package extractors

import (
	"context"
	"errors"
	"fmt"

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

func errorFromLastRow(
	lastRow models.UnknownRowValues,
	indexPrimaryKey int,
	partition models.Partition,
	previousError error,
) error {
	lastIdRawValue := lastRow[indexPrimaryKey]

	lastId, ok := convert.ToInt64(lastIdRawValue)
	if !ok {
		currentPartition := partition
		currentPartition.RetryCounter = 3
		return &custom_errors.ExtractorError{
			Partition: currentPartition,
			HasLastId: true,
			Msg:       fmt.Sprintf("Couldn't cast last id value as int: %s", previousError.Error()),
		}
	}

	return &custom_errors.ExtractorError{
		Partition: partition,
		HasLastId: true,
		LastId:    lastId,
		Msg:       previousError.Error(),
	}
}

func (ex *GenericExtractor) ProcessPartition(
	ctx context.Context,
	tableInfo config.SourceTableInfo,
	columns []models.ColumnType,
	batchSize int,
	partition models.Partition,
	indexPrimaryKey int,
	chBatchesOut chan<- models.Batch,
) (int, error) {
	rowsRead := 0
	query := dbwrapper.ExtractionQuery{
		Schema:     tableInfo.Schema,
		Table:      tableInfo.Table,
		PrimaryKey: tableInfo.PrimaryKey,
		LowerLimit: dbwrapper.ExtractorQueryLimit{
			IsValid:     partition.HasRange && partition.Range.Min > 0,
			IsInclusive: partition.Range.IsMinInclusive,
			Value:       partition.Range.Min,
		},
		UpperLimit: dbwrapper.ExtractorQueryLimit{
			IsValid:     partition.HasRange && partition.Range.Max > 0,
			IsInclusive: partition.Range.IsMaxInclusive,
			Value:       partition.Range.Max,
		},
	}

	rows, err := ex.db.QueryFromObject(ctx, query)

	if err != nil {
		return rowsRead, &custom_errors.ExtractorError{Partition: partition, HasLastId: false, Msg: err.Error()}
	}
	defer rows.Close()

	batchRows := make([]models.UnknownRowValues, 0, batchSize)

	for rows.Next() {
		rowValues := make([]any, len(columns))
		scanArgs := make([]any, len(columns))

		for i := range rowValues {
			scanArgs[i] = &rowValues[i]
		}

		if err := rows.Scan(scanArgs...); err != nil {
			if len(batchRows) == 0 {
				return rowsRead, &custom_errors.ExtractorError{Partition: partition, HasLastId: false, Msg: err.Error()}
			}

			lastRow := batchRows[len(batchRows)-1]

			select {
			case chBatchesOut <- models.Batch{Id: uuid.New(), PartitionId: partition.Id, Rows: batchRows, RetryCounter: 0}:
			case <-ctx.Done():
				return rowsRead, ctx.Err()
			}

			return rowsRead, errorFromLastRow(lastRow, indexPrimaryKey, partition, err)
		}
		rowsRead++

		batchRows = append(batchRows, rowValues)
		if len(batchRows) >= batchSize {
			select {
			case chBatchesOut <- models.Batch{Id: uuid.New(), PartitionId: partition.Id, Rows: batchRows, RetryCounter: 0}:
			case <-ctx.Done():
				return rowsRead, ctx.Err()
			}

			batchRows = make([]models.UnknownRowValues, 0, batchSize)
		}
	}

	if err := rows.Err(); err != nil {
		if errors.Is(err, ctx.Err()) {
			return rowsRead, ctx.Err()
		}

		if len(batchRows) > 0 {
			lastRow := batchRows[len(batchRows)-1]
			return rowsRead, errorFromLastRow(lastRow, indexPrimaryKey, partition, err)
		}

		return rowsRead, &custom_errors.ExtractorError{Partition: partition, HasLastId: false, Msg: err.Error()}
	}

	if len(batchRows) > 0 {
		select {
		case chBatchesOut <- models.Batch{Id: uuid.New(), PartitionId: partition.Id, Rows: batchRows, RetryCounter: 0}:
		case <-ctx.Done():
			return rowsRead, ctx.Err()
		}
	}

	return rowsRead, nil
}