<?php
require_once __DIR__ . '/../db.php';

// Set JSON headers
header('Content-Type: application/json');

// Handle CORS
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS');
header('Access-Control-Allow-Headers: Content-Type, Authorization');

// Handle preflight OPTIONS request
if ($_SERVER['REQUEST_METHOD'] === 'OPTIONS') {
    http_response_code(200);
    exit();
}

$method = $_SERVER['REQUEST_METHOD'];

try {
    switch ($method) {
        case 'GET':
            // Get all todos ordered by created_at DESC
            $stmt = $pdo->query("SELECT * FROM todos ORDER BY created_at DESC");
            $todos = $stmt->fetchAll(PDO::FETCH_ASSOC);
            
            // Convert is_completed to boolean
            foreach ($todos as &$todo) {
                $todo['is_completed'] = (bool) $todo['is_completed'];
            }
            
            http_response_code(200);
            echo json_encode([
                'success' => true,
                'data' => $todos
            ]);
            break;

        case 'POST':
            // Create new todo
            $input = json_decode(file_get_contents('php://input'), true);
            
            if (!isset($input['title']) || trim($input['title']) === '') {
                http_response_code(400);
                echo json_encode([
                    'success' => false,
                    'error' => 'Title is required'
                ]);
                break;
            }
            
            $title = trim($input['title']);
            $description = isset($input['description']) ? trim($input['description']) : '';
            
            $stmt = $pdo->prepare("INSERT INTO todos (title, description) VALUES (?, ?)");
            $stmt->execute([$title, $description]);
            
            $id = $pdo->lastInsertId();
            
            // Fetch the created todo
            $stmt = $pdo->prepare("SELECT * FROM todos WHERE id = ?");
            $stmt->execute([$id]);
            $todo = $stmt->fetch(PDO::FETCH_ASSOC);
            $todo['is_completed'] = (bool) $todo['is_completed'];
            
            http_response_code(201);
            echo json_encode([
                'success' => true,
                'data' => $todo
            ]);
            break;

        case 'PUT':
            // Update todo
            $input = json_decode(file_get_contents('php://input'), true);
            
            if (!isset($input['id'])) {
                http_response_code(400);
                echo json_encode([
                    'success' => false,
                    'error' => 'Todo ID is required'
                ]);
                break;
            }
            
            $id = $input['id'];
            
            // Check if todo exists
            $stmt = $pdo->prepare("SELECT * FROM todos WHERE id = ?");
            $stmt->execute([$id]);
            $todo = $stmt->fetch(PDO::FETCH_ASSOC);
            
            if (!$todo) {
                http_response_code(404);
                echo json_encode([
                    'success' => false,
                    'error' => 'Todo not found'
                ]);
                break;
            }
            
            // Build update query dynamically based on provided fields
            $updates = [];
            $params = [];
            
            if (isset($input['title'])) {
                $updates[] = "title = ?";
                $params[] = trim($input['title']);
            }
            
            if (isset($input['description'])) {
                $updates[] = "description = ?";
                $params[] = trim($input['description']);
            }
            
            if (isset($input['is_completed'])) {
                $updates[] = "is_completed = ?";
                $params[] = $input['is_completed'] ? 1 : 0;
            }
            
            if (empty($updates)) {
                http_response_code(400);
                echo json_encode([
                    'success' => false,
                    'error' => 'No fields to update'
                ]);
                break;
            }
            
            $params[] = $id;
            $sql = "UPDATE todos SET " . implode(', ', $updates) . " WHERE id = ?";
            $stmt = $pdo->prepare($sql);
            $stmt->execute($params);
            
            // Fetch updated todo
            $stmt = $pdo->prepare("SELECT * FROM todos WHERE id = ?");
            $stmt->execute([$id]);
            $todo = $stmt->fetch(PDO::FETCH_ASSOC);
            $todo['is_completed'] = (bool) $todo['is_completed'];
            
            http_response_code(200);
            echo json_encode([
                'success' => true,
                'data' => $todo
            ]);
            break;

        case 'DELETE':
            // Delete todo
            $input = json_decode(file_get_contents('php://input'), true);
            
            if (!isset($input['id'])) {
                http_response_code(400);
                echo json_encode([
                    'success' => false,
                    'error' => 'Todo ID is required'
                ]);
                break;
            }
            
            $id = $input['id'];
            
            // Check if todo exists
            $stmt = $pdo->prepare("SELECT * FROM todos WHERE id = ?");
            $stmt->execute([$id]);
            $todo = $stmt->fetch(PDO::FETCH_ASSOC);
            
            if (!$todo) {
                http_response_code(404);
                echo json_encode([
                    'success' => false,
                    'error' => 'Todo not found'
                ]);
                break;
            }
            
            // Delete the todo
            $stmt = $pdo->prepare("DELETE FROM todos WHERE id = ?");
            $stmt->execute([$id]);
            
            http_response_code(200);
            echo json_encode([
                'success' => true,
                'message' => 'Todo deleted successfully'
            ]);
            break;

        default:
            http_response_code(405);
            echo json_encode([
                'success' => false,
                'error' => 'Method not allowed'
            ]);
            break;
    }
} catch (PDOException $e) {
    http_response_code(500);
    echo json_encode([
        'success' => false,
        'error' => 'Database error: ' . $e->getMessage()
    ]);
} catch (Exception $e) {
    http_response_code(500);
    echo json_encode([
        'success' => false,
        'error' => 'Server error: ' . $e->getMessage()
    ]);
}