package notify

import (
	"context"
	"io"
	"testing"
	"time"

	itransfer "b612.me/notify/internal/transfer"
)

type transferDelayedSource struct {
	*transferBytesSource
	delay time.Duration
}

func newTransferDelayedSource(data []byte, delay time.Duration) *transferDelayedSource {
	return &transferDelayedSource{
		transferBytesSource: newTransferBytesSource(data),
		delay:               delay,
	}
}

func (s *transferDelayedSource) ReadAt(p []byte, off int64) (int, error) {
	time.Sleep(s.delay)
	return s.transferBytesSource.ReadAt(p, off)
}

type transferDelayedWriteStream struct {
	transferWriteCountStream
	delay time.Duration
}

func (s *transferDelayedWriteStream) Write(p []byte) (int, error) {
	time.Sleep(s.delay)
	return s.transferWriteCountStream.Write(p)
}

type transferDelayedCommitSink struct {
	data        []byte
	writeDelay  time.Duration
	syncDelay   time.Duration
	commitDelay time.Duration
}

func newTransferDelayedCommitSink(size int, writeDelay time.Duration, syncDelay time.Duration, commitDelay time.Duration) *transferDelayedCommitSink {
	return &transferDelayedCommitSink{
		data:        make([]byte, size),
		writeDelay:  writeDelay,
		syncDelay:   syncDelay,
		commitDelay: commitDelay,
	}
}

func (s *transferDelayedCommitSink) WriteAt(p []byte, off int64) (int, error) {
	time.Sleep(s.writeDelay)
	if off < 0 {
		return 0, io.ErrShortWrite
	}
	if int(off) > len(s.data) || len(p) > len(s.data)-int(off) {
		return 0, io.ErrShortWrite
	}
	copy(s.data[off:], p)
	return len(p), nil
}

func (s *transferDelayedCommitSink) ReadAt(p []byte, off int64) (int, error) {
	if off < 0 || off >= int64(len(s.data)) {
		return 0, io.EOF
	}
	n := copy(p, s.data[off:])
	if n < len(p) {
		return n, io.EOF
	}
	return n, nil
}

func (s *transferDelayedCommitSink) Sync(context.Context) error {
	time.Sleep(s.syncDelay)
	return nil
}

func (s *transferDelayedCommitSink) Commit(context.Context) error {
	time.Sleep(s.commitDelay)
	return nil
}

func transferRuntimeSnapshotForTest(t *testing.T, runtime *transferRuntime, direction fileTransferDirection, scope string, transferID string) TransferSnapshot {
	t.Helper()
	snapshot, ok := runtime.snapshot(direction, scope, transferID)
	if !ok {
		t.Fatalf("runtime snapshot missing for %s", transferID)
	}
	return convertTransferSnapshot(snapshot)
}

func TestSendTransferSegmentsRecordsTelemetry(t *testing.T) {
	const (
		chunkSize  = 4
		readDelay  = 5 * time.Millisecond
		writeDelay = 4 * time.Millisecond
	)
	data := []byte("0123456789abcdef")
	runtime := newTransferRuntime()
	scope := clientFileScope()
	transferID := "telemetry-send"
	runtime.ensureTransferDescriptor(fileTransferDirectionSend, scope, scope, 0, itransfer.Descriptor{
		ID:      transferID,
		Channel: itransfer.DataChannel,
		Size:    int64(len(data)),
	})

	target := transferSendTarget{
		runtime:      runtime,
		runtimeScope: scope,
		sequenceEn: func(value interface{}) ([]byte, error) {
			segment, ok := value.(itransfer.Segment)
			if !ok {
				t.Fatalf("encoded value type = %T, want itransfer.Segment", value)
			}
			return append([]byte(nil), segment.Payload...), nil
		},
	}
	stream := &transferDelayedWriteStream{delay: writeDelay}
	opt := TransferSendOptions{
		Descriptor: TransferDescriptor{
			ID:      transferID,
			Channel: TransferChannelData,
			Size:    int64(len(data)),
		},
		Source:    newTransferDelayedSource(data, readDelay),
		ChunkSize: chunkSize,
	}

	if err := sendTransferSegments(context.Background(), stream, target, opt, 0, transferSendHooks{}); err != nil {
		t.Fatalf("sendTransferSegments failed: %v", err)
	}

	snapshot := transferRuntimeSnapshotForTest(t, runtime, fileTransferDirectionSend, scope, transferID)
	if got, want := snapshot.SourceReadCount, len(data)/chunkSize; got != want {
		t.Fatalf("source read count = %d, want %d", got, want)
	}
	if got := snapshot.SourceReadDuration; got < time.Duration(snapshot.SourceReadCount)*readDelay {
		t.Fatalf("source read duration = %v, want at least %v", got, time.Duration(snapshot.SourceReadCount)*readDelay)
	}
	if got := snapshot.StreamWriteCount; got < 1 {
		t.Fatalf("stream write count = %d, want at least 1", got)
	}
	if got := snapshot.StreamWriteDuration; got < writeDelay {
		t.Fatalf("stream write duration = %v, want at least %v", got, writeDelay)
	}
}

func TestTransferReceiveSessionCommitRecordsTelemetry(t *testing.T) {
	const (
		writeDelay  = 4 * time.Millisecond
		syncDelay   = 3 * time.Millisecond
		commitDelay = 5 * time.Millisecond
	)
	data := []byte("abcdefgh")
	transferID := "telemetry-receive"
	scope := clientFileScope()
	runtime := newTransferRuntime()
	runtime.ensureTransferDescriptor(fileTransferDirectionReceive, scope, scope, 0, itransfer.Descriptor{
		ID:       transferID,
		Channel:  itransfer.DataChannel,
		Size:     int64(len(data)),
		Checksum: transferTestChecksum(data),
	})

	sink := newTransferDelayedCommitSink(len(data), writeDelay, syncDelay, commitDelay)
	session := newTransferReceiveSession(scope, scope, nil, nil, 0, TransferReceiveOptions{
		Descriptor: TransferDescriptor{
			ID:       transferID,
			Channel:  TransferChannelData,
			Size:     int64(len(data)),
			Checksum: transferTestChecksum(data),
		},
		Sink:             sink,
		SyncOnCheckpoint: true,
		VerifyChecksum:   true,
	})

	if err := session.writeSegment(runtime, transferID, 0, data[:4]); err != nil {
		t.Fatalf("writeSegment first failed: %v", err)
	}
	if err := session.writeSegment(runtime, transferID, 4, data[4:]); err != nil {
		t.Fatalf("writeSegment second failed: %v", err)
	}
	if err := session.commit(context.Background(), runtime, transferID); err != nil {
		t.Fatalf("commit failed: %v", err)
	}

	snapshot := transferRuntimeSnapshotForTest(t, runtime, fileTransferDirectionReceive, scope, transferID)
	if got, want := snapshot.SinkWriteCount, 2; got != want {
		t.Fatalf("sink write count = %d, want %d", got, want)
	}
	if got := snapshot.SinkWriteDuration; got < 2*writeDelay {
		t.Fatalf("sink write duration = %v, want at least %v", got, 2*writeDelay)
	}
	if got := snapshot.SyncDuration; got < 3*syncDelay {
		t.Fatalf("sync duration = %v, want at least %v", got, 3*syncDelay)
	}
	if got := snapshot.VerifyDuration; got <= 0 {
		t.Fatalf("verify duration = %v, want > 0", got)
	}
	if got := snapshot.CommitDuration; got < commitDelay {
		t.Fatalf("commit duration = %v, want at least %v", got, commitDelay)
	}
}

func TestRunTransferSendRecordsCommitWaitTelemetry(t *testing.T) {
	const commitDelay = 6 * time.Millisecond
	data := []byte("commit-wait")
	transferID := "telemetry-commit-wait"
	scope := clientFileScope()
	runtime := newTransferRuntime()
	runtime.ensureTransferDescriptor(fileTransferDirectionSend, scope, scope, 0, itransfer.Descriptor{
		ID:      transferID,
		Channel: itransfer.DataChannel,
		Size:    int64(len(data)),
	})

	target := transferSendTarget{
		runtime:      runtime,
		runtimeScope: scope,
		sequenceEn: func(value interface{}) ([]byte, error) {
			segment, ok := value.(itransfer.Segment)
			if !ok {
				t.Fatalf("encoded value type = %T, want itransfer.Segment", value)
			}
			return append([]byte(nil), segment.Payload...), nil
		},
		sendCommit: func(context.Context, TransferCommitRequest) (TransferCommitResponse, error) {
			time.Sleep(commitDelay)
			return TransferCommitResponse{TransferID: transferID, Accepted: true}, nil
		},
	}
	opt := TransferSendOptions{
		Descriptor: TransferDescriptor{
			ID:      transferID,
			Channel: TransferChannelData,
			Size:    int64(len(data)),
		},
		Source:    newTransferBytesSource(data),
		ChunkSize: len(data),
	}

	if err := runTransferSend(context.Background(), transferDiscardStream{}, opt, 0, target, transferSendHooks{}); err != nil {
		t.Fatalf("runTransferSend failed: %v", err)
	}

	snapshot := transferRuntimeSnapshotForTest(t, runtime, fileTransferDirectionSend, scope, transferID)
	if got := snapshot.CommitWaitDuration; got < commitDelay {
		t.Fatalf("commit wait duration = %v, want at least %v", got, commitDelay)
	}
}