package main

import (
	"fmt"
	"log"
	"net/http"
	"os"
	"strconv"
)

const (
	defaultBindAddress    = ":3000"
	defaultResponseString = "Hello world"
	defaultResponseStatus = http.StatusOK
)

func main() {
	addr, ok := os.LookupEnv("BIND_ADDR")
	if !ok {
		addr = defaultBindAddress
	}

	responseString, ok := os.LookupEnv("RESPONSE_STRING")
	if !ok {
		responseString = defaultResponseString
	}

	var statusCode int
	statusCodeString, ok := os.LookupEnv("STATUS_CODE")
	if ok {
		var err error
		statusCode, err = strconv.Atoi(statusCodeString)
		if err != nil {
			log.Fatal(err)
		}
	} else {
		statusCode = defaultResponseStatus
	}

	http.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
		w.Header().Set("Content-Type", "text/plain")
		w.WriteHeader(statusCode)
		fmt.Fprintf(w, responseString)
	})

	fmt.Printf("Listening on %s...\n", addr)
	log.Fatal(http.ListenAndServe(addr, nil))
}