/* ================================================================
   Book Reader — Shared Styles
   Feature #16, Visual Mode | v1.1
   ALL selectors scoped inside .ai501-book-reader
   ================================================================ */

/* --- CSS Custom Properties (Adaptive defaults) --- */
.ai501-book-reader {
    --br-bg:            #FDFBF7;
    --br-surface:       #F5F0E8;
    --br-text:          #2C2416;
    --br-text-muted:    #6B5D4F;
    --br-accent:        #8B4513;
    --br-accent-hover:  #A0522D;
    --br-border:        #D4C5A9;
    --br-page-shadow:   rgba(44,36,22,0.12);
    --br-page-edge:     #E8DFD0;
    --br-progress-bg:   #E8DFD0;
    --br-progress-fill: #8B4513;
    --br-font-sans:     'Source Sans 3', 'Segoe UI', system-ui, sans-serif;
    --br-flip-duration: 600ms;
    --br-flip-ease:     cubic-bezier(0.645, 0.045, 0.355, 1.0);
    --br-topbar-h:      48px;
    --br-footer-h:      36px;
    --br-progress-h:    3px;
}

/* --- Container --- */
.ai501-book-reader {
    contain: layout style;
    position: relative;
    overflow: hidden;
    display: flex;
    flex-direction: column;
    background: var(--br-bg);
    border: 1px solid var(--br-border);
    border-radius: 8px;
    font-family: Arial, Helvetica, system-ui, sans-serif;
    color: var(--br-text);
    user-select: none;
    -webkit-user-select: none;
}

/* Full-screen mode */
.ai501-book-reader--fullscreen {
    position: fixed !important;
    top: 0; left: 0; right: 0; bottom: 0;
    z-index: 999999;
    height: 100vh !important;
    border: none;
    border-radius: 0;
}

/* --- Top Bar --- */
.ai501-book-reader .ai501-br-topbar {
    display: flex;
    align-items: center;
    height: var(--br-topbar-h);
    padding: 0 12px;
    background: var(--br-surface);
    border-bottom: 1px solid var(--br-border);
    flex-shrink: 0;
    gap: 8px;
    z-index: 10;
}

.ai501-book-reader .ai501-br-topbar__title {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--br-text);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    flex: 1;
    min-width: 0;
}

.ai501-book-reader .ai501-br-topbar__page-label {
    font-size: 0.8125rem;
    color: var(--br-text-muted);
    white-space: nowrap;
}

.ai501-book-reader .ai501-br-topbar__controls {
    display: flex;
    gap: 4px;
    flex-shrink: 0;
}

/* --- Buttons --- */
.ai501-book-reader .ai501-br-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    border: none;
    background: transparent;
    color: var(--br-text-muted);
    cursor: pointer;
    border-radius: 6px;
    transition: background 0.15s, color 0.15s;
    padding: 0;
    font-family: inherit;
}

.ai501-book-reader .ai501-br-btn:hover {
    background: var(--br-border);
    color: var(--br-text);
}

.ai501-book-reader .ai501-br-btn:focus-visible {
    outline: 2px solid var(--br-accent);
    outline-offset: 2px;
}

/* --- Progress Bar --- */
.ai501-book-reader .ai501-br-progress {
    height: var(--br-progress-h);
    background: var(--br-progress-bg);
    flex-shrink: 0;
}

.ai501-book-reader .ai501-br-progress__fill {
    height: 100%;
    background: var(--br-progress-fill);
    transition: width 300ms ease;
    will-change: width;
}

/* --- Page Area --- */
.ai501-book-reader .ai501-br-page-area {
    flex: 1;
    position: relative;
    overflow: hidden;
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 0;
    perspective: 2000px;
}

/* Click zones */
.ai501-book-reader .ai501-br-zone {
    position: absolute;
    top: 0;
    bottom: 0;
    z-index: 5;
    cursor: pointer;
}

.ai501-book-reader .ai501-br-zone--prev {
    left: 0;
    width: 25%;
}

.ai501-book-reader .ai501-br-zone--next {
    right: 0;
    width: 25%;
}

.ai501-book-reader .ai501-br-zone:hover {
    background: rgba(0,0,0,0.03);
}

/* Page container */
.ai501-book-reader .ai501-br-pages {
    position: relative;
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    transform-style: preserve-3d;
    -webkit-transform-style: preserve-3d;
}

/* Individual page */
.ai501-book-reader .ai501-br-page {
    position: absolute;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    -webkit-backface-visibility: hidden;
    opacity: 0;
    pointer-events: none;
    transition: none;
}

.ai501-book-reader .ai501-br-page--active {
    opacity: 1;
    pointer-events: auto;
    z-index: 2;
}

.ai501-book-reader .ai501-br-page--preload {
    opacity: 0;
    z-index: 1;
}

/* Flip animation — forward (next page) */
.ai501-book-reader .ai501-br-page--flip-out {
    animation: ai501BrFlipOut var(--br-flip-duration) var(--br-flip-ease) forwards;
    z-index: 3;
}

.ai501-book-reader .ai501-br-page--flip-in {
    animation: ai501BrFlipIn var(--br-flip-duration) var(--br-flip-ease) forwards;
    z-index: 2;
}

@keyframes ai501BrFlipOut {
    0%   { transform: rotateY(0deg); opacity: 1; }
    50%  { transform: rotateY(-90deg); opacity: 0.6; }
    100% { transform: rotateY(-180deg); opacity: 0; }
}

@keyframes ai501BrFlipIn {
    0%   { transform: rotateY(180deg); opacity: 0; }
    50%  { transform: rotateY(90deg); opacity: 0.6; }
    100% { transform: rotateY(0deg); opacity: 1; }
}

/* Flip backward (previous page) */
.ai501-book-reader .ai501-br-page--flip-out-rev {
    animation: ai501BrFlipOutRev var(--br-flip-duration) var(--br-flip-ease) forwards;
    z-index: 3;
}

.ai501-book-reader .ai501-br-page--flip-in-rev {
    animation: ai501BrFlipInRev var(--br-flip-duration) var(--br-flip-ease) forwards;
    z-index: 2;
}

@keyframes ai501BrFlipOutRev {
    0%   { transform: rotateY(0deg); opacity: 1; }
    50%  { transform: rotateY(90deg); opacity: 0.6; }
    100% { transform: rotateY(180deg); opacity: 0; }
}

@keyframes ai501BrFlipInRev {
    0%   { transform: rotateY(-180deg); opacity: 0; }
    50%  { transform: rotateY(-90deg); opacity: 0.6; }
    100% { transform: rotateY(0deg); opacity: 1; }
}

/* prefers-reduced-motion: instant swap */
@media (prefers-reduced-motion: reduce) {
    .ai501-book-reader .ai501-br-page--flip-out,
    .ai501-book-reader .ai501-br-page--flip-in,
    .ai501-book-reader .ai501-br-page--flip-out-rev,
    .ai501-book-reader .ai501-br-page--flip-in-rev {
        animation: none !important;
        transition: opacity 0.15s ease !important;
    }
}

/* --- Footer --- */
.ai501-book-reader .ai501-br-footer {
    height: var(--br-footer-h);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    border-top: 1px solid var(--br-border);
}

.ai501-book-reader .ai501-br-footer__text {
    font-size: 0.75rem;
    color: var(--br-text-muted);
}

/* --- Panels (TOC + Settings) --- */
.ai501-book-reader .ai501-br-panel {
    position: absolute;
    top: 0;
    bottom: 0;
    width: 300px;
    max-width: 85vw;
    background: var(--br-surface);
    border: 1px solid var(--br-border);
    z-index: 20;
    display: flex;
    flex-direction: column;
    transition: transform 0.3s ease;
    box-shadow: 0 8px 32px rgba(0,0,0,0.15);
}

.ai501-book-reader .ai501-br-panel--toc {
    left: 0;
    transform: translateX(-100%);
    border-left: none;
    border-radius: 0 8px 8px 0;
}

.ai501-book-reader .ai501-br-panel--settings {
    right: 0;
    transform: translateX(100%);
    border-right: none;
    border-radius: 8px 0 0 8px;
}

.ai501-book-reader .ai501-br-panel[aria-hidden="false"] {
    transform: translateX(0);
}

.ai501-book-reader .ai501-br-panel__header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 16px;
    border-bottom: 1px solid var(--br-border);
}

.ai501-book-reader .ai501-br-panel__header h3 {
    margin: 0;
    font-size: 0.9375rem;
    font-weight: 600;
    color: var(--br-text);
}

.ai501-book-reader .ai501-br-panel__close {
    font-size: 1.125rem;
    width: 32px;
    height: 32px;
}

.ai501-book-reader .ai501-br-panel__body {
    flex: 1;
    overflow-y: auto;
    padding: 16px;
}

/* Overlay */
.ai501-book-reader .ai501-br-overlay {
    position: absolute;
    inset: 0;
    background: rgba(0,0,0,0.4);
    z-index: 15;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.3s ease;
}

.ai501-book-reader .ai501-br-overlay[aria-hidden="false"] {
    opacity: 1;
    pointer-events: auto;
}

/* --- Settings --- */
.ai501-book-reader .ai501-br-setting {
    margin-bottom: 20px;
}

.ai501-book-reader .ai501-br-setting__label {
    display: block;
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--br-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 8px;
}

/* Theme toggle (segmented control) */
.ai501-book-reader .ai501-br-theme-toggle,
.ai501-book-reader .ai501-br-zoom-toggle {
    display: flex;
    background: var(--br-bg);
    border: 1px solid var(--br-border);
    border-radius: 6px;
    overflow: hidden;
}

.ai501-book-reader .ai501-br-theme-btn,
.ai501-book-reader .ai501-br-zoom-btn {
    flex: 1;
    padding: 8px 12px;
    border: none;
    background: transparent;
    font-size: 0.8125rem;
    font-family: inherit;
    color: var(--br-text-muted);
    cursor: pointer;
    transition: background 0.15s, color 0.15s;
}

.ai501-book-reader .ai501-br-theme-btn[aria-checked="true"],
.ai501-book-reader .ai501-br-zoom-btn.ai501-br-zoom-btn--active {
    background: var(--br-accent);
    color: #fff;
    font-weight: 600;
}

/* Keyboard shortcuts grid */
.ai501-book-reader .ai501-br-shortcuts {
    display: grid;
    grid-template-columns: auto 1fr;
    gap: 4px 12px;
    font-size: 0.75rem;
    color: var(--br-text-muted);
}

.ai501-book-reader .ai501-br-shortcuts span:nth-child(odd) {
    font-weight: 600;
    color: var(--br-text);
}

/* --- TOC --- */
.ai501-book-reader .ai501-br-toc-list {
    display: flex;
    flex-direction: column;
    gap: 4px;
    padding: 8px;
}

.ai501-book-reader .ai501-br-toc-item {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 8px;
    border: 1px solid transparent;
    border-radius: 6px;
    background: transparent;
    cursor: pointer;
    font-family: inherit;
    font-size: 0.8125rem;
    color: var(--br-text-muted);
    text-align: left;
    transition: background 0.15s, border-color 0.15s;
    width: 100%;
}

.ai501-book-reader .ai501-br-toc-item:hover {
    background: var(--br-bg);
    border-color: var(--br-border);
}

.ai501-book-reader .ai501-br-toc-item--active {
    background: var(--br-bg);
    border-color: var(--br-accent);
    color: var(--br-accent);
    font-weight: 600;
}

.ai501-book-reader .ai501-br-toc-item img {
    width: 40px;
    height: auto;
    border-radius: 3px;
    border: 1px solid var(--br-border);
    flex-shrink: 0;
}

/* --- Accessibility text layer --- */
.ai501-book-reader .ai501-br-text-layer {
    clip: rect(0,0,0,0);
    position: absolute;
    width: 1px;
    height: 1px;
    overflow: hidden;
    white-space: nowrap;
}

/* --- Responsive --- */
@media (max-width: 768px) {
    .ai501-book-reader .ai501-br-topbar__title {
        font-size: 0.75rem;
        max-width: 120px;
    }
    
    .ai501-book-reader .ai501-br-topbar__page-label {
        display: none;
    }
    
    .ai501-book-reader .ai501-br-btn {
        width: 40px;
        height: 40px;
        min-width: 44px;
        min-height: 44px;
    }

    .ai501-book-reader .ai501-br-panel {
        width: 85vw;
    }

    .ai501-book-reader .ai501-br-setting--shortcuts {
        display: none;
    }
}

/* ================================================================
   Loading State (for PDF.js client-side rendering)
   ================================================================ */

.ai501-book-reader .ai501-br-loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 100%;
    gap: 1rem;
    color: var(--br-text-muted);
    font-family: Arial, Helvetica, system-ui, sans-serif;
    font-size: 0.95rem;
}

.ai501-book-reader .ai501-br-spinner {
    width: 36px;
    height: 36px;
    border: 3px solid var(--br-border);
    border-top-color: var(--br-accent);
    border-radius: 50%;
    animation: ai501-br-spin 0.8s linear infinite;
}

@keyframes ai501-br-spin {
    to { transform: rotate(360deg); }
}

@media (prefers-reduced-motion: reduce) {
    .ai501-book-reader .ai501-br-spinner {
        animation: none;
        opacity: 0.5;
    }
}