Small Go Powered parser to query Yahoo api for money xchange rates and store data in redis database

main.go

package main

/*
Test task: Small Go powered parser to query Yahoo api
for money xchange rates and store data
in local redis database.
Time taken ~1 hour
*/

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"os"
	"time"

	"gopkg.in/redis.v3"
)

//API url
const exchangeRateURL = "https://query.yahooapis.com/v1/public/yql?q=select+*+from+yahoo.finance.xchange+where+pair+=+%22USDRUB,EURRUB%22&format=json&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback="

//Rate stores information about exchange rate for current object
type Rate struct {
	ID   string `json:"id"`
	Name string `json:"Name"`
	Rate string `json:"Rate"`
	Ask  string `json:"Ask"`
	Bid  string `json:"Bid"`
}

type responseQuery struct {
	Count       int             `json:"count"`
	Created     time.Time       `json:"created"`
	ResultsRate responseResults `json:"results"`
}

type responseResults struct {
	Rate []Rate `json:"rate"`
}
type response struct {
	Query responseQuery `json:"query"`
}

//GetRates performs getting information from 3rd party api
func GetRates() ([]Rate, error) {
	rP := response{}
	client := &http.Client{}
	req, err := http.NewRequest("GET", exchangeRateURL, nil)
	if err != nil {
		return nil, err
	}
	res, err := client.Do(req)
	if err != nil {
		return nil, err
	}
	defer res.Body.Close()
	if res.StatusCode == 200 {
		raw, err := ioutil.ReadAll(res.Body)
		if err != nil {
			return nil, err
		}
		err = json.Unmarshal(raw, &rP)
		if err != nil {
			return nil, err
		}
		return rP.Query.ResultsRate.Rate, err
	}
	return nil, fmt.Errorf("Wrong status code - %d", res.StatusCode)
}

//RedisStorage is a interface to redis database
type RedisStorage struct {
	Client *redis.Client
}

//InitRedisStorage is a constructor for redis database client, loads config from OS environment values of `REDIS_HOST`,`REDIS_PORT`,`REDIS_AUTHPASS`
func InitRedisStorage() (RedisStorage, error) {
	host := os.Getenv("REDIS_HOST")
	if host == "" {
		host = "localhost"
	}
	port := os.Getenv("REDIS_PORT")
	if port == "" {
		port = "6379"
	}
	auth := os.Getenv("REDIS_AUTHPASS")
	client := redis.NewClient(&redis.Options{
		Addr:     fmt.Sprintf("%s:%s", host, port),
		Password: auth,
		DB:       0, // use default DB
	})

	return RedisStorage{Client: client}, nil
}

//StoreRate saves Rate's values into database
func (rs *RedisStorage) StoreRate(v Rate, now time.Time) error {
	return rs.Client.HMSet(
		v.Name,
		"rate", v.Rate,
		"ask", v.Ask,
		"bid", v.Bid,
		"timestamp", fmt.Sprintf("%d", now.UnixNano())).Err()
}

func main() {
	now := time.Now()
	loc, err := time.LoadLocation("Europe/Moscow")
	if err != nil {
		panic(err)
	}
	rates, err := GetRates()
	if err != nil {
		panic(err)
	}
	fmt.Printf("%s\n", now.In(loc).Format("Mon 2 January 2006 15:04:05"))
	storage, err := InitRedisStorage()
	for _, v := range rates {
		fmt.Printf("%s: Rate: %s. Bid: %s. Ask: %s.\n", v.Name, v.Rate, v.Bid, v.Ask)
		err = storage.StoreRate(v, now)
		if err != nil {
			panic(err)
		}
	}
}