gilo/editor/editor.go

package editor

import (
	"fmt"
	"time"
	"timshome.page/gilo/key"
	"timshome.page/gilo/terminal"
)

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

type point struct {
	x int
	y int
}

type statusMsg struct {
	message string
	created time.Time
}

type editor struct {
	screen *terminal.Screen
	cursor *point
	offset *point
	document *document
	status *statusMsg
	renderX int
}

func New() *editor {
	screen := terminal.Size()

	// Subtract rows for status bar and message bar/prompt
	screen.Rows -= 2

	cursor := &point{0, 0}
	offset := &point{0, 0}
	document := newDocument()
	status := &statusMsg{
		"",
		time.Now(),
	}

	return &editor{
		screen,
		cursor,
		offset,
		document,
		status,
		0,
	}
}

func (e *editor) Open(filename string) {
	e.document.open(filename)
}

func (e *editor) SetStatusMessage(template string, a ...interface{}) {
	e.status = &statusMsg{
		fmt.Sprintf(template, a...),
		time.Now(),
	}
}

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

	switch ch {
	case key.Ctrl('q'):
		// Clean up on exit
		terminal.Write(terminal.ClearScreen + terminal.ResetCursor)

		return false

	case key.Esc:
		// Modifier keys that return ANSI escape sequences
		str := parseEscapeSequence()

		switch str {
		case keyUp,
			keyDown,
			keyLeft,
			keyRight,
			keyPageUp,
			keyPageDown,
			keyHome,
			keyEnd:

			e.moveCursor(str)
		}

	default:
		e.insertChar(ch)
	}

	return true
}

func (e *editor) moveCursor(key string) {
	var row *row
	if e.cursor.y >= e.document.rowCount() {
		row = nil
	} else {
		row = e.document.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.document.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 < e.document.rowCount()-1 {
			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 < e.document.rowCount() {
			e.cursor.y += 1
		}
	case keyPageUp:
		if e.cursor.y > e.screen.Rows {
			e.cursor.y -= e.screen.Rows
		} else {
			e.cursor.y = 0
		}

	case keyPageDown:
		if e.cursor.y+e.screen.Rows > e.document.rowCount() {
			e.cursor.y += e.screen.Rows
		} else {
			e.cursor.y = e.document.rowCount() - 1
		}

	case keyHome:
		e.cursor.x = 0
	case keyEnd:
		if row != nil {
			e.cursor.x = row.size()
		}
	}

	if e.cursor.y < e.document.rowCount() {
		row = e.document.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) insertChar(ch rune) {
	if e.cursor.y == e.document.rowCount() {
		e.document.appendRow("")
	}

	e.document.rows[e.cursor.y].insertRune(ch, e.cursor.x)
	e.cursor.x += 1
}

// 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')
}