package loaders

import (
	"context"
	"errors"
	"sync"
	"sync/atomic"

	"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"
	"github.com/sirupsen/logrus"
)

type loaderAccumulator struct {
	batchSize   int
	rows        []models.UnknownRowValues
	parents     []models.BatchRef
	pendingDone int
}

func (a *loaderAccumulator) add(batch models.Batch) {
	a.rows = append(a.rows, batch.Rows...)
	a.parents = append(a.parents, models.BatchRef{Id: batch.Id})
	a.pendingDone++
}

func (a *loaderAccumulator) ready() bool {
	return len(a.rows) >= a.batchSize
}

func (a *loaderAccumulator) drainPending(wg *sync.WaitGroup) {
	for range a.pendingDone {
		wg.Done()
	}
}

func sendLoadError(
	ctx context.Context,
	err error,
	retryConfig config.RetryConfig,
	failedBatchesCount *int32,
	chErrorsOut chan<- custom_errors.JobError,
) bool {
	atomic.AddInt32(failedBatchesCount, 1)

	var jobErr custom_errors.JobError
	if je, ok := errors.AsType[*custom_errors.JobError](err); ok {
		jobErr = *je
	} else {
		jobErr = custom_errors.JobError{ShouldCancelJob: false, Msg: err.Error(), Prev: err}
	}

	select {
	case <-ctx.Done():
		return false
	case chErrorsOut <- jobErr:
	}

	if atomic.LoadInt32(failedBatchesCount) > int32(retryConfig.MaxFailedBatchesLoad) {
		select {
		case <-ctx.Done():
		case chErrorsOut <- custom_errors.JobError{ShouldCancelJob: true, Msg: "Max failed batches (load) reached"}:
		}
		return false
	}

	return true
}

func (gl *GenericLoader) Consume(
	ctx context.Context,
	tableInfo config.TargetTableInfo,
	columns []models.ColumnType,
	retryConfig config.RetryConfig,
	batchSize int,
	chBatchesIn <-chan models.Batch,
	chErrorsOut chan<- custom_errors.JobError,
	wgActiveBatches *sync.WaitGroup,
	rowsLoaded *int64,
	failedBatchesCount *int32,
) {
	colNames := mapSlice(columns, func(col models.ColumnType) string {
		return col.Name()
	})

	acc := &loaderAccumulator{batchSize: batchSize}
	defer acc.drainPending(wgActiveBatches)

	flush := func() bool {
		if len(acc.rows) == 0 {
			return true
		}
		count := len(acc.parents)
		superBatch := models.Batch{
			Id:            uuid.New(),
			ParentBatches: acc.parents,
			Rows:          acc.rows,
		}
		processedRows, err := gl.ProcessBatchWithRetries(ctx, tableInfo, colNames, retryConfig, superBatch)
		for range count {
			wgActiveBatches.Done()
		}
		acc.pendingDone -= count
		acc.rows = nil
		acc.parents = nil

		if err != nil {
			return sendLoadError(ctx, err, retryConfig, failedBatchesCount, chErrorsOut)
		}

		current := atomic.LoadInt64(rowsLoaded)
		logrus.Debugf("Rows loaded (batch loaded): +%v [current=%v] (%s.%s)", processedRows, current, tableInfo.Schema, tableInfo.Table)
		atomic.AddInt64(rowsLoaded, int64(processedRows))
		return true
	}

	for {
		select {
		case <-ctx.Done():
			return

		case batch, ok := <-chBatchesIn:
			if !ok {
				flush()
				return
			}

			if batchSize <= 0 {
				processedRows, err := gl.ProcessBatchWithRetries(ctx, tableInfo, colNames, retryConfig, batch)
				wgActiveBatches.Done()
				if err != nil {
					if !sendLoadError(ctx, err, retryConfig, failedBatchesCount, chErrorsOut) {
						return
					}
					continue
				}
				current := atomic.LoadInt64(rowsLoaded)
				logrus.Debugf("Rows loaded: +%v [current=%v] (%s.%s)", processedRows, current, tableInfo.Schema, tableInfo.Table)
				atomic.AddInt64(rowsLoaded, int64(processedRows))
				continue
			}

			acc.add(batch)
			if acc.ready() {
				if !flush() {
					return
				}
			}
		}
	}
}