package terminal

import (
	"bufio"
	"fmt"
	"os"

	"golang.org/x/term"
)

var reader = bufio.NewReader(os.Stdin)

func ReadKey() (rune, int) {
	ch, size, err := reader.ReadRune()
	if err != nil {
		panic(err)
	}

	return ch, size
}

// Is this a valid interactive terminal?
func check() {
	if !term.IsTerminal(int(os.Stdin.Fd())) {
		panic("An interactive terminal is required to use a text editor!")
	}
}

// Put the terminal in raw mode
func RawOn() *term.State {
	check()

	oldState, err := term.MakeRaw(int(os.Stdin.Fd()))
	if err != nil {
		panic(err)
	}

	return oldState
}

// Restore the terminal to canonical mode
func RawOff(oldState *term.State) {
	err := term.Restore(int(os.Stdin.Fd()), oldState)
	if err != nil {
		panic(err)
	}
}

func sizeTrick () (rows int, cols int) {
	// Move cursor to location further than likely screen size
	// The cursor will move to maximum available position
	fmt.Print("\x1b[999C\x1b[99B")

	// Ask the terminal where the cursor is
	fmt.Print("\x1b[6n")

	// Read stdin looking for the reported location
	buffer := ""
	for char, _ := ReadKey(); char != 'R'; char, _ = ReadKey() {

		if char == '\x1b' || char == '[' {
			continue
		}

		if char == 'R' || char == '\x00'{
			break
		}

		buffer += string(char)
	}

	_, err := fmt.Sscanf(buffer, "%d;%d", &rows, &cols)
	if err != nil {
		panic(err)
	}

	return rows, cols
}

// Get the size of the terminal in rows and columns
func Size () (rows int, cols int) {
	cols = 80
	rows = 24

	// Try the syscall first
	cols, rows, err := term.GetSize(int(os.Stdin.Fd()))
	if err == nil {
		return rows, cols
	}

	// Figure out the size the hard way
	rows, cols = sizeTrick()

	return rows, cols
}

// Print string to stdout
func Write(s string) {
	fmt.Print(s)
}