add Czech National Bank exchange rate data source

conf/lab.ini

@@ -111,7 +111,7 @@ enable_register = true
 enable_export = true
 
 [exchange_rates]
-# Exchange rates data source, supports "euro_central_bank" currently
+# Exchange rates data source, supports "euro_central_bank", "czech_national_bank" currently
 data_source = euro_central_bank
 
 # Requesting exchange rates data timeout (milliseconds), default is 10000 (10 seconds)

pkg/exchangerates/czech_national_bank_datasource.go

@@ -0,0 +1,165 @@
+package exchangerates
+
+import (
+	"math"
+	"strings"
+	"time"
+
+	"github.com/mayswind/lab/pkg/core"
+	"github.com/mayswind/lab/pkg/errs"
+	"github.com/mayswind/lab/pkg/log"
+	"github.com/mayswind/lab/pkg/models"
+	"github.com/mayswind/lab/pkg/utils"
+	"github.com/mayswind/lab/pkg/validators"
+)
+
+const czechNationalBankDailyExchangeRateUrl = "https://www.cnb.cz/en/financial-markets/foreign-exchange-market/central-bank-exchange-rate-fixing/central-bank-exchange-rate-fixing/daily.txt"
+const czechNationalBankMonthlyOtherExchangeRateUrl = "https://www.cnb.cz/en/financial-markets/foreign-exchange-market/fx-rates-of-other-currencies/fx-rates-of-other-currencies/fx_rates.txt"
+const czechNationalBankExchangeRateReferenceUrl = "https://www.cnb.cz/en/financial-markets/foreign-exchange-market/central-bank-exchange-rate-fixing/central-bank-exchange-rate-fixing/"
+const czechNationalBankDataSource = "Česká národní banka"
+const czechNationalBankBaseCurrency = "CZK"
+
+const czechNationalBankDataUpdateDateFormat = "02 Jan 2006 15:04"
+const czechNationalBankDataUpdateDateTimezone = "Europe/Prague"
+
+// CzechNationalBankDataSource defines the structure of exchange rates data source of Czech National Bank
+type CzechNationalBankDataSource struct {
+	ExchangeRatesDataSource
+}
+
+// GetRequestUrls returns the czech nation bank data source urls
+func (e *CzechNationalBankDataSource) GetRequestUrls() []string {
+	return []string{czechNationalBankMonthlyOtherExchangeRateUrl, czechNationalBankDailyExchangeRateUrl}
+}
+
+// Parse returns the common response entity according to the czech nation bank data source raw response
+func (e *CzechNationalBankDataSource) Parse(c *core.Context, content []byte) (*models.LatestExchangeRateResponse, error) {
+	lines := strings.Split(string(content), "\n")
+
+	if len(lines) < 3 {
+		log.ErrorfWithRequestId(c, "[czech_national_bank_datasource.Parse] content is invalid, content is %s", string(content))
+		return nil, errs.ErrFailedToRequestRemoteApi
+	}
+
+	headerLineItems := strings.Split(lines[0], "#")
+
+	if len(headerLineItems) != 2 {
+		log.ErrorfWithRequestId(c, "[czech_national_bank_datasource.Parse] first line of content is invalid, content is %s", lines[0])
+		return nil, errs.ErrFailedToRequestRemoteApi
+	}
+
+	updateDate := strings.TrimSpace(headerLineItems[0])
+
+	titleLineItems := strings.Split(lines[1], "|")
+	titleItemMap := make(map[string]int)
+
+	for i := 0; i < len(titleLineItems); i++ {
+		titleItemMap[titleLineItems[i]] = i
+	}
+
+	currencyCodeColumnIndex, exists := titleItemMap["Code"]
+
+	if !exists {
+		log.ErrorfWithRequestId(c, "[czech_national_bank_datasource.Parse] missing currency code column in title line, title line is %s", lines[1])
+		return nil, errs.ErrFailedToRequestRemoteApi
+	}
+
+	amountColumnIndex, exists := titleItemMap["Amount"]
+
+	if !exists {
+		log.ErrorfWithRequestId(c, "[czech_national_bank_datasource.Parse] missing amount column in title line, title line is %s", lines[1])
+		return nil, errs.ErrFailedToRequestRemoteApi
+	}
+
+	rateColumnIndex, exists := titleItemMap["Rate"]
+
+	if !exists {
+		log.ErrorfWithRequestId(c, "[czech_national_bank_datasource.Parse] missing rate column in title line, title line is %s", lines[1])
+		return nil, errs.ErrFailedToRequestRemoteApi
+	}
+
+	exchangeRates := make(models.LatestExchangeRateSlice, 0, len(lines)-2)
+
+	for i := 2; i < len(lines); i++ {
+		line := strings.TrimSpace(lines[i])
+		exchangeRate := e.parseExchangeRate(c, line, currencyCodeColumnIndex, amountColumnIndex, rateColumnIndex)
+
+		if exchangeRate != nil {
+			exchangeRates = append(exchangeRates, exchangeRate)
+		}
+	}
+
+	timezone, err := time.LoadLocation(czechNationalBankDataUpdateDateTimezone)
+
+	if err != nil {
+		log.ErrorfWithRequestId(c, "[czech_national_bank_datasource.Parse] failed to get timezone, timezone name is %s", czechNationalBankDataUpdateDateTimezone)
+		return nil, errs.ErrFailedToRequestRemoteApi
+	}
+
+	updateDateTime := updateDate + " 14:30" // Exchange rates of commonly traded currencies are declared every working day after 2.30 p.m.
+	updateTime, err := time.ParseInLocation(czechNationalBankDataUpdateDateFormat, updateDateTime, timezone)
+
+	if err != nil {
+		log.ErrorfWithRequestId(c, "[czech_national_bank_datasource.Parse] failed to parse update date, datetime is %s", updateDateTime)
+		return nil, errs.ErrFailedToRequestRemoteApi
+	}
+
+	latestExchangeRateResp := &models.LatestExchangeRateResponse{
+		DataSource:    czechNationalBankDataSource,
+		ReferenceUrl:  czechNationalBankExchangeRateReferenceUrl,
+		UpdateTime:    updateTime.Unix(),
+		BaseCurrency:  czechNationalBankBaseCurrency,
+		ExchangeRates: exchangeRates,
+	}
+
+	return latestExchangeRateResp, nil
+}
+
+func (e *CzechNationalBankDataSource) parseExchangeRate(c *core.Context, line string, currencyCodeColumnIndex int, amountColumnIndex int, rateColumnIndex int) *models.LatestExchangeRate {
+	if len(line) < 1 {
+		return nil
+	}
+
+	items := strings.Split(line, "|")
+
+	if currencyCodeColumnIndex >= len(items) || amountColumnIndex >= len(items) || rateColumnIndex >= len(items) {
+		log.WarnfWithRequestId(c, "[czech_national_bank_datasource.parseExchangeRate] missing column in data line, line is %s", line)
+		return nil
+	}
+
+	currencyCode := items[currencyCodeColumnIndex]
+
+	if _, exists := validators.AllCurrencyNames[currencyCode]; !exists {
+		return nil
+	}
+
+	amount, err := utils.StringToInt64(items[amountColumnIndex])
+
+	if err != nil {
+		log.WarnfWithRequestId(c, "[czech_national_bank_datasource.parseExchangeRate] failed to parse amount, line is %s", line)
+		return nil
+	}
+
+	rate, err := utils.StringToFloat64(items[rateColumnIndex])
+
+	if err != nil {
+		log.WarnfWithRequestId(c, "[czech_national_bank_datasource.parseExchangeRate] failed to parse rate, line is %s", line)
+		return nil
+	}
+
+	if rate <= 0 {
+		log.WarnfWithRequestId(c, "[czech_national_bank_datasource.parseExchangeRate] rate is invalid, line is %s", line)
+		return nil
+	}
+
+	finalRate := float64(amount) / rate
+
+	if math.IsInf(finalRate, 0) {
+		return nil
+	}
+
+	return &models.LatestExchangeRate{
+		Currency: currencyCode,
+		Rate:     utils.Float64ToString(finalRate),
+	}
+}

pkg/exchangerates/exchange_rates_datasource_container.go

@@ -20,6 +20,9 @@ func InitializeExchangeRatesDataSource(config *settings.Config) error {
 	if config.ExchangeRatesDataSource == settings.EuroCentralBankDataSource {
 		Container.Current = &EuroCentralBankDataSource{}
 		return nil
+	} else if config.ExchangeRatesDataSource == settings.CzechNationalBankDataSource {
+		Container.Current = &CzechNationalBankDataSource{}
+		return nil
 	}
 
 	return errs.ErrInvalidExchangeRatesDataSource

pkg/settings/setting.go

@@ -65,6 +65,7 @@ const (
 // Exchange rates data source types
 const (
 	EuroCentralBankDataSource string = "euro_central_bank"
+	CzechNationalBankDataSource string = "czech_national_bank"
 )
 
 const (
@@ -412,6 +413,8 @@ func loadDataConfiguration(config *Config, configFile *ini.File, sectionName str
 func loadExchangeRatesConfiguration(config *Config, configFile *ini.File, sectionName string) error {
 	if getConfigItemStringValue(configFile, sectionName, "data_source") == EuroCentralBankDataSource {
 		config.ExchangeRatesDataSource = EuroCentralBankDataSource
+	} else if getConfigItemStringValue(configFile, sectionName, "data_source") == CzechNationalBankDataSource {
+		config.ExchangeRatesDataSource = CzechNationalBankDataSource
 	} else {
 		return errs.ErrInvalidExchangeRatesDataSource
 	}

pkg/utils/converter.go

@@ -73,3 +73,13 @@ func StringTryToInt64(str string, defaultValue int64) int64 {
 
 	return num
 }
+
+// Float64ToString returns the textual representation of this number
+func Float64ToString(num float64) string {
+	return strconv.FormatFloat(num, 'f', -1, 64)
+}
+
+// StringToFloat64 parses a textual representation of the number to float64
+func StringToFloat64(str string) (float64, error) {
+	return strconv.ParseFloat(str, 64)
+}