package vaultik_test

import (
	"context"
	"io"
	"path/filepath"
	"testing"

	"github.com/spf13/afero"
	"github.com/stretchr/testify/require"
	"sneak.berlin/go/vaultik/internal/config"
	"sneak.berlin/go/vaultik/internal/database"
	"sneak.berlin/go/vaultik/internal/log"
	"sneak.berlin/go/vaultik/internal/snapshot"
	"sneak.berlin/go/vaultik/internal/storage"
	"sneak.berlin/go/vaultik/internal/ui"
	"sneak.berlin/go/vaultik/internal/vaultik"
)

// TestRestoreAndDeepVerifyRejectSwappedDatabase proves that swapping two
// snapshots' encrypted databases on the store is caught. age decryption
// alone proves only that a database is readable; without an identity check
// restore would happily write the wrong snapshot's files and deep verify
// would report success. After the swap, restore and deep verify of A both
// fail, and the error names the snapshot the database actually holds (B).
func TestRestoreAndDeepVerifyRejectSwappedDatabase(t *testing.T) {
	log.Initialize(log.Config{})
	t.Parallel()

	fs := afero.NewOsFs()
	tempDir := t.TempDir()
	storeDir := filepath.Join(tempDir, "remote")

	chunkSize := int64(64 * 1024)

	storer, err := storage.NewFileStorer(storeDir)
	require.NoError(t, err)

	ctx := context.Background()

	// Two snapshots with different content, backed up into one shared
	// store. Different names give them different remote keys, so their
	// metadata directories are distinct and can be tampered with alone.
	dataA := filepath.Join(tempDir, "srcA")
	require.NoError(t, fs.MkdirAll(dataA, 0o755))
	require.NoError(t, afero.WriteFile(fs, filepath.Join(dataA, "a.bin"),
		bytesPattern("alpha-", int(chunkSize*2)), 0o644))

	dataB := filepath.Join(tempDir, "srcB")
	require.NoError(t, fs.MkdirAll(dataB, 0o755))
	require.NoError(t, afero.WriteFile(fs, filepath.Join(dataB, "b.bin"),
		bytesPattern("beta-", int(chunkSize*2)), 0o644))

	idA := backupNamedSnapshotToStore(ctx, t, fs, dataA, storer,
		filepath.Join(tempDir, "idxA.sqlite"), "alpha")
	idB := backupNamedSnapshotToStore(ctx, t, fs, dataB, storer,
		filepath.Join(tempDir, "idxB.sqlite"), "beta")
	require.NotEqual(t, idA, idB)

	keyA := snapshot.RemoteSnapshotKey(idA)
	keyB := snapshot.RemoteSnapshotKey(idB)
	require.NotEqual(t, keyA, keyB)

	// Baseline: each snapshot verifies against its own intact metadata.
	require.NoError(t, newStoreClient(ctx, t, fs, storer).RunDeepVerify(
		idA, &vaultik.VerifyOptions{Deep: true}))
	require.NoError(t, newStoreClient(ctx, t, fs, storer).RunDeepVerify(
		idB, &vaultik.VerifyOptions{Deep: true}))

	// Swap the two snapshots' encrypted databases on the store.
	swapStoreFiles(t, fs,
		filepath.Join(storeDir, "metadata", keyA, "db.zst.age"),
		filepath.Join(storeDir, "metadata", keyB, "db.zst.age"))

	// Restore of A now decrypts B's database; the identity check must
	// reject it and name the snapshot it actually found.
	restoreErr := newStoreClient(ctx, t, fs, storer).Restore(&vaultik.RestoreOptions{
		SnapshotID: idA,
		TargetDir:  filepath.Join(tempDir, "restoreA"),
	})
	require.Error(t, restoreErr)
	require.ErrorContains(t, restoreErr, idB)

	// Deep verify of A must reject the swapped database for the same reason.
	verifyErr := newStoreClient(ctx, t, fs, storer).RunDeepVerify(
		idA, &vaultik.VerifyOptions{Deep: true})
	require.Error(t, verifyErr)
	require.ErrorContains(t, verifyErr, idB)
}

// TestDeepVerifyRejectsSwappedDatabaseWithEmptyManifest covers the case the
// issue calls out: swapping in a database whose blob set is empty and
// pairing it with an equally empty manifest. The manifest then agrees with
// the database, so every blob-level check passes and deep verify used to
// report success with zero blobs verified. The identity check rejects it
// before any blob check runs.
func TestDeepVerifyRejectsSwappedDatabaseWithEmptyManifest(t *testing.T) {
	log.Initialize(log.Config{})
	t.Parallel()

	fs := afero.NewOsFs()
	tempDir := t.TempDir()
	storeDir := filepath.Join(tempDir, "remote")

	chunkSize := int64(64 * 1024)

	storer, err := storage.NewFileStorer(storeDir)
	require.NoError(t, err)

	ctx := context.Background()

	// Snapshot A: real content, so its manifest lists blobs.
	dataA := filepath.Join(tempDir, "srcA")
	require.NoError(t, fs.MkdirAll(dataA, 0o755))
	require.NoError(t, afero.WriteFile(fs, filepath.Join(dataA, "a.bin"),
		bytesPattern("alpha-", int(chunkSize*2)), 0o644))
	idA := backupNamedSnapshotToStore(ctx, t, fs, dataA, storer,
		filepath.Join(tempDir, "idxA.sqlite"), "alpha")

	// Snapshot C: a single empty file, so it references no blobs and its
	// manifest is empty. This is the database/manifest pair an attacker
	// would swap in to make the blob checks vacuously pass.
	dataC := filepath.Join(tempDir, "srcC")
	require.NoError(t, fs.MkdirAll(dataC, 0o755))
	require.NoError(t, afero.WriteFile(fs,
		filepath.Join(dataC, "empty.bin"), []byte{}, 0o644))
	idC := backupNamedSnapshotToStore(ctx, t, fs, dataC, storer,
		filepath.Join(tempDir, "idxC.sqlite"), "charlie")

	keyA := snapshot.RemoteSnapshotKey(idA)
	keyC := snapshot.RemoteSnapshotKey(idC)

	// Replace A's database and manifest with C's empty pair.
	copyStoreFile(t, fs,
		filepath.Join(storeDir, "metadata", keyC, "db.zst.age"),
		filepath.Join(storeDir, "metadata", keyA, "db.zst.age"))
	copyStoreFile(t, fs,
		filepath.Join(storeDir, "metadata", keyC, "manifest.json.zst"),
		filepath.Join(storeDir, "metadata", keyA, "manifest.json.zst"))

	verifyErr := newStoreClient(ctx, t, fs, storer).RunDeepVerify(
		idA, &vaultik.VerifyOptions{Deep: true})
	require.Error(t, verifyErr)
	require.ErrorContains(t, verifyErr, idC)
}

// backupNamedSnapshotToStore backs up dataDir into the shared storer under
// the given snapshot name and returns the human snapshot ID. Two snapshots
// backed up under different names get different remote keys, so their
// metadata directories on the store are distinct.
func backupNamedSnapshotToStore(
	ctx context.Context, t *testing.T, fs afero.Fs,
	dataDir string, storer storage.Storer, dbPath, name string,
) string {
	t.Helper()

	const (
		chunkSize   = int64(64 * 1024)
		maxBlobSize = int64(512 * 1024)
	)

	cfg := &config.Config{
		AgeRecipients:    []string{testAgePublicKey},
		AgeSecretKey:     testAgeSecretKey,
		CompressionLevel: 3,
		Hostname:         testHostname,
	}

	db, err := database.New(ctx, dbPath)
	require.NoError(t, err)

	repos := database.NewRepositories(db)

	sm := snapshot.NewSnapshotManager(snapshot.SnapshotManagerParams{
		Repos:   repos,
		Storage: storer,
		Config:  cfg,
	})
	sm.SetFilesystem(fs)

	scanner := snapshot.NewScanner(snapshot.ScannerConfig{
		FS:               fs,
		Storage:          storer,
		ChunkSize:        chunkSize,
		MaxBlobSize:      maxBlobSize,
		CompressionLevel: cfg.CompressionLevel,
		AgeRecipients:    cfg.AgeRecipients,
		Repositories:     repos,
	})

	snapshotID, err := sm.CreateSnapshotWithName(
		ctx, cfg.Hostname, name, "test-version", "test-git")
	require.NoError(t, err)

	_, err = scanner.Scan(ctx, dataDir, snapshotID)
	require.NoError(t, err)

	require.NoError(t, sm.CompleteSnapshot(ctx, snapshotID))
	require.NoError(t, sm.ExportSnapshotMetadata(ctx, dbPath, snapshotID))
	require.NoError(t, db.Close())

	return snapshotID
}

// newStoreClient builds a Vaultik that reads only from the store: the
// secret key, the storer, and a filesystem, with no local index. This is
// what restore and deep verify need.
func newStoreClient(
	ctx context.Context, t *testing.T, fs afero.Fs, storer storage.Storer,
) *vaultik.Vaultik {
	t.Helper()

	v := &vaultik.Vaultik{
		Config: &config.Config{
			AgeSecretKey: testAgeSecretKey,
			Hostname:     testHostname,
		},
		Storage: storer,
		Fs:      fs,
		Stdout:  io.Discard,
		Stderr:  io.Discard,
		UI:      ui.NewWithColor(io.Discard, false),
	}
	v.SetContext(ctx)

	return v
}

// swapStoreFiles exchanges the contents of two files on the store.
func swapStoreFiles(t *testing.T, fs afero.Fs, a, b string) {
	t.Helper()

	dataA, err := afero.ReadFile(fs, a)
	require.NoError(t, err)

	dataB, err := afero.ReadFile(fs, b)
	require.NoError(t, err)

	require.NoError(t, afero.WriteFile(fs, a, dataB, 0o644))
	require.NoError(t, afero.WriteFile(fs, b, dataA, 0o644))
}

// copyStoreFile overwrites dst with the contents of src on the store.
func copyStoreFile(t *testing.T, fs afero.Fs, src, dst string) {
	t.Helper()

	data, err := afero.ReadFile(fs, src)
	require.NoError(t, err)

	require.NoError(t, afero.WriteFile(fs, dst, data, 0o644))
}