feat(nextcloud): add custom http date parser to support rfc822 time z…

…one offsets

Signed-off-by: Nikolas Rimikis <leptopoda@users.noreply.github.com>

.cspell/misc.txt

@@ -1,3 +1,4 @@
+asctime
 browsable
 cleartext
 codegen

packages/neon_framework/lib/src/utils/request_manager.dart

@@ -5,14 +5,14 @@ import 'package:built_value/serializer.dart';
 import 'package:dynamite_runtime/http_client.dart';
 import 'package:flutter/foundation.dart';
 import 'package:http/http.dart' as http;
-import 'package:http_parser/http_parser.dart';
 import 'package:logging/logging.dart';
 import 'package:meta/meta.dart';
 import 'package:neon_framework/models.dart';
 import 'package:neon_framework/src/bloc/result.dart';
 import 'package:neon_framework/src/models/account.dart';
 import 'package:neon_framework/storage.dart';
 import 'package:nextcloud/nextcloud.dart';
+import 'package:nextcloud/utils.dart';
 import 'package:rxdart/rxdart.dart';
 import 'package:timezone/timezone.dart' as tz;
 import 'package:xml/xml.dart' as xml;
@@ -368,8 +368,7 @@ class CacheParameters {
   factory CacheParameters.parseHeaders(Map<String, dynamic> headers) {
     tz.TZDateTime? expiry;
     if (headers.containsKey('expires')) {
-      final parsed = parseHttpDate(headers['expires']! as String);
-      expiry = tz.TZDateTime.from(parsed, tz.UTC);
+      expiry = parseHttpDate(headers['expires']! as String);
     }
 
     return CacheParameters(

packages/neon_framework/pubspec.yaml

@@ -31,7 +31,6 @@ dependencies:
   flutter_zxing: ^1.0.0
   go_router: ^13.0.0
   http: ^1.0.0
-  http_parser: ^4.0.0
   image: ^4.0.0
   intersperse: ^2.0.0
   intl: ^0.18.0

packages/neon_framework/test/request_manager_test.dart

@@ -8,11 +8,11 @@ import 'package:built_value/serializer.dart';
 import 'package:dynamite_runtime/http_client.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:http/http.dart';
-import 'package:http_parser/http_parser.dart';
 import 'package:mocktail/mocktail.dart';
 import 'package:neon_framework/src/bloc/result.dart';
 import 'package:neon_framework/src/utils/request_manager.dart';
 import 'package:neon_framework/testing.dart';
+import 'package:nextcloud/utils.dart';
 import 'package:rxdart/rxdart.dart';
 import 'package:timezone/timezone.dart' as tz;
 

packages/nextcloud/lib/src/utils/http_date_parser.dart

@@ -0,0 +1,174 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// ignore_for_file: unnecessary_raw_strings, cascade_invocations, parameter_assignments, always_put_control_body_on_new_line
+
+import 'package:string_scanner/string_scanner.dart';
+import 'package:timezone/timezone.dart' as tz;
+
+const _weekdays = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'];
+const _months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];
+
+final _shortWeekdayRegExp = RegExp(r'Mon|Tue|Wed|Thu|Fri|Sat|Sun');
+final _longWeekdayRegExp = RegExp(r'Monday|Tuesday|Wednesday|Thursday|Friday|Saturday|Sunday');
+final _monthRegExp = RegExp(r'Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec');
+final _digitRegExp = RegExp(r'\d+');
+final _zoneRegExp = RegExp(r'[+|-]');
+
+/// Return a HTTP-formatted string representation of [date].
+///
+/// This follows [RFC 822](http://tools.ietf.org/html/rfc822) as updated by
+/// [RFC 1123](http://tools.ietf.org/html/rfc1123).
+String formatHttpDate(DateTime date) {
+  date = date.toUtc();
+  final buffer = StringBuffer()
+    ..write(_weekdays[date.weekday - 1])
+    ..write(', ')
+    ..write(date.day <= 9 ? '0' : '')
+    ..write(date.day.toString())
+    ..write(' ')
+    ..write(_months[date.month - 1])
+    ..write(' ')
+    ..write(date.year.toString())
+    ..write(date.hour <= 9 ? ' 0' : ' ')
+    ..write(date.hour.toString())
+    ..write(date.minute <= 9 ? ':0' : ':')
+    ..write(date.minute.toString())
+    ..write(date.second <= 9 ? ':0' : ':')
+    ..write(date.second.toString())
+    ..write(' GMT');
+  return buffer.toString();
+}
+
+/// Parses an HTTP-formatted date into a UTC [DateTime].
+///
+/// This follows [RFC 2616](http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.3).
+/// It will throw a [FormatException] if [date] is invalid.
+tz.TZDateTime parseHttpDate(String date) {
+  final scanner = StringScanner(date);
+
+  if (scanner.scan(_longWeekdayRegExp)) {
+    // RFC 850 starts with a long weekday.
+    scanner.expect(', ');
+    final day = _parseInt(scanner, 2);
+    scanner.expect('-');
+    final month = _parseMonth(scanner);
+    scanner.expect('-');
+    final year = 1900 + _parseInt(scanner, 2);
+    scanner.expect(' ');
+    final time = _parseTime(scanner);
+    scanner.expect(' GMT');
+    scanner.expectDone();
+
+    return _makeDateTime(year, month, day, time);
+  }
+
+  // RFC 1123 and asctime both start with a short weekday.
+  scanner.expect(_shortWeekdayRegExp);
+  if (scanner.scan(', ')) {
+    // RFC 1123 follows the weekday with a comma.
+    final day = _parseInt(scanner, 2);
+    scanner.expect(' ');
+    final month = _parseMonth(scanner);
+    scanner.expect(' ');
+    final year = _parseInt(scanner, 4);
+    scanner.expect(' ');
+    final time = _parseTime(scanner);
+    scanner.expect(' ');
+    final offset = _parseLocation(scanner);
+    scanner.expectDone();
+
+    return _makeDateTime(year, month, day, time, offset);
+  }
+
+  // asctime follows the weekday with a space.
+  scanner.expect(' ');
+  final month = _parseMonth(scanner);
+  scanner.expect(' ');
+  final day = scanner.scan(' ') ? _parseInt(scanner, 1) : _parseInt(scanner, 2);
+  scanner.expect(' ');
+  final time = _parseTime(scanner);
+  scanner.expect(' ');
+  final year = _parseInt(scanner, 4);
+  scanner.expectDone();
+
+  return _makeDateTime(year, month, day, time);
+}
+
+/// Parses a short-form month name to a form accepted by [DateTime].
+int _parseMonth(StringScanner scanner) {
+  scanner.expect(_monthRegExp);
+  // DateTime uses 1-indexed months.
+  return _months.indexOf(scanner.lastMatch![0]!) + 1;
+}
+
+/// Parses an int an enforces that it has exactly [digits] digits.
+int _parseInt(StringScanner scanner, int digits) {
+  scanner.expect(_digitRegExp);
+  if (scanner.lastMatch![0]!.length != digits) {
+    scanner.error('expected a $digits-digit number.');
+  }
+
+  return int.parse(scanner.lastMatch![0]!);
+}
+
+/// Parses an timestamp of the form "HH:MM:SS" on a 24-hour clock.
+tz.TZDateTime _parseTime(StringScanner scanner) {
+  final hours = _parseInt(scanner, 2);
+  if (hours >= 24) scanner.error('hours may not be greater than 24.');
+  scanner.expect(':');
+
+  final minutes = _parseInt(scanner, 2);
+  if (minutes >= 60) scanner.error('minutes may not be greater than 60.');
+  scanner.expect(':');
+
+  final seconds = _parseInt(scanner, 2);
+  if (seconds >= 60) scanner.error('seconds may not be greater than 60.');
+
+  return tz.TZDateTime.utc(1, 1, 1, hours, minutes, seconds);
+}
+
+Duration? _parseLocation(StringScanner scanner) {
+  if (scanner.scan('GMT')) {
+    return null;
+  } else if (scanner.scan(_zoneRegExp)) {
+    final modifier = scanner.lastMatch![0]!;
+
+    scanner.expect(RegExp(r'\d{2}'));
+    final hours = int.parse(scanner.lastMatch![0]!);
+
+    scanner.expect(RegExp(r'\d{2}'));
+    final minutes = int.parse(scanner.lastMatch![0]!);
+
+    if (hours >= 99 && minutes > 59) {
+      throw FormatException("invalid timezone offset '$hours$minutes'.");
+    }
+
+    var offset = Duration(hours: hours, minutes: minutes);
+    if (modifier == '-') {
+      offset *= -1;
+    }
+
+    return offset;
+  } else {
+    throw const FormatException('Parsing timezone can not be done unambiguously.');
+  }
+}
+
+/// Returns a UTC [tz.TZDateTime] from the given components.
+///
+/// Validates that [day] is a valid day for [month]. If it's not, throws a
+/// [FormatException].
+tz.TZDateTime _makeDateTime(int year, int month, int day, tz.TZDateTime time, [Duration? offset]) {
+  var dateTime = tz.TZDateTime(tz.UTC, year, month, day, time.hour, time.minute, time.second);
+  if (offset != null) {
+    dateTime = dateTime.add(offset);
+  }
+
+  // If [day] was too large, it will cause [month] to overflow.
+  if (dateTime.month != month) {
+    throw FormatException("invalid day '$day' for month '$month'.");
+  }
+  return dateTime;
+}

packages/nextcloud/lib/src/webdav/file.dart

@@ -1,5 +1,5 @@
-import 'package:http_parser/http_parser.dart';
 import 'package:nextcloud/src/utils/date_time.dart';
+import 'package:nextcloud/src/utils/http_date_parser.dart';
 import 'package:nextcloud/src/webdav/client.dart';
 import 'package:nextcloud/src/webdav/path_uri.dart';
 import 'package:nextcloud/src/webdav/props.dart';
@@ -65,8 +65,7 @@ class WebDavFile {
   /// Last modified date of the file
   late final tz.TZDateTime? lastModified = () {
     if (props.davgetlastmodified != null) {
-      final parsed = parseHttpDate(props.davgetlastmodified!);
-      return tz.TZDateTime.from(parsed, tz.UTC);
+      return parseHttpDate(props.davgetlastmodified!);
     }
     return null;
   }();

packages/nextcloud/lib/utils.dart

@@ -2,3 +2,4 @@
 library;
 
 export 'src/utils/date_time.dart';
+export 'src/utils/http_date_parser.dart';

packages/nextcloud/pubspec.yaml

@@ -19,9 +19,9 @@ dependencies:
   crypton: ^2.0.0
   dynamite_runtime: ^0.2.0
   http: ^1.2.0
-  http_parser: ^4.0.0
   json_annotation: ^4.8.1
   meta: ^1.0.0
+  string_scanner: ^1.1.0
   timezone: ^0.9.2
   universal_io: ^2.0.0
   uri: ^1.0.0