/* ============================================================
   Sao Mai Chat — Design System & Styles
   Premium dark theme with glassmorphism and micro-animations
   ============================================================ */

/* --- CSS Custom Properties (Design Tokens) --- */
:root {
  /* Colors — Light Theme (Default) */
  --clr-bg-primary: hsl(230, 25%, 98%);
  --clr-bg-secondary: hsl(230, 20%, 95%);
  --clr-bg-tertiary: hsl(230, 18%, 92%);
  --clr-surface: hsl(0, 0%, 100%);
  --clr-surface-hover: hsl(230, 16%, 96%);
  --clr-border: hsla(230, 20%, 60%, 0.2);
  --clr-border-focus: hsla(240, 80%, 66%, 0.5);

  --clr-text-primary: hsl(230, 25%, 12%);
  --clr-text-secondary: hsl(230, 15%, 35%);
  --clr-text-muted: hsl(230, 10%, 50%);

  --clr-accent: hsl(240, 80%, 55%);
  --clr-accent-hover: hsl(240, 80%, 45%);
  --clr-accent-glow: hsla(240, 80%, 55%, 0.2);

  --clr-bot-bubble: hsl(0, 0%, 100%);
  --clr-user-bubble: hsl(240, 70%, 56%);
  --clr-user-bubble-hover: hsl(240, 70%, 62%);

  --clr-success: hsl(142, 71%, 40%);
  --clr-warning: hsl(38, 92%, 45%);
  --clr-error: hsl(0, 72%, 48%);

  /* Typography */
  --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --fs-xs: 0.6875rem;    /* 11px */
  --fs-sm: 0.8125rem;    /* 13px */
  --fs-base: 0.9375rem;  /* 15px */
  --fs-lg: 1.125rem;     /* 18px */
  --fs-xl: 1.5rem;       /* 24px */
  --fw-normal: 400;
  --fw-medium: 500;
  --fw-semibold: 600;
  --fw-bold: 700;

  /* Spacing */
  --sp-1: 0.25rem;
  --sp-2: 0.5rem;
  --sp-3: 0.75rem;
  --sp-4: 1rem;
  --sp-5: 1.25rem;
  --sp-6: 1.5rem;
  --sp-8: 2rem;
  --sp-10: 2.5rem;

  /* Border radius */
  --radius-sm: 0.5rem;
  --radius-md: 0.75rem;
  --radius-lg: 1rem;
  --radius-xl: 1.25rem;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 2px hsla(0, 0%, 0%, 0.05);
  --shadow-md: 0 4px 12px hsla(0, 0%, 0%, 0.08);
  --shadow-lg: 0 8px 24px hsla(0, 0%, 0%, 0.12);
  --shadow-glow: 0 0 20px var(--clr-accent-glow);

  /* Transitions */
  --tr-fast: 150ms ease;
  --tr-base: 250ms ease;
  --tr-slow: 400ms cubic-bezier(0.16, 1, 0.3, 1);
}

/* --- Reset & Base --- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-family);
  background: var(--clr-bg-primary);
  color: var(--clr-text-primary);
  line-height: 1.6;
  min-height: 100dvh;
  overflow: hidden;
}

/* --- App Container --- */
.app-container {
  display: flex;
  flex-direction: column;
  height: 100dvh;
  max-width: 56rem;
  margin: 0 auto;
  position: relative;
}

/* --- Header --- */
.app-header {
  flex-shrink: 0;
  padding: var(--sp-4) var(--sp-6);
  background: hsla(230, 25%, 98%, 0.8);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--clr-border);
  z-index: 10;
}

.header-content {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--sp-4);
}

.logo-group {
  display: flex;
  align-items: center;
  gap: var(--sp-3);
}

.logo-icon {
  width: 40px;
  height: 40px;
  flex-shrink: 0;
}

.logo-icon svg {
  width: 100%;
  height: 100%;
  filter: drop-shadow(0 0 8px var(--clr-accent-glow));
}

.logo-group h1 {
  font-size: var(--fs-lg);
  font-weight: var(--fw-bold);
  background: linear-gradient(135deg, var(--clr-accent), hsl(280, 70%, 70%));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -0.02em;
}

.subtitle {
  font-size: var(--fs-xs);
  color: var(--clr-text-muted);
  font-weight: var(--fw-medium);
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: var(--sp-3);
}

.btn-icon {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--clr-surface);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius-sm);
  color: var(--clr-text-secondary);
  cursor: pointer;
  transition: all var(--tr-fast);
}

.btn-icon:hover {
  background: var(--clr-surface-hover);
  color: var(--clr-text-primary);
  border-color: var(--clr-border-focus);
}

.connection-status {
  display: flex;
  align-items: center;
  gap: var(--sp-2);
  padding: var(--sp-1) var(--sp-3);
  background: var(--clr-surface);
  border-radius: var(--radius-full);
  font-size: var(--fs-xs);
  color: var(--clr-text-secondary);
}

.status-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--clr-text-muted);
  transition: background var(--tr-base);
}

.status-dot.online {
  background: var(--clr-success);
  box-shadow: 0 0 6px hsla(142, 71%, 45%, 0.5);
  animation: pulse-dot 2s infinite;
}

@keyframes pulse-dot {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.6; }
}

/* --- Chat Area --- */
.chat-area {
  flex: 1;
  overflow-y: auto;
  padding: var(--sp-6);
}

.chat-area::-webkit-scrollbar {
  width: 6px;
}

.chat-area::-webkit-scrollbar-track {
  background: transparent;
}

.chat-area::-webkit-scrollbar-thumb {
  background: hsla(230, 20%, 40%, 0.3);
  border-radius: 3px;
}

.chat-area::-webkit-scrollbar-thumb:hover {
  background: hsla(230, 20%, 40%, 0.5);
}

/* --- Welcome Card --- */
.welcome-card {
  text-align: center;
  padding: var(--sp-10) var(--sp-6);
  animation: fadeInUp 0.6s var(--tr-slow);
}

.welcome-icon {
  font-size: 3rem;
  margin-bottom: var(--sp-4);
  animation: float 3s ease-in-out infinite;
}

@keyframes float {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-8px); }
}

.welcome-card h2 {
  font-size: var(--fs-xl);
  font-weight: var(--fw-bold);
  margin-bottom: var(--sp-3);
  background: linear-gradient(135deg, var(--clr-text-primary), var(--clr-text-secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.welcome-card > p {
  color: var(--clr-text-secondary);
  font-size: var(--fs-base);
  margin-bottom: var(--sp-6);
}

/* --- Suggestion Chips --- */
.suggestion-chips {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--sp-2);
  max-width: 36rem;
  margin: 0 auto;
}

.chip {
  padding: var(--sp-2) var(--sp-4);
  background: var(--clr-surface);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius-full);
  color: var(--clr-text-secondary);
  font-size: var(--fs-sm);
  font-family: var(--font-family);
  cursor: pointer;
  transition: all var(--tr-fast);
  white-space: nowrap;
}

.chip:hover {
  background: var(--clr-surface-hover);
  border-color: var(--clr-accent);
  color: var(--clr-text-primary);
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}

.chip:active {
  transform: translateY(0);
}

/* --- Messages --- */
.message-row {
  display: flex;
  gap: var(--sp-3);
  margin-bottom: var(--sp-5);
  animation: fadeInUp 0.35s var(--tr-slow);
  max-width: 100%;
}

.message-row.user {
  flex-direction: row-reverse;
}

.avatar {
  width: 32px;
  height: 32px;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  font-size: var(--fs-sm);
}

.bot-avatar {
  background: linear-gradient(135deg, var(--clr-accent), hsl(280, 70%, 60%));
  color: white;
}

.user-avatar {
  background: var(--clr-surface);
  border: 1px solid var(--clr-border);
  color: var(--clr-text-secondary);
}

.bubble {
  max-width: 75%;
  padding: var(--sp-3) var(--sp-4);
  border-radius: var(--radius-lg);
  font-size: var(--fs-base);
  line-height: 1.65;
  word-wrap: break-word;
  overflow-wrap: break-word;
}

.bubble.bot {
  background: var(--clr-bot-bubble);
  border: 1px solid var(--clr-border);
  border-top-left-radius: var(--sp-1);
  color: var(--clr-text-primary);
}

.bubble.user {
  background: linear-gradient(135deg, var(--clr-user-bubble), hsl(260, 60%, 50%));
  border-top-right-radius: var(--sp-1);
  color: white;
}

.message-time {
  font-size: var(--fs-xs);
  color: var(--clr-text-muted);
  margin-top: var(--sp-1);
  padding: 0 var(--sp-1);
}

.message-row.user .message-time {
  text-align: right;
}

/* --- Typing Indicator --- */
.typing-indicator {
  display: flex;
  align-items: flex-start;
  gap: var(--sp-3);
  margin-bottom: var(--sp-5);
  animation: fadeInUp 0.3s var(--tr-slow);
}

.typing-dots {
  display: flex;
  gap: 4px;
  padding: var(--sp-3) var(--sp-4);
  background: var(--clr-bot-bubble);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius-lg);
  border-top-left-radius: var(--sp-1);
}

.typing-dots span {
  width: 7px;
  height: 7px;
  background: var(--clr-text-muted);
  border-radius: 50%;
  animation: bounce 1.4s infinite ease-in-out;
}

.typing-dots span:nth-child(1) { animation-delay: 0s; }
.typing-dots span:nth-child(2) { animation-delay: 0.15s; }
.typing-dots span:nth-child(3) { animation-delay: 0.3s; }

@keyframes bounce {
  0%, 60%, 100% { transform: translateY(0); opacity: 0.4; }
  30% { transform: translateY(-6px); opacity: 1; }
}

/* --- Input Area --- */
.input-area {
  flex-shrink: 0;
  padding: var(--sp-4) var(--sp-6) var(--sp-5);
  background: hsla(230, 25%, 98%, 0.8);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-top: 1px solid var(--clr-border);
}

.input-form {
  max-width: 100%;
}

.input-wrapper {
  display: flex;
  align-items: flex-end;
  gap: var(--sp-3);
  background: var(--clr-surface);
  border: 1px solid var(--clr-border);
  border-radius: var(--radius-lg);
  padding: var(--sp-3);
  transition: border-color var(--tr-fast), box-shadow var(--tr-fast);
}

.input-wrapper:focus-within {
  border-color: var(--clr-accent);
  box-shadow: var(--shadow-glow);
}

.input-wrapper textarea {
  flex: 1;
  background: transparent;
  border: none;
  outline: none;
  color: var(--clr-text-primary);
  font-family: var(--font-family);
  font-size: var(--fs-base);
  line-height: 1.5;
  resize: none;
  max-height: 120px;
  padding: var(--sp-1) var(--sp-2);
}

.input-wrapper textarea::placeholder {
  color: var(--clr-text-muted);
}

.send-button {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--clr-accent);
  border: none;
  border-radius: var(--radius-md);
  color: white;
  cursor: pointer;
  flex-shrink: 0;
  transition: all var(--tr-fast);
}

.send-button:hover:not(:disabled) {
  background: var(--clr-accent-hover);
  transform: scale(1.05);
  box-shadow: var(--shadow-glow);
}

.send-button:disabled {
  opacity: 0.3;
  cursor: not-allowed;
}

.send-button:active:not(:disabled) {
  transform: scale(0.96);
}

.input-hint {
  font-size: var(--fs-xs);
  color: var(--clr-text-muted);
  text-align: center;
  margin-top: var(--sp-2);
}

.input-hint kbd {
  padding: 1px 5px;
  background: var(--clr-surface);
  border: 1px solid var(--clr-border);
  border-radius: 3px;
  font-family: var(--font-family);
  font-size: var(--fs-xs);
}

/* --- Animations --- */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(12px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Streaming text cursor effect */
.streaming .bubble.bot::after {
  content: '▊';
  animation: blink-cursor 0.8s step-end infinite;
  color: var(--clr-accent);
  margin-left: 2px;
}

@keyframes blink-cursor {
  50% { opacity: 0; }
}

/* --- Responsive --- */
@media (max-width: 640px) {
  .app-header {
    padding: var(--sp-3) var(--sp-4);
  }

  .chat-area {
    padding: var(--sp-4);
  }

  .input-area {
    padding: var(--sp-3) var(--sp-4) var(--sp-4);
  }

  .bubble {
    max-width: 85%;
  }

  .welcome-card {
    padding: var(--sp-6) var(--sp-4);
  }

  .welcome-card h2 {
    font-size: var(--fs-lg);
  }

  .suggestion-chips {
    gap: var(--sp-2);
  }

  .chip {
    font-size: var(--fs-xs);
    padding: var(--sp-2) var(--sp-3);
  }

  .input-hint {
    display: none;
  }
}