btc-pay-checker/internal/services/price/conversor.go

package price

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

	"gitea.urkob.com/urko/btc-pay-checker/internal/domain"
	"gitea.urkob.com/urko/btc-pay-checker/kit"
)

type CoinPriceResponse struct {
	Coins map[string]map[string]interface{} `json:"coins"`
}

type PriceConversor struct {
	apiUrl        string
	dollarRateApi string
	client        *http.Client
}

func NewPriceConversor(apiUrl, dollarRateApi string) *PriceConversor {
	return &PriceConversor{
		apiUrl:        apiUrl,
		client:        &http.Client{},
		dollarRateApi: dollarRateApi,
	}
}

type usdConversorResponse struct {
	Result             string             `json:"result"`
	Provider           string             `json:"provider"`
	Documentation      string             `json:"documentation"`
	TermsOfUse         string             `json:"terms_of_use"`
	TimeLastUpdateUnix int                `json:"time_last_update_unix"`
	TimeLastUpdateUtc  string             `json:"time_last_update_utc"`
	TimeNextUpdateUnix int                `json:"time_next_update_unix"`
	TimeNextUpdateUtc  string             `json:"time_next_update_utc"`
	TimeEolUnix        int                `json:"time_eol_unix"`
	BaseCode           string             `json:"base_code"`
	Rates              map[string]float64 `json:"rates"`
}

func (p *PriceConversor) USDTo(c domain.Coin) (float64, error) {
	usd := 0.0
	reqURL := fmt.Sprintf(p.dollarRateApi)
	req, err := http.NewRequest("GET", reqURL, nil)
	if err != nil {
		return usd, fmt.Errorf("http.NewRequest: %s", err)
	}

	kit.WithJSONHeaders(req)

	resp, err := p.client.Do(req)
	if err != nil {
		return usd, fmt.Errorf("client.Do: %s", err)
	}

	bts, err := io.ReadAll(resp.Body)
	if err != nil {
		return usd, fmt.Errorf("iokit.ReadAll: %s", err)
	}

	if resp.StatusCode != http.StatusOK {
		return usd, fmt.Errorf("error %d: %s", resp.StatusCode, string(bts))
	}

	var respBody usdConversorResponse
	if err = json.Unmarshal(bts, &respBody); err != nil {
		return usd, fmt.Errorf("json.Unmarshal: %s", err)
	}

	v, ok := respBody.Rates[string(c)]
	if !ok {
		return usd, fmt.Errorf("coin isn't found")
	}

	return v, nil
}

func (p *PriceConversor) USD(c domain.Coin) (float64, error) {
	usd := 0.0
	reqURL := fmt.Sprintf(p.apiUrl+"/prices/current/%s", c)
	req, err := http.NewRequest("GET", reqURL, nil)
	if err != nil {
		return usd, fmt.Errorf("http.NewRequest: %s", err)
	}

	kit.WithJSONHeaders(req)

	resp, err := p.client.Do(req)
	if err != nil {
		return usd, fmt.Errorf("client.Do: %s", err)
	}

	bts, err := io.ReadAll(resp.Body)
	if err != nil {
		return usd, fmt.Errorf("iokit.ReadAll: %s", err)
	}

	if resp.StatusCode != http.StatusOK {
		return usd, fmt.Errorf("error %d: %s", resp.StatusCode, string(bts))
	}

	var respBody CoinPriceResponse
	if err = json.Unmarshal(bts, &respBody); err != nil {
		return usd, fmt.Errorf("json.Unmarshal: %s", err)
	}

	if _, hasKey := respBody.Coins[string(c)]; !hasKey {
		return usd, fmt.Errorf("coin isn't found")
	}

	if _, hasKey := respBody.Coins[string(c)]["price"]; !hasKey {
		return usd, fmt.Errorf("coin price isn't found")
	}

	usd, ok := respBody.Coins[string(c)]["price"].(float64)
	if !ok {
		return usd, fmt.Errorf("cannot cast price to float64")
	}

	return usd, nil
}

func (p *PriceConversor) UsdToBtc(usdAmount float64) (float64, error) {
	usd, err := p.USD(domain.CoinBTC)
	if err != nil {
		return usdAmount, fmt.Errorf("USDToBtc: %s", err)
	}

	return usdAmount / usd, nil
}

func (p *PriceConversor) BtcToUsd(btcAmount float64) (float64, error) {
	usd, err := p.USD(domain.CoinBTC)
	if err != nil {
		return btcAmount, fmt.Errorf("USDToBtc: %s", err)
	}

	return btcAmount * usd, nil
}