Launch a thread with the specified subject on any 4chan board

4chan.go

package main

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"os/exec"
	"strings"
)

const baseURL = "https://boards.4chan.org"

func main() {
	cliFlags := os.Args[1:]
	var board, topic string
	if len(cliFlags) < 2 {
		board = "g"
		topic = "dpt"
	} else {
		board = cliFlags[0]
		topic = cliFlags[1]
	}
	boardURL := fmt.Sprintf("%s/%s", baseURL, board)
	boardCatalog := fmt.Sprintf("%s/catalog.json", boardURL)
	resp, err := http.Get(boardCatalog)
	checkErr(err, fmt.Sprintf("Could not GET %s catalog JSON", board))
	defer resp.Body.Close()
	catalogJson, err := ioutil.ReadAll(resp.Body)
	checkErr(err, "Could not read response body")
	var threads []map[string]interface{}
	checkErr(json.Unmarshal([]byte(catalogJson), &threads), "Could not unmarshall json")
	threadNum := findThread(threads, &topic)
	if threadNum > 0 {
		// print out a URL to feed into chrome
		_ = exec.Command("google-chrome", fmt.Sprintf("%s/thread/%d", boardURL, threadNum)).Start()
	} else {
		log.Println("Could not find topic. Check catalog")
		_ = exec.Command("google-chrome", fmt.Sprintf("%s/%s", boardURL, topic)).Start()
	}
}

func findThread(threads []map[string]interface{}, topic *string) int {
	for _, page := range threads {
		threads := page["threads"].([]interface{})
		for _, p := range threads {
			post := p.(map[string]interface{})
			sub, exists := post["sub"]
			if !exists {
				continue
			}
			if strings.Contains(strings.ToLower(sub.(string)), *topic) {
				return int(post["no"].(float64))
			}
		}
	}
	return -1
}

func checkErr(err error, message string) {
	if err != nil {
		log.Fatal(message, " ", err)
	}
}

Usage: 4chan <board> <subject>