package transformers

import (
	"context"
	"errors"
	"sync"
	"testing"
	"time"

	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/config"
	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/custom_errors"
	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/models"
	"github.com/google/uuid"
)

const testTimeout = 2 * time.Second

func makeBatch(numRows int) models.Batch {
	rows := make([]models.UnknownRowValues, numRows)
	for i := range rows {
		rows[i] = models.UnknownRowValues{i}
	}
	return models.Batch{Id: uuid.New(), Rows: rows}
}

func noRetry() config.RetryConfig {
	return config.RetryConfig{Attempts: 1}
}

func newTransformer() *MssqlTransformer {
	return &MssqlTransformer{}
}

func uuidColumn() models.ColumnType {
	return models.NewColumnType("col_uuid", false, false, "uniqueidentifier", "uniqueidentifier", "string", false, 0, 0, 0)
}

func runConsume(
	ctx context.Context,
	tr *MssqlTransformer,
	columns []models.ColumnType,
	batchSize int,
	chIn <-chan models.Batch,
	chOut chan<- models.Batch,
	chErr chan<- custom_errors.JobError,
	wg *sync.WaitGroup,
) <-chan struct{} {
	done := make(chan struct{})
	go func() {
		tr.Consume(ctx, columns, noRetry(), batchSize, chIn, chOut, chErr, wg)
		close(done)
	}()
	return done
}

func drainOut(chOut <-chan models.Batch, wg *sync.WaitGroup) []models.Batch {
	var batches []models.Batch
	for {
		select {
		case b := <-chOut:
			batches = append(batches, b)
			wg.Done()
		default:
			return batches
		}
	}
}
func TestBatchAccumulator_Add(t *testing.T) {
	acc := &batchAccumulator{batchSize: 5}
	b1 := makeBatch(2)
	b2 := makeBatch(3)

	acc.add(b1)
	acc.add(b2)

	if len(acc.rows) != 5 {
		t.Errorf("expected 5 rows, got %d", len(acc.rows))
	}
	if len(acc.parents) != 2 {
		t.Fatalf("expected 2 parents, got %d", len(acc.parents))
	}
	if acc.parents[0].Id != b1.Id || acc.parents[1].Id != b2.Id {
		t.Error("parent IDs do not match source batch IDs")
	}
}

func TestBatchAccumulator_Ready(t *testing.T) {
	acc := &batchAccumulator{batchSize: 3}
	acc.add(makeBatch(2))
	if acc.ready() {
		t.Error("should not be ready with 2 rows and batchSize=3")
	}
	acc.add(makeBatch(1))
	if !acc.ready() {
		t.Error("should be ready with 3 rows and batchSize=3")
	}
}

func TestBatchAccumulator_Flush_Empty(t *testing.T) {
	acc := &batchAccumulator{batchSize: 5}
	chOut := make(chan models.Batch, 1)
	var wg sync.WaitGroup

	if !acc.flush(context.Background(), chOut, &wg) {
		t.Error("flush on empty accumulator should return true")
	}
	if len(chOut) != 0 {
		t.Error("flush on empty accumulator should send nothing")
	}
}

func TestBatchAccumulator_Flush_Success(t *testing.T) {
	acc := &batchAccumulator{batchSize: 2}
	b := makeBatch(2)
	acc.add(b)

	chOut := make(chan models.Batch, 1)
	var wg sync.WaitGroup

	if !acc.flush(context.Background(), chOut, &wg) {
		t.Fatal("flush should return true on success")
	}

	select {
	case out := <-chOut:
		wg.Done()
		if len(out.Rows) != 2 {
			t.Errorf("expected 2 rows in flushed batch, got %d", len(out.Rows))
		}
		if len(out.ParentBatches) != 1 || out.ParentBatches[0].Id != b.Id {
			t.Error("flushed batch should reference the source batch as parent")
		}
	default:
		t.Error("expected a batch in chOut after flush")
	}

	if len(acc.rows) != 0 || len(acc.parents) != 0 {
		t.Error("accumulator state should be reset after flush")
	}
	wg.Wait()
}

func TestBatchAccumulator_Flush_ContextCancelled(t *testing.T) {
	acc := &batchAccumulator{batchSize: 2}
	acc.add(makeBatch(2))

	chOut := make(chan models.Batch)
	var wg sync.WaitGroup

	ctx, cancel := context.WithCancel(context.Background())
	cancel()

	if acc.flush(ctx, chOut, &wg) {
		t.Error("flush should return false when context is cancelled")
	}

	wg.Wait()
}

func TestSendTransformError_PlainError(t *testing.T) {
	ch := make(chan custom_errors.JobError, 1)

	sendTransformError(context.Background(), errors.New("something broke"), ch)

	select {
	case e := <-ch:
		if !e.ShouldCancelJob {
			t.Error("plain error should produce ShouldCancelJob=true")
		}
	default:
		t.Error("expected a job error in the channel")
	}
}

func TestSendTransformError_JobError_Passthrough(t *testing.T) {
	ch := make(chan custom_errors.JobError, 1)
	original := &custom_errors.JobError{ShouldCancelJob: false, Msg: "custom msg"}

	sendTransformError(context.Background(), original, ch)

	select {
	case e := <-ch:
		if e.ShouldCancelJob != false || e.Msg != "custom msg" {
			t.Errorf("JobError should pass through unchanged, got %+v", e)
		}
	default:
		t.Error("expected a job error in the channel")
	}
}

func TestSendTransformError_ContextCancelled_Silent(t *testing.T) {
	ch := make(chan custom_errors.JobError, 1)

	ctx, cancel := context.WithCancel(context.Background())
	cancel()

	sendTransformError(ctx, context.Canceled, ch)

	if len(ch) != 0 {
		t.Error("context.Canceled should be silently dropped")
	}
}

func TestSendTransformError_DeadlineExceeded_Silent(t *testing.T) {
	ch := make(chan custom_errors.JobError, 1)

	ctx, cancel := context.WithCancel(context.Background())
	cancel()

	sendTransformError(ctx, context.DeadlineExceeded, ch)

	if len(ch) != 0 {
		t.Error("context.DeadlineExceeded should be silently dropped")
	}
}

func TestConsume_Passthrough_PreservesOriginalBatch(t *testing.T) {
	tr := newTransformer()
	chIn := make(chan models.Batch, 1)
	chOut := make(chan models.Batch, 1)
	chErr := make(chan custom_errors.JobError, 1)
	var wg sync.WaitGroup

	batch := makeBatch(3)
	chIn <- batch
	close(chIn)

	done := runConsume(context.Background(), tr, nil, 0, chIn, chOut, chErr, &wg)

	select {
	case got := <-chOut:
		wg.Done()
		if got.Id != batch.Id {
			t.Error("passthrough should preserve the original batch ID")
		}
		if len(got.Rows) != 3 {
			t.Errorf("expected 3 rows, got %d", len(got.Rows))
		}
	case <-time.After(testTimeout):
		t.Fatal("timeout waiting for output batch")
	}

	<-done
	wg.Wait()
}

func TestConsume_Passthrough_WaitGroupBalanced(t *testing.T) {
	tr := newTransformer()
	chIn := make(chan models.Batch, 3)
	chOut := make(chan models.Batch, 3)
	chErr := make(chan custom_errors.JobError, 1)
	var wg sync.WaitGroup

	for range 3 {
		chIn <- makeBatch(1)
	}
	close(chIn)

	done := runConsume(context.Background(), tr, nil, 0, chIn, chOut, chErr, &wg)
	<-done

	batches := drainOut(chOut, &wg)
	if len(batches) != 3 {
		t.Errorf("expected 3 output batches, got %d", len(batches))
	}

	wg.Wait()
}

func TestConsume_Accumulation_FlushOnThreshold(t *testing.T) {
	tr := newTransformer()
	chIn := make(chan models.Batch, 3)
	chOut := make(chan models.Batch, 2)
	chErr := make(chan custom_errors.JobError, 1)
	var wg sync.WaitGroup

	for range 3 {
		chIn <- makeBatch(1)
	}
	close(chIn)

	done := runConsume(context.Background(), tr, nil, 3, chIn, chOut, chErr, &wg)
	<-done

	batches := drainOut(chOut, &wg)
	if len(batches) != 1 {
		t.Fatalf("expected 1 accumulated batch, got %d", len(batches))
	}
	if len(batches[0].Rows) != 3 {
		t.Errorf("expected 3 rows in accumulated batch, got %d", len(batches[0].Rows))
	}
	wg.Wait()
}

func TestConsume_Accumulation_FlushOnClose(t *testing.T) {
	tr := newTransformer()
	chIn := make(chan models.Batch, 2)
	chOut := make(chan models.Batch, 2)
	chErr := make(chan custom_errors.JobError, 1)
	var wg sync.WaitGroup

	chIn <- makeBatch(1)
	chIn <- makeBatch(1)
	close(chIn)

	done := runConsume(context.Background(), tr, nil, 10, chIn, chOut, chErr, &wg)
	<-done

	batches := drainOut(chOut, &wg)
	if len(batches) != 1 {
		t.Fatalf("expected 1 batch flushed on close, got %d", len(batches))
	}
	if len(batches[0].Rows) != 2 {
		t.Errorf("expected 2 rows, got %d", len(batches[0].Rows))
	}
	wg.Wait()
}

func TestConsume_Accumulation_TracksAllParentBatches(t *testing.T) {
	tr := newTransformer()
	chIn := make(chan models.Batch, 2)
	chOut := make(chan models.Batch, 2)
	chErr := make(chan custom_errors.JobError, 1)
	var wg sync.WaitGroup

	b1 := makeBatch(1)
	b2 := makeBatch(1)
	chIn <- b1
	chIn <- b2
	close(chIn)

	done := runConsume(context.Background(), tr, nil, 10, chIn, chOut, chErr, &wg)
	<-done

	batches := drainOut(chOut, &wg)
	if len(batches) != 1 {
		t.Fatalf("expected 1 output batch, got %d", len(batches))
	}
	parents := batches[0].ParentBatches
	if len(parents) != 2 {
		t.Fatalf("expected 2 parent refs, got %d", len(parents))
	}
	if parents[0].Id != b1.Id || parents[1].Id != b2.Id {
		t.Error("parent IDs should match source batch IDs in order")
	}
	wg.Wait()
}

func TestConsume_Accumulation_MultipleFlushes(t *testing.T) {
	tr := newTransformer()
	chIn := make(chan models.Batch, 5)
	chOut := make(chan models.Batch, 5)
	chErr := make(chan custom_errors.JobError, 1)
	var wg sync.WaitGroup

	for range 5 {
		chIn <- makeBatch(1)
	}
	close(chIn)

	done := runConsume(context.Background(), tr, nil, 2, chIn, chOut, chErr, &wg)
	<-done

	batches := drainOut(chOut, &wg)
	if len(batches) != 3 {
		t.Fatalf("expected 3 output batches (2+2+1 rows), got %d", len(batches))
	}
	totalRows := 0
	for _, b := range batches {
		totalRows += len(b.Rows)
	}
	if totalRows != 5 {
		t.Errorf("expected 5 total rows across all batches, got %d", totalRows)
	}
	wg.Wait()
}

func TestConsume_EmptyInput_NoOutput(t *testing.T) {
	tr := newTransformer()
	chIn := make(chan models.Batch)
	chOut := make(chan models.Batch, 1)
	chErr := make(chan custom_errors.JobError, 1)
	var wg sync.WaitGroup

	close(chIn)

	done := runConsume(context.Background(), tr, nil, 5, chIn, chOut, chErr, &wg)

	select {
	case <-done:
	case <-time.After(testTimeout):
		t.Fatal("timeout: Consume did not exit after empty input channel was closed")
	}

	if len(chOut) != 0 {
		t.Error("expected no output for empty input")
	}
	wg.Wait()
}

func TestConsume_TransformError_SendsJobError(t *testing.T) {
	tr := newTransformer()
	col := uuidColumn()

	chIn := make(chan models.Batch, 1)
	chOut := make(chan models.Batch, 1)
	chErr := make(chan custom_errors.JobError, 1)
	var wg sync.WaitGroup

	batch := models.Batch{
		Id:   uuid.New(),
		Rows: []models.UnknownRowValues{{[]byte{1, 2, 3}}},
	}
	chIn <- batch

	done := runConsume(context.Background(), tr, []models.ColumnType{col}, 0, chIn, chOut, chErr, &wg)

	select {
	case err := <-chErr:
		if !err.ShouldCancelJob {
			t.Error("transform error should set ShouldCancelJob=true")
		}
	case <-time.After(testTimeout):
		t.Fatal("timeout: expected a job error from transform failure")
	}

	<-done
	wg.Wait()
}

func TestConsume_TransformError_NoOutputForwarded(t *testing.T) {
	tr := newTransformer()
	col := uuidColumn()

	chIn := make(chan models.Batch, 1)
	chOut := make(chan models.Batch, 1)
	chErr := make(chan custom_errors.JobError, 1)
	var wg sync.WaitGroup

	batch := models.Batch{
		Id:   uuid.New(),
		Rows: []models.UnknownRowValues{{[]byte{1, 2, 3}}},
	}
	chIn <- batch

	done := runConsume(context.Background(), tr, []models.ColumnType{col}, 0, chIn, chOut, chErr, &wg)
	<-done

	if len(chOut) != 0 {
		t.Error("no batch should be forwarded when transformation fails")
	}
	wg.Wait()
}

func TestConsume_ContextCancellation_Exits(t *testing.T) {
	tr := newTransformer()
	chIn := make(chan models.Batch)
	chOut := make(chan models.Batch, 1)
	chErr := make(chan custom_errors.JobError, 1)
	var wg sync.WaitGroup

	ctx, cancel := context.WithCancel(context.Background())
	done := runConsume(ctx, tr, nil, 0, chIn, chOut, chErr, &wg)

	cancel()

	select {
	case <-done:
	case <-time.After(testTimeout):
		t.Fatal("timeout: Consume did not exit after context cancellation")
	}
	wg.Wait()
}

func TestConsume_Transform_DatetimeConvertedToUTC(t *testing.T) {
	tr := newTransformer()
	col := models.NewColumnType("col_dt", false, false, "datetime", "datetime", "timestamp", false, 0, 0, 0)

	chIn := make(chan models.Batch, 1)
	chOut := make(chan models.Batch, 1)
	chErr := make(chan custom_errors.JobError, 1)
	var wg sync.WaitGroup

	nonUTC := time.Date(2024, 1, 15, 12, 0, 0, 0, time.FixedZone("EST", -5*3600))
	batch := models.Batch{
		Id:   uuid.New(),
		Rows: []models.UnknownRowValues{{nonUTC}},
	}
	chIn <- batch
	close(chIn)

	done := runConsume(context.Background(), tr, []models.ColumnType{col}, 0, chIn, chOut, chErr, &wg)
	<-done

	select {
	case got := <-chOut:
		wg.Done()
		result, ok := got.Rows[0][0].(time.Time)
		if !ok {
			t.Fatal("expected time.Time in output row")
		}
		if result.Location() != time.UTC {
			t.Errorf("expected UTC location after transform, got %v", result.Location())
		}
	default:
		t.Error("expected an output batch")
	}

	wg.Wait()
}

func TestConsume_Transform_NilValueSkipped(t *testing.T) {
	tr := newTransformer()
	col := uuidColumn()

	chIn := make(chan models.Batch, 1)
	chOut := make(chan models.Batch, 1)
	chErr := make(chan custom_errors.JobError, 1)
	var wg sync.WaitGroup

	batch := models.Batch{
		Id:   uuid.New(),
		Rows: []models.UnknownRowValues{{nil}},
	}
	chIn <- batch
	close(chIn)

	done := runConsume(context.Background(), tr, []models.ColumnType{col}, 0, chIn, chOut, chErr, &wg)
	<-done

	select {
	case got := <-chOut:
		wg.Done()
		if got.Rows[0][0] != nil {
			t.Error("nil value should pass through unchanged")
		}
	default:
		t.Error("expected an output batch even when value is nil")
	}

	if len(chErr) != 0 {
		t.Error("nil value should not produce an error")
	}
	wg.Wait()
}