/* * css/style.css
 * Styling for PastPaperHub (index.html and admin.html)
 * Modern, minimal, soft palette, readable typography.
 */

/* --- Variables and Global Reset --- */
:root {
    /* Soft Palette - Light Mode */
    --color-primary: #007bff; /* Blue */
    --color-primary-hover: #0056b3;
    --color-secondary: #6c757d;
    --color-text: #333;
    --color-background: #f8f9fa;
    --color-card-background: #fff;
    --color-border: #dee2e6;
    --color-shadow: rgba(0, 0, 0, 0.1);
    --color-highlight: #ffc107; /* Yellow for search highlight */
    
    /* System Font Stack for no external libraries requirement */
    --font-family-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
    
    /* Spacing */
    --spacing-xs: 4px;
    --spacing-sm: 8px;
    --spacing-md: 16px;
    --spacing-lg: 24px;
    --spacing-xl: 48px;
    
    /* Border Radius */
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    
    /* Transition Speed */
    --transition-speed: 0.3s;
}

/* Dark Mode Variables */
.dark-mode {
    --color-text: #e9ecef;
    --color-background: #212529; /* Dark Gray */
    --color-card-background: #343a40; /* Slightly lighter dark gray */
    --color-border: #495057;
    --color-shadow: rgba(255, 255, 255, 0.1);
    --color-highlight: #ffc107; 
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: var(--font-family-sans);
    line-height: 1.6;
    color: var(--color-text);
    background-color: var(--color-background);
    transition: background-color var(--transition-speed), color var(--transition-speed);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

/* --- Typography --- */

h1, h2, h3, h4 {
    margin-bottom: var(--spacing-md);
    font-weight: 600;
    color: var(--color-text);
}

h1 { font-size: 2rem; }
h2 { font-size: 1.75rem; }
h4 { font-size: 1.15rem; }

p {
    margin-bottom: var(--spacing-md);
}

a {
    color: var(--color-primary);
    text-decoration: none;
    transition: color var(--transition-speed);
}

a:hover {
    color: var(--color-primary-hover);
}

/* --- Header and Navigation --- */

header {
    background-color: var(--color-card-background);
    border-bottom: 1px solid var(--color-border);
    padding: var(--spacing-md) 0;
    box-shadow: 0 2px 4px var(--color-shadow);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo-area {
    display: flex;
    align-items: center;
}

.logo {
    width: 32px;
    height: 32px;
    margin-right: var(--spacing-sm);
}

header h1 {
    margin: 0;
    font-size: 1.5rem;
}

nav ul {
    list-style: none;
    display: flex;
    align-items: center;
}

nav ul li {
    margin-left: var(--spacing-lg);
}

nav ul li a {
    padding: var(--spacing-xs) 0;
    font-weight: 500;
    display: block;
    color: var(--color-text);
    position: relative;
}

nav ul li a:hover, nav ul li a.active {
    color: var(--color-primary);
}

nav ul li a.active::after {
    content: '';
    position: absolute;
    left: 0;
    bottom: -4px;
    width: 100%;
    height: 2px;
    background-color: var(--color-primary);
    transition: width var(--transition-speed);
}

/* Responsive Nav Toggle */
.menu-toggle {
    display: none;
    background: none;
    border: none;
    color: var(--color-text);
    font-size: 1.5rem;
    cursor: pointer;
    padding: 0;
}

/* --- Main Content and Sections --- */

main {
    padding: var(--spacing-xl) 0;
}

section {
    margin-bottom: var(--spacing-xl);
}

/* Hero Section */
.hero {
    text-align: center;
    padding: var(--spacing-lg) 0;
}

.hero h2 {
    font-size: 2.5rem;
}

.hero p {
    color: var(--color-secondary);
    max-width: 600px;
    margin: 0 auto var(--spacing-lg);
}

/* --- Forms, Inputs, and Buttons --- */

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

label {
    display: block;
    margin-bottom: var(--spacing-xs);
    font-weight: 500;
}

input[type="text"], input[type="number"], input[type="search"], select, textarea, input[type="file"] {
    width: 100%;
    padding: var(--spacing-sm);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    background-color: var(--color-card-background);
    color: var(--color-text);
    transition: border-color var(--transition-speed), box-shadow var(--transition-speed);
}

input:focus, select:focus, textarea:focus {
    border-color: var(--color-primary);
    box-shadow: 0 0 0 2px rgba(0, 123, 255, 0.25);
    outline: none;
}

/* Custom file input style if needed, but standard looks fine */
input[type="file"] {
    padding: var(--spacing-sm) 0;
    border: none;
}

.checkbox-group {
    display: flex;
    align-items: center;
}

.checkbox-group label {
    display: inline;
    margin-left: var(--spacing-sm);
}

.btn {
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-sm);
    border: none;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    text-align: center;
    transition: background-color var(--transition-speed), transform 0.1s ease;
    display: inline-block;
}

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

.btn-primary:hover {
    background-color: var(--color-primary-hover);
    transform: translateY(-1px);
}

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

.btn-secondary:hover {
    background-color: #5a6268;
    transform: translateY(-1px);
}

.btn-icon {
    background: none;
    border: 1px solid var(--color-border);
    color: var(--color-text);
    padding: var(--spacing-xs) var(--spacing-sm);
    font-size: 1.2rem;
    line-height: 1;
}

.btn-icon:hover {
    background-color: var(--color-border);
}

/* --- Filter Bar --- */

.filter-bar {
    margin-bottom: var(--spacing-xl);
    padding: var(--spacing-md);
    background-color: var(--color-card-background);
    border-radius: var(--radius-md);
    box-shadow: 0 1px 3px var(--color-shadow);
}

#search-input {
    margin-bottom: var(--spacing-md);
}

.filters {
    display: flex;
    gap: var(--spacing-md);
    flex-wrap: wrap;
    align-items: center;
}

.filters select, .filters button {
    flex: 1;
    min-width: 150px;
}

/* --- Paper Grid and Cards --- */

#papers-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: var(--spacing-lg);
}

.paper-card {
    background-color: var(--color-card-background);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md);
    box-shadow: 0 4px 12px var(--color-shadow);
    transition: transform 0.2s ease-in-out, box-shadow 0.2s ease-in-out, border 0.2s ease-in-out;
    position: relative;
    border: 1px solid transparent; /* for the hover effect */
}

.paper-card:hover, .paper-card:focus {
    transform: translateY(-5px);
    box-shadow: 0 8px 16px rgba(0, 0, 0, 0.2);
    border: 1px solid var(--color-primary);
}

.paper-card:focus {
    outline: none; /* Focus outline replaced by card border */
}

.card-title {
    margin-top: 0;
    margin-bottom: var(--spacing-sm);
    line-height: 1.3;
}

.card-meta {
    font-size: 0.9rem;
    color: var(--color-secondary);
    margin-bottom: var(--spacing-md);
}

.badge {
    position: absolute;
    top: var(--spacing-md);
    right: var(--spacing-md);
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-sm);
    font-size: 0.8rem;
    font-weight: bold;
    color: white;
}

.badge-hot {
    background-color: #dc3545; /* Red */
}

.tag-list {
    margin-bottom: var(--spacing-md);
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-xs);
    min-height: 24px;
}

.tag {
    background-color: var(--color-border);
    color: var(--color-secondary);
    padding: 3px var(--spacing-sm);
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    text-transform: capitalize;
}

.dark-mode .tag {
    background-color: var(--color-border);
    color: var(--color-text);
}

.card-actions {
    display: flex;
    gap: var(--spacing-sm);
    margin-top: var(--spacing-md);
}

.card-actions .btn {
    flex: 1;
}

/* Search Highlight */
mark {
    background-color: var(--color-highlight);
    color: var(--color-text);
    padding: 0;
}

/* Load More */
.load-more-container {
    text-align: center;
    padding-top: var(--spacing-lg);
}

/* No Results */
.no-results-message {
    text-align: center;
    font-size: 1.2rem;
    color: var(--color-secondary);
    padding: var(--spacing-xl) 0;
}


/* --- PDF Viewer Modal --- */

.modal {
    display: none; /* Hidden by default */
    position: fixed;
    z-index: 1000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    overflow: auto;
    background-color: rgba(0, 0, 0, 0.8); /* Black w/ opacity */
    justify-content: center;
    align-items: center;
}

.modal-content {
    background-color: var(--color-card-background);
    margin: 5% auto; /* 5% from top and centered */
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    width: 90%; /* Could be adjusted */
    max-width: 900px;
    position: relative;
    max-height: 90vh;
    display: flex;
    flex-direction: column;
}

.modal-title {
    margin-top: 0;
    margin-bottom: var(--spacing-md);
    font-size: 1.5rem;
}

.iframe-container {
    flex-grow: 1;
    overflow: hidden;
    height: 70vh; /* Set a default height for the iframe container */
}

#pdf-iframe {
    width: 100%;
    height: 100%;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
}

.close-btn {
    position: absolute;
    top: 10px;
    right: 10px;
    color: var(--color-text);
    font-size: 28px;
    font-weight: bold;
    background: none;
    border: none;
    cursor: pointer;
    line-height: 1;
    padding: var(--spacing-xs);
    border-radius: 50%;
    transition: background-color 0.2s;
}

.close-btn:hover, .close-btn:focus {
    color: #dc3545; /* Red for close */
    background-color: var(--color-border);
}

/* --- Footer --- */

footer {
    padding: var(--spacing-md) 0;
    border-top: 1px solid var(--color-border);
    text-align: center;
    color: var(--color-secondary);
    background-color: var(--color-card-background);
    font-size: 0.9rem;
}

/* --- Admin Page Styles --- */

.admin-upload-section {
    max-width: 600px;
    margin: 0 auto;
    padding: var(--spacing-xl) var(--spacing-lg);
    background-color: var(--color-card-background);
    border-radius: var(--radius-lg);
    box-shadow: 0 4px 12px var(--color-shadow);
}

.admin-upload-section h2 {
    text-align: center;
    margin-bottom: var(--spacing-lg);
}

.admin-upload-section .btn-primary {
    width: 100%;
    margin-top: var(--spacing-md);
}

.required {
    color: #dc3545;
    font-weight: bold;
}

.upload-status {
    padding: var(--spacing-md);
    margin-bottom: var(--spacing-md);
    border-radius: var(--radius-md);
    font-weight: bold;
}

.upload-status.success {
    background-color: #d4edda;
    color: #155724;
}

.upload-status.error {
    background-color: #f8d7da;
    color: #721c24;
}

.upload-status.info {
    background-color: #cce5ff;
    color: #004085;
}

.upload-status.warning {
    background-color: #fff3cd;
    color: #856404;
}

.dark-mode .upload-status.success { background-color: #1c7430; color: #d4edda; }
.dark-mode .upload-status.error { background-color: #721c24; color: #f8d7da; }
.dark-mode .upload-status.info { background-color: #004085; color: #cce5ff; }
.dark-mode .upload-status.warning { background-color: #856404; color: #fff3cd; }

.login-bypass {
    text-align: center;
    padding: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
    border: 1px dashed var(--color-border);
    border-radius: var(--radius-md);
    background-color: var(--color-card-background);
}

.uploaded-papers-section {
    max-width: 800px;
    margin: var(--spacing-xl) auto 0;
}

.paper-list {
    list-style: none;
    padding: 0;
}

.paper-list li {
    padding: var(--spacing-sm);
    border-bottom: 1px solid var(--color-border);
}

.paper-list li:last-child {
    border-bottom: none;
}

.paper-list .no-uploads {
    text-align: center;
    color: var(--color-secondary);
    padding: var(--spacing-md);
}


/* --- Media Queries (Responsiveness) --- */

@media (max-width: 900px) {
    .filter-bar {
        flex-direction: column;
    }
    
    .filters {
        width: 100%;
    }
}

@media (max-width: 768px) {
    .header-content {
        flex-wrap: wrap;
    }
    
    /* Responsive Nav Toggle */
    .menu-toggle {
        display: block;
        order: 2; /* Move to the right */
        margin-left: auto;
    }

    #main-nav {
        width: 100%;
    }

    #nav-list {
        display: none;
        flex-direction: column;
        width: 100%;
        margin-top: var(--spacing-md);
        border-top: 1px solid var(--color-border);
        padding-top: var(--spacing-sm);
    }

    #nav-list.open {
        display: flex;
    }

    #nav-list li {
        margin: var(--spacing-sm) 0;
        text-align: center;
    }

    .mode-toggle-item {
        margin-top: var(--spacing-md);
        padding-bottom: var(--spacing-sm);
        border-top: 1px solid var(--color-border);
        width: 100%;
    }
    
    .logo-area {
        margin-bottom: var(--spacing-sm);
    }
    
    .filters {
        gap: var(--spacing-sm);
    }
    
    .filters select, .filters button {
        min-width: unset;
        width: 100%;
    }
    
    .modal-content {
        width: 95%;
        margin: 2% auto;
        padding: var(--spacing-md);
    }
    
    .iframe-container {
        height: 75vh;
    }
}