package dbmeta

import (
	"context"

	"git.bit5.ru/backend/db"
	"git.bit5.ru/backend/errors"
	"git.bit5.ru/backend/meta"

	"go.opentelemetry.io/otel/attribute"
)

type DataCollection struct {
	Db              *db.DBC
	OwnerId         uint32
	sqlFilter       string
	Items           map[uint64]meta.IMetaDataItem
	itemInstance    meta.IMetaDataItem
	ownerFieldIndex int
}

func (coll *DataCollection) Checkin(item meta.IMetaDataItem) (bool, error) {
	if coll.itemInstance.CLASS_ID() != item.CLASS_ID() {
		return false, errors.Errorf("Wrong class element %d for adding to collection %d", item.CLASS_ID(), coll.itemInstance.CLASS_ID())
	}

	id := item.GetIdValue()
	//NOTE: it's considered to be OK
	if id == 0 {
		return false, nil
	}
	coll.Items[item.GetIdValue()] = item
	return true, nil
}

func (coll *DataCollection) Save(ctx context.Context) error {

	ctx, span := tracer.Start(ctx, "DataCollection.Save")
	defer span.End()

	fields := coll.GetDbFields()
	countFields := len(fields)
	if countFields == 0 {
		return errors.New("Fields list is empty")
	}

	countRows := len(coll.Items)
	if countRows == 0 {
		return nil
	}

	allDataWithoutMask := true
	for _, item := range coll.Items {
		bitmaskItem, bitmaskable := item.(meta.IBitmasked)
		if bitmaskable && bitmaskItem.IsMaskFilled() {
			allDataWithoutMask = false
			break
		}
	}

	// NOTE: performance fix: if none of rows have mask we can save all data by one sql query
	if allDataWithoutMask {
		return coll.saveWithoutMask(ctx)
	}

	return coll.saveByMask(ctx)
}

func (coll *DataCollection) saveByMask(ctx context.Context) error {

	ctx, span := tracer.Start(ctx, "DataCollection.saveByMask")
	defer span.End()

	fields := coll.GetDbFields()
	countFields := len(fields)

	tableName := coll.GetTableName()

	span.SetAttributes(
		attribute.String("db.sql.table", tableName),
	)

	for _, item := range coll.Items {
		data := make([]interface{}, countFields)
		item.Export(data)

		// enforcing ownerId
		data[coll.ownerFieldIndex] = coll.OwnerId

		itemFields := make([]string, 0, countFields)
		itemData := make([]interface{}, 0, countFields)

		bitmaskItem, bitmaskable := item.(meta.IBitmasked)

		for fieldInd, fieldName := range fields {
			skipAdding := bitmaskable && bitmaskItem.IsMaskFilled() && !bitmaskItem.HasValue(uint64(fieldInd))
			if skipAdding {
				continue
			}

			itemFields = append(itemFields, fieldName)
			itemData = append(itemData, data[fieldInd])
		}

		sqlSmt := createInsertSQLForFields(ctx, tableName, itemFields, 1)
		_, err := coll.Db.UpdateBySQL(sqlSmt, itemData...).Exec()
		if err != nil {
			log_len := len(sqlSmt)
			if log_len > 200 {
				log_len = 200
			}

			return errors.Errorf("%s (%s)", err.Error(), sqlSmt[0:log_len])
		}
	}
	return nil
}

func (coll *DataCollection) saveWithoutMask(ctx context.Context) error {

	ctx, span := tracer.Start(ctx, "DataCollection.saveWithoutMask")
	defer span.End()

	tableName := coll.GetTableName()

	fields := coll.GetDbFields()
	countFields := len(fields)
	countRows := len(coll.Items)

	span.SetAttributes(
		attribute.String("db.sql.table", tableName),
		attribute.Int("field_amount", countFields),
		attribute.Int("item_amount", countRows),
	)

	offset := 0
	rows := make([]interface{}, countRows*countFields)
	for _, item := range coll.Items {
		start := offset * countFields
		item.Export(rows[start:(start + countFields)])

		ownerValue := rows[start+coll.ownerFieldIndex]
		if ownerValue == uint32(0) {
			rows[start+coll.ownerFieldIndex] = coll.OwnerId
		} else if ownerValue != coll.OwnerId {
			return errors.Errorf("Wrong owner_id in %s value %d (!= %d)", tableName, ownerValue, coll.OwnerId)
		}
		offset++
	}

	sqlSmt := createInsertSQLForFields(ctx, tableName, fields, countRows)
	_, err := coll.Db.UpdateBySQL(sqlSmt, rows...).Exec()
	if err != nil {
		return errors.Errorf("error: %s, sql: %s", err.Error(), sqlSmt)
	}
	return nil
}

func (coll *DataCollection) GetDbFields() []string {
	return coll.itemInstance.GetDbFields()
}

func (coll *DataCollection) GetTableName() string {
	return coll.itemInstance.GetDbTableName()
}

func (coll *DataCollection) init() error {
	coll.Items = make(map[uint64]meta.IMetaDataItem)

	coll.ownerFieldIndex = -1
	ownerField := coll.itemInstance.GetOwnerFieldName()
	for index, field := range coll.itemInstance.GetDbFields() {
		if field == ownerField {
			coll.ownerFieldIndex = index
			break
		}
	}
	if coll.ownerFieldIndex == -1 {
		return errors.New("Owner field not found in fields list")
	}

	return nil
}

func NewDataCollection(db *db.DBC, ownerId uint32, sqlFilter string, itemInstance meta.IMetaDataItem) (*DataCollection, error) {
	data := DataCollection{Db: db, OwnerId: ownerId, sqlFilter: sqlFilter, itemInstance: itemInstance}
	if err := data.init(); err != nil {
		return nil, err
	}
	return &data, nil
}