<?php
/*
Plugin Name: Sudoku
Description: A plugin to display a daily Sudoku puzzle on your WordPress site. Daily puzzles are stored in the database so you can review older puzzles.
Version: 2.2.0
Author: Mike Vahldieck
Author URI: http://it-breeze.info
Plugin URI: http://it-breeze.info
License: GPL2
*/

<?php
/*
Plugin Name: Sudoku
Description: A plugin to display a daily Sudoku puzzle on your WordPress site. Daily puzzles are stored in the database so you can review older puzzles.
Version: 2.2.0
Author: Mike Vahldieck
Author URI: http://it-breeze.info
Plugin URI: http://it-breeze.info
License: GPL2
*/

if ( ! defined( 'ABSPATH' ) ) {
    exit; // Exit if accessed directly
}

/**
 * Create a custom database table on plugin activation.
 */
function daily_sudoku_activate() {
    global $wpdb;
    $table_name     = $wpdb->prefix . 'daily_sudoku';
    $charset_collate = $wpdb->get_charset_collate();
    
    $sql = "CREATE TABLE $table_name (
        id mediumint(9) NOT NULL AUTO_INCREMENT,
        puzzle_date date NOT NULL,
        puzzle longtext NOT NULL,
        solution longtext NOT NULL,
        difficulty varchar(10) DEFAULT 'medium',
        PRIMARY KEY  (id),
        UNIQUE KEY puzzle_date (puzzle_date)
    ) $charset_collate;";
    
    require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );
    dbDelta( $sql );
}
register_activation_hook( __FILE__, 'daily_sudoku_activate' );

/**
 * Shortcode to display the daily sudoku puzzle.
 */
add_shortcode( 'sudoku', 'daily_sudoku_shortcode' );

function daily_sudoku_shortcode() {
    global $wpdb;
    $table_name = $wpdb->prefix . 'daily_sudoku';
    $today      = date( 'Y-m-d' );
    
    // Check if today's puzzle exists in the database.
    $row = $wpdb->get_row( $wpdb->prepare( "SELECT * FROM $table_name WHERE puzzle_date = %s", $today ) );
    
    if ( null === $row ) {
        // Generate a new puzzle if one doesn't exist for today.
        $difficulty = get_option( 'daily_sudoku_difficulty', 'medium' );
        $puzzle_data = daily_sudoku_generate_puzzle( $difficulty );
        
        // Insert the new puzzle into the database as JSON.
        $wpdb->insert(
            $table_name,
            [
                'puzzle_date' => $today,
                'puzzle'      => wp_json_encode( $puzzle_data['puzzle'] ),
                'solution'    => wp_json_encode( $puzzle_data['solution'] ),
                'difficulty'  => $difficulty,
            ],
            [
                '%s',
                '%s',
                '%s',
                '%s',
            ]
        );
    } else {
        // Retrieve puzzle and solution from the database.
        $puzzle_data = [
            'puzzle'   => json_decode( $row->puzzle, true ),
            'solution' => json_decode( $row->solution, true ),
        ];
    }
    
    $puzzle   = $puzzle_data['puzzle'];
    $solution = $puzzle_data['solution'];
    
    ob_start();
    ?>
    <div id="sudoku-container">
        <div id="sudoku-grid">
            <?php foreach ( $puzzle as $row_idx => $row ) : ?>
                <div class="sudoku-row">
                    <?php foreach ( $row as $col_idx => $value ) : ?>
                        <div class="sudoku-cell">
                            <input type="text" maxlength="1" 
                                   data-solution="<?php echo esc_attr( $solution[$row_idx][$col_idx] ); ?>" 
                                   value="<?php echo esc_attr( $value ?: '' ); ?>"
                                   <?php echo $value ? 'readonly' : ''; ?> />
                        </div>
                    <?php endforeach; ?>
                </div>
            <?php endforeach; ?>
        </div>
        <div class="sudoku-controls">
            <button id="check-answer">Check My Answer</button>
            <button id="show-solution">Show Solution</button>
        </div>
    </div>
    <?php
    return ob_get_clean();
}

/**
 * Real Sudoku puzzle generator using backtracking algorithm
 */
function daily_sudoku_generate_puzzle( $difficulty = 'medium' ) {
    // Start with empty grid
    $grid = array_fill(0, 9, array_fill(0, 9, 0));
    
    // Fill the grid completely using backtracking
    daily_sudoku_solve_grid($grid);
    
    // Store the complete solution
    $solution = array_map(function($row) { return array_slice($row, 0); }, $grid);
    
    // Remove numbers based on difficulty to create the puzzle
    $cells_to_remove = daily_sudoku_get_cells_to_remove($difficulty);
    $puzzle = daily_sudoku_create_puzzle($solution, $cells_to_remove);
    
    return [ 'puzzle' => $puzzle, 'solution' => $solution ];
}

/**
 * Solve Sudoku grid using backtracking algorithm
 */
function daily_sudoku_solve_grid(&$grid) {
    for ($row = 0; $row < 9; $row++) {
        for ($col = 0; $col < 9; $col++) {
            if ($grid[$row][$col] == 0) {
                $numbers = range(1, 9);
                shuffle($numbers); // Randomize to get different solutions each time
                
                foreach ($numbers as $num) {
                    if (daily_sudoku_is_valid($grid, $row, $col, $num)) {
                        $grid[$row][$col] = $num;
                        
                        if (daily_sudoku_solve_grid($grid)) {
                            return true;
                        }
                        
                        $grid[$row][$col] = 0; // Backtrack
                    }
                }
                return false;
            }
        }
    }
    return true;
}

/**
 * Check if placing a number at given position is valid
 */
function daily_sudoku_is_valid($grid, $row, $col, $num) {
    // Check row
    for ($x = 0; $x < 9; $x++) {
        if ($grid[$row][$x] == $num) {
            return false;
        }
    }
    
    // Check column
    for ($x = 0; $x < 9; $x++) {
        if ($grid[$x][$col] == $num) {
            return false;
        }
    }
    
    // Check 3x3 box
    $start_row = $row - $row % 3;
    $start_col = $col - $col % 3;
    
    for ($i = 0; $i < 3; $i++) {
        for ($j = 0; $j < 3; $j++) {
            if ($grid[$i + $start_row][$j + $start_col] == $num) {
                return false;
            }
        }
    }
    
    return true;
}

/**
 * Get number of cells to remove based on difficulty
 */
function daily_sudoku_get_cells_to_remove($difficulty) {
    switch ($difficulty) {
        case 'easy':
            return rand(35, 45); // Remove 35-45 numbers (leaving 36-46 clues)
        case 'medium':
            return rand(45, 55); // Remove 45-55 numbers (leaving 26-36 clues)
        case 'hard':
            return rand(55, 65); // Remove 55-65 numbers (leaving 16-26 clues)
        default:
            return rand(45, 55);
    }
}

/**
 * Create puzzle by removing numbers from solved grid
 */
function daily_sudoku_create_puzzle($solution, $cells_to_remove) {
    $puzzle = array_map(function($row) { return array_slice($row, 0); }, $solution);
    
    // Create array of all cell positions
    $positions = [];
    for ($i = 0; $i < 9; $i++) {
        for ($j = 0; $j < 9; $j++) {
            $positions[] = [$i, $j];
        }
    }
    
    // Shuffle positions to remove randomly
    shuffle($positions);
    
    // Remove numbers from random positions
    for ($i = 0; $i < $cells_to_remove && $i < count($positions); $i++) {
        $row = $positions[$i][0];
        $col = $positions[$i][1];
        $puzzle[$row][$col] = '';
    }
    
    return $puzzle;
}

/**
 * Enqueue front-end scripts and styles.
 */
add_action( 'wp_enqueue_scripts', 'daily_sudoku_enqueue_assets' );

function daily_sudoku_enqueue_assets() {
    wp_enqueue_style( 'daily-sudoku-styles', plugin_dir_url( __FILE__ ) . 'sudoku.css' );
    wp_enqueue_script( 'daily-sudoku-scripts', plugin_dir_url( __FILE__ ) . 'sudoku.js', [ 'jquery' ], '2.2.0', true );
}

/**
 * Add admin menu pages for settings and puzzle history.
 */
add_action( 'admin_menu', 'daily_sudoku_add_admin_menu' );

function daily_sudoku_add_admin_menu() {
    add_options_page( 'Daily Sudoku Settings', 'Daily Sudoku', 'manage_options', 'daily-sudoku-settings', 'daily_sudoku_settings_page' );
    // Submenu page to view stored puzzles.
    add_submenu_page( 'options-general.php', 'Puzzle History', 'Puzzle History', 'manage_options', 'daily-sudoku-history', 'daily_sudoku_history_page' );
}

/**
 * Render the settings page.
 */
function daily_sudoku_settings_page() {
    if (isset($_POST['generate_today_puzzle'])) {
        daily_sudoku_force_generate_today_puzzle();
        echo '<div class="notice notice-success"><p>Today\'s puzzle has been regenerated!</p></div>';
    }
    ?>
    <div class="wrap">
        <h1>Daily Sudoku Settings</h1>
        <form method="post" action="options.php">
            <?php
            settings_fields( 'daily_sudoku_settings_group' );
            do_settings_sections( 'daily-sudoku-settings' );
            submit_button();
            ?>
        </form>
        
        <hr>
        <h2>Admin Tools</h2>
        <form method="post">
            <p>Force generate a new puzzle for today (will replace existing puzzle if any):</p>
            <input type="submit" name="generate_today_puzzle" class="button button-secondary" value="Generate New Puzzle for Today">
        </form>
    </div>
    <?php
}

/**
 * Force generate today's puzzle (for admin use)
 */
function daily_sudoku_force_generate_today_puzzle() {
    global $wpdb;
    $table_name = $wpdb->prefix . 'daily_sudoku';
    $today = date('Y-m-d');
    $difficulty = get_option('daily_sudoku_difficulty', 'medium');
    
    // Delete existing puzzle for today
    $wpdb->delete($table_name, ['puzzle_date' => $today], ['%s']);
    
    // Generate new puzzle
    $puzzle_data = daily_sudoku_generate_puzzle($difficulty);
    
    // Insert new puzzle
    $wpdb->insert(
        $table_name,
        [
            'puzzle_date' => $today,
            'puzzle'      => wp_json_encode($puzzle_data['puzzle']),
            'solution'    => wp_json_encode($puzzle_data['solution']),
            'difficulty'  => $difficulty,
        ],
        ['%s', '%s', '%s', '%s']
    );
}

/**
 * Register settings.
 */
add_action( 'admin_init', 'daily_sudoku_register_settings' );

function daily_sudoku_register_settings() {
    register_setting( 'daily_sudoku_settings_group', 'daily_sudoku_difficulty' );

    add_settings_section( 'daily_sudoku_main_section', 'Main Settings', null, 'daily-sudoku-settings' );

    add_settings_field( 
        'daily_sudoku_difficulty', 
        'Default Difficulty Level', 
        'daily_sudoku_difficulty_field_render', 
        'daily-sudoku-settings', 
        'daily_sudoku_main_section' 
    );
}

function daily_sudoku_difficulty_field_render() {
    $value = get_option( 'daily_sudoku_difficulty', 'medium' );
    ?>
    <select name="daily_sudoku_difficulty">
        <option value="easy" <?php selected( $value, 'easy' ); ?>>Easy (36-46 clues)</option>
        <option value="medium" <?php selected( $value, 'medium' ); ?>>Medium (26-36 clues)</option>
        <option value="hard" <?php selected( $value, 'hard' ); ?>>Hard (16-26 clues)</option>
    </select>
    <p class="description">This difficulty will be used for new daily puzzles. Changes take effect the next day.</p>
    <?php
}

/**
 * Render an admin page to view puzzle history.
 */
function daily_sudoku_history_page() {
    global $wpdb;
    $table_name = $wpdb->prefix . 'daily_sudoku';
    
    // Handle delete action
    if (isset($_GET['action']) && $_GET['action'] === 'delete' && isset($_GET['puzzle_id'])) {
        $puzzle_id = intval($_GET['puzzle_id']);
        $wpdb->delete($table_name, ['id' => $puzzle_id], ['%d']);
        echo '<div class="notice notice-success"><p>Puzzle deleted successfully!</p></div>';
    }
    
    $results = $wpdb->get_results( "SELECT * FROM $table_name ORDER BY puzzle_date DESC LIMIT 50" );
    ?>
    <div class="wrap">
        <h1>Daily Sudoku Puzzle History</h1>
        <p>Showing the last 50 puzzles.</p>
        <table class="wp-list-table widefat fixed striped">
            <thead>
                <tr>
                    <th>Date</th>
                    <th>Difficulty</th>
                    <th>Actions</th>
                </tr>
            </thead>
            <tbody>
                <?php if ( $results ) : ?>
                    <?php foreach ( $results as $row ) : ?>
                        <tr>
                            <td><?php echo esc_html( $row->puzzle_date ); ?></td>
                            <td><?php echo esc_html( ucfirst($row->difficulty ?? 'medium') ); ?></td>
                            <td>
                                <a href="<?php echo add_query_arg(['action' => 'delete', 'puzzle_id' => $row->id]); ?>" 
                                   onclick="return confirm('Are you sure you want to delete this puzzle?')" 
                                   class="button button-small">Delete</a>
                            </td>
                        </tr>
                    <?php endforeach; ?>
                <?php else : ?>
                    <tr>
                        <td colspan="3">No puzzles found.</td>
                    </tr>
                <?php endif; ?>
            </tbody>
        </table>
    </div>
    <?php
}
?>