/**
 * 智慧时间轴组件 - 横向展开式
 * Smart Timeline Component - Horizontal Expansion
 */

(function() {
    'use strict';

    // 等待DOM加载完成
    document.addEventListener('DOMContentLoaded', initTimeline);

    function initTimeline() {
        const container = document.querySelector('.timeline-container');
        if (!container) return;

        const items = container.querySelectorAll('.timeline-item');
        if (!items.length) return;

        // 入场动画 - 使用 Intersection Observer
        const observerOptions = {
            threshold: 0.1,
            rootMargin: '0px 0px -50px 0px'
        };

        const observer = new IntersectionObserver((entries) => {
            entries.forEach(entry => {
                if (entry.isIntersecting) {
                    animateItems();
                    observer.unobserve(entry.target);
                }
            });
        }, observerOptions);

        observer.observe(container);

        // 节点逐个入场动画
        function animateItems() {
            items.forEach((item, index) => {
                setTimeout(() => {
                    item.style.opacity = '1';
                    item.style.transform = 'translateY(0)';
                }, index * 80);
            });
        }

        // 初始化节点样式（用于动画）
        items.forEach(item => {
            item.style.opacity = '0';
            item.style.transform = 'translateY(20px)';
            item.style.transition = 'opacity 0.5s ease, transform 0.5s ease, flex 0.5s cubic-bezier(0.25, 0.1, 0.25, 1), background 0.5s ease';
        });

        // 触摸设备支持
        let touchStartX = null;
        let scrollLeft = null;

        container.addEventListener('touchstart', (e) => {
            touchStartX = e.touches[0].pageX;
            scrollLeft = container.scrollLeft;
        }, { passive: true });

        container.addEventListener('touchmove', (e) => {
            if (!touchStartX) return;
            const x = e.touches[0].pageX;
            const walk = (touchStartX - x) * 1.5;
            container.scrollLeft = scrollLeft + walk;
        }, { passive: true });

        container.addEventListener('touchend', () => {
            touchStartX = null;
        });

        // 鼠标滚轮横向滚动（移动端视图时）
        container.addEventListener('wheel', (e) => {
            if (container.scrollWidth > container.clientWidth) {
                if (Math.abs(e.deltaX) < Math.abs(e.deltaY)) {
                    e.preventDefault();
                    container.scrollLeft += e.deltaY;
                }
            }
        }, { passive: false });

        // 拖拽滚动（移动端视图时）
        let isDragging = false;
        let startX;
        let dragScrollLeft;

        container.addEventListener('mousedown', (e) => {
            if (container.scrollWidth <= container.clientWidth) return;
            if (e.target.closest('.timeline-item')) return;
            isDragging = true;
            container.style.cursor = 'grabbing';
            startX = e.pageX - container.offsetLeft;
            dragScrollLeft = container.scrollLeft;
        });

        container.addEventListener('mouseleave', () => {
            isDragging = false;
            container.style.cursor = '';
        });

        container.addEventListener('mouseup', () => {
            isDragging = false;
            container.style.cursor = '';
        });

        container.addEventListener('mousemove', (e) => {
            if (!isDragging) return;
            e.preventDefault();
            const x = e.pageX - container.offsetLeft;
            const walk = (x - startX) * 2;
            container.scrollLeft = dragScrollLeft - walk;
        });

        // 节点点击事件（可扩展）
        items.forEach((item) => {
            item.addEventListener('click', () => {
                // 添加点击反馈动画
                const dot = item.querySelector('.dot');
                if (dot) {
                    dot.style.transform = 'translate(-50%, -50%) scale(2)';
                    setTimeout(() => {
                        dot.style.transform = '';
                    }, 200);
                }
            });
        });

        // 键盘导航支持
        let currentIndex = 0;

        document.addEventListener('keydown', (e) => {
            if (!isElementInViewport(container)) return;

            if (e.key === 'ArrowLeft') {
                currentIndex = Math.max(0, currentIndex - 1);
                scrollToItem(currentIndex);
            } else if (e.key === 'ArrowRight') {
                currentIndex = Math.min(items.length - 1, currentIndex + 1);
                scrollToItem(currentIndex);
            }
        });

        function scrollToItem(index) {
            if (container.scrollWidth <= container.clientWidth) return;

            const item = items[index];
            if (!item) return;

            const containerRect = container.getBoundingClientRect();
            const itemRect = item.getBoundingClientRect();

            const targetScrollLeft = container.scrollLeft + (itemRect.left - containerRect.left) - (containerRect.width / 2) + (itemRect.width / 2);

            container.scrollTo({
                left: targetScrollLeft,
                behavior: 'smooth'
            });
        }

        // ============================================
        // 自动轮播功能 - 从左到右循环展开
        // ============================================
        let autoPlayIndex = 0;
        let autoPlayTimer = null;
        let isUserInteracting = false;
        const autoPlayInterval = 3000; // 每个节点展开持续时间（毫秒）
        const pauseAfterInteraction = 5000; // 用户交互后暂停时间（毫秒）

        // 添加自动展开的CSS类
        function expandItem(index) {
            // 移除所有节点的展开状态
            items.forEach(item => {
                item.classList.remove('auto-expanded');
            });
            // 给当前节点添加展开状态
            if (items[index]) {
                items[index].classList.add('auto-expanded');
            }
        }

        // 自动轮播
        function autoPlay() {
            if (isUserInteracting) return;

            expandItem(autoPlayIndex);
            autoPlayIndex = (autoPlayIndex + 1) % items.length;
        }

        // 启动自动轮播
        function startAutoPlay() {
            if (autoPlayTimer) return;
            autoPlayTimer = setInterval(autoPlay, autoPlayInterval);
            // 立即展开第一个
            autoPlay();
        }

        // 停止自动轮播
        function stopAutoPlay() {
            if (autoPlayTimer) {
                clearInterval(autoPlayTimer);
                autoPlayTimer = null;
            }
            // 移除所有展开状态
            items.forEach(item => {
                item.classList.remove('auto-expanded');
            });
        }

        // 用户交互时暂停自动轮播
        function pauseAutoPlay() {
            isUserInteracting = true;
            stopAutoPlay();

            // 一段时间后恢复自动轮播
            setTimeout(() => {
                isUserInteracting = false;
                if (isElementInViewport(container)) {
                    startAutoPlay();
                }
            }, pauseAfterInteraction);
        }

        // 监听用户交互
        container.addEventListener('mouseenter', pauseAutoPlay);
        container.addEventListener('touchstart', pauseAutoPlay, { passive: true });

        // 使用 Intersection Observer 控制自动轮播
        const autoPlayObserver = new IntersectionObserver((entries) => {
            entries.forEach(entry => {
                if (entry.isIntersecting && !isUserInteracting) {
                    startAutoPlay();
                } else {
                    stopAutoPlay();
                }
            });
        }, { threshold: 0.3 });

        autoPlayObserver.observe(container);

        console.log("Timeline Loaded with Enhanced Labels and Positioning");
    }

    // 工具函数：检查元素是否在视口中
    function isElementInViewport(el) {
        const rect = el.getBoundingClientRect();
        return (
            rect.top < window.innerHeight &&
            rect.bottom > 0
        );
    }
})();