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quote.go
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quote.go
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package main
import (
"encoding/json"
"fmt"
"log"
"net/http"
"strings"
"time"
)
// Quote represents the last price seen for a symbol.
type Quote struct {
Price float64 `json:"price"`
}
// Quotes is a collection of Quote structs keyed by symbol (e.g. AAPL -> Quote{175.00}).
type Quotes map[string]Quote
// State is the state queried at program start up using the Batch API, and then never queried again.
type State struct {
OpenHighLowClose struct {
Open Quote `json:"open"`
Close Quote `json:"close"`
} `json:"ohlc"`
}
// States is a map of symbol -> State.
type States map[string]State
// GetStates attempts to unmarshall the initial program state.
func GetStates(symbols []string) (States, error) {
endpoint := fmt.Sprintf("https://api.iextrading.com/1.0/stock/market/batch?symbols=%s&types=ohlc", strings.Join(symbols, ","))
response, err := http.Get(endpoint)
if err != nil {
fmt.Println(err)
return nil, err
}
defer response.Body.Close()
var states States
return states, json.NewDecoder(response.Body).Decode(&states)
}
// GetQuotes hits the passed in endpoint and attempts to parse it as JSON.
func GetQuotes(endpoint string) (Quotes, error) {
response, err := http.Get(endpoint)
if err != nil {
return nil, err
}
defer response.Body.Close()
var tickers map[string]Quote
return tickers, json.NewDecoder(response.Body).Decode(&tickers)
}
// PollQuotes polls for updated quotes every second and sends them down the channel.
func PollQuotes(endpoint string, quotesQueue chan<- Quotes) {
for {
start := time.Now()
if quotes, err := GetQuotes(endpoint); err != nil {
log.Panicln(err)
} else {
quotesQueue <- quotes
}
// Ensure we're a good consumer and only hit the API once per second.
time.Sleep(time.Second - time.Since(start))
}
}