1 files changed, 164 insertions, 0 deletions
diff --git a/plumbing/object/commitgraph/commitnode_walker_helper.go b/plumbing/object/commitgraph/commitnode_walker_helper.go
new file mode 100644
index 0000000..c54f6ca
--- /dev/null
+++ b/plumbing/object/commitgraph/commitnode_walker_helper.go
@@ -0,0 +1,164 @@
+package commitgraph
+
+import (
+	"math"
+
+	"github.com/go-git/go-git/v5/plumbing"
+
+	"github.com/emirpasic/gods/trees/binaryheap"
+)
+
+// commitNodeStackable represents a common interface between heaps and stacks
+type commitNodeStackable interface {
+	Push(c CommitNode)
+	Pop() (CommitNode, bool)
+	Peek() (CommitNode, bool)
+	Size() int
+}
+
+// commitNodeLifo is a stack implementation using an underlying slice
+type commitNodeLifo struct {
+	l []CommitNode
+}
+
+// Push pushes a new CommitNode to the stack
+func (l *commitNodeLifo) Push(c CommitNode) {
+	l.l = append(l.l, c)
+}
+
+// Pop pops the most recently added CommitNode from the stack
+func (l *commitNodeLifo) Pop() (CommitNode, bool) {
+	if len(l.l) == 0 {
+		return nil, false
+	}
+	c := l.l[len(l.l)-1]
+	l.l = l.l[:len(l.l)-1]
+	return c, true
+}
+
+// Peek returns the most recently added CommitNode from the stack without removing it
+func (l *commitNodeLifo) Peek() (CommitNode, bool) {
+	if len(l.l) == 0 {
+		return nil, false
+	}
+	return l.l[len(l.l)-1], true
+}
+
+// Size returns the number of CommitNodes in the stack
+func (l *commitNodeLifo) Size() int {
+	return len(l.l)
+}
+
+// commitNodeHeap is a stack implementation using an underlying binary heap
+type commitNodeHeap struct {
+	*binaryheap.Heap
+}
+
+// Push pushes a new CommitNode to the heap
+func (h *commitNodeHeap) Push(c CommitNode) {
+	h.Heap.Push(c)
+}
+
+// Pop removes top element on heap and returns it, or nil if heap is empty.
+// Second return parameter is true, unless the heap was empty and there was nothing to pop.
+func (h *commitNodeHeap) Pop() (CommitNode, bool) {
+	c, ok := h.Heap.Pop()
+	if !ok {
+		return nil, false
+	}
+	return c.(CommitNode), true
+}
+
+// Peek returns top element on the heap without removing it, or nil if heap is empty.
+// Second return parameter is true, unless the heap was empty and there was nothing to peek.
+func (h *commitNodeHeap) Peek() (CommitNode, bool) {
+	c, ok := h.Heap.Peek()
+	if !ok {
+		return nil, false
+	}
+	return c.(CommitNode), true
+}
+
+// Size returns number of elements within the heap.
+func (h *commitNodeHeap) Size() int {
+	return h.Heap.Size()
+}
+
+// generationAndDateOrderComparator compares two CommitNode objects based on their generation and commit time.
+// If the left CommitNode object is in a higher generation or is newer than the right one, it returns a -1.
+// If the left CommitNode object is in a lower generation or is older than the right one, it returns a 1.
+// If the two CommitNode objects have the same commit time and generation, it returns 0.
+func generationAndDateOrderComparator(left, right interface{}) int {
+	leftCommit := left.(CommitNode)
+	rightCommit := right.(CommitNode)
+
+	// if GenerationV2 is MaxUint64, then the node is not in the graph
+	if leftCommit.GenerationV2() == math.MaxUint64 {
+		if rightCommit.GenerationV2() == math.MaxUint64 {
+			switch {
+			case rightCommit.CommitTime().Before(leftCommit.CommitTime()):
+				return -1
+			case leftCommit.CommitTime().Before(rightCommit.CommitTime()):
+				return 1
+			}
+			return 0
+		}
+		// left is not in the graph, but right is, so it is newer than the right
+		return -1
+	}
+
+	if rightCommit.GenerationV2() == math.MaxInt64 {
+		// the right is not in the graph, therefore the left is before the right
+		return 1
+	}
+
+	if leftCommit.GenerationV2() == 0 || rightCommit.GenerationV2() == 0 {
+		// We need to assess generation and date
+		if leftCommit.Generation() < rightCommit.Generation() {
+			return 1
+		}
+		if leftCommit.Generation() > rightCommit.Generation() {
+			return -1
+		}
+		switch {
+		case rightCommit.CommitTime().Before(leftCommit.CommitTime()):
+			return -1
+		case leftCommit.CommitTime().Before(rightCommit.CommitTime()):
+			return 1
+		}
+		return 0
+	}
+
+	if leftCommit.GenerationV2() < rightCommit.GenerationV2() {
+		return 1
+	}
+	if leftCommit.GenerationV2() > rightCommit.GenerationV2() {
+		return -1
+	}
+
+	return 0
+}
+
+// composeIgnores composes the ignore list with the provided seenExternal list
+func composeIgnores(ignore []plumbing.Hash, seenExternal map[plumbing.Hash]bool) map[plumbing.Hash]struct{} {
+	if len(ignore) == 0 {
+		seen := make(map[plumbing.Hash]struct{})
+		for h, ext := range seenExternal {
+			if ext {
+				seen[h] = struct{}{}
+			}
+		}
+		return seen
+	}
+
+	seen := make(map[plumbing.Hash]struct{})
+	for _, h := range ignore {
+		seen[h] = struct{}{}
+	}
+	for h, ext := range seenExternal {
+		if ext {
+			seen[h] = struct{}{}
+		}
+	}
+	return seen
+}