add Swiss National Bank exchange rates data source

conf/ezbookkeeping.ini

@@ -346,6 +346,7 @@ custom_map_tile_server_default_zoom_level = 14
 # "czech_national_bank": https://www.cnb.cz/en/financial-markets/foreign-exchange-market/central-bank-exchange-rate-fixing/central-bank-exchange-rate-fixing/
 # "national_bank_of_poland": https://nbp.pl/en/statistic-and-financial-reporting/rates/
 # "bank_of_israel": https://www.boi.org.il/en/economic-roles/financial-markets/exchange-rates/
+# "swiss_national_bank": https://www.snb.ch/en/the-snb/mandates-goals/statistics/statistics-pub/current_interest_exchange_rates
 # "international_monetary_fund": https://www.imf.org/external/np/fin/data/param_rms_mth.aspx
 data_source = euro_central_bank
 

pkg/exchangerates/exchange_rates_datasource_container.go

@@ -35,6 +35,9 @@ func InitializeExchangeRatesDataSource(config *settings.Config) error {
 	} else if config.ExchangeRatesDataSource == settings.BankOfIsraelDataSource {
 		Container.Current = &BankOfIsraelDataSource{}
 		return nil
+	} else if config.ExchangeRatesDataSource == settings.SwissNationalBankDataSource {
+		Container.Current = &SwissNationalBankDataSource{}
+		return nil
 	} else if config.ExchangeRatesDataSource == settings.InternationalMonetaryFundDataSource {
 		Container.Current = &InternationalMonetaryFundDataSource{}
 		return nil

pkg/exchangerates/swiss_national_bank_datasource.go

@@ -0,0 +1,208 @@
+package exchangerates
+
+import (
+	"encoding/xml"
+	"math"
+	"time"
+
+	"github.com/mayswind/ezbookkeeping/pkg/core"
+	"github.com/mayswind/ezbookkeeping/pkg/errs"
+	"github.com/mayswind/ezbookkeeping/pkg/log"
+	"github.com/mayswind/ezbookkeeping/pkg/models"
+	"github.com/mayswind/ezbookkeeping/pkg/utils"
+	"github.com/mayswind/ezbookkeeping/pkg/validators"
+)
+
+const swissNationalBankExchangeRateUrl = "https://www.snb.ch/public/en/rss/exchangeRates"
+const swissNationalBankExchangeRateReferenceUrl = "https://www.snb.ch/en/the-snb/mandates-goals/statistics/statistics-pub/current_interest_exchange_rates"
+const swissNationalBankDataSource = "Swiss National Bank"
+const swissNationalBankBaseCurrency = "CHF"
+
+const swissNationalBankDataUpdateDateFormat = "Mon, 02 Jan 2006 15:04:05 MST"
+const swissNationalBankExchangeRatePeriodDateFormat = "2006-01-02"
+
+// SwissNationalBankDataSource defines the structure of exchange rates data source of the reserve Swiss National Bank
+type SwissNationalBankDataSource struct {
+	ExchangeRatesDataSource
+}
+
+// SwissNationalBankData represents the whole data from the reserve Swiss National Bank
+type SwissNationalBankData struct {
+	XMLName xml.Name                     `xml:"rss"`
+	Channel *SwissNationalBankRssChannel `xml:"channel"`
+}
+
+// SwissNationalBankRssChannel represents the rss channel from the reserve Swiss National Bank
+type SwissNationalBankRssChannel struct {
+	PublishDate string                          `xml:"pubDate"`
+	Items       []*SwissNationalBankChannelItem `xml:"item"`
+}
+
+// SwissNationalBankChannelItem represents the channel item from the reserve Swiss National Bank
+type SwissNationalBankChannelItem struct {
+	Statistics *SwissNationalBankItemStatistics `xml:"statistics"`
+}
+
+// SwissNationalBankItemStatistics represents the item statistics from the reserve Swiss National Bank
+type SwissNationalBankItemStatistics struct {
+	ExchangeRate *SwissNationalBankExchangeRate `xml:"exchangeRate"`
+}
+
+// SwissNationalBankExchangeRate represents the exchange rate from the reserve Swiss National Bank
+type SwissNationalBankExchangeRate struct {
+	BaseCurrency      string                                          `xml:"baseCurrency"`
+	TargetCurrency    string                                          `xml:"targetCurrency"`
+	Observation       *SwissNationalBankExchangeRateObservation       `xml:"observation"`
+	ObservationPeriod *SwissNationalBankExchangeRateObservationPeriod `xml:"observationPeriod"`
+}
+
+// SwissNationalBankExchangeRateObservation represents the exchange rate data from the reserve Swiss National Bank
+type SwissNationalBankExchangeRateObservation struct {
+	Value        string `xml:"value"`
+	Unit         string `xml:"unit"`
+	UnitExponent string `xml:"unit_mult"`
+}
+
+// SwissNationalBankExchangeRateObservationPeriod represents the exchange rate period data from the reserve Swiss National Bank
+type SwissNationalBankExchangeRateObservationPeriod struct {
+	Period string `xml:"period"`
+}
+
+// ToLatestExchangeRateResponse returns a view-object according to original data from the reserve Swiss National Bank
+func (e *SwissNationalBankData) ToLatestExchangeRateResponse(c core.Context) *models.LatestExchangeRateResponse {
+	if e.Channel == nil {
+		log.Errorf(c, "[swiss_national_bank_datasource.ToLatestExchangeRateResponse] rss channel does not exist")
+		return nil
+	}
+
+	if len(e.Channel.Items) < 1 {
+		log.Errorf(c, "[swiss_national_bank_datasource.ToLatestExchangeRateResponse] channel items is empty")
+		return nil
+	}
+
+	latestCurrencyExchangeRateDate := make(map[string]int64)
+	latestExchangeRates := make(map[string]*models.LatestExchangeRate)
+
+	for i := 0; i < len(e.Channel.Items); i++ {
+		item := e.Channel.Items[i]
+
+		if item.Statistics == nil || item.Statistics.ExchangeRate == nil || item.Statistics.ExchangeRate.Observation == nil || item.Statistics.ExchangeRate.ObservationPeriod == nil {
+			continue
+		}
+
+		if item.Statistics.ExchangeRate.BaseCurrency != swissNationalBankBaseCurrency || item.Statistics.ExchangeRate.Observation.Unit != swissNationalBankBaseCurrency {
+			continue
+		}
+
+		if _, exists := validators.AllCurrencyNames[item.Statistics.ExchangeRate.TargetCurrency]; !exists {
+			continue
+		}
+
+		date, err := time.Parse(swissNationalBankExchangeRatePeriodDateFormat, item.Statistics.ExchangeRate.ObservationPeriod.Period)
+
+		if err != nil {
+			log.Warnf(c, "[swiss_national_bank_datasource.ToLatestExchangeRateResponse] failed to parse exchange rate period date, period is %s", item.Statistics.ExchangeRate.ObservationPeriod.Period)
+			continue
+		}
+
+		currency := item.Statistics.ExchangeRate.TargetCurrency
+		latestDate, exists := latestCurrencyExchangeRateDate[currency]
+
+		if !exists || date.Unix() > latestDate {
+			finalExchangeRate := item.Statistics.ExchangeRate.ToLatestExchangeRate(c)
+
+			if finalExchangeRate != nil {
+				latestCurrencyExchangeRateDate[currency] = date.Unix()
+				latestExchangeRates[currency] = finalExchangeRate
+			}
+		}
+	}
+
+	exchangeRates := make(models.LatestExchangeRateSlice, 0, len(e.Channel.Items))
+
+	for _, exchangeRate := range latestExchangeRates {
+		exchangeRates = append(exchangeRates, exchangeRate)
+	}
+
+	updateDateTime := e.Channel.PublishDate
+	updateTime, err := time.Parse(swissNationalBankDataUpdateDateFormat, updateDateTime)
+
+	if err != nil {
+		log.Errorf(c, "[swiss_national_bank_datasource.ToLatestExchangeRateResponse] failed to parse update date, datetime is %s", updateDateTime)
+		return nil
+	}
+
+	latestExchangeRateResp := &models.LatestExchangeRateResponse{
+		DataSource:    swissNationalBankDataSource,
+		ReferenceUrl:  swissNationalBankExchangeRateReferenceUrl,
+		UpdateTime:    updateTime.Unix(),
+		BaseCurrency:  swissNationalBankBaseCurrency,
+		ExchangeRates: exchangeRates,
+	}
+
+	return latestExchangeRateResp
+}
+
+// ToLatestExchangeRate returns a data pair according to original data from the reserve Swiss National Bank
+func (e *SwissNationalBankExchangeRate) ToLatestExchangeRate(c core.Context) *models.LatestExchangeRate {
+	rate, err := utils.StringToFloat64(e.Observation.Value)
+
+	if err != nil {
+		log.Warnf(c, "[swiss_national_bank_datasource.ToLatestExchangeRate] failed to parse rate, currency is %s, rate is %s", e.TargetCurrency, e.Observation.Value)
+		return nil
+	}
+
+	if rate <= 0 {
+		log.Warnf(c, "[swiss_national_bank_datasource.ToLatestExchangeRate] rate is invalid, currency is %s, rate is %s", e.TargetCurrency, e.Observation.Value)
+		return nil
+	}
+
+	unitExponent, err := utils.StringToInt(e.Observation.UnitExponent)
+
+	if err != nil {
+		log.Warnf(c, "[swiss_national_bank_datasource.ToLatestExchangeRate] failed to parse unit, currency is %s, unit exponent is %s", e.TargetCurrency, e.Observation.UnitExponent)
+		return nil
+	}
+
+	finalRate := 1 / rate
+
+	if unitExponent > 1 {
+		finalRate = finalRate / math.Pow10(unitExponent-1)
+	} else if unitExponent < 0 {
+		finalRate = finalRate * math.Pow10(-unitExponent)
+	}
+
+	if math.IsInf(finalRate, 0) {
+		return nil
+	}
+
+	return &models.LatestExchangeRate{
+		Currency: e.TargetCurrency,
+		Rate:     utils.Float64ToString(finalRate),
+	}
+}
+
+// GetRequestUrls returns the the reserve Swiss National Bank data source urls
+func (e *SwissNationalBankDataSource) GetRequestUrls() []string {
+	return []string{swissNationalBankExchangeRateUrl}
+}
+
+// Parse returns the common response entity according to the the reserve Swiss National Bank data source raw response
+func (e *SwissNationalBankDataSource) Parse(c core.Context, content []byte) (*models.LatestExchangeRateResponse, error) {
+	swissNationalBankData := &SwissNationalBankData{}
+	err := xml.Unmarshal(content, swissNationalBankData)
+
+	if err != nil {
+		log.Errorf(c, "[swiss_national_bank_datasource.Parse] failed to parse xml data, content is %s, because %s", string(content), err.Error())
+		return nil, errs.ErrFailedToRequestRemoteApi
+	}
+
+	latestExchangeRateResponse := swissNationalBankData.ToLatestExchangeRateResponse(c)
+
+	if latestExchangeRateResponse == nil {
+		log.Errorf(c, "[swiss_national_bank_datasource.Parse] failed to parse latest exchange rate data, content is %s", string(content))
+		return nil, errs.ErrFailedToRequestRemoteApi
+	}
+
+	return latestExchangeRateResponse, nil
+}