BAPCSalesLiveFeed will show a constant stream of live updates from the /r/bapcsalescanada subreddit. It was hacked together as quickly as possible in preparation for Black Friday.

BAPCSalesCanadaLiveFeed.go

// BAPCSalesLiveFeed will show a constant stream of live updates from the /r/bapcsalescanada subreddit.
// It was hacked together as quickly as possible in preparation for Black Friday.
// Note that this leaks memory _very slowly_ due to us constantly adding IDs to the postCache.
// This isn't a big deal since the amount of data stored is miniscule, but worth noting if you're
// going to be running it non-stop for a couple of years on a memory-constrained system for whatever reason.

package main

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"os"
	"strconv"
	"strings"
	"time"

	"github.com/faiface/beep/speaker"
	"github.com/faiface/beep/wav"
	"github.com/fatih/color"
)

const (
	subreddit = "bapcsalescanada"
	redditURL = "https://www.reddit.com/r/" + subreddit + "/new"
	userAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.77 Safari/537.36"
	// The notification sound comes from https://www.leshylabs.com/apps/sfMaker/
	// Copy-and-paste the string below into the "Sound Text" field, then click on "Load Text".
	// W=44100,f=992.364,v=113.026,V=9.898,t=1.598,T=0.112,_=0.047,d=286.446,D=0.164,p=1.729,b=1.6,r=0.3,c=-27,C=48.503,s=164,S=5.336,z=Down,g=0.419,l=0.33,L=0.605
	soundFile = "notification.wav"
)

var postCache = make(map[string]struct{})

type reddit struct {
	Data struct {
		Children []struct {
			Data struct {
				ID         string  `json:"id"`
				Title      string  `json:"title"`
				Domain     string  `json:"domain"`
				Permalink  string  `json:"permalink"`
				URL        string  `json:"url"`
				CreatedUtc float64 `json:"created_utc"`
			} `json:"data"`
		} `json:"children"`
	} `json:"data"`
}

func main() {
	run(false)
	for range time.Tick(time.Second * 10) {
		run(true)
	}
}

func run(playSound bool) {
	r := parseJSON()

	for i := 0; i <= len(r.Data.Children)-1; i++ {
		item := r.Data.Children[len(r.Data.Children)-1-i].Data

		_, exists := postCache[item.ID]
		if exists {
			continue
		}
		postCache[item.ID] = struct{}{}

		timeInt, err := strconv.Atoi(strings.Split(strconv.FormatFloat(item.CreatedUtc, 'f', 6, 64), ".")[0])
		if err != nil {
			log.Println(color.RedString("Unable to convert UTC time to int: " + err.Error()))
		}
		localTime := color.YellowString(time.Unix(int64(timeInt), int64(0)).Format("3:04PM"))
		title := item.Title

		redditLink := color.BlueString("https://www.reddit.com" + item.Permalink)

		var storeLink string
		if item.Domain != "self."+subreddit {
			storeLink = color.CyanString(item.URL)
		}

		fmt.Println(localTime + " " + title + "\n" + redditLink)
		if storeLink != "" {
			fmt.Println(storeLink)
		}

		fmt.Println(strings.Repeat("-", 80))

		if playSound {
			f, err := os.Open(soundFile)
			if err != nil {
				log.Println(color.RedString("Missing sound file: " + soundFile + ": " + err.Error()))
				playSound = false
				continue
			}
			s, format, err := wav.Decode(f)
			if err != nil {
				log.Println(color.RedString("Unable to decode sound file: " + soundFile + ": " + err.Error()))
				playSound = false
				continue
			}
			speaker.Init(format.SampleRate, format.SampleRate.N(time.Second/10))
			speaker.Play(s)
		}
	}
}

func parseJSON() reddit {
	req, err := http.NewRequest("GET", redditURL+".json", nil)
	if err != nil {
		log.Fatalln(color.RedString("Error retrieving HTTP: " + err.Error()))
	}
	// Setting a User-Agent is required otherwise reddit will block the request.
	req.Header.Set("User-Agent", userAgent)

	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		log.Println(color.RedString("Error receiving a response: " + err.Error()))
		return parseJSON()
	}
	defer resp.Body.Close()

	r := reddit{}
	json.NewDecoder(resp.Body).Decode(&r)
	if err != nil {
		log.Println(color.RedString("Error decoding JSON: " + err.Error()))
		return parseJSON()
	}

	return r
}