/* ============================================================
   Expense & Budget Visualizer — style.css
   Responsive layout (min 320 px), theme variables, base styles
   ============================================================ */

/* ------------------------------------------------------------
   1. Theme tokens — light (default)
   ------------------------------------------------------------ */
[data-theme="light"],
:root {
  --color-bg:       #f5f7fa;
  --color-surface:  #ffffff;
  --color-text:     #1a1a2e;
  --color-text-muted: #6b7280;
  --color-accent:   #4f46e5;
  --color-accent-hover: #4338ca;
  --color-border:   #e5e7eb;
  --color-error:    #dc2626;
  --color-error-bg: #fef2f2;
  --color-success:  #16a34a;
  --color-warning-bg: #fffbeb;
  --color-warning-text: #92400e;
  --color-delete:   #ef4444;
  --color-delete-hover: #dc2626;

  /* Category colours */
  --color-food:      #f59e0b;
  --color-transport: #3b82f6;
  --color-fun:       #8b5cf6;

  /* Transitions — meet the ≤100 ms requirement */
  --transition-theme: background-color 80ms ease, color 80ms ease,
                      border-color 80ms ease, box-shadow 80ms ease;
}

/* ------------------------------------------------------------
   2. Theme tokens — dark
   ------------------------------------------------------------ */
[data-theme="dark"] {
  --color-bg:       #0f172a;
  --color-surface:  #1e293b;
  --color-text:     #f1f5f9;
  --color-text-muted: #94a3b8;
  --color-accent:   #818cf8;
  --color-accent-hover: #6366f1;
  --color-border:   #334155;
  --color-error:    #f87171;
  --color-error-bg: #450a0a;
  --color-success:  #4ade80;
  --color-warning-bg: #1c1917;
  --color-warning-text: #fcd34d;
  --color-delete:   #f87171;
  --color-delete-hover: #ef4444;

  --color-food:      #fbbf24;
  --color-transport: #60a5fa;
  --color-fun:       #a78bfa;
}

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

/* ------------------------------------------------------------
   4. Base / body
   ------------------------------------------------------------ */
html {
  font-size: 16px;
  /* Apply theme transition at root so ALL elements inherit */
  transition: var(--transition-theme);
}

body {
  background-color: var(--color-bg);
  color: var(--color-text);
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial,
               sans-serif;
  line-height: 1.6;
  min-height: 100vh;
  /* Prevent horizontal scroll at any width ≥ 320 px */
  overflow-x: hidden;
  transition: background-color 220ms ease, color 220ms ease, border-color 220ms ease;
}

/* ------------------------------------------------------------
   5. Typography helpers
   ------------------------------------------------------------ */
h1, h2, h3 {
  font-weight: 700;
  line-height: 1.25;
}

h1 { font-size: clamp(1.25rem, 4vw, 1.75rem); }
h2 { font-size: clamp(1rem, 3vw, 1.25rem); }
h3 { font-size: 1rem; }

/* ------------------------------------------------------------
   6. Layout — page wrapper & main grid
   ------------------------------------------------------------ */
.app-wrapper {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  width: 100%;
}

/* Top-level banner (storage unavailable warning) */
.banner {
  background-color: var(--color-warning-bg);
  color: var(--color-warning-text);
  padding: 0.625rem 1rem;
  font-size: 0.875rem;
  text-align: center;
  border-bottom: 1px solid var(--color-border);
  transition: var(--transition-theme);
}

/* ---- Header ---- */
.app-header {
  background-color: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  padding: 0.75rem 1rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 0.5rem;
  transition: background-color 220ms ease, color 220ms ease, border-color 220ms ease;
}

.app-header__title {
  font-size: clamp(1rem, 3.5vw, 1.375rem);
  font-weight: 700;
  color: var(--color-accent);
}

/* ---- Main content area ---- */
.app-main {
  flex: 1;
  width: 100%;
  max-width: 960px;
  margin: 0 auto;
  padding: 1rem;
  display: grid;
  gap: 1rem;
  /* Single-column on narrow screens; two-column on wider screens */
  grid-template-columns: 1fr;
  grid-template-areas:
    "balance"
    "form"
    "list"
    "chart"
    "summary";
}

@media (min-width: 640px) {
  .app-main {
    grid-template-columns: 1fr 1fr;
    grid-template-areas:
      "balance  balance"
      "form     chart"
      "list     list"
      "summary  summary";
  }
}

@media (min-width: 900px) {
  .app-main {
    grid-template-columns: 1fr 1fr 1fr;
    grid-template-areas:
      "balance  balance  balance"
      "form     list     chart"
      "summary  summary  summary";
  }
}

/* ---- Grid area assignments ---- */
#balance-display  { grid-area: balance; }
#transaction-form { grid-area: form; }
#transaction-list-section { grid-area: list; }
#chart-section    { grid-area: chart; }
#monthly-summary  { grid-area: summary; }

/* ------------------------------------------------------------
   7. Card / surface
   ------------------------------------------------------------ */
.card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 0.75rem;
  padding: 1rem;
  transition: var(--transition-theme);
}

/* ------------------------------------------------------------
   8. Balance display  (#balance-display)
      Requirement 3.1 — topmost content area, visually distinct
   ------------------------------------------------------------ */
#balance-display {
  background-color: var(--color-accent);
  color: #fff;
  border-radius: 0.75rem;
  padding: 1.25rem 1.5rem;
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
  transition: background-color 220ms ease, color 220ms ease, transform 220ms ease;
}

#balance-display .balance__label {
  font-size: 0.875rem;
  opacity: 0.85;
  font-weight: 500;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

#balance-display .balance__amount {
  font-size: clamp(1.5rem, 5vw, 2.25rem);
  font-weight: 700;
  word-break: break-all;
}

/* ------------------------------------------------------------
   9. Form styles  (#transaction-form)
   ------------------------------------------------------------ */
.form-group {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
  margin-bottom: 0.75rem;
}

.form-group:last-of-type {
  margin-bottom: 0;
}

label {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--color-text);
  transition: var(--transition-theme);
}

input[type="text"],
input[type="number"],
input[type="month"],
select,
textarea {
  width: 100%;
  padding: 0.5rem 0.75rem;
  font-size: 1rem;
  font-family: inherit;
  color: var(--color-text);
  background-color: var(--color-bg);
  border: 1.5px solid var(--color-border);
  border-radius: 0.5rem;
  outline: none;
  appearance: auto;
  transition: border-color 80ms ease, background-color 80ms ease,
              color 80ms ease, box-shadow 80ms ease;
}

input[type="text"]:focus,
input[type="number"]:focus,
input[type="month"]:focus,
select:focus,
textarea:focus {
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--color-accent) 20%, transparent);
}

input[type="text"][aria-invalid="true"],
input[type="number"][aria-invalid="true"],
select[aria-invalid="true"] {
  border-color: var(--color-error);
}

/* Inline validation errors */
.field-error {
  font-size: 0.8125rem;
  color: var(--color-error);
  margin-top: 0.125rem;
}

#form-errors {
  background-color: var(--color-error-bg);
  border: 1px solid var(--color-error);
  border-radius: 0.5rem;
  padding: 0.625rem 0.875rem;
  margin-bottom: 0.75rem;
  font-size: 0.875rem;
  color: var(--color-error);
  display: none; /* hidden until there are errors */
  transition: var(--transition-theme);
}

#form-errors:not(:empty) {
  display: block;
}

/* ------------------------------------------------------------
   10. Buttons
   ------------------------------------------------------------ */
button,
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.375rem;
  padding: 0.5rem 1rem;
  font-size: 0.9375rem;
  font-family: inherit;
  font-weight: 600;
  border: none;
  border-radius: 0.5rem;
  cursor: pointer;
  white-space: nowrap;
  transition: background-color 80ms ease, color 80ms ease,
              box-shadow 80ms ease, opacity 80ms ease;
}

/* Primary — add transaction */
.btn-primary,
#btn-add {
  width: 100%;
  background-color: var(--color-accent);
  color: #fff;
  margin-top: 0.25rem;
}

.btn-primary:hover,
#btn-add:hover {
  background-color: var(--color-accent-hover);
}

.btn-primary:focus-visible,
#btn-add:focus-visible {
  outline: 3px solid var(--color-accent);
  outline-offset: 2px;
}

/* Delete button — per transaction row */
.btn-delete {
  background-color: transparent;
  color: var(--color-delete);
  border: 1.5px solid var(--color-delete);
  padding: 0.25rem 0.625rem;
  font-size: 0.8125rem;
  border-radius: 0.375rem;
  flex-shrink: 0;
}

.btn-delete:hover {
  background-color: var(--color-delete);
  color: #fff;
}

/* Theme toggle */
#theme-toggle {
  background: transparent;
  border: none;
  padding: 0;
  cursor: pointer;
  transition: transform 180ms ease, filter 180ms ease;
}

#theme-toggle:hover {
  transform: scale(1.04);
  filter: brightness(1.05);
}

#theme-toggle:focus-visible {
  outline: 3px solid var(--color-accent);
  outline-offset: 3px;
  border-radius: 999px;
}

#theme-toggle.is-animating .theme-switch__thumb {
  transform: scale(0.9);
}

.theme-switch__track {
  position: relative;
  display: inline-flex;
  align-items: center;
  width: 3.2rem;
  height: 1.8rem;
  padding: 0.2rem;
  border-radius: 999px;
  background: linear-gradient(90deg, var(--color-accent) 0%, var(--color-border) 100%);
  box-shadow: inset 0 0 0 1px rgba(255,255,255,0.18);
  transition: background 220ms ease, box-shadow 220ms ease;
}

.theme-switch__thumb {
  position: absolute;
  left: 0.2rem;
  display: grid;
  place-items: center;
  width: 1.4rem;
  height: 1.4rem;
  border-radius: 50%;
  background: var(--color-surface);
  box-shadow: 0 2px 6px rgba(15, 23, 42, 0.2);
  transition: transform 220ms ease, background 220ms ease;
}

.theme-switch__icon {
  font-size: 0.8rem;
  line-height: 1;
  transform: translateY(1px);
  transition: transform 220ms ease;
}

[data-theme="dark"] .theme-switch__thumb {
  transform: translateX(1.4rem);
  background: #0f172a;
}

[data-theme="dark"] .theme-switch__track {
  background: linear-gradient(90deg, var(--color-accent) 0%, #475569 100%);
}

[data-theme="dark"] .theme-switch__icon {
  transform: rotate(20deg) translateY(1px);
}

/* Disabled state */
button:disabled,
.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* ------------------------------------------------------------
   11. Transaction list  (#transaction-list)
       Requirements 2.2, 10.3
   ------------------------------------------------------------ */
.list-controls {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
  flex-wrap: wrap;
}

.list-controls label {
  font-size: 0.8125rem;
  white-space: nowrap;
}

.list-controls select {
  font-size: 0.875rem;
  padding: 0.375rem 0.625rem;
  flex: 1;
  min-width: 0;
}

#transaction-list {
  overflow-y: auto;
  max-height: 400px;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  /* Ensure content never causes horizontal overflow */
  overflow-x: hidden;
}

/* Thin scrollbar styling (non-standard but widely supported) */
#transaction-list::-webkit-scrollbar {
  width: 6px;
}
#transaction-list::-webkit-scrollbar-track {
  background: var(--color-bg);
  border-radius: 3px;
}
#transaction-list::-webkit-scrollbar-thumb {
  background: var(--color-border);
  border-radius: 3px;
}

/* Individual transaction row */
.transaction-item {
  display: flex;
  align-items: flex-start;
  gap: 0.625rem;
  padding: 0.625rem 0.75rem;
  background-color: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: 0.5rem;
  /* Prevent row from causing horizontal overflow */
  min-width: 0;
  overflow: hidden;
  transition: var(--transition-theme);
}

.transaction-item__info {
  flex: 1;
  min-width: 0; /* allow text-overflow / wrap inside flex child */
  display: flex;
  flex-direction: column;
  gap: 0.125rem;
}

.transaction-item__name {
  font-weight: 600;
  font-size: 0.9375rem;
  /* Wrap long names rather than overflow */
  overflow-wrap: break-word;
  word-break: break-word;
}

.transaction-item__meta {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  transition: var(--transition-theme);
}

.transaction-item__amount {
  font-weight: 700;
  color: var(--color-text);
  white-space: nowrap;
  transition: var(--transition-theme);
}

/* Category badge */
.category-badge {
  display: inline-block;
  padding: 0.1rem 0.45rem;
  border-radius: 0.25rem;
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  white-space: nowrap;
}

.category-badge--food      { background-color: var(--color-food);      color: #fff; }
.category-badge--transport { background-color: var(--color-transport);  color: #fff; }
.category-badge--fun       { background-color: var(--color-fun);        color: #fff; }

/* Empty-state message */
.empty-state {
  text-align: center;
  padding: 2rem 1rem;
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  font-style: italic;
  transition: var(--transition-theme);
}

/* ------------------------------------------------------------
   12. Spending chart  (#spending-chart / canvas)
   ------------------------------------------------------------ */
#chart-section {
  display: flex;
  flex-direction: column;
}

.chart-wrapper {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  min-height: 200px;
}

#spending-chart {
  /* canvas — Chart.js will set width/height; we constrain via wrapper */
  max-width: 100%;
  max-height: 300px;
}

.chart-placeholder {
  text-align: center;
  color: var(--color-text-muted);
  font-size: 0.9375rem;
  font-style: italic;
  padding: 1rem;
  transition: var(--transition-theme);
}

/* ------------------------------------------------------------
   13. Monthly summary  (#monthly-summary)
   ------------------------------------------------------------ */
.month-controls {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
  flex-wrap: wrap;
}

.month-controls label {
  font-size: 0.875rem;
  white-space: nowrap;
}

.month-controls input[type="month"] {
  font-size: 0.875rem;
  padding: 0.375rem 0.625rem;
  flex: 1;
  min-width: 0;
}

/* ------------------------------------------------------------
   14. Section headings inside cards
   ------------------------------------------------------------ */
.section-heading {
  font-size: 0.875rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-muted);
  margin-bottom: 0.75rem;
  transition: var(--transition-theme);
}

/* ------------------------------------------------------------
   15. Utility classes
   ------------------------------------------------------------ */
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.text-muted {
  color: var(--color-text-muted);
  transition: var(--transition-theme);
}

.mt-1 { margin-top: 0.25rem; }
.mt-2 { margin-top: 0.5rem; }
.mt-3 { margin-top: 0.75rem; }
.mb-1 { margin-bottom: 0.25rem; }
.mb-2 { margin-bottom: 0.5rem; }
.mb-3 { margin-bottom: 0.75rem; }

/* ------------------------------------------------------------
   16. Responsive safety net — no horizontal scroll at 320 px
       (defensive: clamp all potentially overflowing elements)
   ------------------------------------------------------------ */
img, video, canvas, svg, table {
  max-width: 100%;
  height: auto;
}

/* Ensure long unbreakable strings don't overflow */
p, li, td, th, span, div {
  overflow-wrap: break-word;
  word-break: break-word;
}