package vaultik //nolint:testpackage // drives restore through unexported session

import (
	"bytes"
	"context"
	"errors"
	"io"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"syscall"
	"testing"

	"github.com/spf13/afero"
	"github.com/stretchr/testify/assert"
	"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"
)

// errSpyWrite is the injected write failure used to exercise the
// partial-file cleanup path.
var errSpyWrite = errors.New("injected write failure")

// modeSpyFs wraps a real filesystem so restore tests can observe and
// perturb the single output file whose path contains watch. It records
// the on-disk permission bits seen at the moment content is first
// written (the window during which another local user could read it),
// and can inject a write failure or append trailing bytes on close.
type modeSpyFs struct {
	afero.Fs

	watch string

	mu         sync.Mutex
	writeModes []os.FileMode
	failWrite  bool
	trailing   int
}

//nolint:ireturn // afero.Fs.OpenFile is defined to return the interface
func (m *modeSpyFs) OpenFile(
	name string, flag int, perm os.FileMode,
) (afero.File, error) {
	f, err := m.Fs.OpenFile(name, flag, perm)
	if err != nil || !strings.Contains(name, m.watch) {
		return f, err
	}

	return &modeSpyFile{File: f, fs: m, path: name}, nil
}

type modeSpyFile struct {
	afero.File

	fs      *modeSpyFs
	path    string
	written bool
}

func (f *modeSpyFile) Write(p []byte) (int, error) {
	if !f.written {
		f.written = true

		info, err := f.fs.Stat(f.path)
		if err == nil {
			f.fs.mu.Lock()
			f.fs.writeModes = append(f.fs.writeModes, info.Mode().Perm())
			f.fs.mu.Unlock()
		}
	}

	if f.fs.failWrite {
		return 0, errSpyWrite
	}

	return f.File.Write(p)
}

func (f *modeSpyFile) Close() error {
	if f.fs.trailing > 0 {
		_, _ = f.File.Write(bytes.Repeat([]byte{'x'}, f.fs.trailing))
	}

	return f.File.Close()
}

// backupOneFile writes a single source file with the given mode and
// backs it up into a fresh file storer, returning everything a restore
// needs. The index database is closed before returning so the restore
// half runs from the exported metadata and remote bytes only.
func backupOneFile(
	ctx context.Context, t *testing.T, fs afero.Fs, tempDir, name string,
	content []byte, mode os.FileMode,
) (*config.Config, *storage.FileStorer, string, string) {
	t.Helper()

	dataDir := filepath.Join(tempDir, "src")
	require.NoError(t, fs.MkdirAll(dataDir, 0o755))

	srcPath := filepath.Join(dataDir, name)
	require.NoError(t, afero.WriteFile(fs, srcPath, content, mode))
	require.NoError(t, fs.Chmod(srcPath, mode))

	storeDir := t.TempDir()
	dbPath := filepath.Join(tempDir, "index.sqlite")

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

	cfg := &config.Config{
		AgeRecipients: []string{
			"age1ezrjmfpwsc95svdg0y54mums3zevgzu0x0ecq2f7tp8a05gl0sjq9q9wjg",
		},
		AgeSecretKey: "AGE-SECRET-KEY-19CR5YSFW59HM4TLD6GXVEDMZFTVVF7PPHKU" +
			"T68TXSFPK7APHXA2QS2NJA5",
		CompressionLevel: 3,
		Hostname:         "test-host",
		BlobSizeLimit:    config.Size(5 * 1024 * 1024),
	}

	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:        4 * 1024 * 1024,
		MaxBlobSize:      5 * 1024 * 1024,
		CompressionLevel: cfg.CompressionLevel,
		AgeRecipients:    cfg.AgeRecipients,
		Repositories:     repos,
	})

	snapshotID, err := sm.CreateSnapshotWithName(
		ctx, cfg.Hostname, "perms", "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 cfg, storer, snapshotID, srcPath
}

// restoredPathFor returns where backupOneFile's source lands under a
// restore target: restore recreates each file at its original absolute
// path beneath TargetDir.
func restoredPathFor(restoreDir, srcPath string) string {
	return filepath.Join(restoreDir, srcPath)
}

// withUmask022 forces the process umask to 022 for the duration of a
// test, so the difference between a 0600 create and a default create is
// observable. Restored serially (no t.Parallel) so it does not race
// other tests.
func withUmask022(t *testing.T) {
	t.Helper()

	old := syscall.Umask(0o022)

	t.Cleanup(func() { syscall.Umask(old) })
}

// TestRestoreCreatesFileNeverWiderThanStoredMode checks that a file with
// a restrictive stored mode (0600) is never observable with a wider mode
// while its content is being written, and ends at its stored mode.
//
//nolint:paralleltest // sets the process umask; must run serially
func TestRestoreCreatesFileNeverWiderThanStoredMode(t *testing.T) {
	log.Initialize(log.Config{})
	withUmask022(t)

	fs := afero.NewOsFs()
	tempDir := t.TempDir()
	ctx := context.Background()

	content := randomBytes(t, 4096)

	cfg, storer, snapshotID, srcPath := backupOneFile(
		ctx, t, fs, tempDir, "secret.bin", content, 0o600)

	restoreDir := filepath.Join(tempDir, "restored")
	spy := &modeSpyFs{Fs: fs, watch: "secret.bin"}

	v := newRestoreVaultik(ctx, cfg, storer, spy)
	require.NoError(t, v.Restore(&RestoreOptions{
		SnapshotID: snapshotID,
		TargetDir:  restoreDir,
	}))

	spy.mu.Lock()
	observed := append([]os.FileMode(nil), spy.writeModes...)
	spy.mu.Unlock()

	require.NotEmpty(t, observed,
		"spy never saw the output file being written")

	for _, m := range observed {
		assert.Equalf(t, os.FileMode(0o600), m,
			"file was observable at mode %o during write; must be 0600", m)
	}

	// The stored mode is applied after the content is written.
	info, err := fs.Stat(restoredPathFor(restoreDir, srcPath))
	require.NoError(t, err)
	assert.Equal(t, os.FileMode(0o600), info.Mode().Perm())

	got, err := afero.ReadFile(fs, restoredPathFor(restoreDir, srcPath))
	require.NoError(t, err)
	require.True(t, bytes.Equal(got, content))
}

// TestRestoreRemovesPartialFileOnWriteFailure checks that a file whose
// content write fails is not left behind.
//
//nolint:paralleltest // sets the process umask; must run serially
func TestRestoreRemovesPartialFileOnWriteFailure(t *testing.T) {
	log.Initialize(log.Config{})
	withUmask022(t)

	fs := afero.NewOsFs()
	tempDir := t.TempDir()
	ctx := context.Background()

	cfg, storer, snapshotID, srcPath := backupOneFile(
		ctx, t, fs, tempDir, "doomed.bin", randomBytes(t, 4096), 0o600)

	restoreDir := filepath.Join(tempDir, "restored")
	spy := &modeSpyFs{Fs: fs, watch: "doomed.bin", failWrite: true}

	v := newRestoreVaultik(ctx, cfg, storer, spy)
	err := v.Restore(&RestoreOptions{
		SnapshotID: snapshotID,
		TargetDir:  restoreDir,
	})
	require.Error(t, err, "restore should fail when the write fails")

	exists, err := afero.Exists(fs, restoredPathFor(restoreDir, srcPath))
	require.NoError(t, err)
	assert.False(t, exists, "partial file must be removed after a failed write")
}

// TestVerifyRejectsTrailingBytes checks that --verify fails a restored
// file that has bytes past its last chunk.
//
//nolint:paralleltest // sets the process umask; must run serially
func TestVerifyRejectsTrailingBytes(t *testing.T) {
	log.Initialize(log.Config{})
	withUmask022(t)

	fs := afero.NewOsFs()
	tempDir := t.TempDir()
	ctx := context.Background()

	cfg, storer, snapshotID, _ := backupOneFile(
		ctx, t, fs, tempDir, "padded.bin", randomBytes(t, 4096), 0o600)

	restoreDir := filepath.Join(tempDir, "restored")
	// Append one byte to the file as it is written, so its content still
	// matches the stored chunks but it is one byte too long.
	spy := &modeSpyFs{Fs: fs, watch: "padded.bin", trailing: 1}

	v := newRestoreVaultik(ctx, cfg, storer, spy)
	err := v.Restore(&RestoreOptions{
		SnapshotID: snapshotID,
		TargetDir:  restoreDir,
		Verify:     true,
	})
	require.Error(t, err, "verify should fail on a file with trailing bytes")
	assert.ErrorIs(t, err, errFilesFailedVerify)
}

// newRestoreVaultik builds a Vaultik wired for a restore-only test.
func newRestoreVaultik(
	ctx context.Context, cfg *config.Config, storer storage.Storer, fs afero.Fs,
) *Vaultik {
	v := &Vaultik{
		Config:  cfg,
		Storage: storer,
		Fs:      fs,
		Stdout:  io.Discard,
		Stderr:  io.Discard,
		UI:      ui.NewWithColor(io.Discard, false),
	}
	v.SetContext(ctx)

	return v
}