gilo/editor/row.go

package editor

import (
	"strings"
)

type Row struct {
	chars  []rune
	render []rune
}

func newRow(s string) *Row {
	var chars []rune
	var render []rune

	for _, ch := range s {
		chars = append(chars, ch)
		render = append(render, ch)
	}

	return &Row{chars, render}
}

func (r *Row) Size() int {
	return len(r.chars)
}

func (r *Row) RenderSize() int {
	return len(r.render)
}

func (r *Row) insertRune(ch rune, at int) {
	// If insertion index is invalid, just
	// append the rune to the end of the array
	if at < 0 || at >= r.Size() {
		r.chars = append(r.chars, ch)
		r.update()

		return
	}

	var newSlice []rune

	// Split the character array at the insertion point
	start := r.chars[0:at]
	end := r.chars[at:r.Size()]

	// Splice it back together
	newSlice = append(newSlice, start...)
	newSlice = append(newSlice, ch)
	newSlice = append(newSlice, end...)

	r.chars = newSlice
	r.update()
}

func (r *Row) deleteRune(at int) {
	if at < 0 || at >= r.Size() {
		return
	}

	var newSlice []rune

	// Split the character array at the insertion point
	start := r.chars[0:at]
	end := r.chars[at+1 : r.Size()] // Skip the index in question

	// Splice it back together
	newSlice = append(newSlice, start...)
	newSlice = append(newSlice, end...)

	r.chars = newSlice
	r.update()
}

func (r *Row) update() {
	r.render = r.render[:0]
	replacement := strings.Repeat(" ", KiloTabStop)

	str := strings.ReplaceAll(string(r.chars), "\t", replacement)
	for _, ch := range str {
		r.render = append(r.render, ch)
	}
}

func (r *Row) toString() string {
	return string(r.chars)
}

func (r *Row) cursorXToRenderX(cursorX int) int {
	renderX := 0
	i := 0

	for ; i < cursorX; i++ {
		if r.chars[i] == '\t' {
			renderX += (KiloTabStop - 1) - (renderX % KiloTabStop)
		}

		renderX += 1
	}

	return renderX
}