feat(pipeline): add POST /backfill-refs endpoint to retroactively inject source back-references

ingestion/internal/pipeline/backfill_test.go

@@ -0,0 +1,107 @@
+// ingestion/internal/pipeline/backfill_test.go
+package pipeline
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func setupBrainDir(t *testing.T) string {
+	t.Helper()
+	dir := t.TempDir()
+	for _, sub := range []string{"wiki/sources", "wiki/concepts", "wiki/entities"} {
+		require.NoError(t, os.MkdirAll(filepath.Join(dir, sub), 0o755))
+	}
+	return dir
+}
+
+func writeFile(t *testing.T, path, content string) {
+	t.Helper()
+	require.NoError(t, os.MkdirAll(filepath.Dir(path), 0o755))
+	require.NoError(t, os.WriteFile(path, []byte(content), 0o644))
+}
+
+func TestBackfillRefs_UpdatesConcept(t *testing.T) {
+	dir := setupBrainDir(t)
+	writeFile(t, filepath.Join(dir, "wiki/sources/shape-up.md"),
+		"---\ntitle: Shape Up\n---\n\n## Summary\n\nSee [[betting|Betting]].\n")
+	writeFile(t, filepath.Join(dir, "wiki/concepts/betting.md"),
+		"---\ntitle: Betting\n---\n\n## Definition\n\nA resource allocation technique.\n")
+
+	n, err := BackfillRefs(context.Background(), dir)
+	require.NoError(t, err)
+	assert.Equal(t, 1, n)
+
+	got, err := os.ReadFile(filepath.Join(dir, "wiki/concepts/betting.md"))
+	require.NoError(t, err)
+	assert.Contains(t, string(got), "## Sources")
+	assert.Contains(t, string(got), "[[shape-up|Shape Up]]")
+	assert.Contains(t, string(got), "## Definition") // original content preserved
+}
+
+func TestBackfillRefs_Deduplication(t *testing.T) {
+	dir := setupBrainDir(t)
+	writeFile(t, filepath.Join(dir, "wiki/sources/shape-up.md"),
+		"---\ntitle: Shape Up\n---\n\n## Summary\n\nSee [[betting|Betting]].\n")
+	writeFile(t, filepath.Join(dir, "wiki/concepts/betting.md"),
+		"---\ntitle: Betting\n---\n\n## Definition\n\nA technique.\n")
+
+	// Run twice — should not duplicate the ref.
+	_, err := BackfillRefs(context.Background(), dir)
+	require.NoError(t, err)
+	_, err = BackfillRefs(context.Background(), dir)
+	require.NoError(t, err)
+
+	got, err := os.ReadFile(filepath.Join(dir, "wiki/concepts/betting.md"))
+	require.NoError(t, err)
+
+	count := 0
+	for _, line := range splitLines(string(got)) {
+		if line == "- [[shape-up|Shape Up]]" {
+			count++
+		}
+	}
+	assert.Equal(t, 1, count, "ref should appear exactly once after two runs")
+}
+
+func TestBackfillRefs_MultipleSources(t *testing.T) {
+	dir := setupBrainDir(t)
+	writeFile(t, filepath.Join(dir, "wiki/sources/book-a.md"),
+		"---\ntitle: Book A\n---\n\n## Summary\n\nSee [[shaping|Shaping]].\n")
+	writeFile(t, filepath.Join(dir, "wiki/sources/book-b.md"),
+		"---\ntitle: Book B\n---\n\n## Summary\n\nAlso [[shaping|Shaping]].\n")
+	writeFile(t, filepath.Join(dir, "wiki/concepts/shaping.md"),
+		"---\ntitle: Shaping\n---\n\n## Definition\n\nA design activity.\n")
+
+	n, err := BackfillRefs(context.Background(), dir)
+	require.NoError(t, err)
+	assert.Equal(t, 1, n) // one concept page written
+
+	got, err := os.ReadFile(filepath.Join(dir, "wiki/concepts/shaping.md"))
+	require.NoError(t, err)
+	assert.Contains(t, string(got), "[[book-a|Book A]]")
+	assert.Contains(t, string(got), "[[book-b|Book B]]")
+}
+
+func TestBackfillRefs_NoSourcesDir(t *testing.T) {
+	dir := t.TempDir() // no wiki/sources subdir
+	n, err := BackfillRefs(context.Background(), dir)
+	require.NoError(t, err)
+	assert.Equal(t, 0, n)
+}
+
+func TestBackfillRefs_SkipsUnknownSlugs(t *testing.T) {
+	dir := setupBrainDir(t)
+	// Source links to a slug not in inventory and not on disk.
+	writeFile(t, filepath.Join(dir, "wiki/sources/article.md"),
+		"---\ntitle: Article\n---\n\n## Summary\n\nSee [[ghost-slug|Ghost]].\n")
+
+	n, err := BackfillRefs(context.Background(), dir)
+	require.NoError(t, err)
+	assert.Equal(t, 0, n)
+}