package symlinkguard

import (
	"context"
	"errors"
	"os"
	"path/filepath"
	"sync"
	"testing"
	"time"

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

// hyperguild#157: the brain dir is a Syncthing sendreceive folder and
// Syncthing syncs symlinks; several readers follow them out of the brain.
// Until every reader goes through an os.Root, a symlink anywhere in the brain,
// or a directory the scan cannot read (which could hide one), is an incident.

func TestScanReportsSymlinksAtEveryDepthIncludingNestedGit(t *testing.T) {
	brain := t.TempDir()
	outside := t.TempDir()
	require.NoError(t, os.MkdirAll(filepath.Join(brain, "wiki", "w", "facts", ".git"), 0o755))
	require.NoError(t, os.MkdirAll(filepath.Join(brain, ".git", "objects"), 0o755))
	require.NoError(t, os.Symlink(filepath.Join(outside, "f"), filepath.Join(brain, "wiki", "w", "facts", "leak.md")))
	require.NoError(t, os.Symlink(outside, filepath.Join(brain, "wiki", "dirlink")))
	// PR #159 review: only the ROOT .git is skipped; a nested .git is not
	// special to the brain readers, which walk into it.
	require.NoError(t, os.Symlink(filepath.Join(outside, "g"), filepath.Join(brain, "wiki", "w", "facts", ".git", "leak.md")))
	require.NoError(t, os.Symlink(outside, filepath.Join(brain, ".git", "objects", "alt")))

	r, err := Scan(brain)
	require.NoError(t, err)
	assert.ElementsMatch(t, []string{"wiki/w/facts/leak.md", "wiki/dirlink", "wiki/w/facts/.git/leak.md"}, r.Symlinks)
	assert.Empty(t, r.Unreadable)
}

// PR #159 review: WalkDir stopped at the first unreadable directory and the
// startup check passed, while search (which keeps walking) served a planted
// symlink. Scan now records the unreadable dir and keeps going.
func TestScanReportsUnreadableDirsAndKeepsWalkingPastThem(t *testing.T) {
	if os.Geteuid() == 0 {
		t.Skip("root reads mode-000 directories")
	}
	brain := t.TempDir()
	locked := filepath.Join(brain, "aaa")
	require.NoError(t, os.MkdirAll(locked, 0o755))
	require.NoError(t, os.Chmod(locked, 0o000))
	t.Cleanup(func() { _ = os.Chmod(locked, 0o755) })
	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(brain, "zzz-planted")))

	r, err := Scan(brain)
	require.NoError(t, err)
	assert.Equal(t, []string{"aaa"}, r.Unreadable)
	assert.Equal(t, []string{"zzz-planted"}, r.Symlinks, "the walk continues past the unreadable dir")
}

func TestScanResolvesASymlinkedRootAndReportsSymlinkedEntriesInsideIt(t *testing.T) {
	real := t.TempDir()
	link := filepath.Join(t.TempDir(), "brain")
	require.NoError(t, os.Symlink(real, link))
	require.NoError(t, os.WriteFile(filepath.Join(real, "n.md"), []byte("x"), 0o644))
	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(real, "inner")))
	r, err := Scan(link)
	require.NoError(t, err)
	assert.Equal(t, []string{"inner"}, r.Symlinks)
}

func TestScanOfAMissingRootIsErrNotExist(t *testing.T) {
	_, err := Scan(filepath.Join(t.TempDir(), "nope"))
	assert.True(t, errors.Is(err, os.ErrNotExist), "got %v", err)
}

type recNotifier struct {
	mu   sync.Mutex
	msgs []string
	fail int // fail the first N calls
}

func (r *recNotifier) Notify(_ context.Context, m string) error {
	r.mu.Lock()
	defer r.mu.Unlock()
	r.msgs = append(r.msgs, m)
	if r.fail > 0 {
		r.fail--
		return errors.New("ntfy down")
	}
	return nil
}

func (r *recNotifier) count() int { r.mu.Lock(); defer r.mu.Unlock(); return len(r.msgs) }

func TestWatchNotifiesOncePerDistinctSetAndAgainForANewSet(t *testing.T) {
	brain := t.TempDir()
	n := &recNotifier{}
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	go Watch(ctx, brain, 10*time.Millisecond, n)

	time.Sleep(50 * time.Millisecond)
	assert.Zero(t, n.count(), "a clean brain raises nothing")
	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(brain, "first")))
	require.Eventually(t, func() bool { return n.count() == 1 }, 2*time.Second, 10*time.Millisecond)
	time.Sleep(60 * time.Millisecond)
	assert.Equal(t, 1, n.count(), "the same set is reported once, not every tick")
	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(brain, "second")))
	require.Eventually(t, func() bool { return n.count() == 2 }, 2*time.Second, 10*time.Millisecond)
}

// PR #159 review: last was recorded before Notify, so an alert lost to an
// ntfy outage was never retried while the symlink stayed.
func TestWatchRetriesAnAlertThatFailedToSend(t *testing.T) {
	brain := t.TempDir()
	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(brain, "planted")))
	n := &recNotifier{fail: 2}
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	go Watch(ctx, brain, 10*time.Millisecond, n)
	require.Eventually(t, func() bool { return n.count() == 3 }, 2*time.Second, 10*time.Millisecond)
	time.Sleep(60 * time.Millisecond)
	assert.Equal(t, 3, n.count(), "after one successful send, no more")
}

func TestWatchAlertsOnAnUnreadableDir(t *testing.T) {
	if os.Geteuid() == 0 {
		t.Skip("root reads mode-000 directories")
	}
	brain := t.TempDir()
	locked := filepath.Join(brain, "locked")
	require.NoError(t, os.MkdirAll(locked, 0o755))
	require.NoError(t, os.Chmod(locked, 0o000))
	t.Cleanup(func() { _ = os.Chmod(locked, 0o755) })
	n := &recNotifier{}
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	go Watch(ctx, brain, 10*time.Millisecond, n)
	require.Eventually(t, func() bool { return n.count() == 1 }, 2*time.Second, 10*time.Millisecond)
	assert.Contains(t, n.msgs[0], "locked")
}

// PR #159 review: a non-positive interval panicked time.NewTicker inside the
// goroutine and crashlooped the server.
func TestWatchToleratesANonPositiveInterval(t *testing.T) {
	brain := t.TempDir()
	ctx, cancel := context.WithCancel(context.Background())
	done := make(chan struct{})
	go func() { Watch(ctx, brain, 0, nil); close(done) }()
	cancel()
	select {
	case <-done:
	case <-time.After(2 * time.Second):
		t.Fatal("Watch did not return on cancel")
	}
}

// PR #159 round 2: a brain root that can be entered but not listed (mode
// 0100) made WalkDir fail at the root; the error was discarded and Scan
// reported clean, while search (which goes straight into wiki/) still served
// a planted symlink. A root that cannot be listed is now an error.
func TestScanOfAnUnlistableRootIsAnError(t *testing.T) {
	if os.Geteuid() == 0 {
		t.Skip("root lists mode-0100 directories")
	}
	brain := t.TempDir()
	require.NoError(t, os.MkdirAll(filepath.Join(brain, "wiki"), 0o755))
	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(brain, "wiki", "leak.md")))
	require.NoError(t, os.Chmod(brain, 0o100))
	t.Cleanup(func() { _ = os.Chmod(brain, 0o755) })
	_, err := Scan(brain)
	require.Error(t, err)
	assert.False(t, errors.Is(err, os.ErrNotExist), "an unlistable root is not a missing root")
}

// The same set that disappears and comes back is reported again.
func TestWatchReportsASetAgainAfterItWasCleared(t *testing.T) {
	brain := t.TempDir()
	link := filepath.Join(brain, "planted")
	n := &recNotifier{}
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	go Watch(ctx, brain, 10*time.Millisecond, n)
	require.NoError(t, os.Symlink(t.TempDir(), link))
	require.Eventually(t, func() bool { return n.count() == 1 }, 2*time.Second, 10*time.Millisecond)
	require.NoError(t, os.Remove(link))
	time.Sleep(60 * time.Millisecond)
	require.NoError(t, os.Symlink(t.TempDir(), link))
	require.Eventually(t, func() bool { return n.count() == 2 }, 2*time.Second, 10*time.Millisecond)
}