package main

import (
	"bufio"
	"net"
	"net/url"
	"os"
	"strconv"
	"strings"
	"time"
)

func main() {
	url := strings.TrimSpace(os.Getenv("BACKEND_HEALTHCHECK_URL"))
	if url == "" {
		port := strings.TrimSpace(os.Getenv("BACKEND_PORT"))
		if port == "" {
			port = strings.TrimSpace(os.Getenv("PORT"))
		}
		if port == "" {
			port = "3000"
		}
		url = "http://127.0.0.1:" + port + "/health"
	}

	statusCode, err := checkHTTP(url, 3*time.Second)
	if err != nil {
		_, _ = os.Stderr.WriteString("healthcheck request failed: " + err.Error() + "\n")
		os.Exit(1)
	}
	if statusCode < 200 || statusCode >= 400 {
		_, _ = os.Stderr.WriteString("healthcheck returned HTTP " + strconv.Itoa(statusCode) + "\n")
		os.Exit(1)
	}
}

func checkHTTP(rawURL string, timeout time.Duration) (int, error) {
	parsed, err := url.Parse(rawURL)
	if err != nil {
		return 0, err
	}
	host := parsed.Host
	if !strings.Contains(host, ":") {
		host += ":80"
	}
	path := parsed.RequestURI()
	if path == "" {
		path = "/"
	}

	conn, err := net.DialTimeout("tcp", host, timeout)
	if err != nil {
		return 0, err
	}
	defer conn.Close()
	_ = conn.SetDeadline(time.Now().Add(timeout))

	request := "GET " + path + " HTTP/1.1\r\nHost: " + parsed.Host + "\r\nConnection: close\r\n\r\n"
	if _, err := conn.Write([]byte(request)); err != nil {
		return 0, err
	}

	line, err := bufio.NewReader(conn).ReadString('\n')
	if err != nil {
		return 0, err
	}
	parts := strings.Fields(line)
	if len(parts) < 2 {
		return 0, nil
	}
	return strconv.Atoi(parts[1])
}