package main

import (
	"context"
	"fmt"
	"sync"
	"sync/atomic"
	"time"

	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/config"
	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/custom_errors"
	dbwrapper "git.ksdemosapps.com/kylesoda/go-migrate/internal/app/db-wrapper"
	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/etl"
	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/etl/table_analyzers"
	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/models"
	log "github.com/sirupsen/logrus"
	"golang.org/x/sync/errgroup"
)

func processMigrationJob(
	ctx context.Context,
	targetDbWrapper dbwrapper.DbWrapper,
	sourceTableAnalyzer etl.TableAnalyzer,
	targetTableAnalyzer etl.TableAnalyzer,
	extractor etl.Extractor,
	transformer etl.Transformer,
	loader etl.Loader,
	job config.Job,
) JobResult {
	localCtx, cancel := context.WithCancel(ctx)
	defer cancel()

	result := JobResult{
		JobName:   job.Name,
		StartTime: time.Now(),
	}

	var rowsRead, rowsLoaded, rowsFailed int64

	var wgQueryColumnTypes errgroup.Group
	var sourceColTypes, targetColTypes []models.ColumnType

	wgQueryColumnTypes.Go(func() error {
		var err error
		sourceColTypes, err = sourceTableAnalyzer.QueryColumnTypes(localCtx, job.SourceTable.TableInfo)
		if err != nil {
			return err
		}

		return nil
	})

	wgQueryColumnTypes.Go(func() error {
		var err error
		targetColTypes, err = targetTableAnalyzer.QueryColumnTypes(localCtx, job.TargetTable.TableInfo)
		if err != nil {
			return err
		}

		return nil
	})

	err := wgQueryColumnTypes.Wait()
	if err != nil {
		result.Error = err
		return result
	}

	for _, query := range job.PreSQL {
		if _, err := targetDbWrapper.Exec(localCtx, query); err != nil {
			result.Error = err
			return result
		}
	}

	partitions, err := table_analyzers.PartitionRangeGenerator(
		localCtx,
		sourceTableAnalyzer,
		job.SourceTable.TableInfo,
		job.SourceTable.PrimaryKey,
		job.RowsPerPartition,
	)
	if err != nil {
		log.Error("Unexpected error calculating batch ranges: ", err)
	}

	chJobErrors := make(chan custom_errors.JobError, job.QueueSize)
	chLoadersErrors := make(chan custom_errors.LoaderError, job.QueueSize)
	chPartitions := make(chan models.Partition, job.QueueSize)
	chBatchesRaw := make(chan models.Batch, job.QueueSize)
	chBatchesTransformed := make(chan models.Batch, job.QueueSize)

	var wgActivePartitions sync.WaitGroup
	var wgActiveBatches sync.WaitGroup
	var wgExtractors sync.WaitGroup
	var wgTransformers sync.WaitGroup
	var wgLoaders sync.WaitGroup

	go func() {
		if err := custom_errors.JobErrorHandler(localCtx, chJobErrors); err != nil {
			log.Error("Fatal error received from JobErrorHandler, canceling job... - ", err)
			cancel()
			result.Error = err
		}
	}()

	go custom_errors.LoaderErrorHandler(
		localCtx,
		job.Retry,
		job.MaxChunkErrors,
		chLoadersErrors,
		chBatchesTransformed,
		chJobErrors,
		&wgActiveBatches,
	)

	maxExtractors := min(job.MaxExtractors, len(partitions))
	log.Infof("Starting %d extractor(s)...", maxExtractors)

	for range maxExtractors {
		wgExtractors.Go(func() {
			extractor.Consume(
				localCtx,
				job.SourceTable,
				sourceColTypes,
				job.BatchSize,
				chPartitions,
				chBatchesRaw,
				chJobErrors,
				&wgActivePartitions,
				&rowsRead,
			)
		})
	}

	wgActivePartitions.Add(len(partitions))
	go func() {
		for _, batch := range partitions {
			chPartitions <- batch
		}
	}()

	log.Infof("Starting %d transformer(s)...", maxExtractors)

	for range maxExtractors {
		wgTransformers.Go(func() {
			transformer.Exec(
				localCtx,
				sourceColTypes,
				chBatchesRaw,
				chBatchesTransformed,
				chJobErrors,
				&wgActiveBatches,
			)
		})
	}

	log.Infof("Starting %d loader(s)...", job.MaxLoaders)

	for range job.MaxLoaders {
		wgLoaders.Go(func() {
			loader.Exec(
				localCtx,
				job.TargetTable,
				targetColTypes,
				chBatchesTransformed,
				chLoadersErrors,
				chJobErrors,
				&wgActiveBatches,
				&rowsLoaded,
			)
		})
	}

	go func() {
		log.Debugf("Waiting for goroutines (%v)", job.Name)

		wgActivePartitions.Wait()
		log.Debugf("wgActivePartitions is empty (%v)", job.Name)
		close(chPartitions)
		log.Debugf("chPartitions is closed (%v)", job.Name)

		wgExtractors.Wait()
		log.Debugf("wgExtractors is empty (%v)", job.Name)
		close(chBatchesRaw)
		log.Debugf("chBatchesRaw is closed (%v)", job.Name)

		wgTransformers.Wait()
		log.Debugf("wgTransformers is empty (%v)", job.Name)

		wgActiveBatches.Wait()
		log.Debugf("wgActiveBatches is empty (%v)", job.Name)
		close(chBatchesTransformed)
		log.Debugf("chBatchesTransformed is empty (%v)", job.Name)
		close(chLoadersErrors)
		log.Debugf("chLoadersErrors is empty (%v)", job.Name)

		wgLoaders.Wait()
		log.Debugf("wgLoaders is empty (%v)", job.Name)

		cancel()
	}()

	for _, query := range job.PostSQL {
		if _, err := targetDbWrapper.Exec(localCtx, query); err != nil {
			result.Error = err
			return result
		}
	}

	log.Debugf("waiting for local context to be done (%v)", job.Name)
	<-localCtx.Done()
	log.Debugf("local context done (%v)", job.Name)

	if ctx.Err() != nil {
		result.Error = ctx.Err()
	}

	result.Duration = time.Since(result.StartTime)
	result.RowsRead = atomic.LoadInt64(&rowsRead)
	result.RowsLoaded = atomic.LoadInt64(&rowsLoaded)
	result.RowsFailed = atomic.LoadInt64(&rowsFailed)

	if result.RowsRead != result.RowsLoaded {
		result.Error = fmt.Errorf("Row count mismatch: extracted %d rows but loaded %d rows (failed: %d)", result.RowsRead, result.RowsLoaded, result.RowsFailed)
	}

	return result
}