1 files changed, 99 insertions, 0 deletions
diff --git a/git/diff.go b/git/diff.go
new file mode 100644
index 0000000..f7e5b0e
--- /dev/null
+++ b/git/diff.go
@@ -0,0 +1,99 @@
+package git
+
+import (
+	"fmt"
+	"log"
+	"strings"
+
+	"github.com/bluekeyes/go-gitdiff/gitdiff"
+	"github.com/go-git/go-git/v5/plumbing/object"
+)
+
+type TextFragment struct {
+	Header string
+	Lines  []gitdiff.Line
+}
+
+type Diff struct {
+	Name struct {
+		Old string
+		New string
+	}
+	TextFragments []TextFragment
+}
+
+// A nicer git diff representation.
+type NiceDiff struct {
+	Commit struct {
+		Message string
+		Author  object.Signature
+		This    string
+		Parent  string
+	}
+	Stat struct {
+		FilesChanged int
+		Insertions   int
+		Deletions    int
+	}
+	Diff []Diff
+}
+
+func (g *GitRepo) Diff() (*NiceDiff, error) {
+	c, err := g.r.CommitObject(g.h)
+	if err != nil {
+		return nil, fmt.Errorf("commit object: %w", err)
+	}
+
+	var parent *object.Commit
+	if len(c.ParentHashes) > 0 {
+		parent, err = c.Parent(0)
+		if err != nil {
+			return nil, fmt.Errorf("getting parent: %w", err)
+		}
+	} else {
+		parent = c
+	}
+
+	patch, err := parent.Patch(c)
+	if err != nil {
+		return nil, fmt.Errorf("patch: %w", err)
+	}
+
+	diffs, _, err := gitdiff.Parse(strings.NewReader(patch.String()))
+	if err != nil {
+		log.Println(err)
+	}
+
+	nd := NiceDiff{}
+	nd.Commit.This = c.Hash.String()
+	nd.Commit.Parent = parent.Hash.String()
+	nd.Commit.Author = c.Author
+	nd.Commit.Message = c.Message
+	ndiff := Diff{}
+
+	for _, d := range diffs {
+		ndiff.Name.New = d.NewName
+		ndiff.Name.Old = d.OldName
+
+		for _, tf := range d.TextFragments {
+			ndiff.TextFragments = append(ndiff.TextFragments, TextFragment{
+				Header: tf.Header(),
+				Lines:  tf.Lines,
+			})
+			for _, l := range tf.Lines {
+				switch l.Op {
+				case gitdiff.OpAdd:
+					nd.Stat.Insertions += 1
+				case gitdiff.OpDelete:
+					nd.Stat.Deletions += 1
+				}
+			}
+		}
+
+		nd.Diff = append(nd.Diff, ndiff)
+	}
+
+	nd.Stat.FilesChanged = len(diffs)
+
+	return &nd, nil
+}