/* ============================================
   Button Component System
   Created: 2025-01-27
   Purpose: 統一されたボタンデザインシステム
   ============================================ */

/* ============================================
   Button Base Styles
   ============================================ */

.btn {
  /* Base button properties */
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  
  /* Typography */
  font-family: var(--font-family-base);
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-medium);
  line-height: var(--line-height-none);
  text-decoration: none;
  text-align: center;
  white-space: nowrap;
  
  /* Layout */
  padding: var(--space-3) var(--space-4);
  border: var(--border-width-2) solid transparent;
  border-radius: var(--radius-md);
  
  /* Visual */
  cursor: pointer;
  transition: all var(--transition-fast);
  user-select: none;
  
  /* Disabled state */
  opacity: 1;
}

.btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
  pointer-events: none;
}

/* Focus state for accessibility */
.btn:focus {
  outline: none;
  box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.3);
}

/* ============================================
   Button Variants - Color Schemes
   ============================================ */

/* Primary Button - Main actions */
.btn-primary {
  background: var(--gradient-primary);
  color: var(--color-white);
  border-color: transparent;
  box-shadow: var(--shadow-sm);
}

.btn-primary:hover:not(:disabled) {
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.btn-primary:active {
  transform: translateY(0);
  box-shadow: var(--shadow-sm);
}

/* Secondary Button - Secondary actions */
.btn-secondary {
  background: var(--color-white);
  color: var(--color-secondary);
  border-color: var(--color-secondary);
  box-shadow: var(--shadow-sm);
}

.btn-secondary:hover:not(:disabled) {
  background: var(--color-secondary);
  color: var(--color-white);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.btn-secondary:active {
  transform: translateY(0);
  background: var(--color-secondary-dark);
}

/* Success Button - Positive actions */
.btn-success {
  background: var(--color-success);
  color: var(--color-white);
  border-color: transparent;
  box-shadow: var(--shadow-sm);
}

.btn-success:hover:not(:disabled) {
  background: var(--color-success-dark);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.btn-success:active {
  transform: translateY(0);
  background: var(--color-success-dark);
}

/* Warning Button - Caution actions */
.btn-warning {
  background: var(--color-warning);
  color: var(--color-white);
  border-color: transparent;
  box-shadow: var(--shadow-sm);
}

.btn-warning:hover:not(:disabled) {
  background: var(--color-warning-dark);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.btn-warning:active {
  transform: translateY(0);
  background: var(--color-warning-dark);
}

/* Error Button - Destructive actions */
.btn-error {
  background: var(--color-error);
  color: var(--color-white);
  border-color: transparent;
  box-shadow: var(--shadow-sm);
}

.btn-error:hover:not(:disabled) {
  background: var(--color-error-dark);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.btn-error:active {
  transform: translateY(0);
  background: var(--color-error-dark);
}

/* Info Button - Informational actions */
.btn-info {
  background: var(--color-info);
  color: var(--color-white);
  border-color: transparent;
  box-shadow: var(--shadow-sm);
}

.btn-info:hover:not(:disabled) {
  background: var(--color-info-dark);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.btn-info:active {
  transform: translateY(0);
  background: var(--color-info-dark);
}

/* Ghost Button - Subtle actions */
.btn-ghost {
  background: transparent;
  color: var(--text-secondary);
  border-color: var(--color-gray-300);
}

.btn-ghost:hover:not(:disabled) {
  background: var(--color-gray-50);
  color: var(--text-primary);
  border-color: var(--color-gray-400);
}

.btn-ghost:active {
  background: var(--color-gray-100);
}

/* Link Button - Text-only actions */
.btn-link {
  background: transparent;
  color: var(--color-info);
  border-color: transparent;
  padding: var(--space-2) var(--space-3);
  text-decoration: underline;
  box-shadow: none;
}

.btn-link:hover:not(:disabled) {
  color: var(--color-info-dark);
  background: transparent;
  transform: none;
  box-shadow: none;
  text-decoration: none;
}

.btn-link:active {
  color: var(--color-info-dark);
}

/* White Button - Subtle white background button */
.btn-white {
  background: var(--color-white);
  color: var(--color-gray-700);
  border-color: var(--color-gray-300);
  border-width: var(--border-width-2);
  box-shadow: var(--shadow-sm);
}

.btn-white:hover:not(:disabled) {
  background: var(--color-gray-50);
  border-color: var(--color-gray-400);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.btn-white:active {
  transform: translateY(0);
  box-shadow: var(--shadow-sm);
}

/* ============================================
   Button Sizes
   ============================================ */

.btn-sm {
  padding: var(--space-2) var(--space-3);
  font-size: var(--font-size-sm);
  border-radius: var(--radius-base);
}

.btn-md {
  padding: var(--space-3) var(--space-4);
  font-size: var(--font-size-base);
  border-radius: var(--radius-md);
}

.btn-lg {
  padding: var(--space-4) var(--space-6);
  font-size: var(--font-size-lg);
  border-radius: var(--radius-lg);
}

.btn-xl {
  padding: var(--space-5) var(--space-8);
  font-size: var(--font-size-xl);
  border-radius: var(--radius-lg);
}

/* ============================================
   Button Shapes
   ============================================ */

.btn-rounded {
  border-radius: var(--radius-full);
}

.btn-square {
  border-radius: var(--radius-sm);
}

/* ============================================
   Button States
   ============================================ */

.btn-loading {
  position: relative;
  color: transparent;
  pointer-events: none;
}

.btn-loading::after {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  width: 16px;
  height: 16px;
  margin: -8px 0 0 -8px;
  border: 2px solid transparent;
  border-top-color: currentColor;
  border-radius: 50%;
  animation: btn-spin 1s linear infinite;
}

@keyframes btn-spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

/* ============================================
   Button Groups
   ============================================ */

.btn-group {
  display: inline-flex;
  gap: var(--space-2);
}

.btn-group .btn {
  border-radius: var(--radius-md);
}

.btn-group .btn:first-child {
  border-top-right-radius: 0;
  border-bottom-right-radius: 0;
}

.btn-group .btn:last-child {
  border-top-left-radius: 0;
  border-bottom-left-radius: 0;
}

.btn-group .btn:not(:first-child):not(:last-child) {
  border-radius: 0;
}

/* ============================================
   Icon Buttons
   ============================================ */

.btn-icon {
  padding: var(--space-3);
  width: auto;
  min-width: 44px;
  height: 44px;
  border-radius: var(--radius-md);
}

.btn-icon-sm {
  padding: var(--space-2);
  min-width: 36px;
  height: 36px;
  border-radius: var(--radius-base);
}

.btn-icon-lg {
  padding: var(--space-4);
  min-width: 52px;
  height: 52px;
  border-radius: var(--radius-lg);
}

.btn-icon svg {
  width: 20px;
  height: 20px;
}

.btn-icon-sm svg {
  width: 16px;
  height: 16px;
}

.btn-icon-lg svg {
  width: 24px;
  height: 24px;
}

/* ============================================
   Special Button Variants
   ============================================ */

/* AI Button - Special styling for AI features */
.btn-ai {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: var(--color-white);
  border-color: transparent;
  box-shadow: var(--shadow-primary);
}

.btn-ai:hover:not(:disabled) {
  background: linear-gradient(135deg, #5a6fd8 0%, #6a4190 100%);
  transform: translateY(-2px);
  box-shadow: 0 8px 25px rgba(102, 126, 234, 0.4);
}

.btn-ai:active {
  transform: translateY(-1px);
}

/* ============================================
   Responsive Design
   ============================================ */

@media (max-width: 768px) {
  .btn {
    padding: var(--space-3) var(--space-4);
    font-size: var(--font-size-base);
  }
  
  .btn-sm {
    padding: var(--space-2) var(--space-3);
    font-size: var(--font-size-sm);
  }
  
  .btn-lg {
    padding: var(--space-4) var(--space-5);
    font-size: var(--font-size-lg);
  }
  
  .btn-xl {
    padding: var(--space-5) var(--space-6);
    font-size: var(--font-size-xl);
  }
}

@media (max-width: 480px) {
  .btn {
    padding: var(--space-3);
    font-size: var(--font-size-sm);
    width: 100%;
    justify-content: center;
  }
  
  .btn-group {
    width: 100%;
  }
  
  .btn-group .btn {
    flex: 1;
  }
}

/* ============================================
   Legacy Support
   ============================================ */

/* Support for existing button classes */
.btn:not([class*="btn-"]) {
  /* Default to primary if no variant is specified */
  background: var(--gradient-primary);
  color: var(--color-white);
  border-color: transparent;
  box-shadow: var(--shadow-sm);
}

.btn:not([class*="btn-"]):hover:not(:disabled) {
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}