// Copyright 2022 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package domain

import (
	"github.com/pingcap/errors"
	"github.com/pingcap/tidb/sessionctx"
	"github.com/pingcap/tidb/statistics/handle"
)

// HistoricalStatsWorker indicates for dump historical stats
type HistoricalStatsWorker struct {
	tblCH chan int64
	sctx  sessionctx.Context
}

// SendTblToDumpHistoricalStats send tableID to worker to dump historical stats
func (w *HistoricalStatsWorker) SendTblToDumpHistoricalStats(tableID int64) {
	w.tblCH <- tableID
}

// DumpHistoricalStats dump stats by given tableID
func (w *HistoricalStatsWorker) DumpHistoricalStats(tableID int64, statsHandle *handle.Handle) error {
	historicalStatsEnabled, err := statsHandle.CheckHistoricalStatsEnable()
	if err != nil {
		return errors.Errorf("check tidb_enable_historical_stats failed: %v", err)
	}
	if !historicalStatsEnabled {
		return nil
	}
	sctx := w.sctx
	is := GetDomain(sctx).InfoSchema()
	tbl, existed := is.TableByID(tableID)
	if !existed {
		return errors.Errorf("cannot get table by id %d", tableID)
	}
	tblInfo := tbl.Meta()
	dbInfo, existed := is.SchemaByTable(tblInfo)
	if !existed {
		return errors.Errorf("cannot get DBInfo by TableID %d", tableID)
	}
	if _, err := statsHandle.RecordHistoricalStatsToStorage(dbInfo.Name.O, tblInfo); err != nil {
		return errors.Errorf("record table %s.%s's historical stats failed", dbInfo.Name.O, tblInfo.Name.O)
	}
	return nil
}

// GetOneHistoricalStatsTable gets one tableID from channel, only used for test
func (w *HistoricalStatsWorker) GetOneHistoricalStatsTable() int64 {
	return <-w.tblCH
}