ynab-portfolio-monitor/providers/bitcoinElectrum/fiat.go

package bitcoinElectrum

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"time"
)

const fiatConvertURL = "https://api.coingecko.com/api/v3/coins/bitcoin?localization=false&tickers=false&market_data=true&community_data=false&developer_data=false&sparkline=false"

type coinGeckoResponse struct {
	MarketData struct {
		CurrentPrice struct {
			CAD int `json:"cad"`
		} `json:"current_price"`
	} `json:"market_data"`
}

func convertBTCToCAD(amount int64, coinGeckoApiKey string) (int64, error) {
	coinGeckoData := &coinGeckoResponse{}

	req, err := http.NewRequest("GET", fmt.Sprintf("%s&x-cg-demo-api-key=%s", fiatConvertURL, coinGeckoApiKey), nil)
	if err != nil {
		return 0, fmt.Errorf("failed to create new GET request: %v", err)
	}

	client := http.Client{Transport: &http.Transport{ResponseHeaderTimeout: 15 * time.Second}}
	res, err := client.Do(req)
	if err != nil {
		return 0, fmt.Errorf("http GET request failed: %v", err)
	}

	err = processResponse(res, coinGeckoData)
	if err != nil {
		return 0, fmt.Errorf("failed to process response: %v", err)
	}

	return (amount * int64(coinGeckoData.MarketData.CurrentPrice.CAD*1000)) / 100000000, nil // one BTC = one hundred million satoshi's
}

// processResponse takes the body of an HTTP response, and either returns
// the error code, or unmarshalls the JSON response, extracts
// rate limit info, and places it into the object
// output parameter. This function closes the response body after reading it.
func processResponse(res *http.Response, out interface{}) error {
	body, err := io.ReadAll(res.Body)
	res.Body.Close()
	if err != nil {
		return fmt.Errorf("failed to read response body: %v", err)
	}

	if res.StatusCode != 200 && res.StatusCode != 201 {
		return fmt.Errorf("unexpected http status code '%d': %v", res.StatusCode, err)
	}

	err = json.Unmarshal(body, out)
	if err != nil {
		return fmt.Errorf("failed to unmarshal response body: %v", err)
	}
	return nil
}