<?php

declare(strict_types=1);

/**
 * @author Robert Strutts
 * @copyright (c) 2026, Robert Strutts
 * @license MIT
 */

namespace IOcornerstone\Framework\Database;

/**
 * Description of BuildSQL
 *
 * @author Robert Strutts
 */
class BuildSQL
{

    /**
     * Generate CREATE TABLE SQL from an existing MySQL table.
     */
    public function generateCreateTable(\PDO $pdo, string $table): string
    {
        $sql = "
        SELECT
            COLUMN_NAME,
            COLUMN_TYPE,
            IS_NULLABLE,
            COLUMN_DEFAULT,
            EXTRA,
            COLUMN_KEY,
            COLUMN_COMMENT
        FROM INFORMATION_SCHEMA.COLUMNS
        WHERE TABLE_SCHEMA = DATABASE()
          AND TABLE_NAME = ?
        ORDER BY ORDINAL_POSITION
    ";

        $stmt = $pdo->prepare($sql);
        $stmt->execute([$table]);

        $columns = [];
        $primary = [];

        while ($row = $stmt->fetch(\PDO::FETCH_ASSOC)) {
            $line = '`' . $row['COLUMN_NAME'] . '` ' . $row['COLUMN_TYPE'];

            if ($row['IS_NULLABLE'] === 'NO') {
                $line .= ' NOT NULL';
            }

            if ($row['COLUMN_DEFAULT'] !== null) {
                $default = $row['COLUMN_DEFAULT'];

                if (strtoupper($default) === 'CURRENT_TIMESTAMP') {
                    $line .= ' DEFAULT CURRENT_TIMESTAMP';
                } else {
                    $line .= ' DEFAULT ' . $pdo->quote($default);
                }
            }

            if (!empty($row['EXTRA'])) {
                $line .= ' ' . strtoupper($row['EXTRA']);
            }

            if (!empty($row['COLUMN_COMMENT'])) {
                $line .= ' COMMENT ' . $pdo->quote($row['COLUMN_COMMENT']);
            }

            $columns[] = $line;

            if ($row['COLUMN_KEY'] === 'PRI') {
                $primary[] = '`' . $row['COLUMN_NAME'] . '`';
            }
        }

        if (!empty($primary)) {
            $columns[] = 'PRIMARY KEY (' . implode(', ', $primary) . ')';
        }

        return "CREATE TABLE IF NOT EXISTS `{$table}` (\n    "
                . implode(",\n    ", $columns)
                . "\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;";
    }
    
}