Tldraw/packages/editor/src/lib/editor/shapeutils/LineShapeUtil/components/getLinePath.ts

import {
	CubicSpline2d,
	getStrokeOutlinePoints,
	getStrokePoints,
	Polyline2d,
	setStrokePointRadii,
	Vec2d,
} from '@tldraw/primitives'
import { TLLineShape } from '@tldraw/tlschema'
import { getSvgPathFromStroke, getSvgPathFromStrokePoints } from '../../../../utils/svg'

export function getLinePoints(spline: CubicSpline2d | Polyline2d) {
	const { segments } = spline

	const allPoints: Vec2d[] = []

	for (let j = 0, k = segments.length; j < k; j++) {
		const segment = segments[j]
		const lut = segment.lut

		const n = lut.length - 1

		if (j > 0) {
			allPoints.push(Vec2d.Lrp(lut[0], lut[1], 0.25))
		} else {
			allPoints.push(lut[0])
		}

		for (let i = 1; i < n; i++) {
			allPoints.push(lut[i])
		}

		if (j < k - 1) {
			allPoints.push(Vec2d.Lrp(lut[n - 1], lut[n], 0.75))
		} else {
			allPoints.push(lut[n])
		}
	}

	return allPoints
}

export function getLineDrawFreehandOptions(strokeWidth: number) {
	return {
		size: strokeWidth,
		thinning: 0.4,
		streamline: 0,
		smoothing: 0.5,
		simulatePressure: true,
		last: true,
	}
}

export function getLineSolidFreehandOptions(strokeWidth: number) {
	return {
		size: strokeWidth,
		thinning: 0,
		streamline: 0,
		smoothing: 0.5,
		simulatePressure: false,
		last: true,
	}
}

export function getLineStrokePoints(
	shape: TLLineShape,
	spline: CubicSpline2d | Polyline2d,
	strokeWidth: number
) {
	const points = getLinePoints(spline)

	const options = getLineDrawFreehandOptions(strokeWidth)

	return getStrokePoints(points, options)
}

export function getLineDrawStrokeOutlinePoints(
	shape: TLLineShape,
	spline: CubicSpline2d | Polyline2d,
	strokeWidth: number
) {
	const options = getLineDrawFreehandOptions(strokeWidth)
	return getStrokeOutlinePoints(
		setStrokePointRadii(getLineStrokePoints(shape, spline, strokeWidth), options),
		options
	)
}

export function getLineSolidStrokeOutlinePoints(
	shape: TLLineShape,
	spline: CubicSpline2d | Polyline2d,
	strokeWidth: number
) {
	const options = getLineSolidFreehandOptions(strokeWidth)
	return getStrokeOutlinePoints(getLineStrokePoints(shape, spline, strokeWidth), options)
}

export function getLineDrawPath(
	shape: TLLineShape,
	spline: CubicSpline2d | Polyline2d,
	strokeWidth: number
) {
	const stroke = getLineDrawStrokeOutlinePoints(shape, spline, strokeWidth)
	return getSvgPathFromStroke(stroke)
}

export function getLineSolidPath(
	shape: TLLineShape,
	spline: CubicSpline2d | Polyline2d,
	strokeWidth: number
) {
	const outlinePoints = getLineSolidStrokeOutlinePoints(shape, spline, strokeWidth)
	return getSvgPathFromStroke(outlinePoints)
}

export function getLineIndicatorPath(
	shape: TLLineShape,
	spline: CubicSpline2d | Polyline2d,
	strokeWidth: number
) {
	if (shape.props.dash === 'draw') {
		const strokePoints = getLineStrokePoints(shape, spline, strokeWidth)
		return getSvgPathFromStrokePoints(strokePoints)
	}

	return spline.path
}