Complete refactor to clean up project

lib/core/services/api_client.dart

@@ -0,0 +1,202 @@
+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';
+}