RPG_City_Maker_Reborn/fortifications.go

package main

import (
	"image"
	"image/color"
	"math"
	"math/rand"
	"sort"
)

const (
	minWallWidthPercent  = minBuildingSizePercent
	maxWallWidthPercent  = maxBuildingSizePercent
	wallWidthPercentStep = buildingSizePercentStep

	minTurretSizePercent  = 0.2
	maxTurretSizePercent  = maxWallWidthPercent
	turretSizePercentStep = 0.1
)

func clampWallWidthPercent(v float64) float64 {
	if v < minWallWidthPercent {
		return minWallWidthPercent
	}
	if v > maxWallWidthPercent {
		return maxWallWidthPercent
	}
	return v
}

func snapWallWidthPercent(v float64) float64 {
	v = clampWallWidthPercent(v)
	steps := math.Round((v - minWallWidthPercent) / wallWidthPercentStep)
	return clampWallWidthPercent(minWallWidthPercent + steps*wallWidthPercentStep)
}

func normalizeWallWidthPercentRange(minPercent, maxPercent float64) (float64, float64) {
	minPercent = snapWallWidthPercent(minPercent)
	maxPercent = snapWallWidthPercent(maxPercent)
	if minPercent > maxPercent {
		minPercent, maxPercent = maxPercent, minPercent
	}
	return minPercent, maxPercent
}

func getWallWidthRangePixels(settings *Settings, width, height int) (float64, float64) {
	minPercent, maxPercent := normalizeWallWidthPercentRange(settings.MinWallWidth, settings.MaxWallWidth)
	avgDim := averageImageDimension(width, height)
	if avgDim < 1 {
		avgDim = 1
	}
	minPx := (minPercent / 100.0) * avgDim
	maxPx := (maxPercent / 100.0) * avgDim
	if minPx < 1 {
		minPx = 1
	}
	if maxPx < 1 {
		maxPx = 1
	}
	return minPx, maxPx
}

func clampTurretSizePercent(v float64) float64 {
	if v < minTurretSizePercent {
		return minTurretSizePercent
	}
	if v > maxTurretSizePercent {
		return maxTurretSizePercent
	}
	return v
}

func snapTurretSizePercent(v float64) float64 {
	v = clampTurretSizePercent(v)
	steps := math.Round((v - minTurretSizePercent) / turretSizePercentStep)
	return clampTurretSizePercent(minTurretSizePercent + steps*turretSizePercentStep)
}

func getTurretSizePixels(settings *Settings, width, height int) float64 {
	sizePercent := snapTurretSizePercent(settings.TurretSize)
	avgDim := averageImageDimension(width, height)
	if avgDim < 1 {
		avgDim = 1
	}
	sizePx := (sizePercent / 100.0) * avgDim
	if sizePx < 1 {
		sizePx = 1
	}
	return sizePx
}

// GateInfo describes one traversable gate cut through a wall ring.
type GateInfo struct {
	WallID      int
	Center      image.Point
	Normal      [2]float64
	LeftTurret  image.Point
	RightTurret image.Point
	InnerEnd    image.Point
	OuterEnd    image.Point
}

// FortificationLayout holds the final fortification geometry and masks.
type FortificationLayout struct {
	Mask          *PixelMask
	WallIDByPixel []int
	Coverages     []float64
	Gates         []GateInfo
	GateMask      *PixelMask
	Turrets       []TurretPlacement
}

// TurretPlacement describes one turret centered on a wall.
type TurretPlacement struct {
	WallID  int
	Center  image.Point
	Angle   float64
	IsGate  bool
	IsWater bool
}

type wallSample struct {
	Point image.Point
	Angle float64
	RunID int
	Pos   int
	Index int
}

// GenerateFortifications builds wall geometry, gate openings, and turret placements.
func GenerateFortifications(
	img *image.RGBA,
	width, height int,
	settings *Settings,
	waterMask *PixelMask,
	roadNodes []*PointOfInterest,
	seed int64,
) (*FortificationLayout, [][]image.Point) {
	layout := &FortificationLayout{
		Mask:          NewPixelMask(width, height),
		WallIDByPixel: make([]int, width*height),
		GateMask:      NewPixelMask(width, height),
	}
	if settings == nil || settings.NumWalls <= 0 || settings.CityCoverage <= 0 || width <= 0 || height <= 0 {
		return layout, nil
	}
	if img == nil {
		img = image.NewRGBA(image.Rect(0, 0, width, height))
	}
	if waterMask == nil {
		waterMask = NewPixelMask(width, height)
	}

	randSrc := rand.New(rand.NewSource(seed))
	minWallWidthPx, maxWallWidthPx := getWallWidthRangePixels(settings, width, height)
	outerCoverage := clamp(settings.CityCoverage, 1, 100)
	totalWalls := max(1, settings.NumWalls)
	layout.Coverages = make([]float64, 0, totalWalls)

	for wallIndex := 0; wallIndex < totalWalls; wallIndex++ {
		coverage := outerCoverage * float64(totalWalls-wallIndex) / float64(totalWalls)
		coverage = clamp(coverage, 1, 100)
		layout.Coverages = append(layout.Coverages, coverage)

		nodes := estimateWallNodeCount(coverage)
		loop := generateWallLoop(width, height, coverage, settings.WallCurvyness, nodes, randSrc, roadNodes)
		if len(loop) < 3 {
			continue
		}

		wallWidthPx := minWallWidthPx
		if maxWallWidthPx > minWallWidthPx {
			wallWidthPx += randSrc.Float64() * (maxWallWidthPx - minWallWidthPx)
		}
		wallWidth := max(1, int(math.Round(wallWidthPx)))
		wallID := wallIndex + 1

		runs := splitWallPathByWater(loop, waterMask)
		if len(runs) == 0 {
			continue
		}

		samples := rasterizeWallRuns(layout, runs, wallWidth, wallID)
		if len(samples) == 0 {
			continue
		}

		center := averagePoint(samplesToPoints(samples))
		turretSizePx := getTurretSizePixels(settings, width, height)
		gates, gateSampleIndexes := buildGatesForWall(layout, settings, samples, center, wallIndex, wallID, wallWidth, turretSizePx, width, height)
		layout.Gates = append(layout.Gates, gates...)
		layout.Turrets = append(layout.Turrets, buildWaterEndpointTurrets(samples, wallID)...)
		layout.Turrets = append(layout.Turrets, buildGateTurrets(samples, gates, wallID)...)
		layout.Turrets = append(layout.Turrets, buildNaturalTurrets(settings, samples, gateSampleIndexes, coverage, outerCoverage, wallID)...)
	}

	layout.Turrets = dedupeTurretPlacements(layout.Turrets, width, height)
	drawWallMask(img, layout.Mask)
	return layout, nil
}

func splitWallPathByWater(loop []image.Point, waterMask *PixelMask) [][]image.Point {
	if len(loop) < 2 {
		return nil
	}
	if waterMask == nil {
		run := make([]image.Point, len(loop))
		copy(run, loop)
		return [][]image.Point{run}
	}

	var runs [][]image.Point
	current := make([]image.Point, 0, len(loop))
	appendPoint := func(p image.Point) {
		if len(current) == 0 || current[len(current)-1] != p {
			current = append(current, p)
		}
	}
	flush := func() {
		if len(current) > 1 {
			run := make([]image.Point, len(current))
			copy(run, current)
			runs = append(runs, run)
		}
		current = current[:0]
	}

	for i := 0; i < len(loop)-1; i++ {
		seg := bresenhamPoints(loop[i], loop[i+1])
		for _, p := range seg {
			if waterMask.GetPoint(p) {
				flush()
				continue
			}
			appendPoint(p)
		}
	}
	flush()
	return runs
}

func rasterizeWallRuns(layout *FortificationLayout, runs [][]image.Point, wallWidth, wallID int) []wallSample {
	if layout == nil || layout.Mask == nil || wallWidth < 1 {
		return nil
	}
	samples := make([]wallSample, 0)
	globalIndex := 0
	radius := max(1, wallWidth/2)

	paintDisk := func(cx, cy int) {
		for dy := -radius; dy <= radius; dy++ {
			yy := cy + dy
			if yy < 0 || yy >= layout.Mask.Height {
				continue
			}
			for dx := -radius; dx <= radius; dx++ {
				if dx*dx+dy*dy > radius*radius {
					continue
				}
				xx := cx + dx
				if xx < 0 || xx >= layout.Mask.Width {
					continue
				}
				layout.Mask.SetXY(xx, yy)
				if len(layout.WallIDByPixel) == layout.Mask.Width*layout.Mask.Height {
					layout.WallIDByPixel[yy*layout.Mask.Width+xx] = wallID
				}
			}
		}
	}

	for runID, run := range runs {
		if len(run) < 2 {
			continue
		}
		for i := 0; i < len(run)-1; i++ {
			a := run[i]
			b := run[i+1]
			drawSegmentSelective(a.X, a.Y, b.X, b.Y, paintDisk)
		}
		for i, p := range run {
			samples = append(samples, wallSample{Point: p, Angle: wallSampleAngle(run, i), RunID: runID, Pos: i, Index: globalIndex})
			globalIndex++
		}
	}

	return samples
}

func wallSampleAngle(run []image.Point, idx int) float64 {
	prev := run[max(0, idx-1)]
	next := run[min(len(run)-1, idx+1)]
	return math.Atan2(float64(next.Y-prev.Y), float64(next.X-prev.X))
}

func samplesToPoints(samples []wallSample) []image.Point {
	points := make([]image.Point, 0, len(samples))
	for _, sample := range samples {
		points = append(points, sample.Point)
	}
	return points
}

func buildGatesForWall(
	layout *FortificationLayout,
	settings *Settings,
	samples []wallSample,
	center image.Point,
	wallIndex, wallID, wallWidth int,
	turretSizePx float64,
	width, height int,
) ([]GateInfo, []int) {
	if layout == nil || len(samples) == 0 || settings == nil || settings.GateCount <= 0 {
		return nil, nil
	}

	gateCount := max(1, settings.GateCount>>wallIndex)
	if gateCount > len(samples) {
		gateCount = len(samples)
	}
	_, maxRoadPx := getRoadWidthRangePixels(settings, width, height)
	roadWidth := max(1, int(math.Round(maxRoadPx)))
	turretGap := turretSizePx * 0.75
	centerSeparation := turretSizePx + turretGap
	requiredMargin := max(3, int(math.Ceil(centerSeparation)))

	runLengths := make(map[int]int)
	for _, sample := range samples {
		runLengths[sample.RunID]++
	}

	used := make([]int, 0, gateCount)
	gates := make([]GateInfo, 0, gateCount)

	for gateIdx := 0; gateIdx < gateCount; gateIdx++ {
		target := int(math.Round((float64(gateIdx)+0.5)*float64(len(samples))/float64(gateCount))) % len(samples)
		sampleIdx := nearestUsableGateSample(samples, target, used, requiredMargin, runLengths)
		if sampleIdx < 0 {
			continue
		}
		used = append(used, sampleIdx)
		sample := samples[sampleIdx]

		tx := math.Cos(sample.Angle)
		ty := math.Sin(sample.Angle)
		nx := -ty
		ny := tx
		if float64(sample.Point.X-center.X)*nx+float64(sample.Point.Y-center.Y)*ny < 0 {
			nx = -nx
			ny = -ny
		}

		halfSep := centerSeparation * 0.5
		left := clampPoint(image.Point{
			X: int(math.Round(float64(sample.Point.X) + tx*halfSep)),
			Y: int(math.Round(float64(sample.Point.Y) + ty*halfSep)),
		}, width, height)
		right := clampPoint(image.Point{
			X: int(math.Round(float64(sample.Point.X) - tx*halfSep)),
			Y: int(math.Round(float64(sample.Point.Y) - ty*halfSep)),
		}, width, height)

		reach := float64(max(wallWidth, roadWidth)) + turretSizePx
		inner := clampPoint(image.Point{
			X: int(math.Round(float64(sample.Point.X) - nx*reach)),
			Y: int(math.Round(float64(sample.Point.Y) - ny*reach)),
		}, width, height)
		outer := clampPoint(image.Point{
			X: int(math.Round(float64(sample.Point.X) + nx*reach)),
			Y: int(math.Round(float64(sample.Point.Y) + ny*reach)),
		}, width, height)

		gate := GateInfo{
			WallID:      wallID,
			Center:      sample.Point,
			Normal:      [2]float64{nx, ny},
			LeftTurret:  left,
			RightTurret: right,
			InnerEnd:    inner,
			OuterEnd:    outer,
		}
		cutGateOpening(layout, gate, wallWidth, roadWidth)
		gates = append(gates, gate)
	}

	return gates, used
}

func nearestUsableGateSample(samples []wallSample, target int, used []int, margin int, runLengths map[int]int) int {
	if len(samples) == 0 {
		return -1
	}
	bestIdx := -1
	bestCost := math.MaxFloat64
	for idx, sample := range samples {
		runLen := runLengths[sample.RunID]
		if sample.Pos < margin || sample.Pos >= runLen-margin {
			continue
		}
		ok := true
		for _, other := range used {
			if other == idx {
				ok = false
				break
			}
			if samples[other].RunID == sample.RunID && abs(samples[other].Pos-sample.Pos) < margin {
				ok = false
				break
			}
		}
		if !ok {
			continue
		}
		cost := math.Abs(float64(idx - target))
		if cost < bestCost {
			bestCost = cost
			bestIdx = idx
		}
	}
	return bestIdx
}

func cutGateOpening(layout *FortificationLayout, gate GateInfo, wallWidth, roadWidth int) {
	if layout == nil || layout.Mask == nil {
		return
	}
	clearWidth := max(wallWidth+2, roadWidth+2)
	scratch := image.NewRGBA(image.Rect(0, 0, layout.Mask.Width, layout.Mask.Height))
	clearMask := NewPixelMask(layout.Mask.Width, layout.Mask.Height)
	drawLineMasked(scratch, gate.InnerEnd.X, gate.InnerEnd.Y, gate.OuterEnd.X, gate.OuterEnd.Y, color.RGBA{}, clearWidth, clearMask)
	for y := 0; y < layout.Mask.Height; y++ {
		row := y * layout.Mask.Width
		for x := 0; x < layout.Mask.Width; x++ {
			if clearMask.Data[row+x] == 0 {
				continue
			}
			layout.Mask.ClearXY(x, y)
			if len(layout.WallIDByPixel) == layout.Mask.Width*layout.Mask.Height {
				layout.WallIDByPixel[row+x] = 0
			}
		}
	}

	gateWidth := max(roadWidth+2, wallWidth+2)
	drawLineMasked(scratch, gate.OuterEnd.X, gate.OuterEnd.Y, gate.InnerEnd.X, gate.InnerEnd.Y, color.RGBA{}, gateWidth, layout.GateMask)
}

func buildWaterEndpointTurrets(samples []wallSample, wallID int) []TurretPlacement {
	if len(samples) == 0 {
		return nil
	}
	runFirst := make(map[int]wallSample)
	runLast := make(map[int]wallSample)
	runOrder := make([]int, 0)
	for _, sample := range samples {
		if _, exists := runFirst[sample.RunID]; !exists {
			runFirst[sample.RunID] = sample
			runOrder = append(runOrder, sample.RunID)
		}
		runLast[sample.RunID] = sample
	}

	out := make([]TurretPlacement, 0, len(runOrder)*2)
	for _, runID := range runOrder {
		first := runFirst[runID]
		last := runLast[runID]
		out = append(out,
			TurretPlacement{WallID: wallID, Center: first.Point, Angle: first.Angle, IsWater: true},
			TurretPlacement{WallID: wallID, Center: last.Point, Angle: last.Angle, IsWater: true},
		)
	}
	return out
}

func buildGateTurrets(samples []wallSample, gates []GateInfo, wallID int) []TurretPlacement {
	if len(gates) == 0 {
		return nil
	}
	out := make([]TurretPlacement, 0, len(gates)*2)
	for _, gate := range gates {
		angle := nearestSampleAngle(samples, gate.Center)
		out = append(out,
			TurretPlacement{WallID: wallID, Center: gate.LeftTurret, Angle: angle, IsGate: true},
			TurretPlacement{WallID: wallID, Center: gate.RightTurret, Angle: angle, IsGate: true},
		)
	}
	return out
}

func buildNaturalTurrets(settings *Settings, samples []wallSample, gateSampleIndexes []int, coverage, outerCoverage float64, wallID int) []TurretPlacement {
	if settings == nil || len(samples) == 0 {
		return nil
	}

	scale := 1.0
	if outerCoverage > 0 {
		scale = coverage / outerCoverage
	}
	stepPct := clamp(settings.TurretSpacing*scale, 0, 100)
	step := int(math.Round((stepPct / 100.0) * float64(len(samples))))
	if step < 1 {
		step = 1
	}

	runLengths := make(map[int]int)
	for _, sample := range samples {
		runLengths[sample.RunID]++
	}
	blocked := make(map[int]bool)
	for _, idx := range gateSampleIndexes {
		blocked[idx] = true
	}
	for _, sample := range samples {
		runLen := runLengths[sample.RunID]
		if sample.Pos == 0 || sample.Pos == runLen-1 {
			blocked[sample.Index] = true
		}
	}

	turrets := make([]TurretPlacement, 0)
	for i := 0; i < len(samples); i += step {
		candidate := samples[i]
		tooClose := false
		for _, other := range samples {
			if !blocked[other.Index] || other.RunID != candidate.RunID {
				continue
			}
			if abs(other.Pos-candidate.Pos) < step {
				tooClose = true
				break
			}
		}
		if tooClose {
			continue
		}
		blocked[candidate.Index] = true
		turrets = append(turrets, TurretPlacement{WallID: wallID, Center: candidate.Point, Angle: candidate.Angle})
	}
	return turrets
}

func nearestSampleAngle(samples []wallSample, center image.Point) float64 {
	bestIdx := -1
	bestD2 := math.MaxInt
	for i, sample := range samples {
		dx := sample.Point.X - center.X
		dy := sample.Point.Y - center.Y
		d2 := dx*dx + dy*dy
		if d2 < bestD2 {
			bestD2 = d2
			bestIdx = i
		}
	}
	if bestIdx < 0 {
		return 0
	}
	return samples[bestIdx].Angle
}

func dedupeTurretPlacements(turrets []TurretPlacement, width, height int) []TurretPlacement {
	if len(turrets) == 0 || width <= 0 || height <= 0 {
		return turrets
	}
	seen := make(map[int]bool)
	out := make([]TurretPlacement, 0, len(turrets))
	for _, turret := range turrets {
		if turret.Center.X < 0 || turret.Center.Y < 0 || turret.Center.X >= width || turret.Center.Y >= height {
			continue
		}
		key := turret.Center.Y*width + turret.Center.X
		if seen[key] {
			continue
		}
		seen[key] = true
		out = append(out, turret)
	}
	return out
}

func estimateWallNodeCount(coverage float64) int {
	nodes := int(math.Round(20 + coverage*0.7))
	if nodes < 20 {
		nodes = 20
	}
	if nodes > 96 {
		nodes = 96
	}
	return nodes
}

// generateWallLoop builds a closed wall path using two sine waves for large and small curvature.
func generateWallLoop(width, height int, coverage, curvyness float64, nodes int, randSrc *rand.Rand, roadNodes []*PointOfInterest) []image.Point {
	if width <= 0 || height <= 0 || nodes < 3 {
		return nil
	}

	centerX, centerY, radiusX, radiusY := wallEllipseFromRoadNodes(width, height, coverage, roadNodes)
	curveScale := clamp(curvyness, 0, 100) / 100.0
	largePhase := randSrc.Float64() * 2 * math.Pi
	smallPhase := randSrc.Float64() * 2 * math.Pi
	largeAmp := 0.18 * curveScale
	smallAmp := 0.08 * curveScale
	largeFreq := 3.0 + randSrc.Float64()*1.5
	smallFreq := 7.0 + randSrc.Float64()*3.0

	points := make([]image.Point, 0, nodes+1)
	for i := 0; i < nodes; i++ {
		t := 2 * math.Pi * float64(i) / float64(nodes)
		warp := 1.0 +
			largeAmp*math.Sin(largeFreq*t+largePhase) +
			smallAmp*math.Sin(smallFreq*t+smallPhase)
		if warp < 0.55 {
			warp = 0.55
		}
		x := int(math.Round(centerX + radiusX*warp*math.Cos(t)))
		y := int(math.Round(centerY + radiusY*warp*math.Sin(t)))
		if x < 0 {
			x = 0
		}
		if y < 0 {
			y = 0
		}
		if x >= width {
			x = width - 1
		}
		if y >= height {
			y = height - 1
		}
		points = append(points, image.Point{X: x, Y: y})
	}
	if len(points) > 0 {
		points = append(points, points[0])
	}
	return points
}

func wallEllipseFromRoadNodes(width, height int, coverage float64, roadNodes []*PointOfInterest) (centerX, centerY, radiusX, radiusY float64) {
	centerX = float64(width-1) * 0.5
	centerY = float64(height-1) * 0.5
	coverageRadius := math.Sqrt(clamp(coverage, 1, 100) / 100.0)
	radiusX = centerX * coverageRadius
	radiusY = centerY * coverageRadius

	if len(roadNodes) == 0 {
		return centerX, centerY, radiusX, radiusY
	}

	var sumX, sumY float64
	for _, node := range roadNodes {
		sumX += float64(node.X)
		sumY += float64(node.Y)
	}
	centerX = sumX / float64(len(roadNodes))
	centerY = sumY / float64(len(roadNodes))

	dists := make([]float64, 0, len(roadNodes))
	var sx, sy float64
	for _, node := range roadNodes {
		dx := float64(node.X) - centerX
		dy := float64(node.Y) - centerY
		dists = append(dists, math.Hypot(dx, dy))
		sx += dx * dx
		sy += dy * dy
	}
	sort.Float64s(dists)
	q := clamp(coverage, 1, 100) / 100.0
	idx := int(math.Ceil(q*float64(len(dists)))) - 1
	if idx < 0 {
		idx = 0
	}
	if idx >= len(dists) {
		idx = len(dists) - 1
	}
	baseRadius := dists[idx]
	if baseRadius < 10 {
		baseRadius = 10
	}

	stdX := math.Sqrt(sx / float64(len(roadNodes)))
	stdY := math.Sqrt(sy / float64(len(roadNodes)))
	aspect := 1.0
	if stdY > 0.001 {
		aspect = stdX / stdY
	}
	aspect = clamp(aspect, 0.65, 1.55)
	radiusX = baseRadius * aspect
	radiusY = baseRadius / aspect

	maxRadiusX := math.Max(5, math.Min(centerX, float64(width-1)-centerX))
	maxRadiusY := math.Max(5, math.Min(centerY, float64(height-1)-centerY))
	radiusX = clamp(radiusX, 5, maxRadiusX)
	radiusY = clamp(radiusY, 5, maxRadiusY)

	return centerX, centerY, radiusX, radiusY
}

func bresenhamPoints(a, b image.Point) []image.Point {
	pts := make([]image.Point, 0, max(abs(b.X-a.X), abs(b.Y-a.Y))+1)
	x0, y0 := a.X, a.Y
	x1, y1 := b.X, b.Y
	dx := abs(x1 - x0)
	dy := abs(y1 - y0)
	sx := -1
	if x0 < x1 {
		sx = 1
	}
	sy := -1
	if y0 < y1 {
		sy = 1
	}
	err := dx - dy
	for {
		pts = append(pts, image.Point{X: x0, Y: y0})
		if x0 == x1 && y0 == y1 {
			break
		}
		e2 := 2 * err
		if e2 > -dy {
			err -= dy
			x0 += sx
		}
		if e2 < dx {
			err += dx
			y0 += sy
		}
	}
	return pts
}

func drawSegmentSelective(x0, y0, x1, y1 int, plot func(x, y int)) {
	dx := abs(x1 - x0)
	dy := abs(y1 - y0)
	sx := -1
	if x0 < x1 {
		sx = 1
	}
	sy := -1
	if y0 < y1 {
		sy = 1
	}
	err := dx - dy
	for {
		plot(x0, y0)
		if x0 == x1 && y0 == y1 {
			break
		}
		e2 := 2 * err
		if e2 > -dy {
			err -= dy
			x0 += sx
		}
		if e2 < dx {
			err += dx
			y0 += sy
		}
	}
}

// drawWallMask paints the wall mask and is used for final fortification redraws.
func drawWallMask(img *image.RGBA, wallMask *PixelMask) {
	if img == nil || wallMask == nil {
		return
	}
	black := color.RGBA{R: 0, G: 0, B: 0, A: 255}
	for y := 0; y < wallMask.Height; y++ {
		row := y * wallMask.Width
		for x := 0; x < wallMask.Width; x++ {
			if wallMask.Data[row+x] != 0 {
				img.Set(x, y, black)
			}
		}
	}
}

// GenerateTurrets renders all configured turret placements and returns their mask.
func GenerateTurrets(
	img *image.RGBA,
	width, height int,
	settings *Settings,
	layout *FortificationLayout,
	_ *PixelMask,
	_ *PixelMask,
	_ []*Road,
) *PixelMask {
	mask := NewPixelMask(width, height)
	if img == nil {
		img = image.NewRGBA(image.Rect(0, 0, width, height))
	}
	if settings == nil || !settings.ShowTurrets || layout == nil {
		return mask
	}

	radius := max(1, int(math.Round(getTurretSizePixels(settings, width, height)/2.0)))
	shape := settings.TurretShape
	if shape != "square" {
		shape = "circular"
	}
	turretColor := color.RGBA{R: 220, G: 25, B: 25, A: 255}

	for _, turret := range layout.Turrets {
		drawTurret(img, mask, turret.Center, turret.Angle, radius, shape, turretColor)
	}
	return mask
}

func drawTurret(img *image.RGBA, mask *PixelMask, center image.Point, angle float64, radius int, shape string, col color.RGBA) {
	if img == nil || mask == nil || radius < 1 {
		return
	}
	cosA := math.Cos(angle)
	sinA := math.Sin(angle)
	extent := radius + 1
	for dy := -extent; dy <= extent; dy++ {
		for dx := -extent; dx <= extent; dx++ {
			x := center.X + dx
			y := center.Y + dy
			if !mask.InBounds(x, y) {
				continue
			}
			draw := false
			if shape == "square" {
				lx := float64(dx)*cosA + float64(dy)*sinA
				ly := -float64(dx)*sinA + float64(dy)*cosA
				draw = math.Abs(lx) <= float64(radius) && math.Abs(ly) <= float64(radius)
			} else {
				draw = dx*dx+dy*dy <= radius*radius
			}
			if !draw {
				continue
			}
			mask.SetXY(x, y)
			img.Set(x, y, col)
		}
	}
}

// drawTurretMask repaints the turret mask and is used in the final redraw pass.
func drawTurretMask(img *image.RGBA, turretMask *PixelMask) {
	if img == nil || turretMask == nil {
		return
	}
	turretColor := color.RGBA{R: 220, G: 25, B: 25, A: 255}
	for y := 0; y < turretMask.Height; y++ {
		row := y * turretMask.Width
		for x := 0; x < turretMask.Width; x++ {
			if turretMask.Data[row+x] != 0 {
				img.Set(x, y, turretColor)
			}
		}
	}
}

func clampPoint(p image.Point, width, height int) image.Point {
	if p.X < 0 {
		p.X = 0
	}
	if p.Y < 0 {
		p.Y = 0
	}
	if p.X >= width {
		p.X = width - 1
	}
	if p.Y >= height {
		p.Y = height - 1
	}
	return p
}