<?php

/**
 * Database connection class for SQLite
 */
class Database {
    private static $instance = null;
    private $pdo;

    /**
     * Private constructor to prevent multiple instances
     */
    private function __construct() {
        $dbPath = __DIR__ . '/../formulaire/test.db';

        if (!file_exists($dbPath)) {
            throw new Exception("Database file not found: " . $dbPath);
        }

        try {
            $this->pdo = new PDO('sqlite:' . $dbPath);
            $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            $this->pdo->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
        } catch (PDOException $e) {
            error_log("Database connection failed: " . $e->getMessage());
            throw $e;
        }
    }

    /**
     * Get singleton instance
     */
    public static function getInstance() {
        if (self::$instance === null) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    /**
     * Get PDO connection
     */
    public function getConnection() {
        return $this->pdo;
    }

    /**
     * Get all published theses with pagination
     */
    public function getPublishedTheses($limit = 10, $offset = 0) {
        $sql = "SELECT * FROM v_theses_public ORDER BY year DESC, title ASC LIMIT :limit OFFSET :offset";
        $stmt = $this->pdo->prepare($sql);
        $stmt->bindValue(':limit', $limit, PDO::PARAM_INT);
        $stmt->bindValue(':offset', $offset, PDO::PARAM_INT);
        $stmt->execute();
        return $stmt->fetchAll();
    }

    /**
     * Count all published theses
     */
    public function countPublishedTheses() {
        $sql = "SELECT COUNT(*) as count FROM theses WHERE is_published = 1";
        $stmt = $this->pdo->query($sql);
        $result = $stmt->fetch();
        return $result['count'];
    }

    /**
     * Get thesis by ID with all related data
     */
    public function getThesisById($id) {
        $sql = "SELECT * FROM v_theses_full WHERE id = :id AND is_published = 1";
        $stmt = $this->pdo->prepare($sql);
        $stmt->bindValue(':id', $id, PDO::PARAM_INT);
        $stmt->execute();
        $thesis = $stmt->fetch();

        if (!$thesis) {
            return null;
        }

        // Get associated files
        $thesis['files'] = $this->getThesisFiles($id);

        return $thesis;
    }

    /**
     * Get files associated with a thesis
     */
    public function getThesisFiles($thesisId) {
        $sql = "SELECT * FROM thesis_files WHERE thesis_id = :thesis_id ORDER BY file_type, uploaded_at";
        $stmt = $this->pdo->prepare($sql);
        $stmt->bindValue(':thesis_id', $thesisId, PDO::PARAM_INT);
        $stmt->execute();
        return $stmt->fetchAll();
    }

    /**
     * Prevent cloning
     */
    private function __clone() {}

    /**
     * Prevent unserialization
     */
    public function __wakeup() {
        throw new Exception("Cannot unserialize singleton");
    }
}