gopad/editor.go

package main

import (
	"os"
	"path/filepath"

	"github.com/bloeys/gopad/settings"
	"github.com/inkyblackness/imgui-go/v4"
)

const (
	linesPerNode int = 100
)

type Line struct {
	chars []rune
}

type LinesNode struct {
	Lines [linesPerNode]Line
	Next  *LinesNode
}

type Editor struct {
	FileName     string
	FilePath     string
	FileContents string

	CursorX int
	CursorY int

	SelectionStart  int
	SelectionLength int

	IsModified bool

	LinesHead *LinesNode
	LineCount int
}

func (e *Editor) SetCursorPos(x, y int) {
	e.CursorX = x
	e.CursorY = y
}

func (e *Editor) Render(drawStartPos, winSize *imgui.Vec2) {

	e.CursorY = clampInt(e.CursorY, 0, e.LineCount)
	e.CursorX = clampInt(e.CursorX, 0, e.GetLineCharCount(e.CursorY))

	//Draw window
	imgui.SetNextWindowPos(*drawStartPos)
	imgui.SetNextWindowSize(*winSize)
	imgui.BeginV("editorText", nil, imgui.WindowFlagsNoCollapse|imgui.WindowFlagsNoDecoration|imgui.WindowFlagsNoMove)

	imgui.PushStyleColor(imgui.StyleColorFrameBg, settings.EditorBgColor)
	imgui.PushStyleColor(imgui.StyleColorTextSelectedBg, settings.TextSelectionColor)

	//Add padding to text
	drawStartPos.X += 10
	drawStartPos.Y += 10

	//Draw lines
	lineHeight := imgui.TextLineHeightWithSpacing()
	linesToDraw := int(winSize.Y / lineHeight)
	println("Lines to draw:", linesToDraw)

	dl := imgui.WindowDrawList()
	for i := 0; i < linesToDraw; i++ {
		dl.AddText(*drawStartPos, imgui.PackedColorFromVec4(imgui.Vec4{X: 1, Y: 1, Z: 1, W: 1}), string(e.GetLine(e.CursorY+i).chars))
		drawStartPos.Y += lineHeight
	}
}

func (e *Editor) GetLine(lineNum int) *Line {

	if lineNum > e.LineCount {
		return &Line{
			chars: []rune{},
		}
	}

	curr := e.LinesHead

	//Advance to correct node
	nodeNum := lineNum / linesPerNode
	lineNum -= nodeNum * linesPerNode
	for nodeNum > 0 {
		curr = curr.Next
		nodeNum--
	}

	return &curr.Lines[lineNum]
}

func (e *Editor) GetLineCharCount(lineNum int) int {

	curr := e.LinesHead

	//Advance to correct node
	nodeNum := lineNum / linesPerNode
	lineNum -= nodeNum * linesPerNode
	for nodeNum > 0 {
		curr = curr.Next
		nodeNum--
	}

	return len(curr.Lines[lineNum].chars)
}

func ParseLines(fileContents string) (*LinesNode, int) {

	head := NewLineNode()

	lineCount := 0
	start := 0
	end := 0
	currLine := 0
	currNode := head
	for i := 0; i < len(fileContents); i++ {

		if fileContents[i] != '\n' {
			end++
			continue
		}

		lineCount++
		currNode.Lines[currLine].chars = []rune(fileContents[start:end])

		end++
		start = end
		currLine++
		if currLine == linesPerNode {
			currLine = 0
			currNode.Next = NewLineNode()
			currNode = currNode.Next
		}
	}

	return head, lineCount
}

func NewLineNode() *LinesNode {

	n := LinesNode{}
	for i := 0; i < len(n.Lines); i++ {
		n.Lines[i].chars = []rune{}
	}

	return &n
}

func clampInt(x, min, max int) int {

	if x > max {
		return max
	}

	if x < min {
		return min
	}

	return x
}

func NewScratchEditor() *Editor {

	e := &Editor{
		FileName:  "**scratch**",
		LinesHead: NewLineNode(),
	}
	return e
}

func NewEditor(fPath string) *Editor {

	b, err := os.ReadFile(fPath)
	if err != nil {
		panic(err)
	}

	e := &Editor{
		FileName:     filepath.Base(fPath),
		FilePath:     fPath,
		FileContents: string(b),
	}
	e.LinesHead, e.LineCount = ParseLines(e.FileContents)
	return e
}