package api

import (
	"crypto/tls"
	"fmt"
	"io"
	"net/http"
	"sort"
	"time"

	"github.com/mayswind/ezbookkeeping/pkg/core"
	"github.com/mayswind/ezbookkeeping/pkg/errs"
	"github.com/mayswind/ezbookkeeping/pkg/exchangerates"
	"github.com/mayswind/ezbookkeeping/pkg/log"
	"github.com/mayswind/ezbookkeeping/pkg/models"
	"github.com/mayswind/ezbookkeeping/pkg/settings"
	"github.com/mayswind/ezbookkeeping/pkg/utils"
)

// ExchangeRatesApi represents exchange rate api
type ExchangeRatesApi struct {
	ApiUsingConfig
}

// Initialize a exchange rate api singleton instance
var (
	ExchangeRates = &ExchangeRatesApi{
		ApiUsingConfig: ApiUsingConfig{
			container: settings.Container,
		},
	}
)

// LatestExchangeRateHandler returns latest exchange rate data
func (a *ExchangeRatesApi) LatestExchangeRateHandler(c *core.WebContext) (any, *errs.Error) {
	dataSource := exchangerates.Container.Current

	if dataSource == nil {
		return nil, errs.ErrInvalidExchangeRatesDataSource
	}

	uid := c.GetCurrentUid()

	transport := http.DefaultTransport.(*http.Transport).Clone()
	utils.SetProxyUrl(transport, a.CurrentConfig().ExchangeRatesProxy)

	if a.CurrentConfig().ExchangeRatesSkipTLSVerify {
		transport.TLSClientConfig = &tls.Config{
			InsecureSkipVerify: true,
		}
	}

	client := &http.Client{
		Transport: transport,
		Timeout:   time.Duration(a.CurrentConfig().ExchangeRatesRequestTimeout) * time.Millisecond,
	}

	requests, err := dataSource.BuildRequests()

	if err != nil {
		log.Errorf(c, "[exchange_rates.LatestExchangeRateHandler] failed to build requests for user \"uid:%d\", because %s", uid, err.Error())
		return nil, errs.ErrFailedToRequestRemoteApi
	}

	exchangeRateResps := make([]*models.LatestExchangeRateResponse, 0, len(requests))

	for i := 0; i < len(requests); i++ {
		req := requests[i]
		req.Header.Set("User-Agent", fmt.Sprintf("ezBookkeeping/%s", settings.Version))

		resp, err := client.Do(req)

		if err != nil {
			log.Errorf(c, "[exchange_rates.LatestExchangeRateHandler] failed to request latest exchange rate data for user \"uid:%d\", because %s", uid, err.Error())
			return nil, errs.ErrFailedToRequestRemoteApi
		}

		if resp.StatusCode != 200 {
			log.Errorf(c, "[exchange_rates.LatestExchangeRateHandler] failed to get latest exchange rate data response for user \"uid:%d\", because response code is not 200", uid)
			return nil, errs.ErrFailedToRequestRemoteApi
		}

		defer resp.Body.Close()
		body, err := io.ReadAll(resp.Body)

		log.Debugf(c, "[exchange_rates.LatestExchangeRateHandler] response#%d is %s", i, body)

		exchangeRateResp, err := dataSource.Parse(c, body)

		if err != nil {
			log.Errorf(c, "[exchange_rates.LatestExchangeRateHandler] failed to parse response for user \"uid:%d\", because %s", uid, err.Error())
			return nil, errs.Or(err, errs.ErrFailedToRequestRemoteApi)
		}

		exchangeRateResps = append(exchangeRateResps, exchangeRateResp)
	}

	lastExchangeRateResponse := exchangeRateResps[len(exchangeRateResps)-1]
	allExchangeRatesMap := make(map[string]string)

	for i := 0; i < len(exchangeRateResps); i++ {
		exchangeRateResp := exchangeRateResps[i]

		for j := 0; j < len(exchangeRateResp.ExchangeRates); j++ {
			exchangeRate := exchangeRateResp.ExchangeRates[j]
			allExchangeRatesMap[exchangeRate.Currency] = exchangeRate.Rate
		}
	}

	allExchangeRatesMap[lastExchangeRateResponse.BaseCurrency] = "1"
	allExchangeRates := make(models.LatestExchangeRateSlice, 0, len(allExchangeRatesMap))

	for currency, rate := range allExchangeRatesMap {
		allExchangeRates = append(allExchangeRates, &models.LatestExchangeRate{
			Currency: currency,
			Rate:     rate,
		})
	}

	sort.Sort(allExchangeRates)

	finalExchangeRateResponse := &models.LatestExchangeRateResponse{
		DataSource:    lastExchangeRateResponse.DataSource,
		ReferenceUrl:  lastExchangeRateResponse.ReferenceUrl,
		UpdateTime:    lastExchangeRateResponse.UpdateTime,
		BaseCurrency:  lastExchangeRateResponse.BaseCurrency,
		ExchangeRates: allExchangeRates,
	}

	return finalExchangeRateResponse, nil
}