Some terminal UI example

terminal.go

package main

import (
	"bytes"
	"fmt"
	"os"
	"os/exec"
	"strings"
)

func main() {
	r, c := initialize()
	clear()
	move(0, 0)
	fmt.Printf("Rows: %d, Columns: %d", r, c)
	move(1, 0)
	fmt.Print(strings.Repeat("#", c))
	for i := 2; i < r-2; i++ {
		move(i, 0)
		fmt.Print("#")
		move(i, c-1)
		fmt.Print("#")
	}
	move(r-2, 0)
	fmt.Print(strings.Repeat("#", c))

	x := 2
	y := 1

	for {
		move(x, y)
		input, err := readInput()
		if err != nil {
			fmt.Fprintf(os.Stderr, "Error: %s\n", err)
			break
		}

		if input == "ESC" {
			break
		} else if input == "SPACE" {
			fmt.Printf("#")
		} else if input == "UP" {
			x -= 1
		} else if input == "DOWN" {
			x += 1
		} else if input == "LEFT" {
			y -= 1
		} else if input == "RIGHT" {
			y += 1
		} else if input == "C" {
			fmt.Printf(" ")
		}
	}

	move(r-1, 0)
	cleanup()
}

func initialize() (rows int, columns int) {
	var output bytes.Buffer

	cmd := exec.Command("stty", "cbreak", "-echo", "size")
	cmd.Stdout = &output
	cmd.Stdin = os.Stdin
	cmd.Stderr = os.Stderr

	err := cmd.Run()
	if err != nil {
		panic(err)
	}

	_, err = fmt.Sscanf(output.String(), "%d %d", &rows, &columns)
	if err != nil {
		panic(fmt.Errorf("Unable to read screen size: %s", err))
	}

	return
}

func cleanup() {
	cmd := exec.Command("stty", "-cbreak", "echo")
	cmd.Stdin = os.Stdin
	cmd.Stderr = os.Stderr

	err := cmd.Run()
	if err != nil {
		panic(err)
	}
}

func clear() {
	fmt.Print("\x1b[2J")
}

func move(x, y int) {
	fmt.Printf("\x1b[%d;%df", x+1, y+1)
}

func resize() (rows int, columns int) {
	var output bytes.Buffer

	cmd := exec.Command("stty", "size")
	cmd.Stdout = &output
	cmd.Stdin = os.Stdin
	cmd.Stderr = os.Stderr

	err := cmd.Run()
	if err != nil {
		panic(err)
	}

	_, err = fmt.Sscanf(output.String(), "%d %d", &rows, &columns)
	if err != nil {
		panic(fmt.Errorf("Unable to read screen size: %s", err))
	}

	return
}

func readInput() (string, error) {
	buffer := make([]byte, 100)

	cnt, err := os.Stdin.Read(buffer)
	if err != nil {
		return "", nil
	}

	if cnt == 1 && buffer[0] == 0x1b {
		return "ESC", nil
	} else if cnt == 1 && buffer[0] == ' ' {
		return "SPACE", nil
	} else if cnt == 1 && buffer[0] == 'c' {
		return "C", nil
	} else if cnt >= 3 {
		if buffer[0] == 0x1b && buffer[1] == '[' {
			switch buffer[2] {
			case 'A':
				return "UP", nil
			case 'B':
				return "DOWN", nil
			case 'C':
				return "RIGHT", nil
			case 'D':
				return "LEFT", nil
			}
		}
	}

	return "", nil
}