import 'dart:convert';
import 'dart:io';

import 'package:flutter/foundation.dart';
import 'package:http/http.dart' as http;
import 'package:logging/logging.dart';
import 'package:path_provider/path_provider.dart';

import '../models/sheet.dart';

/// HTTP client for communicating with the Sheetless API server.
///
/// Handles authentication, sheet listing, and PDF downloads.
/// Provides caching for PDF files on native platforms.
class ApiClient {
  final _log = Logger('ApiClient');
  final String baseUrl;
  String? token;

  ApiClient({required this.baseUrl, this.token});

  /// Whether the client has an authentication token set.
  bool get isAuthenticated => token != null;

  // ---------------------------------------------------------------------------
  // Authentication
  // ---------------------------------------------------------------------------

  /// Authenticates with the server and stores the JWT token.
  ///
  /// Throws an [Exception] if login fails.
  Future<void> login(String username, String password) async {
    _log.info('Logging in...');
    final url = Uri.parse('$baseUrl/auth/login');

    final response = await http.post(
      url,
      headers: {'Content-Type': 'application/json'},
      body: jsonEncode({'username': username, 'password': password}),
    );

    if (response.statusCode == 200) {
      final responseData = jsonDecode(response.body);
      token = responseData['token'];
      _log.info('Login successful');
    } else {
      throw ApiException(
        'Login failed',
        statusCode: response.statusCode,
        body: response.body,
      );
    }
  }

  /// Clears the authentication token.
  void logout() {
    token = null;
    _log.info('Logged out successfully');
  }

  // ---------------------------------------------------------------------------
  // HTTP Helpers
  // ---------------------------------------------------------------------------

  Map<String, String> _buildHeaders({bool isBinary = false}) {
    return {
      'Authorization': 'Bearer $token',
      if (!isBinary) 'Content-Type': 'application/json',
    };
  }

  /// Performs a GET request to the given endpoint.
  Future<http.Response> get(
    String endpoint, {
    bool isBinary = false,
  }) async {
    final url = Uri.parse('$baseUrl$endpoint');
    final response =
        await http.get(url, headers: _buildHeaders(isBinary: isBinary));

    if (response.statusCode != 200) {
      _log.warning(
        "GET '$endpoint' failed: ${response.statusCode}\n${response.body}",
      );
      throw ApiException(
        'GET request failed',
        statusCode: response.statusCode,
        body: response.body,
      );
    }

    return response;
  }

  /// Performs a POST request with JSON body.
  Future<http.Response> post(
    String endpoint,
    Map<String, dynamic> body,
  ) async {
    final url = Uri.parse('$baseUrl$endpoint');

    final response = await http.post(
      url,
      headers: _buildHeaders(),
      body: jsonEncode(body),
    );

    if (response.statusCode != 200 && response.statusCode != 201) {
      _log.warning(
        "POST '$endpoint' failed: ${response.statusCode}\n${response.body}",
      );
      throw ApiException(
        'POST request failed',
        statusCode: response.statusCode,
        body: response.body,
      );
    }

    return response;
  }

  /// Performs a POST request with form-encoded body.
  Future<http.Response> postFormData(String endpoint, String body) async {
    final url = Uri.parse('$baseUrl$endpoint');

    final response = await http.post(
      url,
      headers: {
        'Authorization': 'Bearer $token',
        'Content-Type': 'application/x-www-form-urlencoded',
      },
      body: body,
    );

    if (response.statusCode != 200 && response.statusCode != 201) {
      _log.warning(
        "POST Form '$endpoint' failed: ${response.statusCode}\n${response.body}",
      );
      throw ApiException(
        'POST Form request failed',
        statusCode: response.statusCode,
        body: response.body,
      );
    }

    return response;
  }

  // ---------------------------------------------------------------------------
  // Sheet Operations
  // ---------------------------------------------------------------------------

  /// Fetches the list of all sheets from the server.
  Future<List<Sheet>> fetchSheets() async {
    final response = await get('/api/sheets/list');
    final data = jsonDecode(response.body);

    return (data['sheets'] as List<dynamic>)
        .map((sheet) => Sheet.fromJson(sheet as Map<String, dynamic>))
        .toList();
  }

  /// Downloads PDF data for a sheet.
  ///
  /// Returns the raw PDF bytes. For caching, use [getPdfFileCached] instead.
  Future<Uint8List> fetchPdfData(String sheetUuid) async {
    final response = await get('/api/sheets/get/$sheetUuid', isBinary: true);
    _log.info('PDF downloaded for sheet $sheetUuid');
    return response.bodyBytes;
  }

  /// Gets a cached PDF file for a sheet, downloading if necessary.
  ///
  /// On web platforms, use [fetchPdfData] instead as file caching
  /// is not supported.
  Future<File> getPdfFileCached(String sheetUuid) async {
    final cacheDir = await getTemporaryDirectory();
    final cachedFile = File('${cacheDir.path}/$sheetUuid.pdf');

    if (await cachedFile.exists()) {
      _log.info('PDF found in cache: ${cachedFile.path}');
      return cachedFile;
    }

    final pdfData = await fetchPdfData(sheetUuid);
    await cachedFile.writeAsBytes(pdfData);
    _log.info('PDF cached at: ${cachedFile.path}');
    return cachedFile;
  }
}

/// Exception thrown when an API request fails.
class ApiException implements Exception {
  final String message;
  final int statusCode;
  final String body;

  ApiException(this.message, {required this.statusCode, required this.body});

  @override
  String toString() => 'ApiException: $message (status: $statusCode)\n$body';
}