOM Elements ───
    const progressFill    = document.getElementById('progressFill');
    const currentSlideEl  = document.getElementById('currentSlide');
    const totalSlidesEl   = document.getElementById('totalSlides');
    const prevBtn         = document.getElementById('prevBtn');
    const nextBtn         = document.getElementById('nextBtn');
    const slides          = document.querySelectorAll('.slide');

    // ─── Init ───
    function init() {
        totalSlidesEl.textContent = totalSlides;
        updateUI(1);
        bindEvents();
        handleHash();
    }

    // ─── Event Binding ───
    function bindEvents() {
        prevBtn.addEventListener('click', goToPrev);
        nextBtn.addEventListener('click', goToNext);
        document.addEventListener('keydown', handleKeyDown);

        // Touch swipe
        let touchStartX = 0;
        document.addEventListener('touchstart', e => {
            touchStartX = e.changedTouches[0].screenX;
        }, { passive: true });

        document.addEventListener('touchend', e => {
            const diff = touchStartX - e.changedTouches[0].screenX;
            if (Math.abs(diff) > 50) {
                diff > 0 ? goToNext() : goToPrev();
            }
        }, { passive: true });

        // Mouse wheel (throttled)
        let wheelLock = false;
        document.addEventListener('wheel', e => {
            if (wheelLock) return;
            wheelLock = true;
            setTimeout(() => { wheelLock = false; }, 800);
            e.deltaY > 0 ? goToNext() : goToPrev();
        }, { passive: true });
    }

    // ─── Keyboard Handler ───
    function handleKeyDown(e) {
        switch (e.key) {
            case 'ArrowRight':
            case ' ':
            case 'Enter':
                e.preventDefault();
                goToNext();
                break;
            case 'ArrowLeft':
            case 'Backspace':
                e.preventDefault();
                goToPrev();
                break;
            case 'Home':
                e.preventDefault();
                goToSlide(1);
                break;
            case 'End':
                e.preventDefault();
                goToSlide(totalSlides);
                break;
        }

        // Number keys 1–9 for quick jump
        const num = parseInt(e.key);
        if (!isNaN(num) && num >= 1 && num <= Math.min(totalSlides, 9)) {
            goToSlide(num);
        }
    }

    // ─── Navigation ───
    function goToNext() {
        if (currentSlide < totalSlides && !isAnimating) goToSlide(currentSlide + 1);
    }

    function goToPrev() {
        if (currentSlide > 1 && !isAnimating) goToSlide(currentSlide - 1);
    }

    function goToSlide(n) {
        if (n === currentSlide || n < 1 || n > totalSlides || isAnimating) return;

        isAnimating = true;
        currentSlide = n;

        slides.forEach((slide, i) => {
            const num = i + 1;
            slide.classList.remove('active', 'prev');

            if (num === currentSlide) {
                slide.classList.add('active');
                triggerAnimations(slide);
            } else if (num < currentSlide) {
                slide.classList.add('prev');
            }
        });

        updateUI(currentSlide);
        setTimeout(() => { isAnimating = false; }, 500);
    }

    // ─── UI Update ───
    function updateUI(n) {
        currentSlideEl.textContent = n;
        progressFill.style.width = `${(n / totalSlides) * 100}%`;

        prevBtn.style.opacity       = n === 1            ? '0.3' : '1';
        prevBtn.style.pointerEvents = n === 1            ? 'none' : 'auto';
        nextBtn.style.opacity       = n === totalSlides  ? '0.3' : '1';
        nextBtn.style.pointerEvents = n === totalSlides  ? 'none' : 'auto';

        history.replaceState(null, null, `#slide-${n}`);
    }

    // ─── Re-trigger CSS animations when a slide becomes active ───
    function triggerAnimations(slide) {
        const els = slide.querySelectorAll('.agenda-item, [style*="--delay"]');
        els.forEach(el => {
            el.style.animation = 'none';
            void el.offsetHeight;   // reflow
            el.style.animation = null;
        });
    }

    // ─── URL Hash Support ───
    function handleHash() {
        const hash = window.location.hash;
        if (hash && hash.startsWith('#slide-')) {
            const n = parseInt(hash.replace('#slide-', ''));
            if (n >= 1 && n <= totalSlides) goToSlide(n);
        }
    }

    window.addEventListener('hashchange', handleHash);

    // ─── Public API ───
    window.PresentationAPI = {
        next:           goToNext,
        prev:           goToPrev,
        goTo:           goToSlide,
        getCurrentSlide: () => currentSlide,
        getTotalSlides:  () => totalSlides
    };

    // ─── Boot ───
    if (document.readyState === 'loading') {
        document.addEventListener('DOMContentLoaded', init);
    } else {
        init();
    }

})();