client.go

package poloniex

import (
	"crypto/hmac"
	"crypto/sha512"
	"encoding/hex"
	"errors"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"net/http/httputil"
	"net/url"
	"strconv"
	"strings"
	"time"
)

type client struct {
	apiKey      string
	apiSecret   string
	httpClient  *http.Client
	throttle    <-chan time.Time
	httpTimeout time.Duration
	debug       bool
}

var (
	// Technically 6 req/s allowed, but we're being nice / playing it safe.
	reqInterval = 200 * time.Millisecond
)

// NewClient return a new Poloniex HTTP client
func NewClient(apiKey, apiSecret string) (c *client) {
	return &client{apiKey, apiSecret, &http.Client{}, time.Tick(reqInterval), 30 * time.Second, false}
}

// NewClientWithCustomTimeout returns a new Poloniex HTTP client with custom timeout
func NewClientWithCustomTimeout(apiKey, apiSecret string, timeout time.Duration) (c *client) {
	return &client{apiKey, apiSecret, &http.Client{}, time.Tick(reqInterval), timeout, false}
}

func (c client) dumpRequest(r *http.Request) {
	if r == nil {
		log.Print("dumpReq ok: <nil>")
		return
	}
	dump, err := httputil.DumpRequest(r, true)
	if err != nil {
		log.Print("dumpReq err:", err)
	} else {
		log.Print("dumpReq ok:", string(dump))
	}
}

func (c client) dumpResponse(r *http.Response) {
	if r == nil {
		log.Print("dumpResponse ok: <nil>")
		return
	}
	dump, err := httputil.DumpResponse(r, true)
	if err != nil {
		log.Print("dumpResponse err:", err)
	} else {
		log.Print("dumpResponse ok:", string(dump))
	}
}

// doTimeoutRequest do a HTTP request with timeout
func (c *client) doTimeoutRequest(timer *time.Timer, req *http.Request) (*http.Response, error) {
	// Do the request in the background so we can check the timeout
	type result struct {
		resp *http.Response
		err  error
	}
	done := make(chan result, 1)
	go func() {
		if c.debug {
			c.dumpRequest(req)
		}
		resp, err := c.httpClient.Do(req)
		if c.debug {
			c.dumpResponse(resp)
		}
		done <- result{resp, err}
	}()
	// Wait for the read or the timeout
	select {
	case r := <-done:
		return r.resp, r.err
	case <-timer.C:
		return nil, errors.New("timeout on reading data from Poloniex API")
	}
}

func (c *client) makeReq(method, resource string, payload map[string]string, authNeeded bool, respCh chan<- []byte, errCh chan<- error) {
	body := []byte{}
	connectTimer := time.NewTimer(c.httpTimeout)

	var rawurl string
	if strings.HasPrefix(resource, "http") {
		rawurl = resource
	} else {
		rawurl = fmt.Sprintf("%s/%s", API_BASE, resource)
	}

	formValues := url.Values{}
	for key, value := range payload {
		formValues.Set(key, value)
	}
	formData := formValues.Encode()

	req, err := http.NewRequest(method, rawurl, strings.NewReader(formData))
	if err != nil {
		respCh <- body
		errCh <- errors.New("You need to set API Key and API Secret to call this method")
		return
	}

	if authNeeded {
		if len(c.apiKey) == 0 || len(c.apiSecret) == 0 {
			respCh <- body
			errCh <- errors.New("You need to set API Key and API Secret to call this method")
			return
		}

		mac := hmac.New(sha512.New, []byte(c.apiSecret))
		_, err := mac.Write([]byte(formData))
		if err != nil {
			errCh <- err
		}
		sig := hex.EncodeToString(mac.Sum(nil))
		req.Header.Add("Key", c.apiKey)
		req.Header.Add("Sign", sig)
	}

	if method == "POST" || method == "PUT" {
		req.Header.Add("Content-Type", "application/x-www-form-urlencoded")
	}

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

	resp, err := c.doTimeoutRequest(connectTimer, req)
	if err != nil {
		respCh <- body
		errCh <- err
		return
	}

	defer resp.Body.Close()

	body, err = ioutil.ReadAll(resp.Body)
	if err != nil {
		respCh <- body
		errCh <- err
		return
	}
	if resp.StatusCode != 200 {
		respCh <- body
		errCh <- errors.New(resp.Status)
		return
	}

	respCh <- body
	errCh <- nil
	close(respCh)
	close(errCh)
}

// do prepare and process HTTP request to Poloniex API
func (c *client) do(method, resource string, payload map[string]string, authNeeded bool) (response []byte, err error) {
	respCh := make(chan []byte)
	errCh := make(chan error)
	<-c.throttle
	go c.makeReq(method, resource, payload, authNeeded, respCh, errCh)
	response = <-respCh
	err = <-errCh
	return
}

// doCommand prepares an authorized command-request for Poloniex's tradingApi
func (c *client) doCommand(command string, payload map[string]string) (response []byte, err error) {
	if payload == nil {
		payload = make(map[string]string)
	}

	payload["command"] = command
	payload["nonce"] = strconv.FormatInt(time.Now().UnixNano(), 10)

	return c.do("POST", "tradingApi", payload, true)
}