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Sample Code from a project in golang
// THIS SNIPPET FETCHS THE EXISTING CURRENCIES FROM THE EXCHANGES THRU REST API CALLS
// THE PURPOSE IS TO BYPASS THE CALL TO DYNAMODB FROM WEBSOCKETS CODE AND HAVE A MORE ACCURATE LIST OF CURRENCY PER EXCHANGE.
//@todo:
// handle errors better
// export cL variable holding the current data from exchanges
package currencyfetch
import (
"encoding/json"
"fmt"
"io/ioutil"
"net/http"
)
// CoinRest interface holder for rest api incoming data
type CoinRest interface{}
// FetchCurrencies return a list with all pairs per exchange
func FetchCurrencies() map[string][]string {
// general use channel to receive async from functions calling the rest api's
var c = make(chan []string)
// cL -> "coin list" contains a dictionary of array containing the pairs within it.
// It holds the exchange as key and the currencies supported on that specific exchange as a slice
// ie:
// exchange: currency
// gdax: ["BTC", "EUR", "LTC", "GBP", "USD", "ETH", "BCH"]
// data structure that holds the whole exchanges supported currecy list.
var cL = make(map[string][]string)
// range over the rest api list and call the api's function.
for k, v := range exchangeList() {
switch k {
case "hitbtc":
go fethHitbtc(v, c)
cL[k] = <-c
case "gdax":
go fethGdax(v, c)
cL[k] = <-c
case "bitmex":
go fetchBitmex(v, c)
cL[k] = <-c
case "poloniex":
go fetchPoloniex(v, c)
cL[k] = <-c
case "binance":
go fetchBinance(v, c)
cL[k] = <-c
}
}
// holds the final data with exchanges and currencies
// @todo: needs to change it to be exported and consumed by other code.
// fmt.Println("Currency List ->> ", cL)
// socketsclient.WSHitbtc(cL)
// testing new code. return the entire list of pairs per exchange
return cL
}
// Helper function common used to by the function below to call the rest api for each exchange.
// Function: Receives two arguments and returns the data by pointer to the caller:
// - url string which is the exchange rest api
// - coins pointer interface which receives the data from the rest call and returns to the caller function.
func restAPICaller(url string, coins *CoinRest) {
response, err := http.Get(url)
if err != nil {
fmt.Println("there was an error -> ", err)
}
defer response.Body.Close()
bytes, _ := ioutil.ReadAll(response.Body)
json.Unmarshal(bytes, &coins)
}
// Fetchs the currency list from POLONIEX thru rest call
// Function: Receives two arguemts and feed data thru the channel back to the caller:
// - url string which is the exchange rest api
// - c channel which is where it feeds the data back to the caller once ready
// it call "restAPICaller" function passing the rest url and a coin interface pointer
// to retrieve the data
func fetchPoloniex(url string, c chan []string) {
cList := make([]string, 100)
var coins CoinRest
restAPICaller(url, &coins)
for i := range coins.(map[string]interface{}) {
cList = append(cList, i)
}
c <- cList
}
// Fetchs the currency list from BITMEX thru rest call
// Function: Receives two arguemts and feed data thru the channel back to the caller:
// - url string which is the exchange rest api
// - c channel which is where it feeds the data back to the caller once ready
// it call "restAPICaller" function passing the rest url and a coin interface pointer
// to retrieve the data
func fetchBitmex(url string, c chan []string) {
cList := make([]string, 0)
var coins CoinRest
restAPICaller(url, &coins)
for _, v := range coins.([]interface{}) {
s := v.(map[string]interface{})
cList = append(cList, s["rootSymbol"].(string))
}
c <- cList
}
// Fetchs the currency list from BINANCE thru rest call
// Function: Receives two arguemts and feed data thru the channel back to the caller:
// - url string which is the exchange rest api
// - c channel which is where it feeds the data back to the caller once ready
// it call "restAPICaller" function passing the rest url and a coin interface pointer
// to retrieve the data
func fetchBinance(url string, c chan []string) {
cList := make([]string, 100)
var coins CoinRest
restAPICaller(url, &coins)
for i, v := range coins.(map[string]interface{}) {
if i == "symbols" {
for _, coin := range v.([]interface{}) {
s := coin.(map[string]interface{})
cList = append(cList, s["baseAsset"].(string))
}
}
}
c <- cList
}
// Fetchs the currency list from HITBTC thru rest call which had the same data structure
// Function: Receives two arguemts and feed data thru the channel back to the caller:
// - url string which is the exchange rest api
// - c channel which is where it feeds the data back to the caller once ready
// it call "restAPICaller" function passing the rest url and a coin interface pointer
// to retrieve the data
func fethHitbtc(url string, c chan []string) {
cList := make([]string, 900)
var coins CoinRest
restAPICaller(url, &coins)
for _, coin := range coins.([]interface{}) {
s := coin.(map[string]interface{})
cList = append(cList, s["id"].(string))
}
c <- cList
}
// Fetchs the currency list from GDAX thru rest call which had the same data structure
// Function: Receives two arguemts and feed data thru the channel back to the caller:
// - url string which is the exchange rest api
// - c channel which is where it feeds the data back to the caller once ready
// it call "restAPICaller" function passing the rest url and a coin interface pointer
// to retrieve the data
func fethGdax(url string, c chan []string) {
cList := make([]string, 0)
var coins CoinRest
restAPICaller(url, &coins)
for _, coin := range coins.([]interface{}) {
s := coin.(map[string]interface{})
cList = append(cList, s["id"].(string))
}
// fmt.Println("GDAX REST -> ", cList)
c <- cList
}
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