:root {
    --primary: #7c3aed;
    --primary-light: #a855f7;
    --primary-dark: #5b21b6;
    --background: #0f172a;
    --surface: #1e293b;
    --card: #334155;
    --text: #f8fafc;
    --text-secondary: #cbd5e1;
    --text-muted: #94a3b8;
    --border: #334155;
    --border-light: #475569;
    --success: #10b981;
    --warning: #f59e0b;
    --danger: #ef4444;
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.3), 0 1px 2px 0 rgba(0, 0, 0, 0.2);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.3), 0 4px 6px -2px rgba(0, 0, 0, 0.2);
    --composer-height: 80px;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--background);
    color: var(--text);
    height: 100vh;
    overflow: hidden;
}

.app {
    display: flex;
    height: 100vh;
    background: var(--background);
}

/* Sidebar */
.sidebar {
    width: 320px;
    background: linear-gradient(180deg, #111827 0%, #0f172a 60%);
    border-right: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    flex-shrink: 0;
}

.sidebar-header {
    padding: 24px;
    border-bottom: 1px solid var(--border);
}

.user-info {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 20px;
    background: rgba(255,255,255,0.02);
    padding: 10px;
    border-radius: 12px;
}

.avatar {
    width: 40px;
    height: 40px;
    background: var(--primary);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
    color: white;
}

.user-details .username {
    font-weight: 600;
    color: var(--text);
    font-size: 16px;
}

.user-details .status {
    font-size: 12px;
    color: var(--success);
}

.new-chat-btn {
    width: 100%;
    padding: 12px 16px;
    background: linear-gradient(90deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: white;
    border: none;
    border-radius: 10px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    box-shadow: 0 8px 20px rgba(124, 58, 237, 0.25);
}

.new-chat-btn:hover {
    background: var(--primary-dark);
    transform: translateY(-1px);
}

.history-section {
    flex: 1;
    padding: 20px 24px;
    overflow-y: auto;
}

.history-section h3 {
    font-size: 14px;
    font-weight: 600;
    color: #a5b4fc;
    margin-bottom: 16px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.history-list {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.history-item {
    padding: 12px 16px;
    border-radius: 8px;
    cursor: pointer;
    color: var(--text-secondary);
    transition: all 0.2s ease;
    font-size: 14px;
    border: 1px solid transparent;
}

.history-item:hover {
    background: rgba(124,58,237,0.12);
    border-color: rgba(124,58,237,0.25);
    color: var(--text);
}

.history-item.active {
    background: linear-gradient(90deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: white;
    border-color: transparent;
    box-shadow: 0 6px 16px rgba(124,58,237,0.35);
}

.history-preview {
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

/* three-dot menu */
.history-menu-btn {
    position: absolute;
    right: 8px;
    top: 50%;
    transform: translateY(-50%);
    background: transparent;
    border: none;
    color: var(--text-secondary);
    display: none;
    cursor: pointer;
    padding: 4px 6px;
    border-radius: 6px;
}

.history-item:hover .history-menu-btn,
.history-item.active .history-menu-btn { display: inline-flex; }

.history-menu-btn:hover { background: var(--card); }

.history-menu {
    position: absolute;
    right: 8px;
    top: calc(100% - 6px);
    min-width: 140px;
    background: linear-gradient(180deg, #1f2937 0%, #111827 100%);
    border: 1px solid var(--border);
    border-radius: 8px;
    box-shadow: var(--shadow-lg);
    display: none;
    z-index: 10;
}

.history-menu.open { display: block; }

.history-menu button {
    width: 100%;
    text-align: left;
    background: transparent;
    border: none;
    color: var(--text-secondary);
    padding: 10px 12px;
    cursor: pointer;
}

.history-menu button:hover { background: #374151; color: var(--text); }
.history-menu .danger { color: #f87171; }
.history-menu .danger:hover { background: rgba(248, 113, 113, 0.15); }

/* inline delete button for history items */
.history-item {
    display: flex;
    align-items: center;
    gap: 8px;
    position: relative;
    padding-right: 36px; /* reserve space for delete icon */
}

.history-delete {
    display: none;
    color: var(--text-muted);
    background: transparent;
    border: none;
    cursor: pointer;
    padding: 4px;
    border-radius: 6px;
    position: absolute;
    right: 8px;
    top: 50%;
    transform: translateY(-50%);
}

.history-item:hover .history-delete {
    display: inline-flex;
}

/* Always show delete on the active item */
.history-item.active .history-delete {
    display: inline-flex;
}

.history-delete:hover {
    color: #fff;
    background: rgba(239, 68, 68, 0.18);
}

.sidebar-footer {
    padding: 24px;
    border-top: 1px solid var(--border);
}

.logout-btn {
    width: 100%;
    padding: 10px;
    background: transparent;
    color: var(--text-secondary);
    border: 1px solid var(--border);
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s ease;
}

.logout-btn:hover {
    background: var(--danger);
    color: white;
    border-color: var(--danger);
}

/* Chat Area */
.chat-area {
    flex: 1;
    display: flex;
    flex-direction: column;
    background: var(--background);
    height: 100vh;
    position: relative;
}

.chat-header {
    padding: 20px 24px;
    border-bottom: 1px solid var(--border);
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: var(--surface);
    flex-shrink: 0;
}

.chat-title h2 {
    font-size: 24px;
    font-weight: 700;
    color: var(--primary);
    margin-bottom: 4px;
}

.chat-subtitle {
    font-size: 14px;
    color: var(--text-secondary);
}

.chat-actions {
    display: flex;
    gap: 8px;
    align-items: center;
}

.action-btn {
    padding: 8px 16px;
    border: 1px solid var(--border);
    background: var(--surface);
    color: var(--text-secondary);
    border-radius: 8px;
    cursor: pointer;
    font-size: 14px;
    transition: all 0.2s ease;
}

.action-btn:hover {
    background: var(--card);
    color: var(--text);
}

.action-btn.danger:hover {
    background: var(--danger);
    color: white;
    border-color: var(--danger);
}

/* Messages Container - Fixed height calculation */
.messages-container {
    flex: 1;
    overflow-y: auto;
    padding: 24px;
    padding-bottom: calc(var(--composer-height) + 24px);
    background: var(--background);
}

.messages {
    max-width: 800px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    gap: 16px;
    width: 100%;
    min-height: 0;
}

.msg {
    display: flex;
    max-width: 80%;
    animation: fadeIn 0.3s ease;
}

.msg.user {
    align-self: flex-end;
    flex-direction: row-reverse;
}

.msg.bot {
    align-self: flex-start;
}

.msg-content {
    background: var(--surface);
    padding: 16px 20px;
    border-radius: 18px;
    box-shadow: var(--shadow);
    position: relative;
    border: 1px solid var(--border);
}

.msg.user .msg-content {
    background: var(--primary);
    color: white;
    border-bottom-right-radius: 6px;
    border-color: var(--primary-dark);
}

.msg.bot .msg-content {
    border-bottom-left-radius: 6px;
}

.msg-meta {
    font-size: 12px;
    color: var(--text-muted);
    margin-bottom: 8px;
    font-weight: 500;
}

.msg.user .msg-meta {
    color: rgba(255, 255, 255, 0.8);
}

.msg-text {
    line-height: 1.5;
    white-space: pre-wrap;
    word-break: break-word;
}

/* Message Composer - Fixed positioning */
.message-composer {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    padding: 20px 24px;
    background: var(--surface);
    border-top: 1px solid var(--border);
    height: var(--composer-height);
    display: flex;
    align-items: center;
    z-index: 100;
}

.composer-input {
    max-width: 800px;
    margin: 0 auto;
    display: flex;
    align-items: flex-end;
    gap: 12px;
    background: var(--background);
    border: 2px solid var(--border);
    border-radius: 24px;
    padding: 12px 8px 12px 20px;
    transition: all 0.2s ease;
    width: 100%;
    min-height: 56px;
}

.composer-input:focus-within {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(124, 58, 237, 0.2);
}

.composer-input textarea,
.composer-input input[type="text"] {
    flex: 1;
    border: none;
    background: transparent;
    font-size: 16px;
    color: var(--text);
    outline: none;
    resize: none;
    min-height: 24px;
    max-height: 120px;
    line-height: 1.5;
    font-family: inherit;
    padding: 8px 0;
}

.composer-input textarea::placeholder,
.composer-input input[type="text"]::placeholder {
    color: var(--text-muted);
}

.composer-input textarea {
    overflow-y: auto;
}

.file-upload-btn {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: var(--card);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all 0.2s ease;
    font-size: 18px;
    color: var(--text-secondary);
    border: 1px solid var(--border);
}

.file-upload-btn:hover {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

.file-upload-btn input {
    display: none;
}

.send-btn {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: var(--primary);
    color: white;
    border: none;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
    font-weight: bold;
}

.send-btn:hover {
    background: var(--primary-dark);
    transform: scale(1.05);
}

.send-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none;
}

/* Typing Indicator */
.typing {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 16px 20px;
    background: var(--surface);
    border-radius: 18px;
    border-bottom-left-radius: 6px;
    box-shadow: var(--shadow);
    max-width: 80px;
    border: 1px solid var(--border);
}

.typing-dots {
    display: flex;
    gap: 4px;
}

.typing-dot {
    width: 8px;
    height: 8px;
    background: var(--text-muted);
    border-radius: 50%;
    animation: typing 1.5s infinite;
}

.typing-dot:nth-child(2) { animation-delay: 0.2s; }
.typing-dot:nth-child(3) { animation-delay: 0.4s; }

/* Drag and Drop */
.app.dragging::after {
    content: "Drop PDF file here";
    position: absolute;
    inset: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    font-weight: 600;
    color: var(--primary);
    background: rgba(124, 58, 237, 0.1);
    border: 3px dashed var(--primary);
    z-index: 1000;
    pointer-events: none;
    animation: pulse 2s infinite;
}

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

@keyframes typing {
    0%, 60%, 100% { transform: translateY(0); }
    30% { transform: translateY(-10px); }
}

@keyframes pulse {
    0%, 100% { background: rgba(124, 58, 237, 0.05); }
    50% { background: rgba(124, 58, 237, 0.1); }
}

/* Scrollbar */
::-webkit-scrollbar {
    width: 6px;
}

::-webkit-scrollbar-track {
    background: transparent;
}

::-webkit-scrollbar-thumb {
    background: var(--border);
    border-radius: 3px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-muted);
}

/* Responsive */
@media (max-width: 768px) {
    .sidebar {
        width: 280px;
    }
    
    .chat-header {
        padding: 16px;
    }
    
    .messages-container {
        padding: 16px;
        padding-bottom: calc(var(--composer-height) + 16px);
    }
    
    .message-composer {
        padding: 16px;
    }
}