// usage:
// go build -o waybar-gammastep gammastep.go
package main

import (
	"encoding/json"
	"log"
	"os"
	"os/exec"
	"os/signal"
	"strings"

	. "syscall"
)

func main() {
	var (
		update = make(chan os.Signal, 1)
		cancel = make(chan os.Signal, 1)
	)
	signal.Notify(update, SIGUSR1, SIGUSR2, SIGHUP)
	signal.Notify(cancel, SIGTERM, SIGINT)

	// could use golang.org/x/sys/unix.Prctl here
	// but I want to avoid the dependency
	if _, _, e := Syscall6(SYS_PRCTL,
		uintptr(PR_SET_PDEATHSIG),
		uintptr(SIGTERM),
		0, 0, 0, 0); e != 0 {
		log.Printf("error: %v", e)
		os.Exit(1)
	}

	lookup()
	for {
		select {
		case sig := <-update:
			switch sig {
			case SIGUSR1:
				printJson("day")
			case SIGUSR2:
				printJson("night")
			case SIGHUP:
				lookup()
			}
		case <-cancel:
			log.Printf("%v exiting\n", os.Args[0])
			os.Exit(0)
		}
	}
}

func printJson(phase string) {
	_ = json.NewEncoder(os.Stdout).Encode(map[string]interface{}{
		"class":   phase,
		"alt":     phase,
		"tooltip": "gamma: " + phase,
		"text":    phase,
	})
}

func lookup() {
	cmdEnv, ok := os.LookupEnv("GAMMA_COMMAND")
	if !ok {
		printJson("unknown")
		return
	}
	log.Println(cmdEnv)
	b, err := exec.Command("bash", "-c", cmdEnv).Output()
	if err != nil {
		log.Printf("error: %v", err)
		return
	}
	phase := strings.TrimSpace(string(b))
	printJson(phase)
}