bug: introduce WithSnapshot to maintain incrementally and effitiently a snapshot

1 files changed, 58 insertions, 0 deletions

diff --git a/bug/with_snapshot.go b/bug/with_snapshot.go
new file mode 100644
index 00000000..0aa3b37d
--- /dev/null
+++ b/bug/with_snapshot.go
@@ -0,0 +1,58 @@
+package bug
+
+import "github.com/MichaelMure/git-bug/repository"
+
+var _ Interface = &WithSnapshot{}
+
+// WithSnapshot encapsulate a Bug and maintain the corresponding Snapshot efficiently
+type WithSnapshot struct {
+	*Bug
+	snap *Snapshot
+}
+
+// Snapshot return the current snapshot
+func (b *WithSnapshot) Snapshot() *Snapshot {
+	if b.snap == nil {
+		snap := b.Bug.Compile()
+		b.snap = &snap
+	}
+	return b.snap
+}
+
+// Append intercept Bug.Append() to update the snapshot efficiently
+func (b *WithSnapshot) Append(op Operation) {
+	b.Bug.Append(op)
+
+	if b.snap == nil {
+		return
+	}
+
+	snap := op.Apply(*b.snap)
+	b.snap = &snap
+}
+
+// Commit intercept Bug.Commit() to update the snapshot efficiently
+func (b *WithSnapshot) Commit(repo repository.Repo) error {
+	err := b.Bug.Commit(repo)
+
+	if err != nil {
+		b.snap = nil
+		return err
+	}
+
+	// Commit() shouldn't change anything of the bug state apart from the
+	// initial ID set
+
+	if b.snap == nil {
+		return nil
+	}
+
+	b.snap.id = b.Bug.id
+	return nil
+}
+
+// Merge intercept Bug.Merge() and clear the snapshot
+func (b *WithSnapshot) Merge(repo repository.Repo, other Interface) (bool, error) {
+	b.snap = nil
+	return b.Bug.Merge(repo, other)
+}