package api

import (
	"io/ioutil"
	"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"
)

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

// Initialize a exchange rate api singleton instance
var (
	ExchangeRates = &ExchangeRatesApi{}
)

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

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

	uid := c.GetCurrentUid()

	client := &http.Client{
		Timeout: time.Duration(settings.Container.Current.ExchangeRatesRequestTimeout) * time.Millisecond,
	}

	urls := dataSource.GetRequestUrls()
	exchangeRateResps := make([]*models.LatestExchangeRateResponse, 0, len(urls))

	for i := 0; i < len(urls); i++ {
		resp, err := client.Get(urls[i])

		if err != nil {
			log.ErrorfWithRequestId(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.ErrorfWithRequestId(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 := ioutil.ReadAll(resp.Body)
		exchangeRateResp, err := dataSource.Parse(c, body)

		if err != nil {
			log.ErrorfWithRequestId(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
}