piframe-go/cmd/ui/ui.go

package main

import (
	"io"
	"log"
	"os"
	"os/exec"
	"os/signal"
	"syscall"
	"time"

	"github.com/gdamore/tcell"
	"github.com/rivo/tview"
)

const (
	CMD_FIM            = "/usr/local/bin/pf-fim.sh"
	SLIDESHOW_INTERVAL = 300 * time.Second
)

func main() {
	// fim placeholder so we can operate on it when a signal is received
	var fim *exec.Cmd = nil

	// Setup signal listening
	sigs := make(chan os.Signal)
	signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)
	defer func() { close(sigs) }()

	// Goroutine to handle os signals (nuke fim so we can get to config ui)
	go func() {
		for range sigs {
			if fim != nil { // Just in case someone lays on ctrl-c or similar during startup
				if err := fim.Process.Kill(); err != nil {
					log.Fatalf("failed to kill fim : %s", err)
				}
			}
		}
	}()

	// Run slideshow
	fim = exec.Command(CMD_FIM)

	// Setup stdin for fim to control slideshow
	stdin, err := fim.StdinPipe()
	if err != nil {
		log.Fatalf("Error getting fim stdin : %s", err)
	}

	// Advance slideshow every interval as defined in const()
	ticker := time.NewTicker(SLIDESHOW_INTERVAL)
	stop_ticker := make(chan struct{})
	go func() {
		for {
			select {
			case <-ticker.C:
				_, err = io.WriteString(stdin, "n")
				if err != nil {
					log.Fatalf("Error advancing slides : %s", err)
				}
			case <-stop_ticker:
				ticker.Stop()
				stdin.Close()
				return
			}
		}
	}()

	// Run fim
	if err := fim.Run(); err != nil {
		// Unwrap the error a bit so we can find out if a signal killed fim or something else
		// An exit code of -1 means the program didn't exit in time or was terminated by a signal (per the docs)
		if exitError, ok := err.(*exec.ExitError); ok && exitError.ExitCode() != -1 {
			log.Fatalf("Error running fim : %s", err)
		}
	}

	// Stop fim slideshow advancing go routine
	close(stop_ticker)

	// Run config UI when slideshow stops
	app := tview.NewApplication()
	frame := tview.NewFrame(tview.NewBox().SetBackgroundColor(tcell.ColorBlack)).
		SetBorders(2, 2, 2, 2, 4, 4).
		AddText("PiFrame", true, tview.AlignCenter, tcell.ColorWhite).
		AddText("Configuration Utility", true, tview.AlignCenter, tcell.ColorRed)
	if err := app.SetRoot(frame, true).EnableMouse(true).Run(); err != nil {
		log.Fatalf("Error running UI : %s", err)
	}
}