<?php
/**
 * Database connection and helpers.
 * Uses SQLite via PDO — no external database server required.
 *
 * The database file path is configurable via the DATABASE_PATH env var.
 * Defaults to data/protocol_droid.db relative to the project root.
 */

function db_path(): string {
    $configured = getenv('DATABASE_PATH');
    if ($configured) return $configured;
    return __DIR__ . '/../data/protocol_droid.db';
}

function db(): PDO {
    static $pdo = null;
    if ($pdo === null) {
        $path = db_path();
        $dir = dirname($path);
        if (!is_dir($dir)) {
            mkdir($dir, 0775, true);
        }
        $dsn = "sqlite:{$path}";
        try {
            $pdo = new PDO($dsn, null, null, [
                PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
                PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
                PDO::ATTR_EMULATE_PREPARES => false,
            ]);
            // Enable foreign key enforcement (off by default in SQLite)
            $pdo->exec('PRAGMA foreign_keys = ON');
        } catch (PDOException $e) {
            http_response_code(500);
            echo json_encode(['error' => 'Database connection failed']);
            exit;
        }
    }
    return $pdo;
}

function db_init(): void {
    $sql = file_get_contents(__DIR__ . '/../schema.sql');
    if (!$sql) return;
    db()->exec($sql);
}

function db_query(string $sql, array $params = []): PDOStatement {
    $stmt = db()->prepare($sql);
    $stmt->execute($params);
    return $stmt;
}

function db_one(string $sql, array $params = []): ?array {
    $stmt = db_query($sql, $params);
    $row = $stmt->fetch();
    return $row ?: null;
}

function db_all(string $sql, array $params = []): array {
    $stmt = db_query($sql, $params);
    return $stmt->fetchAll();
}

function db_insert(string $table, array $data): int {
    $cols = implode(', ', array_map(fn($c) => "`$c`", array_keys($data)));
    $placeholders = implode(', ', array_fill(0, count($data), '?'));
    $sql = "INSERT INTO {$table} ({$cols}) VALUES ({$placeholders})";
    db_query($sql, array_values($data));
    return (int) db()->lastInsertId();
}

function db_update(string $table, array $data, string $where, array $whereParams): int {
    $set = implode(', ', array_map(fn($c) => "`$c` = ?", array_keys($data)));
    $sql = "UPDATE {$table} SET {$set} WHERE {$where}";
    $stmt = db_query($sql, array_merge(array_values($data), $whereParams));
    return $stmt->rowCount();
}

function slugify(string $text): string {
    $slug = strtolower($text);
    $slug = preg_replace('/[^a-z0-9]+/', '-', $slug);
    $slug = trim($slug, '-');
    $slug = substr($slug, 0, 128);
    return $slug ?: 'untitled';
}

function ensure_unique_slug(string $base): string {
    $slug = $base;
    $i = 1;
    while (db_one("SELECT slug FROM protocols WHERE slug = ?", [$slug]) ||
           db_one("SELECT slug FROM collections WHERE slug = ?", [$slug])) {
        $slug = $base . '-' . $i++;
    }
    return $slug;
}