package lease

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

	"github.com/benbjohnson/litestream"
	lsfile "github.com/benbjohnson/litestream/file"
)

func TestGenerationRefusedSnapshotReleasesWAL(t *testing.T) {
	path := filepath.Join(t.TempDir(), "source.db")
	seedDB(t, path)
	db := litestream.NewDB(path)
	db.MonitorInterval = 0
	db.Replica = litestream.NewReplicaWithClient(db, lsfile.NewReplicaClient(t.TempDir()))
	db.Replica.MonitorEnabled = false
	if err := db.Open(); err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() { db.Close(context.Background()) })
	if err := db.SyncAndWait(t.Context()); err != nil {
		t.Fatal(err)
	}
	countWAL := func() int {
		t.Helper()
		fds, err := os.ReadDir("/proc/self/fd")
		if err != nil {
			t.Fatal(err)
		}
		count := 0
		for _, fd := range fds {
			name, err := os.Readlink(filepath.Join("/proc/self/fd", fd.Name()))
			if err == nil && name == path+"-wal" {
				count++
			}
		}
		return count
	}
	baseline := countWAL()
	pos, reader, err := db.SnapshotReader(t.Context())
	if err != nil {
		t.Fatal(err)
	}
	pipe := reader.(*io.PipeReader)
	t.Cleanup(func() { pipe.Close() })
	deadline := time.Now().Add(time.Second)
	for countWAL() == baseline && time.Now().Before(deadline) {
		time.Sleep(time.Millisecond)
	}
	if countWAL() <= baseline {
		t.Fatal("snapshot did not hold its WAL descriptor")
	}
	client := &generationClient{client: db.Replica.Client, check: func(context.Context) error { return ErrLost }}
	if _, err := client.WriteLTXFile(t.Context(), litestream.SnapshotLevel, 1, pos.TXID, reader); !errors.Is(err, ErrLost) {
		t.Fatal(err)
	}
	deadline = time.Now().Add(time.Second)
	for countWAL() > baseline && time.Now().Before(deadline) {
		time.Sleep(time.Millisecond)
	}
	if got := countWAL(); got != baseline {
		t.Fatalf("refused snapshot retained WAL descriptors: got %d, want %d", got, baseline)
	}
}