package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"io"
	"os"
	"os/exec"
	"os/signal"
	"sync"
	"syscall"
	"time"

	"golang.org/x/sys/unix"
)

type Service struct {
	CMD  string   `json:"cmd"`
	Args []string `json:"args"`
	PWD  string   `json:"pwd"`

	cmd *exec.Cmd
}

type Config struct {
	Services []*Service `json:"services"`
}

func printErr(err error) {
	fmt.Fprintf(os.Stderr, "[qini] Err: %s\n", err.Error())
}

func printInfo(info string) {
	fmt.Fprintf(os.Stderr, "[qini] Inf: %s\n", info)
}

var verbose bool

func debug(s string, a ...any) {
	if verbose {
		fmt.Fprintf(os.Stderr, "[qini] debug: %s\n", fmt.Sprintf(s, a...))
	}
}

func stopAllServices(services []*Service) {
	for _, s := range services {
		if s.cmd.Process == nil {
			continue
		}

		debug("send SIGINT to [%s]", s.CMD)
		s.cmd.Process.Signal(syscall.SIGINT)

		go func(s *Service) {
			time.Sleep(15 * time.Second)
			if s.cmd.Process != nil && s.cmd.ProcessState == nil {
				debug("send SIGKILL to [%s]", s.CMD)
				s.cmd.Process.Kill()
			}
		}(s)
	}
}

func runServices(services []*Service) int {
	if len(services) == 0 {
		printInfo("no services in config")
		return 1
	}

	var (
		r *io.PipeReader
		w *io.PipeWriter

		lock sync.Mutex
		once sync.Once
		wg   sync.WaitGroup

		exitCode int
	)

	lock.Lock()

	for i, s := range services {
		s.cmd = exec.Command(s.CMD, s.Args...)

		s.cmd.SysProcAttr = &syscall.SysProcAttr{
			Setsid: false,
		}

		if s.PWD != "" {
			s.cmd.Dir = s.PWD
		}

		if r != nil {
			s.cmd.Stdin = r
		}

		if i+1 < len(services) {
			r, w = io.Pipe()
			s.cmd.Stdout = w
		} else {
			s.cmd.Stdout = os.Stdout
		}

		wg.Add(1)
		go func(w *io.PipeWriter) {
			defer wg.Done()

			defer func() {
				if w != nil {
					w.Close()
				}

				once.Do(func() {
					lock.Lock()
					defer lock.Unlock()

					debug("stop all services")

					stopAllServices(services)
					exitCode = s.cmd.ProcessState.ExitCode()
				})
			}()

			debug("run service [%s]", s.CMD)
			err := s.cmd.Run()
			if err != nil {
				printErr(err)
			}
			debug("service [%s] done, err: [%v]", s.CMD, err)
		}(w)
	}

	lock.Unlock()

	debug("wait servises")
	wg.Wait()
	debug("all servises stoped")

	return exitCode
}

func loadConfig(cfg *Config, configFile string) error {
	f, err := os.Open(configFile)
	if err != nil {
		return err
	}

	defer f.Close()

	return json.NewDecoder(f).Decode(cfg)
}

func forwardSignals(services []*Service) {
	signals := []os.Signal{syscall.SIGTERM, syscall.SIGINT, syscall.SIGQUIT}
	sigCh := make(chan os.Signal, 1)
	signal.Notify(sigCh, signals...)

	for sig := range sigCh {
		for _, s := range services {
			if s.cmd.Process == nil {
				continue
			}

			syscall.Kill(s.cmd.Process.Pid, (sig).(syscall.Signal))
		}
	}
}

func forwardSignals2(services []*Service) {
	sigCh := make(chan os.Signal, 1)
	signal.Notify(sigCh, syscall.SIGCHLD)

	for _ = range sigCh {
		printInfo("chld")
		for _, c := range services {
			if c.cmd.ProcessState != nil {

			}
		}
	}
}

func main() {
	verbose = true

	err := unix.Prctl(unix.PR_SET_CHILD_SUBREAPER, 1, 0, 0, 0)
	if err != nil {
		printErr(err)
	}

	var configFile string
	flag.StringVar(&configFile, "c", "./config.json", "JSON config file")
	flag.Parse()

	var cfg Config

	err = loadConfig(&cfg, configFile)
	if err != nil {
		printErr(err)
		os.Exit(1)
	}

	go forwardSignals(cfg.Services)
	go forwardSignals2(cfg.Services)

	exitCode := runServices(cfg.Services)
	os.Exit(exitCode)
}