init; project structure & bybit provider

internal/provider/bybit/bybit.go

@@ -0,0 +1,74 @@
+// package bybit provides rates of cryptocurrencies from bybit exchange orderbook.
+package bybit
+
+import (
+	"context"
+	"crypto_alert_bot/internal/config"
+	"crypto_alert_bot/internal/entities"
+	"crypto_alert_bot/internal/provider"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"time"
+
+	"github.com/shopspring/decimal"
+)
+
+const (
+	// mainnetURL  = "https://api.bybit.com"
+	httpTimeout = time.Second * 10
+)
+
+type Bybit struct {
+	log    *slog.Logger
+	cfg    *config.Bybit
+	client *http.Client
+}
+
+func New(log *slog.Logger, cfg *config.Bybit) provider.Provider {
+	return &Bybit{
+		log: log,
+		cfg: cfg,
+		client: &http.Client{
+			Timeout: httpTimeout,
+		},
+	}
+}
+
+func (b *Bybit) symbol(pair *entities.Pair) string {
+	return fmt.Sprintf("%s%s", pair.BaseCurrency, pair.QuoteCurrency)
+}
+
+// Price returns the current price of the pair (base currency / quote currency).
+// e.g. BTC/USDT.
+func (b *Bybit) Price(ctx context.Context, pair entities.Pair) (*entities.Price, error) {
+	// build request
+	req := marketOrderbookReq{
+		Category: categorySpot,
+		Symbol:   b.symbol(&pair),
+	}
+	var resp marketOrderbookResp
+	// make request
+	err := b.makeRequest(ctx, http.MethodGet, "/v5/market/orderbook", req, &resp)
+	if err != nil {
+		return nil, fmt.Errorf("failed to make request: %w", err)
+	}
+	// get results
+	if len(resp.A) == 0 || len(resp.B) == 0 {
+		return nil, fmt.Errorf("incorrect response: nil data")
+	}
+	if len(resp.A[0]) != 2 || len(resp.B[0]) != 2 {
+		return nil, fmt.Errorf("incorrect response: nil prices")
+	}
+
+	askPrice := decimal.RequireFromString(resp.A[0][0])
+	bidPrice := decimal.RequireFromString(resp.B[0][0])
+	spread := askPrice.Sub(bidPrice)
+
+	return &entities.Price{
+		Ask:    askPrice,
+		Bid:    bidPrice,
+		Spread: spread,
+		Pair:   pair,
+	}, nil
+}