gilo/editor/editor.go

package editor

import (
	"fmt"
	"timshome.page/gilo/fn"
	"timshome.page/gilo/terminal"
)

const KiloVersion = "0.0.1"

// ----------------------------------------------------------------------------
// !Editor
// ----------------------------------------------------------------------------

type cursor struct {
	x int
	y int
}

type editor struct {
	screen *terminal.Screen
	cursor *cursor
}

func New() *editor {
	screen := terminal.Size()
	cursor := &cursor { 0, 0 }

	return &editor{screen, cursor }
}

func (e *editor) RefreshScreen() {
	ab := newBuffer()

	ab.append(terminal.HideCursor)
	ab.append(terminal.ResetCursor)

	e.drawRows(ab)
	ab.append(terminal.MoveCursor(e.cursor.x, e.cursor.y))

	ab.append(terminal.ShowCursor)

	terminal.Write(ab.toString())
}

func (e *editor) ProcessKeypress() bool {
	ch, _ := terminal.ReadKey()

	// Clean up on exit
	if ch == fn.Ctrl('q') {
		terminal.Write(terminal.ClearScreen + terminal.ResetCursor)

		return false
	}

	switch ch {
	case 'w', 'a', 's', 'd':
		e.moveCursor(ch)
	default:
		// Do nothing!
	}

	return true
}

func (e *editor) drawRows(ab *buffer) {
	for y :=0; y < e.screen.Rows; y += 1 {
		if y == e.screen.Rows / 3 {
			welcome := fmt.Sprintf("Gilo editor -- version %s", KiloVersion)
			if len(welcome) > e.screen.Cols {
				welcome = fn.TruncateString(welcome, e.screen.Cols)
			}

			padding := (e.screen.Cols - len(welcome)) / 2
			if padding > 0 {
				ab.appendRune('~')
				padding--
			}

			for padding > 0 {
				padding--
				ab.appendRune(' ')
			}

			ab.append(welcome)
		} else {
			ab.appendRune('~')
		}

		ab.append(terminal.ClearLine)

		if y < (e.screen.Rows - 1) {
			ab.append("\r\n")
		}
	}
}

func (e *editor) moveCursor (key rune) {
	switch key {
	case 'a':
		e.cursor.x -= 1
	case 'd':
		e.cursor.x += 1
	case 'w':
		e.cursor.y -= 1
	case 's':
		e.cursor.y += 1
	}
}