package service

import (
	"context"
	"fmt"
	"time"

	"github.com/pkg/errors"
	log "github.com/sirupsen/logrus"

	"github.com/c9s/bbgo/pkg/datasource/csvsource"
	exchange2 "github.com/c9s/bbgo/pkg/exchange"
	"github.com/c9s/bbgo/pkg/types"
)

type BacktestServiceCSV struct {
	kLines      map[types.Interval][]types.KLine
	path        string
	market      types.MarketType
	granularity types.MarketDataType
}

func NewBacktestServiceCSV(
	path string,
	market types.MarketType,
	granularity types.MarketDataType,
) BackTestable {
	return &BacktestServiceCSV{
		kLines:      make(map[types.Interval][]types.KLine),
		path:        path,
		market:      market,
		granularity: granularity,
	}
}

func (s *BacktestServiceCSV) Verify(
	sourceExchange types.Exchange, symbols []string, startTime time.Time, endTime time.Time,
) error {
	// TODO: use isFutures here
	_, _, isIsolated, isolatedSymbol := exchange2.GetSessionAttributes(sourceExchange)
	// override symbol if isolatedSymbol is not empty
	if isIsolated && len(isolatedSymbol) > 0 {
		err := csvsource.Download(
			s.path,
			isolatedSymbol,
			sourceExchange.Name(),
			s.market,
			s.granularity,
			startTime,
			endTime,
		)
		if err != nil {
			return errors.Errorf("downloading csv data: %v", err)
		}
	}

	return nil
}

func (s *BacktestServiceCSV) Sync(
	ctx context.Context, exchange types.Exchange, symbol string, intervals []types.Interval,
	startTime, endTime time.Time,
) error {

	log.Infof("starting fresh csv sync %s %s: %s <=> %s", exchange.Name(), symbol, startTime, endTime)

	path := fmt.Sprintf("%s/%s/%s", s.path, exchange.Name().String(), symbol)

	var reader csvsource.MakeCSVTickReader

	switch exchange.Name() {
	case types.ExchangeBinance:
		reader = csvsource.NewBinanceCSVTickReader
	case types.ExchangeBybit:
		reader = csvsource.NewBybitCSVTickReader
	case types.ExchangeOKEx:
		reader = csvsource.NewOKExCSVTickReader
	default:
		return fmt.Errorf("%s not supported yet.. care to fix it? PR's welcome ;)", exchange.Name().String())
	}

	kLineMap, err := csvsource.ReadTicksFromCSVWithDecoder(
		path,
		symbol,
		intervals,
		csvsource.MakeCSVTickReader(reader),
	)
	if err != nil {
		return errors.Errorf("reading csv data: %v", err)
	}

	s.kLines = kLineMap

	return nil
}

// QueryKLine queries the klines from the database
func (s *BacktestServiceCSV) QueryKLine(
	ex types.ExchangeName, symbol string, interval types.Interval, orderBy string, limit int,
) (*types.KLine, error) {
	log.Infof("querying last kline exchange = %s AND symbol = %s AND interval = %s", ex, symbol, interval)
	if _, ok := s.kLines[interval]; !ok || len(s.kLines[interval]) == 0 {
		return nil, errors.New("interval not initialized")
	}
	return &s.kLines[interval][len(s.kLines[interval])-1], nil
}

// QueryKLinesForward is used for querying klines to back-testing
func (s *BacktestServiceCSV) QueryKLinesForward(
	exchange types.ExchangeName, symbol string, interval types.Interval, startTime time.Time, limit int,
) ([]types.KLine, error) {
	// Sample implementation (modify as needed):
	var result []types.KLine

	// Access klines data based on exchange, symbol, and interval
	exchangeKLines, ok := s.kLines[interval]
	if !ok {
		return nil, fmt.Errorf("no kLines for specified interval %s", interval.String())
	}

	// Filter klines based on startTime and limit
	for _, kline := range exchangeKLines {
		if kline.StartTime.After(startTime) {
			result = append(result, kline)
			if len(result) >= limit {
				break
			}
		}
	}

	return result, nil
}

func (s *BacktestServiceCSV) QueryKLinesBackward(
	exchange types.ExchangeName, symbol string, interval types.Interval, endTime time.Time, limit int,
) ([]types.KLine, error) {
	var result []types.KLine

	// Access klines data based on interval
	exchangeKLines, ok := s.kLines[interval]
	if !ok {
		return nil, fmt.Errorf("no kLines for specified interval %s", interval.String())
	}

	// Reverse iteration through klines and filter based on endTime and limit
	for i := len(exchangeKLines) - 1; i >= 0; i-- {
		kline := exchangeKLines[i]

		if kline.StartTime.Before(endTime) {
			result = append(result, kline)
			if len(result) >= limit {
				break
			}
		}
	}

	return result, nil
}

func (s *BacktestServiceCSV) QueryKLinesCh(
	since, until time.Time, exchange types.Exchange, symbols []string, intervals []types.Interval,
) (chan types.KLine, chan error) {
	if len(symbols) == 0 {
		return returnError(errors.Errorf("symbols is empty when querying kline, please check your strategy setting. "))
	}

	ch := make(chan types.KLine, len(s.kLines))
	go func() {
		defer close(ch)
		for _, kline := range s.kLines[intervals[0]] {
			ch <- kline
		}
	}()

	return ch, nil
}