/* Button — canonical definition (control-sizing-standard §2)
 * Single source of truth for all interactive buttons in the app shell.
 * No page or module may redefine .btn size, padding, or font with raw px/rem.
 *
 * Requires: tokens.css (control-sizing block), spacing.css, typography.css
 *
 * Usage:
 *   <button class="btn">Default (md)</button>
 *   <button class="btn btn--primary">Primary action</button>
 *   <button class="btn btn--sm btn--ghost">Dense ghost</button>
 *   <button class="btn btn--lg btn--primary">Hero action</button>
 *
 * Legacy compat:
 *   .btn-sm is aliased to .btn.btn--sm so existing markup keeps working.
 */

/* ── Base button (md = 36px default) ── */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--control-gap);               /* 8px */
  height: var(--control-h-md);           /* 36px */
  padding: 0 var(--control-px-md);       /* 0 16px */
  font-size: var(--control-font-md);     /* 13px */
  font-weight: var(--weight-medium);     /* 500 */
  font-family: inherit;
  line-height: 1;
  border-radius: var(--radius-base);     /* 8px */
  border: 1px solid var(--border-default);
  background: var(--surface-card);
  color: var(--text-primary);
  cursor: pointer;
  white-space: nowrap;
  text-decoration: none;
  box-sizing: border-box;
  transition: background 0.12s ease, border-color 0.12s ease, color 0.12s ease;
  user-select: none;
}

.btn:hover:not(:disabled) {
  background: var(--surface-hover);
}

.btn:focus-visible {
  outline: 2px solid var(--focus-ring-color, var(--color-brand-500));
  outline-offset: 2px;
}

.btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

/* ── Size variants ── */

/* Small — 28px (dense rows, inline filters, chips) */
.btn--sm {
  height: var(--control-h-sm);           /* 28px */
  padding: 0 var(--control-px-sm);       /* 0 12px */
  font-size: var(--control-font-sm);     /* 12px */
}

/* Large — 44px (hero / touch / Start control) */
.btn--lg {
  height: var(--control-h-lg);           /* 44px */
  padding: 0 var(--control-px-lg);       /* 0 20px */
  font-size: var(--control-font-lg);     /* 14px */
}

/* ── Intent variants — color only, never size ── */

/* Primary — filled brand blue */
.btn--primary {
  background: var(--color-brand-500);
  border-color: var(--color-brand-500);
  color: #fff;
}

.btn--primary:hover:not(:disabled) {
  background: var(--color-brand-600);
  border-color: var(--color-brand-600);
}

/* Ghost — transparent background, visible on hover */
.btn--ghost {
  background: transparent;
  border-color: transparent;
  color: var(--text-secondary);
}

.btn--ghost:hover:not(:disabled) {
  background: var(--surface-hover);
  color: var(--text-primary);
  border-color: transparent;
}

/* Danger — outlined in error red */
.btn--danger {
  background: transparent;
  border-color: var(--color-error-500);
  color: var(--color-error-500);
}

.btn--danger:hover:not(:disabled) {
  background: rgba(239, 68, 68, 0.08);
}

/* ── Icon sizing inside buttons ── */
.btn .icon {
  width: var(--control-icon-md);    /* 16px */
  height: var(--control-icon-md);
  flex-shrink: 0;
}

.btn--sm .icon {
  width: var(--control-icon-sm);   /* 14px */
  height: var(--control-icon-sm);
}

/* ── Full-width variant ── */
.btn-full-width {
  width: 100%;
}

/* ── Legacy aliases — existing markup using .btn-sm keeps working ── */
/* .btn-sm alone already works because it sets the same properties as .btn.btn--sm.
   This rule ensures any element with only .btn-sm still gets base btn styles. */
.btn-sm:not(.btn) {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--control-gap);
  height: var(--control-h-sm);
  padding: 0 var(--control-px-sm);
  font-size: var(--control-font-sm);
  font-weight: var(--weight-medium);
  font-family: inherit;
  line-height: 1;
  border-radius: var(--radius-base);
  border: 1px solid var(--border-default);
  background: var(--surface-card);
  color: var(--text-primary);
  cursor: pointer;
  white-space: nowrap;
  text-decoration: none;
  box-sizing: border-box;
  transition: background 0.12s ease, border-color 0.12s ease;
  user-select: none;
}

.btn-sm:not(.btn):hover:not(:disabled) {
  background: var(--surface-hover);
}

.btn-sm:not(.btn):focus-visible {
  outline: 2px solid var(--focus-ring-color, var(--color-brand-500));
  outline-offset: 2px;
}

/* Legacy intent modifiers that coexist with .btn-sm */
.btn-primary  { background: var(--color-brand-500); border-color: var(--color-brand-500); color: #fff; }
.btn-primary:hover:not(:disabled) { background: var(--color-brand-600); border-color: var(--color-brand-600); }
.btn-secondary { background: var(--surface-card); border-color: var(--border-default); color: var(--text-primary); }
.btn-success   { background: var(--color-success-500); border-color: var(--color-success-500); color: #fff; }
.btn-danger    { background: transparent; border-color: var(--color-error-500); color: var(--color-error-500); }
.btn-danger:hover:not(:disabled) { background: rgba(239, 68, 68, 0.08); }
.btn-warning   { background: var(--color-warning-500); border-color: var(--color-warning-500); color: #fff; }
.btn-error     { background: transparent; border-color: var(--color-error-500); color: var(--color-error-500); }