package vaultik_test

import (
	"bytes"
	"context"
	"os"
	"path/filepath"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"sneak.berlin/go/vaultik/internal/database"
	"sneak.berlin/go/vaultik/internal/log"
	"sneak.berlin/go/vaultik/internal/storage"
	"sneak.berlin/go/vaultik/internal/storage/faultstore"
	"sneak.berlin/go/vaultik/internal/vaultik"
)

// These tests cover https://git.eeqj.de/sneak/vaultik/issues/239: a
// file:// destination at a volume's mount point leaves an empty directory
// behind when the volume is unplugged. While the local index holds
// snapshots, a destination that answers that it has no
// vaultik-destination.txt is not present, so no command may write to it
// or conclude from it that the local snapshots are gone.

// markerFile is the name of the file a backup writes at the root of the
// destination.
const markerFile = "vaultik-destination.txt"

// backUpThenUnplugMountPoint backs up to a file:// destination, then
// moves the destination directory away and leaves an empty directory in
// its place, as unplugging a volume mounted there would. It returns the
// path of that empty directory.
func backUpThenUnplugMountPoint(
	ctx context.Context, t *testing.T,
) (*vaultik.Vaultik, *database.Repositories, *bytes.Buffer, string) {
	t.Helper()

	storeDir := filepath.Join(t.TempDir(), "mnt")
	v, repos, out := backUpToFileDestination(ctx, t, storeDir)

	require.NoError(t, os.Rename(storeDir, storeDir+"-unplugged"))
	require.NoError(t, os.Mkdir(storeDir, 0o750))

	return v, repos, out, storeDir
}

// assertUntouched checks that the local index still holds its one
// snapshot and that nothing was written to the empty mount point.
func assertUntouched(
	ctx context.Context, t *testing.T,
	repos *database.Repositories, storeDir string,
) {
	t.Helper()

	snapshots, err := repos.Snapshots.ListRecent(ctx, listRecentTestLimit)
	require.NoError(t, err)
	assert.Len(t, snapshots, 1, "no local snapshot record may be deleted")

	entries, err := os.ReadDir(storeDir)
	require.NoError(t, err)
	assert.Empty(t, entries, "nothing may be written to the empty mount point")
}

// TestFirstBackupWritesMarker checks that a backup writes the marker
// file at the root of the destination.
func TestFirstBackupWritesMarker(t *testing.T) {
	log.Initialize(log.Config{})
	t.Parallel()

	storeDir := t.TempDir()
	backUpToFileDestination(context.Background(), t, storeDir)

	assert.FileExists(t, filepath.Join(storeDir, markerFile))
}

// TestBackupRefusesDestinationWithoutMarker checks that snapshot create
// --prune writes nothing and drops no local snapshot record when the
// destination has no marker.
func TestBackupRefusesDestinationWithoutMarker(t *testing.T) {
	log.Initialize(log.Config{})
	t.Parallel()

	ctx := context.Background()
	v, repos, _, storeDir := backUpThenUnplugMountPoint(ctx, t)

	err := v.CreateSnapshot(&vaultik.SnapshotCreateOptions{
		Cron:  true,
		Prune: true,
	})
	require.ErrorContains(t, err, markerFile)

	assertUntouched(ctx, t, repos, storeDir)
}

// TestBackupGoesOnWhenMarkerCannotBeChecked checks that a backup goes on
// and writes the marker when looking it up fails with an error other
// than not found, as S3 answers credentials that allow only PUT
// (https://git.eeqj.de/sneak/vaultik/issues/389), and that a marker
// that is not found still stops it.
func TestBackupGoesOnWhenMarkerCannotBeChecked(t *testing.T) {
	log.Initialize(log.Config{})
	t.Parallel()

	ctx := context.Background()
	storeDir := t.TempDir()
	v, repos, _ := backUpToFileDestination(ctx, t, storeDir)

	// Removed so the test sees the backup write it again: with the
	// look-up failing, the backup cannot tell that it is gone.
	markerPath := filepath.Join(storeDir, markerFile)
	require.NoError(t, os.Remove(markerPath))

	store := faultstore.New(v.Storage)
	store.OnStat = func(key string) bool { return key == markerFile }
	v.Storage = store

	require.NoError(t, backUp(v, "second"))
	localSnapshotID(ctx, t, repos, "second")
	assert.FileExists(t, markerPath)

	require.NoError(t, os.Remove(markerPath))

	store.OnStat = nil

	require.ErrorContains(t, backUp(v, "third"), markerFile)
}

// TestBackupChecksMarkerBeforeDroppingIncompleteSnapshots checks that
// snapshot create writes nothing when the local index holds only an
// incomplete snapshot and the destination has no marker. The backup drops
// incomplete snapshots before it scans; checked after that, the local
// index would hold none and nothing would be checked.
func TestBackupChecksMarkerBeforeDroppingIncompleteSnapshots(t *testing.T) {
	log.Initialize(log.Config{})
	t.Parallel()

	ctx := context.Background()
	storeDir := t.TempDir()
	v, repos := newFileDestinationVaultik(ctx, t, storeDir)

	require.NoError(t, repos.Snapshots.Create(ctx, nil, &database.Snapshot{
		ID:        "host_first_2026-01-02T03:04:05Z",
		Hostname:  "host",
		StartedAt: time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC),
	}))

	err := backUp(v, "first")
	require.ErrorContains(t, err, markerFile)

	assertUntouched(ctx, t, repos, storeDir)
}

// TestPruneRefusesDestinationWithoutMarker checks that prune fails and
// deletes no local snapshot record when the destination has no marker.
func TestPruneRefusesDestinationWithoutMarker(t *testing.T) {
	log.Initialize(log.Config{})
	t.Parallel()

	ctx := context.Background()
	v, repos, _, storeDir := backUpThenUnplugMountPoint(ctx, t)

	err := v.Prune(&vaultik.PruneOptions{Force: true})
	require.ErrorContains(t, err, markerFile)

	assertUntouched(ctx, t, repos, storeDir)
}

// TestPurgeRefusesDestinationWithoutMarker checks that snapshot purge
// fails and deletes no local snapshot record when the destination has no
// marker.
func TestPurgeRefusesDestinationWithoutMarker(t *testing.T) {
	log.Initialize(log.Config{})
	t.Parallel()

	ctx := context.Background()
	v, repos, _, storeDir := backUpThenUnplugMountPoint(ctx, t)

	err := v.PurgeSnapshotsWithOptions(&vaultik.SnapshotPurgeOptions{
		KeepLatest: true,
		Force:      true,
	})
	require.ErrorContains(t, err, markerFile)

	assertUntouched(ctx, t, repos, storeDir)
}

// TestNukeRemoteRefusesDestinationWithoutMarker checks that remote nuke
// fails, deletes no local snapshot record, and neither reports the
// destination empty nor advises running nuke again when the destination
// has no marker.
func TestNukeRemoteRefusesDestinationWithoutMarker(t *testing.T) {
	log.Initialize(log.Config{})
	t.Parallel()

	ctx := context.Background()
	v, repos, out, storeDir := backUpThenUnplugMountPoint(ctx, t)

	err := v.NukeRemote(true)
	require.ErrorContains(t, err, markerFile)
	assert.NotContains(t, out.String(), "now empty")
	assert.NotContains(t, out.String(), "vaultik remote nuke --force")

	assertUntouched(ctx, t, repos, storeDir)
}

// TestRemoveSnapshotWarnsWhenDestinationHasNoMarker checks that snapshot
// remove warns that the metadata could not be removed from a destination
// without a marker, instead of reporting that it was.
func TestRemoveSnapshotWarnsWhenDestinationHasNoMarker(t *testing.T) {
	log.Initialize(log.Config{})
	t.Parallel()

	ctx := context.Background()
	v, repos, out, _ := backUpThenUnplugMountPoint(ctx, t)

	result, err := v.RemoveSnapshot(localSnapshotID(ctx, t, repos, "first"),
		&vaultik.RemoveOptions{Force: true})
	require.NoError(t, err)

	assert.False(t, result.RemoteRemoved)
	assert.Contains(t, out.String(),
		"Could not remove snapshot metadata from remote")
	assert.Contains(t, out.String(), markerFile)
	assert.NotContains(t, out.String(),
		"Removed snapshot metadata from remote storage")
}

// TestRemoveSnapshotOnlyOnDestinationFailsWithoutMarker checks that
// snapshot remove, for a snapshot that is only on the destination, fails
// saying the destination is not present when it has no marker, instead
// of saying the snapshot does not exist.
func TestRemoveSnapshotOnlyOnDestinationFailsWithoutMarker(t *testing.T) {
	log.Initialize(log.Config{})
	t.Parallel()

	ctx := context.Background()
	storeDir := filepath.Join(t.TempDir(), "mnt")
	v, repos, _ := backUpToFileDestination(ctx, t, storeDir)
	require.NoError(t, backUp(v, "second"))

	id := localSnapshotID(ctx, t, repos, "first")
	_, err := v.RemoveSnapshot(id,
		&vaultik.RemoveOptions{Force: true, LocalOnly: true})
	require.NoError(t, err)

	// Unplug the volume: an empty directory stays at its mount point.
	require.NoError(t, os.Rename(storeDir, storeDir+"-unplugged"))
	require.NoError(t, os.Mkdir(storeDir, 0o750))

	_, err = v.RemoveSnapshot(id, &vaultik.RemoveOptions{Force: true})
	require.ErrorContains(t, err, markerFile)
	require.ErrorContains(t, err, "mount the volume")

	assertUntouched(ctx, t, repos, storeDir)
}

// TestListSnapshotsWarnsWhenDestinationHasNoMarker checks that snapshot
// list warns and shows the local index alone when the destination has no
// marker, without reporting the local snapshot as missing from it.
func TestListSnapshotsWarnsWhenDestinationHasNoMarker(t *testing.T) {
	log.Initialize(log.Config{})
	t.Parallel()

	ctx := context.Background()
	v, repos, out, _ := backUpThenUnplugMountPoint(ctx, t)
	id := localSnapshotID(ctx, t, repos, "first")

	require.NoError(t, v.ListSnapshots(false))

	assert.Contains(t, out.String(), "Could not list backup destination store")
	assert.Contains(t, out.String(), markerFile)
	assert.Contains(t, out.String(), id)
	assert.NotContains(t, out.String(), "not found in backup destination store")
}

// TestListSnapshotsAfterStorageURLChangeToEmptyDirectory checks that
// snapshot list, after storage_url is changed to an empty directory,
// warns only that the local index is bound to a different destination:
// the local snapshots are stored at the old one, so the new one's lack
// of a marker says nothing. With --json the local row is not on the new
// destination, so remote_present is false, not unknown.
func TestListSnapshotsAfterStorageURLChangeToEmptyDirectory(t *testing.T) {
	log.Initialize(log.Config{})
	t.Parallel()

	ctx := context.Background()
	v, repos, out := backUpToFileDestination(ctx, t, t.TempDir())
	id := localSnapshotID(ctx, t, repos, "first")

	newDir := t.TempDir()
	store, err := storage.NewFileStorer(newDir)
	require.NoError(t, err)

	v.Storage = store
	v.Config.StorageURL = "file://" + newDir

	require.NoError(t, v.ListSnapshots(false))

	assert.Contains(t, out.String(), id)
	assert.Contains(t, out.String(),
		"local index is bound to a different backup destination")
	assert.NotContains(t, out.String(), "Could not list backup destination store")
	assert.NotContains(t, out.String(), markerFile)

	out.Reset()
	require.NoError(t, v.ListSnapshots(true))

	rows := decodeListJSON(t, out.String())
	require.Len(t, rows, 1)
	require.NotNil(t, rows[0].RemotePresent)
	assert.False(t, *rows[0].RemotePresent)
}

// TestBackupAfterNukeRemoteSucceeds checks that remote nuke leaves the
// destination ready for a new first backup, which writes the marker
// again.
func TestBackupAfterNukeRemoteSucceeds(t *testing.T) {
	log.Initialize(log.Config{})
	t.Parallel()

	storeDir := t.TempDir()
	v, _, _ := backUpToFileDestination(context.Background(), t, storeDir)

	require.NoError(t, v.NukeRemote(true))
	assert.NoFileExists(t, filepath.Join(storeDir, markerFile))

	require.NoError(t, backUp(v, "second"))
	assert.FileExists(t, filepath.Join(storeDir, markerFile))
}