package main

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

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

var ch chan struct{}

func init() {
	ch = make(chan struct{})
}

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)
	}

loop:
	for {
		time.Sleep(time.Second)

		for _, s := range services {
			if s.cmd.Process != nil && s.cmd.ProcessState == nil {
				continue loop
			}
		}

		os.Exit(1)
	}
}

func runServices(services []*Service) error {
	if len(services) == 0 {
		return errors.New("no services in config")
	}

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

	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
		}

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

		go func(s *Service, w *io.PipeWriter) {
			s.cmd.Wait()
			w.Close()
			debug("service done [%s]", s.CMD)
		}(s, w)
	}

	return nil
}

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)

	var once sync.Once

	for range sigCh {
		debug("chld")
		for _, c := range services {
			debug("%v", c.cmd.ProcessState)
			if c.cmd.ProcessState != nil {
				once.Do(func() {
					debug("stop all services")
					stopAllServices(services)
				})
			}
		}
	}
}

func main() {
	verbose = false

	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.BoolVar(&verbose, "v", false, "Show debug output")
	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)

	runServices(cfg.Services)
	//os.Exit(exitCode)

	<-ch
}