<?php

require_once __DIR__ . '/config.php';

/**
 * Unified Database connection class for Post-ERG thesis database
 * Combines functionality from both front-backend and formulaire
 * Supports both singleton (front-backend) and direct instantiation (formulaire)
 */
class Database {
    private static $instance = null;
    private $pdo;
    private $dbPath;

    /**
     * Constructor - public to support both singleton and direct instantiation
     * @param string $dbPath Optional database path override
     */
    public function __construct($dbPath = null) {
        $this->dbPath = $this->determineDatabasePath($dbPath);

        try {
            $this->pdo = new PDO('sqlite:' . $this->dbPath);
            $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            $this->pdo->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);

            // Enable foreign key constraints
            $this->pdo->exec('PRAGMA foreign_keys = ON');
        } catch (PDOException $e) {
            error_log("Database connection failed: " . $e->getMessage());
            throw new Exception("Impossible de se connecter à la base de données.");
        }
    }

    /**
     * Determine database path
     * Uses centralized config from config.php
     * Priority: custom path > config.php settings
     */
    private function determineDatabasePath($customPath = null) {
        // Allow explicit override
        if ($customPath !== null && file_exists($customPath)) {
            return $customPath;
        }

        // Use centralized configuration
        return getDatabasePath();
    }

    /**
     * Get singleton instance (for front-backend)
     * @return Database
     */
    public static function getInstance() {
        if (self::$instance === null) {
            self::$instance = new self();
        }
        return self::$instance;
    }

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

    /**
     * Get PDO instance (alias for formulaire compatibility)
     * @return PDO
     */
    public function getPDO() {
        return $this->pdo;
    }

    // ========================================================================
    // TRANSACTION SUPPORT (from formulaire)
    // ========================================================================

    /**
     * Begin a transaction
     */
    public function beginTransaction() {
        return $this->pdo->beginTransaction();
    }

    /**
     * Commit a transaction
     */
    public function commit() {
        return $this->pdo->commit();
    }

    /**
     * Rollback a transaction
     */
    public function rollback() {
        return $this->pdo->rollback();
    }

    // ========================================================================
    // PUBLIC SITE METHODS (from front-backend)
    // ========================================================================

    /**
     * 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 (for public site)
     */
    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 thesis by ID (for admin - includes unpublished)
     * @param int $id Thesis ID
     * @return array|null Thesis data or null if not found
     */
    public function getThesis($id) {
        $stmt = $this->pdo->prepare("SELECT * FROM v_theses_full WHERE id = ?");
        $stmt->execute([$id]);
        return $stmt->fetch();
    }

    /**
     * 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();
    }

    // ========================================================================
    // SEARCH FUNCTIONALITY (from front-backend - secure implementation)
    // ========================================================================

    /**
     * Escape LIKE wildcards in user input to prevent wildcard injection
     */
    private function escapeLikeString($string) {
        return str_replace(['\\', '%', '_'], ['\\\\', '\\%', '\\_'], $string);
    }

    /**
     * Validate and sanitize search parameters
     * @throws InvalidArgumentException if validation fails
     */
    private function validateSearchParams($params) {
        $validated = [];

        if (!empty($params['query'])) {
            $query = trim($params['query']);
            if (strlen($query) > 200) {
                throw new InvalidArgumentException("Search query too long (max 200 characters)");
            }
            $validated['query'] = $this->escapeLikeString($query);
        }

        if (!empty($params['year'])) {
            $year = intval($params['year']);
            if ($year < 1900 || $year > 2100) {
                throw new InvalidArgumentException("Invalid year");
            }
            $validated['year'] = $year;
        }

        if (!empty($params['orientation'])) {
            $orientation = trim($params['orientation']);
            if (strlen($orientation) > 100) {
                throw new InvalidArgumentException("Orientation name too long");
            }
            $validated['orientation'] = $this->escapeLikeString($orientation);
        }

        if (!empty($params['ap_program'])) {
            $ap = trim($params['ap_program']);
            if (strlen($ap) > 100) {
                throw new InvalidArgumentException("AP program name too long");
            }
            $validated['ap_program'] = $this->escapeLikeString($ap);
        }

        if (!empty($params['finality'])) {
            $finality = trim($params['finality']);
            if (strlen($finality) > 100) {
                throw new InvalidArgumentException("Finality name too long");
            }
            $validated['finality'] = $this->escapeLikeString($finality);
        }

        if (!empty($params['keyword'])) {
            $keyword = trim($params['keyword']);
            if (strlen($keyword) > 100) {
                throw new InvalidArgumentException("Keyword too long");
            }
            $validated['keyword'] = $this->escapeLikeString($keyword);
        }

        if (!empty($params['format'])) {
            $format = trim($params['format']);
            if (strlen($format) > 100) {
                throw new InvalidArgumentException("Format name too long");
            }
            $validated['format'] = $this->escapeLikeString($format);
        }

        if (!empty($params['language'])) {
            $language = trim($params['language']);
            if (strlen($language) > 50) {
                throw new InvalidArgumentException("Language name too long");
            }
            $validated['language'] = $this->escapeLikeString($language);
        }

        if (isset($params['is_doctoral'])) {
            $validated['is_doctoral'] = (bool)$params['is_doctoral'];
        }

        return $validated;
    }

    /**
     * Search theses with filters (secure implementation)
     */
    public function searchTheses($params = [], $limit = 20, $offset = 0) {
        $params = $this->validateSearchParams($params);
        $limit = max(1, min(100, intval($limit)));
        $offset = max(0, intval($offset));

        $conditions = ["is_published = 1"];
        $bindings = [];

        if (!empty($params['query'])) {
            $conditions[] = "(
                title LIKE :query ESCAPE '\\' OR
                subtitle LIKE :query ESCAPE '\\' OR
                synopsis LIKE :query ESCAPE '\\' OR
                authors LIKE :query ESCAPE '\\' OR
                supervisors LIKE :query ESCAPE '\\' OR
                keywords LIKE :query ESCAPE '\\'
            )";
            $bindings[':query'] = '%' . $params['query'] . '%';
        }

        if (!empty($params['year'])) {
            $conditions[] = "year = :year";
            $bindings[':year'] = $params['year'];
        }

        if (!empty($params['orientation'])) {
            $conditions[] = "orientation LIKE :orientation ESCAPE '\\'";
            $bindings[':orientation'] = '%' . $params['orientation'] . '%';
        }

        if (!empty($params['ap_program'])) {
            $conditions[] = "ap_program LIKE :ap_program ESCAPE '\\'";
            $bindings[':ap_program'] = '%' . $params['ap_program'] . '%';
        }

        if (!empty($params['finality'])) {
            $conditions[] = "finality_type LIKE :finality ESCAPE '\\'";
            $bindings[':finality'] = '%' . $params['finality'] . '%';
        }

        if (!empty($params['keyword'])) {
            $conditions[] = "keywords LIKE :keyword ESCAPE '\\'";
            $bindings[':keyword'] = '%' . $params['keyword'] . '%';
        }

        if (!empty($params['format'])) {
            $conditions[] = "formats LIKE :format ESCAPE '\\'";
            $bindings[':format'] = '%' . $params['format'] . '%';
        }

        if (!empty($params['language'])) {
            $conditions[] = "languages LIKE :language ESCAPE '\\'";
            $bindings[':language'] = '%' . $params['language'] . '%';
        }

        if (isset($params['is_doctoral'])) {
            $conditions[] = "is_doctoral = :is_doctoral";
            $bindings[':is_doctoral'] = $params['is_doctoral'] ? 1 : 0;
        }

        $whereClause = implode(' AND ', $conditions);
        $sql = "SELECT * FROM v_theses_public WHERE $whereClause ORDER BY year DESC, title ASC LIMIT :limit OFFSET :offset";

        $stmt = $this->pdo->prepare($sql);
        foreach ($bindings as $key => $value) {
            $stmt->bindValue($key, $value);
        }
        $stmt->bindValue(':limit', $limit, PDO::PARAM_INT);
        $stmt->bindValue(':offset', $offset, PDO::PARAM_INT);

        $stmt->execute();
        return $stmt->fetchAll();
    }

    /**
     * Count search results
     */
    public function countSearchResults($params = []) {
        $params = $this->validateSearchParams($params);
        $conditions = ["is_published = 1"];
        $bindings = [];

        if (!empty($params['query'])) {
            $conditions[] = "(
                title LIKE :query ESCAPE '\\' OR
                subtitle LIKE :query ESCAPE '\\' OR
                synopsis LIKE :query ESCAPE '\\' OR
                authors LIKE :query ESCAPE '\\' OR
                supervisors LIKE :query ESCAPE '\\' OR
                keywords LIKE :query ESCAPE '\\'
            )";
            $bindings[':query'] = '%' . $params['query'] . '%';
        }

        if (!empty($params['year'])) {
            $conditions[] = "year = :year";
            $bindings[':year'] = $params['year'];
        }

        if (!empty($params['orientation'])) {
            $conditions[] = "orientation LIKE :orientation ESCAPE '\\'";
            $bindings[':orientation'] = '%' . $params['orientation'] . '%';
        }

        if (!empty($params['ap_program'])) {
            $conditions[] = "ap_program LIKE :ap_program ESCAPE '\\'";
            $bindings[':ap_program'] = '%' . $params['ap_program'] . '%';
        }

        if (!empty($params['finality'])) {
            $conditions[] = "finality_type LIKE :finality ESCAPE '\\'";
            $bindings[':finality'] = '%' . $params['finality'] . '%';
        }

        if (!empty($params['keyword'])) {
            $conditions[] = "keywords LIKE :keyword ESCAPE '\\'";
            $bindings[':keyword'] = '%' . $params['keyword'] . '%';
        }

        if (!empty($params['format'])) {
            $conditions[] = "formats LIKE :format ESCAPE '\\'";
            $bindings[':format'] = '%' . $params['format'] . '%';
        }

        if (!empty($params['language'])) {
            $conditions[] = "languages LIKE :language ESCAPE '\\'";
            $bindings[':language'] = '%' . $params['language'] . '%';
        }

        if (isset($params['is_doctoral'])) {
            $conditions[] = "is_doctoral = :is_doctoral";
            $bindings[':is_doctoral'] = $params['is_doctoral'] ? 1 : 0;
        }

        $whereClause = implode(' AND ', $conditions);
        $sql = "SELECT COUNT(*) as count FROM v_theses_public WHERE $whereClause";

        $stmt = $this->pdo->prepare($sql);
        foreach ($bindings as $key => $value) {
            $stmt->bindValue($key, $value);
        }

        $stmt->execute();
        $result = $stmt->fetch();
        return $result['count'];
    }

    /**
     * Get all available years from published theses
     */
    public function getAvailableYears() {
        $sql = "SELECT DISTINCT year FROM theses WHERE is_published = 1 ORDER BY year DESC";
        $stmt = $this->pdo->query($sql);
        return $stmt->fetchAll(PDO::FETCH_COLUMN);
    }

    /**
     * Get all orientations
     */
    public function getOrientations() {
        $sql = "SELECT * FROM orientations ORDER BY name";
        $stmt = $this->pdo->query($sql);
        return $stmt->fetchAll();
    }

    /**
     * Alias for formulaire compatibility
     */
    public function getAllOrientations() {
        return $this->getOrientations();
    }

    /**
     * Get all AP programs
     */
    public function getApPrograms() {
        $sql = "SELECT * FROM ap_programs ORDER BY name";
        $stmt = $this->pdo->query($sql);
        return $stmt->fetchAll();
    }

    /**
     * Alias for formulaire compatibility
     */
    public function getAllAPPrograms() {
        return $this->getApPrograms();
    }

    /**
     * Get all finality types
     */
    public function getFinalityTypes() {
        $sql = "SELECT * FROM finality_types ORDER BY name";
        $stmt = $this->pdo->query($sql);
        return $stmt->fetchAll();
    }

    /**
     * Alias for formulaire compatibility
     */
    public function getAllFinalityTypes() {
        return $this->getFinalityTypes();
    }

    /**
     * Get all keywords used in published theses
     */
    public function getUsedKeywords() {
        $sql = "SELECT DISTINCT k.* FROM keywords k
                INNER JOIN thesis_keywords tk ON k.id = tk.keyword_id
                INNER JOIN theses t ON tk.thesis_id = t.id
                WHERE t.is_published = 1
                ORDER BY k.keyword";
        $stmt = $this->pdo->query($sql);
        return $stmt->fetchAll();
    }

    /**
     * Get all format types
     */
    public function getFormatTypes() {
        $sql = "SELECT * FROM format_types ORDER BY name";
        $stmt = $this->pdo->query($sql);
        return $stmt->fetchAll();
    }

    /**
     * Alias for formulaire compatibility
     */
    public function getAllFormatTypes() {
        return $this->getFormatTypes();
    }

    /**
     * Get all languages
     */
    public function getLanguages() {
        $sql = "SELECT * FROM languages ORDER BY name";
        $stmt = $this->pdo->query($sql);
        return $stmt->fetchAll();
    }

    /**
     * Alias for formulaire compatibility
     */
    public function getAllLanguages() {
        return $this->getLanguages();
    }

    // ========================================================================
    // CRUD METHODS (from formulaire)
    // ========================================================================

    /**
     * Find or create an author
     */
    public function findOrCreateAuthor($name, $email = null) {
        $stmt = $this->pdo->prepare("SELECT id FROM authors WHERE name = ?");
        $stmt->execute([$name]);
        $author = $stmt->fetch();

        if ($author) {
            if ($email && $email !== '') {
                $updateStmt = $this->pdo->prepare("UPDATE authors SET email = ? WHERE id = ?");
                $updateStmt->execute([$email, $author['id']]);
            }
            return $author['id'];
        }

        $stmt = $this->pdo->prepare("INSERT INTO authors (name, email) VALUES (?, ?)");
        $stmt->execute([$name, $email]);
        return $this->pdo->lastInsertId();
    }

    /**
     * Find or create a supervisor
     */
    public function findOrCreateSupervisor($name) {
        $stmt = $this->pdo->prepare("SELECT id FROM supervisors WHERE name = ?");
        $stmt->execute([$name]);
        $supervisor = $stmt->fetch();

        if ($supervisor) {
            return $supervisor['id'];
        }

        $stmt = $this->pdo->prepare("INSERT INTO supervisors (name) VALUES (?)");
        $stmt->execute([$name]);
        return $this->pdo->lastInsertId();
    }

    /**
     * Find or create a keyword
     */
    public function findOrCreateKeyword($keyword) {
        $keyword = trim($keyword);
        if (empty($keyword)) {
            return null;
        }

        $stmt = $this->pdo->prepare("SELECT id FROM keywords WHERE keyword = ?");
        $stmt->execute([$keyword]);
        $kw = $stmt->fetch();

        if ($kw) {
            return $kw['id'];
        }

        $stmt = $this->pdo->prepare("INSERT INTO keywords (keyword) VALUES (?)");
        $stmt->execute([$keyword]);
        return $this->pdo->lastInsertId();
    }

    /**
     * Get orientation ID by name
     */
    public function getOrientationId($name) {
        $stmt = $this->pdo->prepare("SELECT id FROM orientations WHERE name = ?");
        $stmt->execute([$name]);
        $result = $stmt->fetch();
        return $result ? $result['id'] : null;
    }

    /**
     * Get AP program ID by name
     */
    public function getAPProgramId($name) {
        $stmt = $this->pdo->prepare("SELECT id FROM ap_programs WHERE name = ?");
        $stmt->execute([$name]);
        $result = $stmt->fetch();
        return $result ? $result['id'] : null;
    }

    /**
     * Get finality type ID by name
     */
    public function getFinalityId($name) {
        $stmt = $this->pdo->prepare("SELECT id FROM finality_types WHERE name = ?");
        $stmt->execute([$name]);
        $result = $stmt->fetch();
        return $result ? $result['id'] : null;
    }

    /**
     * Get language ID by name
     */
    public function getLanguageId($name) {
        $stmt = $this->pdo->prepare("SELECT id FROM languages WHERE name = ?");
        $stmt->execute([$name]);
        $result = $stmt->fetch();
        return $result ? $result['id'] : null;
    }

    /**
     * Get format type ID by name
     */
    public function getFormatId($name) {
        $stmt = $this->pdo->prepare("SELECT id FROM format_types WHERE name = ?");
        $stmt->execute([$name]);
        $result = $stmt->fetch();
        return $result ? $result['id'] : null;
    }

    /**
     * Insert a thesis file record
     */
    public function insertThesisFile($thesisId, $fileType, $filePath, $fileName, $fileSize, $mimeType) {
        $stmt = $this->pdo->prepare("
            INSERT INTO thesis_files (thesis_id, file_type, file_path, file_name, file_size, mime_type)
            VALUES (?, ?, ?, ?, ?, ?)
        ");
        $stmt->execute([$thesisId, $fileType, $filePath, $fileName, $fileSize, $mimeType]);
        return $this->pdo->lastInsertId();
    }

    // ========================================================================
    // SINGLETON PATTERN ENFORCEMENT
    // ========================================================================

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

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