/**
 * 懒加载样式
 * 提供加载状态、动画效果和占位符样式
 */

/* ===== 基础懒加载样式 ===== */
.lazy-img,
.lazy-bg {
    transition: opacity 0.3s ease-in-out;
}

/* 视频不应用opacity过渡，避免有声音没画面的问题 */
.lazy-video {
    /* 视频元素不设置opacity相关样式 */
}

/* 加载中状态 */
.lazy-loading {
    position: relative;
}

.lazy-loading::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(90deg, #f0f0f0 25%, #e0e0e0 50%, #f0f0f0 75%);
    background-size: 200% 100%;
    animation: shimmer 1.5s infinite;
    z-index: 1;
}

/* 加载完成状态 */
.lazy-loaded {
    opacity: 1;
}

/* 加载错误状态 */
.lazy-error {
    position: relative;
    background-color: #f8f9fa;
}

.lazy-error::after {
    content: '⚠️';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 24px;
    color: #6c757d;
    z-index: 2;
}

/* ===== 图片懒加载样式 ===== */
img.lazy-img {
    /* 初始状态 */
    opacity: 0;
}

/* 加载完成后显示 */
img.lazy-img.lazy-loaded {
    opacity: 1;
}

/* ===== 视频懒加载样式 ===== */
video.lazy-video {
    /* 视频不设置opacity，避免有声音没画面的问题 */
    /* 可以通过其他方式提供加载反馈 */
}

video.lazy-video.lazy-loaded {
    /* 加载完成状态 */
}

/* 加载中的占位符 */
img.lazy-img.lazy-loading {
    background-color: #f8f9fa;
    min-height: 200px;
}

img.lazy-img.lazy-loading::before {
    border-radius: inherit;
}

/* 错误状态 */
img.lazy-img.lazy-error {
    min-height: 200px;
    background-color: #f8f9fa;
    border: 2px dashed #dee2e6;
}

img.lazy-img.lazy-error::after {
    content: '🖼️ 图片加载失败';
    font-size: 14px;
    color: #6c757d;
    white-space: nowrap;
}

/* ===== 背景图懒加载样式 ===== */
.lazy-bg {
    /* 初始状态 */
    opacity: 0;
    background-color: #f8f9fa;
}

/* 加载完成后显示 */
.lazy-bg.lazy-loaded {
    opacity: 1;
}

/* 加载中状态 */
.lazy-bg.lazy-loading {
    position: relative;
}

.lazy-bg.lazy-loading::before {
    border-radius: inherit;
}

/* 错误状态 */
.lazy-bg.lazy-error {
    background-color: #f8f9fa;
    background-image: repeating-linear-gradient(
        45deg,
        transparent,
        transparent 10px,
        rgba(0,0,0,.1) 10px,
        rgba(0,0,0,.1) 20px
    );
}

.lazy-bg.lazy-error::after {
    content: '🖼️ 背景图片加载失败';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 14px;
    color: #6c757d;
    background: rgba(255, 255, 255, 0.9);
    padding: 8px 12px;
    border-radius: 4px;
    white-space: nowrap;
}

/* ===== 动画效果 ===== */
@keyframes shimmer {
    0% {
        background-position: -200% 0;
    }
    100% {
        background-position: 200% 0;
    }
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ===== 高级效果类 ===== */

/* 淡入效果 */
.lazy-fade-in {
    animation: fadeIn 0.5s ease-in-out;
}

/* 滑入效果 */
.lazy-slide-up {
    animation: slideUp 0.6s ease-out;
}

/* 模糊到清晰效果 */
.lazy-blur {
    filter: blur(5px);
    transition: filter 0.3s ease-in-out;
}

.lazy-blur.lazy-loaded {
    filter: blur(0);
}

/* ===== 占位符样式 ===== */

/* 骨架屏效果 */
.lazy-skeleton {
    background: linear-gradient(90deg, #f0f0f0 25%, #e0e0e0 50%, #f0f0f0 75%);
    background-size: 200% 100%;
    animation: shimmer 1.5s infinite;
}

.lazy-skeleton.lazy-loaded {
    background: none;
    animation: none;
}

/* 渐变占位符 */
.lazy-gradient-placeholder {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

.lazy-gradient-placeholder.lazy-loaded {
    background: none;
}

/* 颜色占位符 */
.lazy-color-placeholder {
    background-color: #e9ecef;
}

.lazy-color-placeholder.lazy-loaded {
    background-color: transparent;
}

/* ===== 响应式优化 ===== */

/* 移动端优化 */
@media (max-width: 768px) {
    .lazy-loading::before {
        animation-duration: 1s; /* 移动端加快动画速度 */
    }
    
    img.lazy-img.lazy-loading {
        min-height: 150px; /* 移动端减小占位符高度 */
    }
    
    .lazy-error::after {
        font-size: 12px; /* 移动端减小错误提示字体 */
    }
}

/* 高DPI屏幕优化 */
@media (-webkit-min-device-pixel-ratio: 2), (min-resolution: 192dpi) {
    .lazy-loading::before {
        background-size: 400% 100%; /* 高DPI屏幕使用更细腻的动画 */
    }
}

/* ===== 特殊场景样式 ===== */

/* 卡片中的懒加载图片 */
.card .lazy-img.lazy-loading {
    min-height: 200px;
}

.card .lazy-img.lazy-error {
    min-height: 200px;
}

/* 头像懒加载 */
.avatar.lazy-img {
    border-radius: 50%;
}

.avatar.lazy-img.lazy-loading {
    min-height: auto;
    width: 100%;
    aspect-ratio: 1;
}

.avatar.lazy-img.lazy-loading::before {
    border-radius: 50%;
}

.avatar.lazy-img.lazy-error {
    min-height: auto;
    width: 100%;
    aspect-ratio: 1;
}

.avatar.lazy-img.lazy-error::after {
    content: '👤';
    font-size: 50%;
}

/* 缩略图懒加载 */
.thumbnail.lazy-img.lazy-loading {
    min-height: 100px;
}

.thumbnail.lazy-img.lazy-error {
    min-height: 100px;
}

.thumbnail.lazy-img.lazy-error::after {
    font-size: 12px;
    content: '🖼️';
}

/* ===== 性能优化 ===== */

/* 减少重绘 */
.lazy-img,
.lazy-bg {
    will-change: opacity;
}

.lazy-loading {
    will-change: opacity;
}

/* 硬件加速 */
.lazy-fade-in,
.lazy-slide-up {
    transform: translateZ(0);
}

/* ===== 可访问性 ===== */

/* 减少动画（用户偏好） */
@media (prefers-reduced-motion: reduce) {
    .lazy-img,
    .lazy-bg,
    .lazy-loading::before {
        animation: none;
        transition: none;
    }
    
    .lazy-fade-in,
    .lazy-slide-up {
        animation: none;
    }
}

/* 高对比度模式 */
@media (prefers-contrast: high) {
    .lazy-loading::before {
        background: linear-gradient(90deg, #000 25%, #333 50%, #000 75%);
    }
    
    .lazy-error {
        border-color: #000;
    }
    
    .lazy-error::after {
        color: #000;
        background: #fff;
    }
}