refactor(yaad): split oversized files for code clarity

Code-clarity cleanup: split oversized Go files into smaller same-package files without behavior changes.

Author: Patel230

engine/engine_mock_graph_test.go

@@ -0,0 +1,141 @@
+//nolint:gocritic
+package engine
+
+import (
+	"context"
+
+	"github.com/GrayCodeAI/yaad/graph"
+	"github.com/GrayCodeAI/yaad/intent"
+	"github.com/GrayCodeAI/yaad/storage"
+)
+
+// This file is part of package engine tests. It holds mockGraph (the
+// in-memory graph.Graph test double) and newTestEngine, moved verbatim out
+// of engine_test.go for readability; behavior is unchanged.
+
+// ---------------------------------------------------------------------------
+// mockGraph — in-memory implementation of graph.Graph backed by storage
+// ---------------------------------------------------------------------------
+
+type mockGraph struct {
+	store storage.Storage
+}
+
+func newMockGraph(store storage.Storage) *mockGraph {
+	return &mockGraph{store: store}
+}
+
+func (g *mockGraph) AddNode(ctx context.Context, n *storage.Node) error {
+	return g.store.CreateNode(ctx, n)
+}
+
+func (g *mockGraph) AddEdge(ctx context.Context, e *storage.Edge) error {
+	return g.store.CreateEdge(ctx, e)
+}
+
+func (g *mockGraph) RemoveNode(ctx context.Context, id string) error {
+	return g.store.DeleteNode(ctx, id)
+}
+
+func (g *mockGraph) RemoveEdge(ctx context.Context, id string) error {
+	return g.store.DeleteEdge(ctx, id)
+}
+
+func (g *mockGraph) ExtractSubgraph(ctx context.Context, startID string, maxDepth int) (*graph.Subgraph, error) {
+	ids, err := g.BFS(ctx, startID, maxDepth)
+	if err != nil {
+		return nil, err
+	}
+	sg := &graph.Subgraph{}
+	for _, id := range ids {
+		n, err := g.store.GetNode(ctx, id)
+		if err == nil {
+			sg.Nodes = append(sg.Nodes, n)
+		}
+	}
+	idSet := make(map[string]bool, len(ids))
+	for _, id := range ids {
+		idSet[id] = true
+	}
+	for _, id := range ids {
+		edges, _ := g.store.GetEdgesFrom(ctx, id)
+		for _, e := range edges {
+			if idSet[e.ToID] {
+				sg.Edges = append(sg.Edges, e)
+			}
+		}
+	}
+	return sg, nil
+}
+
+func (g *mockGraph) BFS(ctx context.Context, startID string, maxDepth int) ([]string, error) {
+	_, err := g.store.GetNode(ctx, startID)
+	if err != nil {
+		return nil, nil
+	}
+	visited := map[string]bool{startID: true}
+	queue := []struct {
+		id    string
+		depth int
+	}{{startID, 0}}
+	var result []string
+	result = append(result, startID)
+
+	for len(queue) > 0 {
+		curr := queue[0]
+		queue = queue[1:]
+		if curr.depth >= maxDepth {
+			continue
+		}
+		edges, _ := g.store.GetEdgesFrom(ctx, curr.id)
+		edgesTo, _ := g.store.GetEdgesTo(ctx, curr.id)
+		allEdges := append(edges, edgesTo...)
+		for _, e := range allEdges {
+			var next string
+			if e.FromID == curr.id {
+				next = e.ToID
+			} else {
+				next = e.FromID
+			}
+			if !visited[next] {
+				visited[next] = true
+				result = append(result, next)
+				queue = append(queue, struct {
+					id    string
+					depth int
+				}{next, curr.depth + 1})
+			}
+		}
+	}
+	return result, nil
+}
+
+func (g *mockGraph) IntentBFS(ctx context.Context, startID string, maxDepth int, queryIntent intent.Intent) ([]string, error) {
+	// For mock, delegate to plain BFS (intent weights are ignored)
+	return g.BFS(ctx, startID, maxDepth)
+}
+
+func (g *mockGraph) Impact(ctx context.Context, filePath string, maxDepth int) ([]string, error) {
+	return nil, nil
+}
+
+func (g *mockGraph) Ancestors(ctx context.Context, id string) ([]string, error) {
+	return nil, nil
+}
+
+func (g *mockGraph) Descendants(ctx context.Context, id string) ([]string, error) {
+	return nil, nil
+}
+
+// ---------------------------------------------------------------------------
+// helper
+// ---------------------------------------------------------------------------
+
+func newTestEngine() *Engine {
+	ms := newMockStorage()
+	return New(ms, newMockGraph(ms))
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------