/* ─────────────────────────────────────────────
   layout.css — Grid Structure & Responsive Breakpoints

   ONLY structural layout lives here.
   Component appearance → sidebar.css, messages.css, input.css, components.css

   Mobile-first → tablet → desktop → large → ultra.
   Sidebar toggle via #sidebar-toggle checkbox.
   Folding device support via viewport segments.
   ───────────────────────────────────────────── */


/* ─── Body Grid ─── */

body {
  display: grid;
  grid-template-rows: 1fr auto;
  grid-template-columns: 1fr;
  grid-template-areas:
    "chat"
    "input";
  height: 100dvh;
  height: 100vh;
  overflow: hidden;
}


/* ─── Sidebar — off-canvas by default (mobile) ─── */

#sidebar {
  position: fixed;
  inset-block: 0;
  inset-inline-start: 0;
  z-index: var(--z-sidebar);
  width: var(--sidebar-width);
  max-width: calc(100vw - 3rem);
  transform: translateX(-100%);
  transition: transform var(--duration-normal) var(--ease-out);
  will-change: transform;
  overflow: hidden;
}


/* ─── Sidebar Backdrop (mobile / tablet overlay) ─── */

#sidebar-backdrop {
  display: none;
  position: fixed;
  inset: 0;
  z-index: var(--z-backdrop);
  background: var(--color-backdrop);
  opacity: 0;
  transition: opacity var(--duration-normal) var(--ease-out);
  cursor: default;
}


/* ─── Sidebar Open State (checkbox hack) ─── */

#sidebar-toggle:checked ~ #sidebar-backdrop {
  display: block;
  opacity: 1;
}

#sidebar-toggle:checked ~ #sidebar {
  transform: translateX(0);
}


/* ─── Main Chat Area ─── */

#chat {
  grid-area: chat;
  display: grid;
  grid-template-rows: auto 1fr auto;
  min-height: 0;
  overflow: hidden;
}


/* ─── Chat Header ─── */

#chat-header {
  display: flex;
  align-items: center;
  gap: var(--gutter);
  padding: var(--gutter);
  border-block-end: 1px solid var(--color-border);
  min-height: var(--header-height);
}

#btn-sidebar {
  display: grid;
  place-items: center;
  width: var(--control-h);
  height: var(--control-h);
  flex-shrink: 0;
  cursor: pointer;
  border-radius: var(--radius-sm);
  color: var(--color-text-3);
  transition: background var(--duration-fast) var(--ease-out),
              color var(--duration-fast) var(--ease-out);
  -webkit-tap-highlight-color: transparent;
}

#btn-sidebar:hover {
  background: var(--color-surface-1);
  color: var(--color-text-1);
}

#btn-sidebar i {
  font-size: 18px;
  line-height: 1;
}

#persona-selector {
  margin-left: auto;
  appearance: none;
  -webkit-appearance: none;
  padding: var(--space-1) var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-surface-1);
  color: var(--color-text-2);
  font-family: var(--font-ui);
  font-size: var(--text-sm);
  font-weight: 500;
  height: var(--control-h);
  max-width: 200px;
  min-width: 0;
  text-overflow: ellipsis;
  overflow: hidden;
  white-space: nowrap;
  cursor: pointer;
  outline: none;
  transition: border-color var(--duration-fast) var(--ease-out);
}

#persona-selector:focus {
  border-color: var(--color-text-3);
}

#persona-selector option {
  background: var(--color-surface-1);
  color: var(--color-text-1);
}


/* ─── Input Bar — structural grid only ─── */

#input-bar {
  grid-area: input;
}


/* ═══════════════════════════════════════════════════════════════
   BREAKPOINTS
   ═══════════════════════════════════════════════════════════════ */


/* ─────────────────────────────────────────────
   Tablet — 768px+
   Sidebar still overlay, wider padding
   ───────────────────────────────────────────── */

@media (min-width: 768px) {
  /* header padding now driven by --gutter in variables.css */
}


/* ─────────────────────────────────────────────
   Desktop — 1024px+
   Sidebar persistent, no overlay / backdrop
   ───────────────────────────────────────────── */

@media (min-width: 1024px) {

  body {
    grid-template-columns: var(--sidebar-width) 1fr;
    grid-template-rows: 1fr auto;
    grid-template-areas:
      "sidebar chat"
      "sidebar input";
  }

  #sidebar {
    grid-area: sidebar;
    position: relative;
    transform: none;
    transition: none;
    width: 100%;
    max-width: none;
  }

  /* Backdrop not needed on desktop */
  #sidebar-backdrop {
    display: none !important;
  }

  /* Sidebar always visible on desktop — hide toggle */
  #btn-sidebar {
    display: none;
  }


}


/* ─────────────────────────────────────────────
   Large — 1280px+
   Wider sidebar, constrained content width
   ───────────────────────────────────────────── */

@media (min-width: 1280px) {

  body {
    grid-template-columns: var(--sidebar-width-lg) 1fr;
  }


}


/* ─────────────────────────────────────────────
   Ultra — 1800px+
   Just tightens max-widths, nothing structural
   ───────────────────────────────────────────── */


/* ─────────────────────────────────────────────
   Folding Devices — dual-screen viewport segments
   Sidebar on left segment, chat on right.
   ───────────────────────────────────────────── */

@media (horizontal-viewport-segments: 2) {

  body {
    grid-template-columns:
      env(viewport-segment-width 0 0, var(--sidebar-width))
      1fr;
    grid-template-areas:
      "sidebar chat"
      "sidebar input";
    column-gap: env(viewport-segment-left 1 0, 0px);
  }

  #sidebar {
    position: relative;
    transform: none;
    max-width: none;
    width: 100%;
  }

  #sidebar-backdrop {
    display: none !important;
  }

  #btn-sidebar {
    display: none;
  }

  #btn-sidebar {
    display: none;
  }
}


/* ─────────────────────────────────────────────
   Safe areas — notched devices, rounded corners
   ───────────────────────────────────────────── */

@supports (padding: env(safe-area-inset-left)) {
  #sidebar {
    padding-inline-start: env(safe-area-inset-left, 0px);
  }
}