// 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)
}