package api

import (
	"os"
	"path/filepath"
	"strings"
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

// seedNote writes a note directly to disk and returns its relPath.
func seedNote(t *testing.T, brainDir, rel, content string) string {
	t.Helper()
	full := filepath.Join(brainDir, filepath.FromSlash(rel))
	require.NoError(t, os.MkdirAll(filepath.Dir(full), 0o755))
	require.NoError(t, os.WriteFile(full, []byte(content), 0o644))
	return rel
}

func TestUpdateNoteSupersedesAndStamps(t *testing.T) {
	brainDir := t.TempDir()
	rel := seedNote(t, brainDir, "wiki/jepa-fx/facts/val-vol.md",
		"---\nwing: jepa-fx\nhall: facts\ncreated_at: 2026-01-01T00:00:00Z\ncustom: keep-me\n---\n# Old\n\nold body\n")

	relPath, hash, priorHash, err := UpdateNote(brainDir, UpdateNoteOptions{
		Path:    rel,
		Content: "# New\n\nnew body\n",
		Reason:  "facts changed",
	})
	require.NoError(t, err)
	assert.Equal(t, rel, relPath)
	assert.NotEmpty(t, hash)
	assert.NotEmpty(t, priorHash)
	assert.NotEqual(t, hash, priorHash)

	got, err := os.ReadFile(filepath.Join(brainDir, filepath.FromSlash(rel)))
	require.NoError(t, err)
	s := string(got)
	// Body replaced.
	assert.Contains(t, s, "# New")
	assert.NotContains(t, s, "old body")
	// Prior fields preserved.
	assert.Contains(t, s, "wing: jepa-fx")
	assert.Contains(t, s, "hall: facts")
	assert.Contains(t, s, "created_at: 2026-01-01T00:00:00Z")
	assert.Contains(t, s, "custom: keep-me")
	// Supersession stamped.
	assert.Contains(t, s, "updated_at:")
	assert.Contains(t, s, "supersedes: "+priorHash)
	assert.Contains(t, s, "supersede_reason: facts changed")
}

func TestUpdateNoteResolvesByWingHallSlug(t *testing.T) {
	brainDir := t.TempDir()
	seedNote(t, brainDir, "wiki/jepa-fx/facts/val-vol.md",
		"---\nwing: jepa-fx\nhall: facts\n---\nold\n")

	relPath, _, _, err := UpdateNote(brainDir, UpdateNoteOptions{
		Wing: "jepa-fx", Hall: "facts", Slug: "val-vol",
		Content: "new\n",
	})
	require.NoError(t, err)
	assert.Equal(t, "wiki/jepa-fx/facts/val-vol.md", relPath)
}

func TestUpdateNoteErrorsOnMissingAndDoesNotCreate(t *testing.T) {
	brainDir := t.TempDir()

	_, _, _, err := UpdateNote(brainDir, UpdateNoteOptions{
		Wing: "jepa-fx", Hall: "facts", Slug: "ghost",
		Content: "x\n",
	})
	require.Error(t, err)
	assert.Contains(t, err.Error(), "does not exist")

	// No file created.
	_, statErr := os.Stat(filepath.Join(brainDir, "wiki/jepa-fx/facts/ghost.md"))
	assert.True(t, os.IsNotExist(statErr), "missing-target update must not create a note")
}

func TestUpdateNoteRejectsTraversal(t *testing.T) {
	brainDir := t.TempDir()
	_, _, _, err := UpdateNote(brainDir, UpdateNoteOptions{
		Path:    "../escape.md",
		Content: "x\n",
	})
	require.Error(t, err)
}

func TestReadNoteReturnsFrontmatterBodyHash(t *testing.T) {
	brainDir := t.TempDir()
	rel := seedNote(t, brainDir, "wiki/jepa-fx/facts/n.md",
		"---\nwing: jepa-fx\nhall: facts\n---\n# Body\n\ntext\n")

	fm, body, hash, err := ReadNote(brainDir, rel)
	require.NoError(t, err)
	assert.Equal(t, "jepa-fx", fm["wing"])
	assert.Equal(t, "facts", fm["hall"])
	assert.Equal(t, "# Body\n\ntext\n", body)

	// Hash matches ContentHash of the raw bytes on disk (round-trip).
	raw, _ := os.ReadFile(filepath.Join(brainDir, filepath.FromSlash(rel)))
	assert.Equal(t, ContentHash(raw), hash)
}

func TestReadNoteRejectsTraversal(t *testing.T) {
	brainDir := t.TempDir()
	_, _, _, err := ReadNote(brainDir, "../../etc/passwd")
	require.Error(t, err)
}

func TestUpdateThenReadRoundTripsHash(t *testing.T) {
	brainDir := t.TempDir()
	rel := seedNote(t, brainDir, "wiki/a/facts/n.md", "---\nwing: a\nhall: facts\n---\nold\n")

	_, hash, _, err := UpdateNote(brainDir, UpdateNoteOptions{Path: rel, Content: "new\n"})
	require.NoError(t, err)

	_, _, readHash, err := ReadNote(brainDir, rel)
	require.NoError(t, err)
	assert.Equal(t, hash, readHash, "update content_hash must round-trip through ReadNote")
}

func TestContentHashStable(t *testing.T) {
	assert.Equal(t, ContentHash([]byte("abc")), ContentHash([]byte("abc")))
	assert.NotEqual(t, ContentHash([]byte("abc")), ContentHash([]byte("abd")))
	assert.True(t, strings.HasPrefix(ContentHash([]byte("")), "")) // hex, non-panicking
}