feat: add diff view

lib/screens/gl_commit.dart

@@ -1,9 +1,9 @@
 import 'package:flutter/material.dart';
 import 'package:git_touch/models/auth.dart';
 import 'package:git_touch/models/gitlab.dart';
-import 'package:git_touch/models/code.dart';
 import 'package:git_touch/scaffolds/refresh_stateful.dart';
 import 'package:git_touch/widgets/app_bar_title.dart';
+import 'package:git_touch/widgets/diff_view.dart';
 import 'package:provider/provider.dart';
 
 class GlCommitScreen extends StatelessWidget {
@@ -20,22 +20,14 @@ class GlCommitScreen extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final code = Provider.of<CodeModel>(context);
-
     return RefreshStatefulScaffold<List<GitlabDiff>>(
       title: AppBarTitle('Commits'),
       fetchData: () => _query(context),
       bodyBuilder: (items, _) {
         return Column(
+          crossAxisAlignment: CrossAxisAlignment.start,
           children: <Widget>[
-            for (var item in items)
-              Text(
-                item.diff,
-                style: TextStyle(
-                  fontFamily: code.fontFamilyUsed,
-                  fontSize: 14,
-                ),
-              )
+            for (var item in items) DiffView(item.diff),
           ],
         );
       },

lib/widgets/diff_view.dart

@@ -0,0 +1,84 @@
+import 'package:flutter/material.dart';
+import 'package:git_touch/models/code.dart';
+import 'package:git_touch/models/theme.dart';
+import 'package:provider/provider.dart';
+
+class DiffLine {
+  String type;
+  int lineNumber;
+  String content;
+  DiffLine({
+    @required this.type,
+    @required this.lineNumber,
+    @required this.content,
+  });
+}
+
+class DiffChunk {
+  String heading;
+  List<DiffLine> lines;
+  DiffChunk({@required this.heading, @required this.lines});
+}
+
+class DiffView extends StatelessWidget {
+  final String source;
+  DiffView(this.source);
+
+  @override
+  Widget build(BuildContext context) {
+    final code = Provider.of<CodeModel>(context);
+    final theme = Provider.of<ThemeModel>(context);
+
+    final lines = source.split('\n');
+    final chunks = <DiffChunk>[];
+    var offset = 0;
+    for (final line in lines) {
+      if (line.startsWith('@@')) {
+        chunks.add(DiffChunk(heading: line, lines: []));
+        offset = int.parse(line.substring(4).split(',')[0]);
+      } else {
+        chunks.last.lines.add(DiffLine(
+          type: line.isEmpty ? null : line[0],
+          lineNumber: offset,
+          content: line,
+        ));
+        offset++;
+      }
+    }
+
+    return DefaultTextStyle(
+      child: Column(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: [
+          for (var c in chunks)
+            Column(
+              crossAxisAlignment: CrossAxisAlignment.start,
+              children: [
+                Text(
+                  c.heading,
+                  style: TextStyle(
+                    color: theme.palette.tertiaryText,
+                    backgroundColor: Color(0xfffafafa),
+                  ),
+                ),
+                for (var l in c.lines)
+                  Text(
+                    l.content,
+                    style: TextStyle(
+                      backgroundColor: l.type == '-'
+                          ? Color(0x00fbe9eb)
+                          : l.type == '+' ? Color(0xffecfdf0) : null,
+                    ),
+                  ),
+              ],
+            ),
+        ],
+      ),
+      style: TextStyle(
+        fontFamily: code.fontFamilyUsed,
+        fontSize: 14,
+        color: theme.palette.text,
+      ),
+    );
+  }
+}