refactor(patch): initialize DiffHunk with all the information accessible immediately

lib/src/patch.dart

@@ -1,5 +1,6 @@
 import 'dart:ffi';
 
+import 'package:ffi/ffi.dart';
 import 'package:libgit2dart/libgit2dart.dart';
 import 'package:libgit2dart/src/bindings/libgit2_bindings.dart';
 import 'package:libgit2dart/src/bindings/patch.dart' as bindings;
@@ -197,14 +198,49 @@ class Patch {
     final length = bindings.numHunks(_patchPointer);
     final hunks = <DiffHunk>[];
 
-    for (var i = 0; i < length; i++) {
-      final hunk = bindings.hunk(patchPointer: _patchPointer, hunkIndex: i);
+    for (var index = 0; index < length; index++) {
+      final hunk = bindings.hunk(patchPointer: _patchPointer, hunkIndex: index);
+      final hunkPointer = hunk['hunk']! as Pointer<git_diff_hunk>;
+      final linesCount = hunk['linesN']! as int;
+
+      final lines = <DiffLine>[];
+      for (var i = 0; i < linesCount; i++) {
+        final linePointer = bindings.lines(
+          patchPointer: _patchPointer,
+          hunkIndex: index,
+          lineOfHunk: i,
+        );
+        lines.add(
+          DiffLine._(
+            origin: GitDiffLine.values.singleWhere(
+              (e) => linePointer.ref.origin == e.value,
+            ),
+            oldLineNumber: linePointer.ref.old_lineno,
+            newLineNumber: linePointer.ref.new_lineno,
+            numLines: linePointer.ref.num_lines,
+            contentOffset: linePointer.ref.content_offset,
+            content: linePointer.ref.content
+                .cast<Utf8>()
+                .toDartString(length: linePointer.ref.content_len),
+          ),
+        );
+      }
+
+      final intHeader = <int>[];
+      for (var i = 0; i < hunkPointer.ref.header_len; i++) {
+        intHeader.add(hunkPointer.ref.header[i]);
+      }
+
       hunks.add(
-        DiffHunk(
-          _patchPointer,
-          hunk['hunk']! as Pointer<git_diff_hunk>,
-          hunk['linesN']! as int,
-          i,
+        DiffHunk._(
+          linesCount: linesCount,
+          index: index,
+          oldStart: hunkPointer.ref.old_start,
+          oldLines: hunkPointer.ref.old_lines,
+          newStart: hunkPointer.ref.new_start,
+          newLines: hunkPointer.ref.new_lines,
+          header: String.fromCharCodes(intHeader),
+          lines: lines,
         ),
       );
     }
@@ -251,3 +287,83 @@ class PatchStats {
         'deletions: $deletions}';
   }
 }
+
+class DiffHunk {
+  const DiffHunk._({
+    required this.linesCount,
+    required this.index,
+    required this.oldStart,
+    required this.oldLines,
+    required this.newStart,
+    required this.newLines,
+    required this.header,
+    required this.lines,
+  });
+
+  /// Number of total lines in this hunk.
+  final int linesCount;
+
+  /// Index of this hunk in the patch.
+  final int index;
+
+  /// Starting line number in 'old file'.
+  final int oldStart;
+
+  /// Number of lines in 'old file'.
+  final int oldLines;
+
+  /// Starting line number in 'new file'.
+  final int newStart;
+
+  /// Number of lines in 'new file'.
+  final int newLines;
+
+  /// Header of a hunk.
+  final String header;
+
+  /// List of lines in a hunk of a patch.
+  final List<DiffLine> lines;
+
+  @override
+  String toString() {
+    return 'DiffHunk{linesCount: $linesCount, index: $index, '
+        'oldStart: $oldStart, oldLines: $oldLines, newStart: $newStart, '
+        'newLines: $newLines, header: $header}';
+  }
+}
+
+class DiffLine {
+  const DiffLine._({
+    required this.origin,
+    required this.oldLineNumber,
+    required this.newLineNumber,
+    required this.numLines,
+    required this.contentOffset,
+    required this.content,
+  });
+
+  /// Type of the line.
+  final GitDiffLine origin;
+
+  /// Line number in old file or -1 for added line.
+  final int oldLineNumber;
+
+  /// Line number in new file or -1 for deleted line.
+  final int newLineNumber;
+
+  /// Number of newline characters in content.
+  final int numLines;
+
+  /// Offset in the original file to the content.
+  final int contentOffset;
+
+  /// Content of the diff line.
+  final String content;
+
+  @override
+  String toString() {
+    return 'DiffLine{oldLineNumber: $oldLineNumber, '
+        'newLineNumber: $newLineNumber, numLines: $numLines, '
+        'contentOffset: $contentOffset, content: $content}';
+  }
+}