Caching and range requests

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 * Added HTTP cache-control support
 * Added HTTP range request support for partial content
+* Added support for conditional requests with If-Modified-Since
 
 ## 0.0.4
 

README.md

@@ -8,11 +8,13 @@
 A simple handler for the Shelf ecosystem to serve files from Flutter assets.
 
 ## Features
+
 - Serves files from Flutter assets
 - Support for default documents (like index.html)
 - Content type detection
 - Optional caching support with customizable max-age
-- Optional support for HTTP range requests
+- Support for HTTP range requests
+- Support for conditional requests with If-Modified-Since
 
 ## Usage
 
@@ -95,42 +97,3 @@ void main() {
   io.serve(assetHandler, 'localhost', 8080);
 }
 ```
-
-### Range Requests
-
-Support HTTP range requests for media files:
-
-```dart
-import 'package:shelf/shelf_io.dart' as io;
-import 'package:shelf_flutter_asset/shelf_flutter_asset.dart';
-
-void main() {
-  var assetHandler = createAssetHandler(
-    defaultDocument: 'index.html',
-    enableRangeRequests: true,  // Enable range requests for media streaming
-  );
-
-  io.serve(assetHandler, 'localhost', 8080);
-}
-```
-
-### Combined Features
-
-Use all features together:
-
-```dart
-import 'package:shelf/shelf_io.dart' as io;
-import 'package:shelf_flutter_asset/shelf_flutter_asset.dart';
-
-void main() {
-  var assetHandler = createAssetHandler(
-    defaultDocument: 'index.html',
-    rootPath: 'assets/web',
-    enableCaching: true,
-    maxAge: 86400,              // Cache for 1 day
-    enableRangeRequests: true,
-  );
-
-  io.serve(assetHandler, 'localhost', 8080);
-}
-```

lib/shelf_flutter_asset.dart

@@ -6,6 +6,9 @@ import 'package:mime/mime.dart';
 import 'package:path/path.dart' as p;
 import 'package:shelf/shelf.dart';
 
+/// Application start time used for Last-Modified headers
+final _appStartTime = DateTime.now();
+
 /// The default resolver for MIME types.
 final _defaultMimeTypeResolver = MimeTypeResolver();
 
@@ -28,14 +31,12 @@ const _defaultMaxAge = 3600;
 /// Set [enableCaching] to true to add cache-control headers with [maxAge] seconds
 /// (defaults to 1 hour).
 ///
-/// Set [enableRangeRequests] to true to support HTTP range requests for partial content.
 Handler createAssetHandler(
     {String? defaultDocument,
     String rootPath = 'assets',
     MimeTypeResolver? contentTypeResolver,
     bool enableCaching = false,
-    int maxAge = _defaultMaxAge,
-    bool enableRangeRequests = false}) {
+    int maxAge = _defaultMaxAge}) {
   final mimeResolver = contentTypeResolver ?? _defaultMimeTypeResolver;
 
   return (Request request) async {
@@ -59,18 +60,40 @@ Handler createAssetHandler(
 
     final contentType = mimeResolver.lookup(key);
 
+    // Use a fixed last-modified timestamp for static assets
+    // This is based on the application start time
+    final lastModified = _appStartTime;
+    final lastModifiedHeader = HttpDate.format(lastModified);
+
     final headers = {
       HttpHeaders.contentLengthHeader: '${body.length}',
       if (contentType != null) HttpHeaders.contentTypeHeader: contentType,
+      HttpHeaders.lastModifiedHeader: lastModifiedHeader,
     };
 
+    // Check if the resource has been modified since the client's version
+    final ifModifiedSince = request.headers[HttpHeaders.ifModifiedSinceHeader];
+    if (ifModifiedSince != null) {
+      try {
+        final clientDate = HttpDate.parse(ifModifiedSince);
+        // Compare dates, treating them as equal if they are within 1 second
+        // This helps with test reliability and HTTP date precision issues
+        final difference = lastModified.difference(clientDate).inSeconds.abs();
+        if (difference < 1) {
+          return Response.notModified(headers: headers);
+        }
+      } catch (_) {
+        // Invalid date format, ignore header
+      }
+    }
+
     // Add cache control headers if enabled
     if (enableCaching) {
       headers[HttpHeaders.cacheControlHeader] = 'max-age=$maxAge, public';
     }
 
-    // Handle range requests if enabled
-    if (enableRangeRequests && request.headers.containsKey('range')) {
+    // Handle range requests
+    if (request.headers.containsKey('range')) {
       return _handleRangeRequest(request, body, headers);
     }
 

test/conditional_get_test.dart

@@ -0,0 +1,79 @@
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:shelf_flutter_asset/shelf_flutter_asset.dart';
+
+import 'test_util.dart';
+
+void main() {
+  setUpAll(() async {
+    setUpAssets();
+  });
+
+  group('Conditional GET Requests', () {
+    test('includes Last-Modified header in response', () async {
+      final handler = createAssetHandler();
+      final request = makeRequest(
+        path: '/index.html',
+      );
+      final response = await handler(request);
+
+      expect(response.statusCode, equals(200));
+      expect(response.headers[HttpHeaders.lastModifiedHeader], isNotNull);
+      expect(response.headers[HttpHeaders.lastModifiedHeader], isNotEmpty);
+    });
+
+    test('returns 304 Not Modified for valid If-Modified-Since header',
+        () async {
+      // Create a single handler instance for all requests in this test
+      // to ensure we get the same Last-Modified timestamp
+      final handler = createAssetHandler();
+
+      // First get the Last-Modified value
+      final initialRequest = makeRequest(path: '/index.html');
+      final initialResponse = await handler(initialRequest);
+      final lastModified =
+          initialResponse.headers[HttpHeaders.lastModifiedHeader]!;
+
+      // Then make a conditional request with that same timestamp
+      final conditionalRequest = makeRequest(
+        path: '/index.html',
+        headers: {HttpHeaders.ifModifiedSinceHeader: lastModified},
+      );
+
+      final conditionalResponse = await handler(conditionalRequest);
+
+      expect(conditionalResponse.statusCode, equals(304));
+      expect(await conditionalResponse.read().toList(), isEmpty);
+    });
+
+    test('returns 200 OK for If-Modified-Since header with old date', () async {
+      final handler = createAssetHandler();
+
+      // Use a date from the past
+      final oldDate = HttpDate.format(DateTime(2000, 1, 1));
+
+      final request = makeRequest(
+        path: '/index.html',
+        headers: {HttpHeaders.ifModifiedSinceHeader: oldDate},
+      );
+      final response = await handler(request);
+
+      expect(response.statusCode, equals(200));
+      expect(await response.read().toList(), isNotEmpty);
+    });
+
+    test('ignores invalid If-Modified-Since header', () async {
+      final handler = createAssetHandler();
+
+      final request = makeRequest(
+        path: '/index.html',
+        headers: {HttpHeaders.ifModifiedSinceHeader: 'invalid-date-format'},
+      );
+      final response = await handler(request);
+
+      expect(response.statusCode, equals(200));
+      expect(await response.read().toList(), isNotEmpty);
+    });
+  });
+}

test/range_request_test.dart

@@ -9,27 +9,14 @@ void main() {
   });
 
   group('Range Requests', () {
-    test('range request support disabled by default', () async {
+    test('range request returns valid range', () async {
       final handler = createAssetHandler();
       final request = makeRequest(
         path: '/index.html',
         headers: {'range': 'bytes=0-10'},
       );
       final response = await handler(request);
 
-      expect(response.statusCode, equals(200));
-      expect(response.headers['accept-ranges'], isNull);
-      expect(response.headers['content-range'], isNull);
-    });
-
-    test('valid range request returns partial content', () async {
-      final handler = createAssetHandler(enableRangeRequests: true);
-      final request = makeRequest(
-        path: '/index.html',
-        headers: {'range': 'bytes=0-10'},
-      );
-      final response = await handler(request);
-
       expect(response.statusCode, equals(206));
       expect(response.headers['accept-ranges'], equals('bytes'));
       expect(response.headers['content-range'], isNotNull);
@@ -41,7 +28,7 @@ void main() {
     });
 
     test('invalid range format returns 416', () async {
-      final handler = createAssetHandler(enableRangeRequests: true);
+      final handler = createAssetHandler();
       final request = makeRequest(
         path: '/index.html',
         headers: {'range': 'invalid-range-format'},
@@ -52,7 +39,7 @@ void main() {
     });
 
     test('range outside file bounds returns 416', () async {
-      final handler = createAssetHandler(enableRangeRequests: true);
+      final handler = createAssetHandler();
       final request = makeRequest(
         path: '/index.html',
         headers: {'range': 'bytes=100000-200000'},
@@ -64,7 +51,7 @@ void main() {
     });
 
     test('open-ended range request works', () async {
-      final handler = createAssetHandler(enableRangeRequests: true);
+      final handler = createAssetHandler();
       final request = makeRequest(
         path: '/index.html',
         headers: {'range': 'bytes=10-'},
@@ -77,7 +64,7 @@ void main() {
     });
 
     test('head request with range returns no body', () async {
-      final handler = createAssetHandler(enableRangeRequests: true);
+      final handler = createAssetHandler();
       final request = makeRequest(
         method: 'HEAD',
         path: '/index.html',