gilo/editor/editor.go

package editor

import (
	"bufio"
	"log"
	"os"
	"timshome.page/gilo/terminal"
)

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

type point struct {
	x int
	y int
}

type editor struct {
	screen *terminal.Screen
	cursor *point
	offset *point
	rows []*row
}

func New() *editor {
	screen := terminal.Size()
	cursor := &point { 0, 0 }
	offset := &point { 0, 0 }
	var rows []*row

	return &editor{
		screen,
		cursor,
		offset,
		rows,
	}
}

func (e *editor) Open(filename string) {
	file, err := os.Open(filename)
	if err != nil {
		log.Fatalf("failed to open file")
	}
	defer file.Close()

	scanner := bufio.NewScanner(file)
	scanner.Split(bufio.ScanLines)

	for scanner.Scan() {
		e.appendRow(scanner.Text())
	}
}

func (e *editor) ProcessKeypress() bool {
	var str string

	ch, _ := terminal.ReadKey()
	if isCtrl(ch) {
		switch ch {
		case ctrl('q'):
			// Clean up on exit
			terminal.Write(terminal.ClearScreen + terminal.ResetCursor)

			return false
		}
	}

	if ch == '\x1b' {
		str = 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) {
	var row *row
	if e.cursor.y > len(e.rows) {
		row = nil
	} else {
		row = e.rows[e.cursor.y]
	}

	switch key {
	case keyLeft:
		if e.cursor.x != 0 {
			e.cursor.x -= 1
		}

		// Move from beginning of current row to end of previous row
		if e.cursor.y > 0 {
			e.cursor.y -= 1
			e.cursor.x = e.rows[e.cursor.y].Size()
		}
	case keyRight:
		if row != nil && e.cursor.x < row.Size() {
			e.cursor.x += 1
		}

		// Move from end of current line to beginning of next line
		if row != nil && e.cursor.x == row.Size() {
			e.cursor.y += 1
			e.cursor.x = 0
		}
	case keyUp:
		if e.cursor.y != 0 {
			e.cursor.y -= 1
		}
	case keyDown:
		if e.cursor.y < len(e.rows) {
			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:
		if row != nil {
			e.cursor.x = row.Size()
		}
	}

	if e.cursor.y > len(e.rows) {
		row = nil
	} else {
		row = e.rows[e.cursor.y]
		rowLen := row.Size()

		// Snap to the end of a shorter line from a longer one
		if e.cursor.x > rowLen {
			e.cursor.x = rowLen
		}
	}
}

func (e *editor) appendRow(s string) {
	newRow := NewRow(s)
	e.rows = append(e.rows, newRow)
}

// Convert the raw ANSI escape sequences to the type of key input
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' {
			// \eOH \eOF
			if runes[0] == 'O' {
				switch runes[1] {
				case 'H':
					return keyHome
				case 'F':
					return keyEnd
				}
			}
			// \e[A
			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
				}
			}
		}

		// \e[1~
		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')
}