/* ==========================================================================
   Shared Components
   Reusable patterns extracted from page-specific CSS files.
   Loaded globally in base.html — always available.
   Mobile-first: base targets 320px+, enhanced at 481px+
   ========================================================================== */

/* --------------------------------------------------------------------------
   Page Container — centered content column (42rem)
   Used by: about, article, admin, error, tags, categories, articles
   -------------------------------------------------------------------------- */

.page-container {
    max-width: var(--max-content-width);
    margin: 0 auto;
    padding: var(--spacing-6) var(--spacing-4);
}

@media (min-width: 481px) {
    .page-container {
        padding: var(--spacing-8) var(--spacing-4);
    }
}

/* --------------------------------------------------------------------------
   Empty State — centered, muted placeholder when a list has no items
   Used by: feed, articles, search, tags, categories, tag, category, drafts, admin
   -------------------------------------------------------------------------- */

.empty-state {
    text-align: center;
    padding: var(--spacing-12) 0;
    color: var(--color-text-muted);
}

.empty-state h2 {
    font-size: var(--font-size-xl);
    margin: 0 0 var(--spacing-2);
}

.empty-state p {
    margin: 0;
}

.empty-state-cta {
    display: inline-block;
    margin-top: var(--spacing-4);
    padding: var(--spacing-2) var(--spacing-6);
    background: var(--color-primary);
    color: var(--color-text-inverse);
    border-radius: var(--radius-lg);
    font-weight: 500;
    font-size: var(--font-size-sm);
    text-decoration: none;
    transition: background-color var(--transition-fast);
}

.empty-state-cta:hover {
    background: var(--color-primary-dark);
    color: var(--color-text-inverse);
    text-decoration: none;
}

/* --------------------------------------------------------------------------
   Content Stream — vertical card list (42rem centered)
   Used by: feed, articles, search, tag, category, drafts, admin
   -------------------------------------------------------------------------- */

.content-stream {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-4);
    max-width: var(--max-content-width);
    margin: 0 auto;
    padding-bottom: var(--spacing-8);
}

/* --------------------------------------------------------------------------
   Breadcrumb — semantic navigation trail
   Used by: article, tag, category (3-level pages only)
   -------------------------------------------------------------------------- */

.breadcrumb {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
}

.breadcrumb-list {
    list-style: none;
    max-width: var(--max-content-width);
    margin: 0 auto;
    padding: var(--spacing-3) var(--spacing-4);
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-1);
}

.breadcrumb-item + .breadcrumb-item::before {
    content: "/";
    margin-right: var(--spacing-1);
    color: var(--color-text-muted);
    opacity: 0.5;
}

.breadcrumb-item a {
    color: var(--color-text-secondary);
    text-decoration: none;
}

.breadcrumb-item a:hover {
    color: var(--color-primary);
    text-decoration: underline;
}

.breadcrumb-current {
    color: var(--color-text-primary);
}

/* --------------------------------------------------------------------------
   Form Controls — labels, inputs, textareas, validation
   -------------------------------------------------------------------------- */

.form-group {
    margin-bottom: var(--spacing-5);
}

.form-label {
    display: block;
    font-weight: 500;
    color: var(--color-text-primary);
    margin-bottom: var(--spacing-2);
    font-size: var(--font-size-sm);
}

.required {
    color: var(--color-error);
}

.form-input,
.form-textarea {
    width: 100%;
    padding: var(--spacing-3);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    font-size: var(--font-size-base);
    font-family: inherit;
    background-color: var(--color-bg-primary);
    color: var(--color-text-primary);
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
    box-sizing: border-box;
    -webkit-appearance: none;
}

.form-input:focus,
.form-textarea:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px var(--color-focus-ring);
}

.form-input.error,
.form-textarea.error {
    border-color: var(--color-error);
}

.form-textarea {
    resize: vertical;
    min-height: 120px;
}

.field-error {
    color: var(--color-error);
    font-size: var(--font-size-xs);
    margin-top: var(--spacing-1);
}

.form-note {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
    margin-top: var(--spacing-4);
}

/* --------------------------------------------------------------------------
   Input Group — search bar (input + button, shared border)
   Used by: search page, 404 page
   -------------------------------------------------------------------------- */

.input-group {
    display: flex;
    border-radius: var(--radius-lg);
    overflow: hidden;
    border: 1px solid var(--color-border);
    transition: border-color var(--transition-fast);
}

.input-group:focus-within {
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px var(--color-focus-ring);
}

.input-group-input {
    flex: 1;
    padding: var(--spacing-3) var(--spacing-4);
    border: none;
    font-size: var(--font-size-base);
    font-family: inherit;
    background-color: var(--color-bg-primary);
    color: var(--color-text-primary);
}

.input-group-input:focus {
    outline: none;
}

.input-group-btn {
    padding: var(--spacing-3) var(--spacing-4);
    background-color: var(--color-bg-tertiary);
    color: var(--color-text-secondary);
    border: none;
    border-left: 1px solid var(--color-border);
    cursor: pointer;
    transition: color var(--transition-fast);
    display: flex;
    align-items: center;
}

.input-group-btn:hover {
    color: var(--color-primary);
}

/* --------------------------------------------------------------------------
   Spinner — inline loading indicator
   -------------------------------------------------------------------------- */

.spinner {
    display: inline-block;
    width: 12px;
    height: 12px;
    border: 2px solid currentColor;
    border-radius: 50%;
    border-top-color: transparent;
    animation: spin 0.8s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}