//nolint:testpackage // sets the unexported fields of Instance
package cli

import (
	"bytes"
	"io"
	"os"
	"path/filepath"
	"runtime"
	"strconv"
	"strings"
	"sync"
	"testing"
	"time"

	"git.eeqj.de/sneak/secret/internal/secret"
	"git.eeqj.de/sneak/secret/internal/vault"
	"github.com/awnumar/memguard"
	"github.com/spf13/afero"
	"github.com/spf13/cobra"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

const (
	// lockWait is how long a test waits for something that must happen
	// once the lock is free.
	lockWait = 10 * time.Second

	// testPassphrase protects the passphrase unlockers the tests create.
	testPassphrase = "test-passphrase"

	// testInput is a file outside the state directory that commands read.
	testInput = "/input"
)

// lockInBackground starts taking the state directory lock and returns a
// channel that delivers the function releasing it once it has been taken.
func lockInBackground(t *testing.T, fs afero.Fs) <-chan func() {
	t.Helper()

	taken := make(chan func(), 1)

	go func() {
		release, err := vault.LockStateDir(fs, testStateDir)
		if assert.NoError(t, err) {
			taken <- release
		}
	}()

	return taken
}

// addAtOnce runs one add of the secret name per value, all at once, and
// returns their errors. Each add is given mnemonic, which a forced add
// needs.
func addAtOnce(
	fs afero.Fs, stateDir, name string, force bool, values []string,
	mnemonic *memguard.LockedBuffer,
) []error {
	errs := make(chan error, len(values))

	for _, value := range values {
		go func() {
			cli := NewCLIInstanceWithStateDir(fs, stateDir)
			cli.Mnemonic = mnemonic
			cli.cmd = &cobra.Command{}
			cli.cmd.SetIn(strings.NewReader(value))

			errs <- cli.AddSecret(name, force)
		}()
	}

	results := make([]error, 0, len(values))
	for range values {
		results = append(results, <-errs)
	}

	return results
}

// numbered returns count distinct values starting with prefix.
func numbered(prefix string, count int) []string {
	values := make([]string, 0, count)
	for i := range count {
		values = append(values, prefix+"-"+strconv.Itoa(i))
	}

	return values
}

// TestConcurrentAddsKeepEveryVersion runs adds of one secret at once, on
// the in-memory and on the real filesystem. Without the state directory
// lock, adds of a new secret all find it absent and replace each other, and
// forced adds read the same highest version number and overwrite each
// other's version. With it they behave as if run one after another.
//
//nolint:paralleltest // times commands against the in-memory lock all tests share
func TestConcurrentAddsKeepEveryVersion(t *testing.T) {
	mnemonic := testMnemonicBuffer(t)

	const adds = 8

	for _, tc := range []struct {
		name     string
		fs       afero.Fs
		stateDir string
	}{
		{"memory", afero.NewMemMapFs(), testStateDir},
		{"real", afero.NewOsFs(), t.TempDir()},
	} {
		t.Run(tc.name, func(t *testing.T) {
			_, err := vault.CreateVault(tc.fs, tc.stateDir, "default", mnemonic)
			require.NoError(t, err)

			// One add creates the secret; the others find that it exists
			created := 0

			for _, err := range addAtOnce(tc.fs, tc.stateDir, "shared", false,
				numbered("create", adds), mnemonic) {
				if err == nil {
					created++
				} else {
					require.ErrorIs(t, err, vault.ErrSecretExists)
				}
			}

			require.Equal(t, 1, created, "exactly one add creates the secret")

			// Every forced add stores a version of its own
			for _, err := range addAtOnce(tc.fs, tc.stateDir, "shared", true,
				numbered("force", adds), mnemonic) {
				require.NoError(t, err)
			}

			vlt, err := vault.GetCurrentVault(tc.fs, tc.stateDir)
			require.NoError(t, err)

			vlt.Mnemonic = mnemonic

			vaultDir, err := vlt.GetDirectory()
			require.NoError(t, err)

			versions, err := secret.ListVersions(tc.fs,
				filepath.Join(vaultDir, "secrets.d", "shared"))
			require.NoError(t, err)
			require.Len(t, versions, adds+1, "one version per successful add")

			values := make(map[string]bool, len(versions))

			for _, version := range versions {
				value, err := vlt.GetSecretVersion("shared", version)
				require.NoError(t, err)

				values[string(value.Bytes())] = true
				value.Destroy()
			}

			assert.Len(t, values, adds+1, "every add stored its own value")
		})
	}
}

// readNotifier passes reads through to Reader and closes reading at the
// first one.
type readNotifier struct {
	io.Reader

	reading chan struct{}
	once    sync.Once
}

func (r *readNotifier) Read(p []byte) (int, error) {
	r.once.Do(func() { close(r.reading) })

	return r.Reader.Read(p)
}

// TestEncryptPipedIntoAdd runs `secret encrypt key | secret add name` in
// one process, starting encrypt once add is reading its input. Had add
// taken the state directory lock before reading, it would hold the lock
// while waiting for encrypt's output, and encrypt would wait for the lock
// to store its key: neither would finish.
//
//nolint:paralleltest // times commands against the in-memory lock all tests share
func TestEncryptPipedIntoAdd(t *testing.T) {
	fs := afero.NewMemMapFs()
	_, err := vault.CreateVault(fs, testStateDir, "default", testMnemonicBuffer(t))
	require.NoError(t, err)
	require.NoError(t, afero.WriteFile(fs, testInput, []byte("piped"), 0o600))

	pipeReader, pipeWriter := io.Pipe()
	// If the test gives up, this makes add's read fail, so that both
	// commands return and release the lock the other tests use
	t.Cleanup(func() { _ = pipeReader.Close() })

	const commands = 2

	input := &readNotifier{Reader: pipeReader, reading: make(chan struct{})}
	results := make(chan error, commands)

	go func() {
		add := NewCLIInstanceWithStateDir(fs, testStateDir)
		add.cmd = &cobra.Command{}
		add.cmd.SetIn(input)

		results <- add.AddSecret("encrypted", false)
	}()

	go func() {
		<-input.reading

		encrypt := NewCLIInstanceWithStateDir(fs, testStateDir)
		encrypt.cmd = &cobra.Command{}
		encrypt.cmd.SetOut(pipeWriter)

		err := encrypt.Encrypt("key", testInput, "")
		// Ends add's input, as the end of the pipe does
		_ = pipeWriter.CloseWithError(err)

		results <- err
	}()

	timeout := time.After(lockWait)

	for range commands {
		select {
		case err := <-results:
			require.NoError(t, err)
		case <-timeout:
			t.Fatal("secret encrypt piped into secret add never finished")
		}
	}
}

// TestFailedCommandReleasesLock checks that a command failing after it
// took the state directory lock leaves the lock free for the next command.
func TestFailedCommandReleasesLock(t *testing.T) {
	t.Parallel()

	fs := afero.NewMemMapFs()
	cli := NewCLIInstanceWithStateDir(fs, testStateDir)

	// Fails once it holds the lock: there is no current vault. Without
	// --force it would fail before taking the lock, on the check it makes
	// before asking.
	err := cli.RemoveSecret(&cobra.Command{}, "missing", true)
	require.Error(t, err)

	select {
	case release := <-lockInBackground(t, fs):
		release()
	case <-time.After(lockWait):
		t.Fatal("the failed command left the state directory locked")
	}
}

// stateDirModTimes returns the modification time of every file and
// directory under the test state directory. Any change a command makes, even
// rewriting a file with the same content, changes it.
func stateDirModTimes(t *testing.T, fs afero.Fs) map[string]int64 {
	t.Helper()

	modTimes := make(map[string]int64)

	err := afero.Walk(fs, testStateDir,
		func(path string, info os.FileInfo, err error) error {
			if err != nil {
				return err
			}

			modTimes[path] = info.ModTime().UnixNano()

			return nil
		})
	require.NoError(t, err)

	return modTimes
}

// setupEveryCommand makes what each command in
// TestChangingCommandsWaitForLock needs: the current vault "work" with two
// versions of "test/secret", the vault "other" without a long-term key, for
// vault import, and the file testInput. There is no vault "default", which
// init creates. If withUnlocker is set, it also gives "work" a passphrase
// unlocker, which is slow. It returns the older version and the unlocker's
// ID.
func setupEveryCommand(
	t *testing.T, fs afero.Fs, withUnlocker bool,
) (string, string) {
	t.Helper()

	mnemonic := testMnemonicBuffer(t)

	other, err := vault.CreateVault(fs, testStateDir, "other", mnemonic)
	require.NoError(t, err)

	otherDir, err := other.GetDirectory()
	require.NoError(t, err)
	require.NoError(t, fs.Remove(filepath.Join(otherDir, "pub.age")))

	vlt, err := vault.CreateVault(fs, testStateDir, "work", mnemonic)
	require.NoError(t, err)

	addTestSecret(t, vlt, []byte("older"), false)
	addTestSecret(t, vlt, []byte("newer"), true)

	vaultDir, err := vlt.GetDirectory()
	require.NoError(t, err)

	versions, err := secret.ListVersions(fs,
		filepath.Join(vaultDir, "secrets.d", "test%secret"))
	require.NoError(t, err)
	require.Len(t, versions, 2)

	unlockerID := ""

	if withUnlocker {
		passphrase := memguard.NewBufferFromBytes([]byte(testPassphrase))
		defer passphrase.Destroy()

		unlocker, err := vlt.CreatePassphraseUnlocker(passphrase)
		require.NoError(t, err)

		unlockerID = unlocker.GetID()
	}

	require.NoError(t, afero.WriteFile(fs, testInput, []byte("input"), 0o600))

	// Newest first
	return versions[1], unlockerID
}

// waitingForLock reports whether a goroutine is stopped in
// vault.LockStateDir, waiting for the in-memory filesystem's lock. The
// stack trace of such a goroutine starts with the reason it waits,
// "[sync.Mutex.Lock]", and names LockStateDir.
func waitingForLock() bool {
	stacks := make([]byte, 1<<20)
	stacks = stacks[:runtime.Stack(stacks, true)]

	for goroutine := range bytes.SplitSeq(stacks, []byte("\n\n")) {
		if bytes.Contains(goroutine, []byte("[sync.Mutex.Lock")) &&
			bytes.Contains(goroutine, []byte("vault.LockStateDir(")) {
			return true
		}
	}

	return false
}

// requireWaitsForLock runs a command, given what setupEveryCommand made,
// while holding the state directory lock. The command must neither finish
// nor change anything before it waits for the lock, and must succeed once
// the lock is released.
func requireWaitsForLock(
	t *testing.T,
	withUnlocker bool,
	run func(cli *Instance, olderVersion, unlockerID string) error,
) {
	t.Helper()

	fs := afero.NewMemMapFs()
	olderVersion, unlockerID := setupEveryCommand(t, fs, withUnlocker)
	before := stateDirModTimes(t, fs)

	release, err := vault.LockStateDir(fs, testStateDir)
	require.NoError(t, err)

	// Released at most once, and also if the test fails while holding it,
	// so that later tests can take it
	release = sync.OnceFunc(release)
	defer release()

	unlockPassphrase := memguard.NewBufferFromBytes([]byte(testPassphrase))
	defer unlockPassphrase.Destroy()

	cli := NewCLIInstanceWithStateDir(fs, testStateDir)
	cli.Mnemonic = testMnemonicBuffer(t)
	cli.UnlockPassphrase = unlockPassphrase
	cli.cmd = &cobra.Command{}
	cli.cmd.SetIn(strings.NewReader("value"))
	cli.cmd.SetOut(io.Discard)

	done := make(chan error, 1)

	go func() { done <- run(cli, olderVersion, unlockerID) }()

	timeout := time.After(lockWait)

	for !waitingForLock() {
		select {
		case err := <-done:
			t.Fatalf("finished while the lock was held, with error %v", err)
		case <-timeout:
			t.Fatal("never waited for the lock")
		case <-time.After(time.Millisecond):
		}
	}

	assert.Equal(t, before, stateDirModTimes(t, fs),
		"changed the state directory before waiting for the lock")

	release()

	select {
	case err := <-done:
		require.NoError(t, err)
	case <-time.After(lockWait):
		t.Fatal("did not finish once the lock was released")
	}
}

// TestChangingCommandsWaitForLock checks that each command that changes the
// state directory waits for its lock.
//
//nolint:paralleltest // waitingForLock sees any test's command waiting for the lock
func TestChangingCommandsWaitForLock(t *testing.T) {
	for _, tc := range []struct {
		name         string
		withUnlocker bool
		run          func(cli *Instance, olderVersion, unlockerID string) error
	}{
		{"add", false, func(cli *Instance, _, _ string) error {
			return cli.AddSecret("added", false)
		}},
		{"import", false, func(cli *Instance, _, _ string) error {
			return cli.ImportSecret(cli.cmd, "imported", testInput, false)
		}},
		{"generate secret", false, func(cli *Instance, _, _ string) error {
			return cli.GenerateSecret(cli.cmd, "generated", 16, "base58", false)
		}},
		{"encrypt", false, func(cli *Instance, _, _ string) error {
			return cli.Encrypt("key", testInput, "")
		}},
		{"rm --force", false, func(cli *Instance, _, _ string) error {
			return cli.RemoveSecret(cli.cmd, "test/secret", true)
		}},
		{"move", false, func(cli *Instance, _, _ string) error {
			return cli.MoveSecret(cli.cmd, "test/secret", "moved", false)
		}},
		{"version promote", false, func(cli *Instance, olderVersion, _ string) error {
			return cli.PromoteVersion(cli.cmd, "test/secret", olderVersion)
		}},
		{"version rm --force", false, func(cli *Instance, olderVersion, _ string) error {
			return cli.RemoveVersion(cli.cmd, "test/secret", olderVersion, true)
		}},
		{"vault create", false, func(cli *Instance, _, _ string) error {
			return cli.CreateVault(cli.cmd, "created")
		}},
		{"vault select", false, func(cli *Instance, _, _ string) error {
			return cli.SelectVault(cli.cmd, "other")
		}},
		{"vault import", false, func(cli *Instance, _, _ string) error {
			return cli.VaultImport(cli.cmd, "other")
		}},
		{"vault rm --force", false, func(cli *Instance, _, _ string) error {
			return cli.RemoveVault(cli.cmd, "other", true)
		}},
		{"unlocker add", false, func(cli *Instance, _, _ string) error {
			return cli.UnlockersAdd("passphrase", cli.cmd)
		}},
		{"unlocker rm --force", true, func(cli *Instance, _, unlockerID string) error {
			return cli.UnlockersRemove(unlockerID, true, cli.cmd)
		}},
		{"unlocker select", true, func(cli *Instance, _, unlockerID string) error {
			return cli.UnlockerSelect(unlockerID)
		}},
		{"init", false, func(cli *Instance, _, _ string) error {
			return cli.Init(cli.cmd)
		}},
	} {
		t.Run(tc.name, func(t *testing.T) {
			requireWaitsForLock(t, tc.withUnlocker, tc.run)
		})
	}
}

// TestEncryptWithExistingKeyTakesNoLock checks that secret encrypt with a
// key that already exists, which only reads the state directory, finishes
// while another command holds the state directory lock.
//
//nolint:paralleltest // times commands against the in-memory lock all tests share
func TestEncryptWithExistingKeyTakesNoLock(t *testing.T) {
	mnemonic := testMnemonicBuffer(t)

	fs := afero.NewMemMapFs()
	_, err := vault.CreateVault(fs, testStateDir, "default", mnemonic)
	require.NoError(t, err)
	require.NoError(t, afero.WriteFile(fs, testInput, []byte("input"), 0o600))

	encrypt := NewCLIInstanceWithStateDir(fs, testStateDir)
	encrypt.Mnemonic = mnemonic
	encrypt.cmd = &cobra.Command{}
	encrypt.cmd.SetOut(io.Discard)

	// Stores the key
	require.NoError(t, encrypt.Encrypt("key", testInput, ""))

	release, err := vault.LockStateDir(fs, testStateDir)
	require.NoError(t, err)
	// Also frees a waiting encrypt if the test fails, so that it releases
	// the lock the other tests use
	defer release()

	done := make(chan error, 1)

	go func() { done <- encrypt.Encrypt("key", testInput, "") }()

	select {
	case err := <-done:
		require.NoError(t, err)
	case <-time.After(lockWait):
		t.Fatal("secret encrypt with an existing key waited for the lock")
	}
}

// TestEncryptStreamsUnlocked checks that secret encrypt has released the
// state directory lock by the time it writes its output. Holding it while
// streaming would stall every other changing command for as long as the
// stream lasts, and forever when the other end of the pipe is one of them.
//
//nolint:paralleltest // times commands against the in-memory lock all tests share
func TestEncryptStreamsUnlocked(t *testing.T) {
	fs := afero.NewMemMapFs()
	_, err := vault.CreateVault(fs, testStateDir, "default", testMnemonicBuffer(t))
	require.NoError(t, err)
	require.NoError(t, afero.WriteFile(fs, testInput, []byte("streamed"), 0o600))

	outputReader, outputWriter := io.Pipe()
	done := make(chan error, 1)

	go func() {
		encrypt := NewCLIInstanceWithStateDir(fs, testStateDir)
		encrypt.cmd = &cobra.Command{}
		encrypt.cmd.SetOut(outputWriter)

		err := encrypt.Encrypt("key", testInput, "")
		_ = outputWriter.CloseWithError(err)

		done <- err
	}()

	// The first byte of output: encrypt is streaming now, and blocked
	// writing until it is read
	_, err = io.ReadFull(outputReader, make([]byte, 1))
	require.NoError(t, err)

	taken := lockInBackground(t, fs)

	select {
	case release := <-taken:
		release()
	case <-time.After(lockWait):
		// Let encrypt finish, so that it releases the lock, then free it
		// again for the tests that follow
		_, _ = io.Copy(io.Discard, outputReader)

		(<-taken)()
		t.Fatal("secret encrypt held the lock while streaming")
	}

	_, err = io.Copy(io.Discard, outputReader)
	require.NoError(t, err)
	require.NoError(t, <-done)
}