gilo/editor/editor.go

package editor

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

// ----------------------------------------------------------------------------
// !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) ProcessKeypress() bool {
	var str string

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

		return false
	}

	if ch == '\x1b' {
		str = string('\x1b') + parseEscapeSequence()
	} else {
		str = string(ch)
	}

	switch str {
	case keyUp, keyDown, keyLeft, keyRight, keyPageUp, keyPageDown, keyHome, keyEnd:
		e.moveCursor(str)
		return true
	default:
		// Do something later
		terminal.Write("Code: %v", str)
	}

	return true
}

func (e *editor) moveCursor (key string) {
	switch key {
	case keyLeft:
		if e.cursor.x != 0 {
			e.cursor.x -= 1
		}
	case keyRight:
		if e.cursor.x != e.screen.Cols-1 {
			e.cursor.x += 1
		}
	case keyUp:
		if e.cursor.y != 0 {
			e.cursor.y -= 1
		}
	case keyDown:
		if e.cursor.y != e.screen.Rows-1 {
			e.cursor.y += 1
		}
	case keyPageUp:
		e.cursor.y = 0
	case keyPageDown:
		e.cursor.y = e.screen.Rows
	case keyHome:
		e.cursor.x = 0
	case keyEnd:
		e.cursor.x = e.screen.Cols
	}
}

func parseEscapeSequence () string {
	var runes []rune

	for i := 0; i < 3; i++ {
		ch, size := terminal.ReadKey()
		if size == 0 {
			return "\x1b"
		}
		runes = append(runes, ch)

		if i == 1 && runes[1] >= 'A' {
			if runes[0] == 'O' {
				switch runes[1] {
				case 'H':
					return keyHome
				case 'F':
					return keyEnd
				}
			}
			if runes[0] == '[' {
				switch runes[1] {
				case 'A':
					return keyUp
				case 'B':
					return keyDown
				case 'C':
					return keyRight
				case 'D':
					return keyLeft
				case 'H':
					return keyHome
				case 'F':
					return keyEnd
				}
			}
		}

		if i == 2 && runes[0] == '[' && runes[2] == '~' {
			switch runes[1] {
			case '1':
				return keyHome
			case '3':
				return keyDelete
			case '4':
				return keyEnd
			case '5':
				return keyPageUp
			case '6':
				return keyPageDown
			case '7':
				return keyHome
			case '8':
				return keyEnd
			}
		}
	}

	return string('\x1b')
}