client.go

package api


import (
	"bytes"
	"context"
	"crypto/hmac"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"

	"github.com/pkg/errors"

	"github.com/c9s/requestgen"
)

const defaultHTTPTimeout = time.Second * 15
const RestBaseURL = "https://api.kucoin.com/api"
const SandboxRestBaseURL = "https://openapi-sandbox.kucoin.com/api"

type RestClient struct {
	requestgen.BaseAPIClient

	Key, Secret, Passphrase string
	KeyVersion              string
}

func NewClient() *RestClient {
	u, err := url.Parse(RestBaseURL)
	if err != nil {
		panic(err)
	}

	return &RestClient{
		BaseAPIClient: requestgen.BaseAPIClient{
			BaseURL: u,
			HttpClient: &http.Client{
				Timeout: defaultHTTPTimeout,
			},
		},
		KeyVersion: "2",
	}
}

func (c *RestClient) Auth(key, secret, passphrase string) {
	c.Key = key
	c.Secret = secret
	c.Passphrase = passphrase
}

// NewAuthenticatedRequest creates new http request for authenticated routes.
func (c *RestClient) NewAuthenticatedRequest(ctx context.Context, method, refURL string, params url.Values, payload interface{}) (*http.Request, error) {
	if len(c.Key) == 0 {
		return nil, errors.New("empty api key")
	}

	if len(c.Secret) == 0 {
		return nil, errors.New("empty api secret")
	}

	rel, err := url.Parse(refURL)
	if err != nil {
		return nil, err
	}

	if params != nil {
		rel.RawQuery = params.Encode()
	}

	pathURL := c.BaseURL.ResolveReference(rel)
	path := pathURL.Path
	if rel.RawQuery != "" {
		path += "?" + rel.RawQuery
	}

	body, err := castPayload(payload)
	if err != nil {
		return nil, err
	}

	req, err := http.NewRequestWithContext(ctx, method, pathURL.String(), bytes.NewReader(body))
	if err != nil {
		return nil, err
	}

	req.Header.Add("Content-Type", "application/json")
	req.Header.Add("Accept", "application/json")

	// Build authentication headers
	c.attachAuthHeaders(req, method, path, body)
	return req, nil
}

func (c *RestClient) attachAuthHeaders(req *http.Request, method string, path string, body []byte) {
	// Set location to UTC so that it outputs "2020-12-08T09:08:57.715Z"
	t := time.Now().In(time.UTC)
	// timestamp := t.Format("2006-01-02T15:04:05.999Z07:00")
	timestamp := strconv.FormatInt(t.UnixNano()/int64(time.Millisecond), 10)
	signKey := timestamp + strings.ToUpper(method) + path + string(body)
	signature := sign(c.Secret, signKey)

	req.Header.Add("KC-API-KEY", c.Key)
	req.Header.Add("KC-API-SIGN", signature)
	req.Header.Add("KC-API-TIMESTAMP", timestamp)
	req.Header.Add("KC-API-PASSPHRASE", sign(c.Secret, c.Passphrase))
	req.Header.Add("KC-API-KEY-VERSION", c.KeyVersion)
}

// sign uses sha256 to sign the payload with the given secret
func sign(secret, payload string) string {
	var sig = hmac.New(sha256.New, []byte(secret))
	_, err := sig.Write([]byte(payload))
	if err != nil {
		return ""
	}

	return base64.StdEncoding.EncodeToString(sig.Sum(nil))
}

func castPayload(payload interface{}) ([]byte, error) {
	if payload != nil {
		switch v := payload.(type) {
		case string:
			return []byte(v), nil

		case []byte:
			return v, nil

		default:
			body, err := json.Marshal(v)
			return body, err
		}
	}

	return nil, nil
}