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 a single gate in a wall ring.
type GateInfo struct {
	WallID      int
	Center      image.Point // midpoint of the gap
	Normal      [2]float64  // outward normal (perpendicular to wall, pointing outward)
	LeftTurret  image.Point // turret on the left side of the road
	RightTurret image.Point // turret on the right side of the road
	InnerEnd    image.Point // road endpoint just inside the wall
	OuterEnd    image.Point // road endpoint just outside the wall
}

type FortificationLayout struct {
	Mask          *PixelMask
	WallIDByPixel []int
	Coverages     []float64
	Gates         []GateInfo
}

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),
	}
	if settings.NumWalls <= 0 || settings.CityCoverage <= 0 {
		return layout, nil
	}
	if waterMask == nil {
		waterMask = NewPixelMask(width, height)
	}
	if img == nil {
		img = image.NewRGBA(image.Rect(0, 0, width, height))
	}

	randSrc := rand.New(rand.NewSource(seed))
	minWidthPx, maxWidthPx := getWallWidthRangePixels(settings, width, height)
	wallColor := color.RGBA{R: 0, G: 0, B: 0, A: 255}

	walls := make([][]image.Point, 0, settings.NumWalls)
	outerCoverage := clamp(settings.CityCoverage, 1, 100)
	totalWalls := max(1, settings.NumWalls)
	prevCoverage := 101.0
	layout.Coverages = make([]float64, 0, totalWalls)

	for i := 0; i < totalWalls; i++ {
		baseCoverage := outerCoverage * float64(totalWalls-i) / float64(totalWalls)
		coverage := baseCoverage
		if i > 0 {
			coverage += randSrc.Float64()*10.0 - 5.0
		}
		coverage = clamp(coverage, 1, 100)
		if coverage >= prevCoverage {
			coverage = prevCoverage - 1
			if coverage < 1 {
				coverage = 1
			}
		}
		prevCoverage = coverage
		layout.Coverages = append(layout.Coverages, coverage)

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

		wallWidthPx := minWidthPx
		if maxWidthPx > minWidthPx {
			wallWidthPx = minWidthPx + randSrc.Float64()*(maxWidthPx-minWidthPx)
		}
		wallWidth := int(math.Round(wallWidthPx))
		if wallWidth < 1 {
			wallWidth = 1
		}

		pixels := drawWallLoopWithWaterGaps(img, wallPath, wallColor, wallWidth, layout.Mask, waterMask, layout.WallIDByPixel, i+1)
		if len(pixels) > 0 {
			walls = append(walls, pixels)
		}
	}

	computeGatesForLayout(img, layout, walls, settings, width, height, waterMask)

	return layout, walls
}

// computeGatesForLayout computes gate positions for all wall rings.
// Gates are placed at regular intervals along each wall (GateSpacing % of circumference).
// Each gate consists of: left turret, gap (3x road width), right turret.
// The gap is cleared from the wall mask so roads can pass through.
func computeGatesForLayout(
	img *image.RGBA,
	layout *FortificationLayout,
	walls [][]image.Point,
	settings *Settings,
	width, height int,
	waterMask *PixelMask,
) {
	if layout == nil || settings.GateSpacing <= 0 || len(walls) == 0 {
		return
	}

	_, maxRoadPx := getRoadWidthRangePixels(settings, width, height)
	roadWidth := maxRoadPx
	if roadWidth < 1 {
		roadWidth = 1
	}
	gapHalf := roadWidth * 1.5 // gap is 3x road width total, so 1.5 each side

	sizePx := getTurretSizePixels(settings, width, height)
	turretRadius := int(math.Round(sizePx / 2.0))
	if turretRadius < 1 {
		turretRadius = 1
	}
	shape := settings.TurretShape
	if shape != "square" {
		shape = "circular"
	}
	gateColor := color.RGBA{R: 220, G: 25, B: 25, A: 255}
	bgColor := color.RGBA{R: 0, G: 0, B: 0, A: 0} // transparent to clear wall pixels

	for wallIdx, wallPixels := range walls {
		wallID := wallIdx + 1
		if len(wallPixels) == 0 {
			continue
		}

		// Collect boundary pixels for this wall, sorted by angle around centroid.
		centroid := averagePoint(wallPixels)
		type boundaryPt struct {
			p     image.Point
			angle float64
		}
		bpts := make([]boundaryPt, 0, len(wallPixels))
		for _, p := range wallPixels {
			if !isBoundaryWallPixel(p.X, p.Y, layout.Mask) {
				continue
			}
			a := math.Atan2(float64(p.Y-centroid.Y), float64(p.X-centroid.X))
			bpts = append(bpts, boundaryPt{p, a})
		}
		if len(bpts) < 8 {
			continue
		}
		sort.Slice(bpts, func(i, j int) bool { return bpts[i].angle < bpts[j].angle })

		// Determine step between gates as fraction of boundary pixel count.
		spacing := clamp(settings.GateSpacing, 1, 100)
		step := int(math.Round((spacing / 100.0) * float64(len(bpts))))
		if step < 1 {
			step = 1
		}
		if step > len(bpts) {
			continue // spacing > 100%, no gate
		}

		for i := 0; i < len(bpts); i += step {
			gateCenter := bpts[i].p

			// Estimate wall tangent and normal at this point.
			tx, ty, ok := estimateWallTangent(gateCenter, layout.Mask)
			if !ok {
				continue
			}
			// Normal = perpendicular to tangent, pointing outward from centroid.
			nx, ny := -ty, tx
			cx := float64(gateCenter.X) - float64(centroid.X)
			cy := float64(gateCenter.Y) - float64(centroid.Y)
			if cx*nx+cy*ny < 0 {
				nx, ny = -nx, -ny
			}

			// Clear the gap in the wall mask (3x road width centered on gateCenter).
			gapInt := int(math.Ceil(gapHalf))
			for dy := -gapInt * 3; dy <= gapInt*3; dy++ {
				for dx := -gapInt * 3; dx <= gapInt*3; dx++ {
					// Only erase pixels that are close to the perpendicular axis (along wall normal).
					// Project (dx,dy) onto tangent — must be within gapHalf.
					tanProj := math.Abs(float64(dx)*tx + float64(dy)*ty)
					if tanProj > gapHalf {
						continue
					}
					xx := gateCenter.X + dx
					yy := gateCenter.Y + dy
					if !layout.Mask.InBounds(xx, yy) {
						continue
					}
					if waterMask != nil && waterMask.GetXY(xx, yy) {
						continue
					}
					if layout.WallIDByPixel[yy*width+xx] == wallID {
						layout.Mask.ClearXY(xx, yy)
						layout.WallIDByPixel[yy*width+xx] = 0
						if img != nil {
							img.Set(xx, yy, bgColor)
						}
					}
				}
			}

			// Place turrets on both sides of the gap.
			leftCenter := image.Point{
				X: int(math.Round(float64(gateCenter.X) + tx*gapHalf)),
				Y: int(math.Round(float64(gateCenter.Y) + ty*gapHalf)),
			}
			rightCenter := image.Point{
				X: int(math.Round(float64(gateCenter.X) - tx*gapHalf)),
				Y: int(math.Round(float64(gateCenter.Y) - ty*gapHalf)),
			}
			// Snap to wall center line.
			if lc, ok := snapPointToWallCenter(leftCenter, layout.Mask, turretRadius*6); ok {
				leftCenter = lc
			}
			if rc, ok := snapPointToWallCenter(rightCenter, layout.Mask, turretRadius*6); ok {
				rightCenter = rc
			}

			turretMaskTemp := NewPixelMask(width, height)
			drawTurret(img, turretMaskTemp, leftCenter, turretRadius, shape, gateColor)
			drawTurret(img, turretMaskTemp, rightCenter, turretRadius, shape, gateColor)

			// The road must pass through the midpoint between the two turrets.
			// After snapping, leftCenter and rightCenter may have drifted from gateCenter,
			// so rebase the road axis on their actual midpoint.
			turretMidX := float64(leftCenter.X+rightCenter.X) / 2.0
			turretMidY := float64(leftCenter.Y+rightCenter.Y) / 2.0

			// Compute inner/outer road endpoints just past the wall, projected from turret midpoint.
			reach := float64(turretRadius) + roadWidth + 2
			innerEnd := image.Point{
				X: int(math.Round(turretMidX - nx*reach)),
				Y: int(math.Round(turretMidY - ny*reach)),
			}
			outerEnd := image.Point{
				X: int(math.Round(turretMidX + nx*reach)),
				Y: int(math.Round(turretMidY + ny*reach)),
			}
			// Clamp to image bounds.
			clampPt := func(p image.Point) image.Point {
				if p.X < 0 {
					p.X = 0
				}
				if p.X >= width {
					p.X = width - 1
				}
				if p.Y < 0 {
					p.Y = 0
				}
				if p.Y >= height {
					p.Y = height - 1
				}
				return p
			}
			innerEnd = clampPt(innerEnd)
			outerEnd = clampPt(outerEnd)

			// Validate: innerEnd should be closer to centroid than outerEnd.
			// If not, the normal is pointing the wrong way — flip inner/outer.
			innerDistToCentroid := math.Hypot(float64(innerEnd.X-centroid.X), float64(innerEnd.Y-centroid.Y))
			outerDistToCentroid := math.Hypot(float64(outerEnd.X-centroid.X), float64(outerEnd.Y-centroid.Y))
			if innerDistToCentroid > outerDistToCentroid {
				innerEnd, outerEnd = outerEnd, innerEnd
			}

			// Reject gate if both ends landed on the same side of the wall
			// (i.e. both are inside or outside — the road would double back).
			// Check: innerEnd must not be in wall, outerEnd must not be in wall,
			// and they must be on opposite sides (one closer to centroid, one farther).
			// A strong sign of a doubling-back gate: inner and outer are very close together
			// relative to the wall thickness, or the road segment crosses no wall pixels.
			innerInWall := layout.Mask.GetXY(innerEnd.X, innerEnd.Y)
			outerInWall := layout.Mask.GetXY(outerEnd.X, outerEnd.Y)
			if innerInWall || outerInWall {
				// At least one end is still inside the wall — not a clean crossing.
				// Extend reach until both are clear.
				for extraReach := reach + 1; extraReach <= reach+float64(turretRadius)*4+roadWidth*4; extraReach += 1 {
					candidateInner := clampPt(image.Point{
						X: int(math.Round(float64(gateCenter.X) - nx*extraReach)),
						Y: int(math.Round(float64(gateCenter.Y) - ny*extraReach)),
					})
					candidateOuter := clampPt(image.Point{
						X: int(math.Round(float64(gateCenter.X) + nx*extraReach)),
						Y: int(math.Round(float64(gateCenter.Y) + ny*extraReach)),
					})
					if !layout.Mask.GetXY(candidateInner.X, candidateInner.Y) &&
						!layout.Mask.GetXY(candidateOuter.X, candidateOuter.Y) {
						innerEnd = candidateInner
						outerEnd = candidateOuter
						// Re-check orientation.
						id := math.Hypot(float64(innerEnd.X-centroid.X), float64(innerEnd.Y-centroid.Y))
						od := math.Hypot(float64(outerEnd.X-centroid.X), float64(outerEnd.Y-centroid.Y))
						if id > od {
							innerEnd, outerEnd = outerEnd, innerEnd
						}
						break
					}
				}
			}

			// Final rejection: if the straight line from innerEnd to outerEnd doesn't
			// cross any wall pixels, this gate will produce a doubling-back road.
			// Count wall pixels along the path.
			gateLine := bresenhamPoints(innerEnd, outerEnd)
			wallCrossings := 0
			for _, gp := range gateLine {
				if layout.Mask.GetXY(gp.X, gp.Y) {
					wallCrossings++
				}
			}
			if wallCrossings == 0 {
				// The road wouldn't cross the wall at all — skip this gate.
				continue
			}

			layout.Gates = append(layout.Gates, GateInfo{
				WallID:      wallID,
				Center:      gateCenter,
				Normal:      [2]float64{nx, ny},
				LeftTurret:  leftCenter,
				RightTurret: rightCenter,
				InnerEnd:    innerEnd,
				OuterEnd:    outerEnd,
			})
		}
	}
}

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

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, baseRadiusX, baseRadiusY := wallEllipseFromRoadNodes(width, height, coverage, roadNodes)
	curveScale := clamp(curvyness, 0, 100) / 100.0
	warpAmp := 0.20 * curveScale
	phaseA := randSrc.Float64() * 2 * math.Pi
	phaseB := randSrc.Float64() * 2 * math.Pi

	out := make([]image.Point, 0, nodes+1)
	for i := 0; i < nodes; i++ {
		t := (2 * math.Pi * float64(i)) / float64(nodes)
		warp := 1.0 + warpAmp*(0.6*math.Sin(3*t+phaseA)+0.4*math.Sin(5*t+phaseB))
		if warp < 0.7 {
			warp = 0.7
		}
		rx := baseRadiusX * warp
		ry := baseRadiusY * warp
		x := int(math.Round(centerX + rx*math.Cos(t)))
		y := int(math.Round(centerY + ry*math.Sin(t)))
		if x < 0 {
			x = 0
		}
		if x >= width {
			x = width - 1
		}
		if y < 0 {
			y = 0
		}
		if y >= height {
			y = height - 1
		}
		out = append(out, image.Point{X: x, Y: y})
	}
	if len(out) > 0 {
		out = append(out, out[0])
	}
	return out
}

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
	}

	sumX, sumY := 0.0, 0.0
	for _, n := range roadNodes {
		sumX += float64(n.X)
		sumY += float64(n.Y)
	}
	centerX = sumX / float64(len(roadNodes))
	centerY = sumY / float64(len(roadNodes))

	dists := make([]float64, 0, len(roadNodes))
	var sx, sy float64
	for _, n := range roadNodes {
		dx := float64(n.X) - centerX
		dy := float64(n.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 drawWallLoopWithWaterGaps(
	img *image.RGBA,
	loop []image.Point,
	col color.RGBA,
	width int,
	wallMask *PixelMask,
	waterMask *PixelMask,
	wallIDByPixel []int,
	wallID int,
) []image.Point {
	if len(loop) < 2 || wallMask == nil {
		return nil
	}
	seen := make(map[int]bool)
	pixels := make([]image.Point, 0, len(loop)*8)
	radius := max(1, width/2)

	for i := 0; i < len(loop)-1; i++ {
		a := loop[i]
		b := loop[i+1]
		drawSegmentSelective(a.X, a.Y, b.X, b.Y, func(x, y int) {
			if !wallMask.InBounds(x, y) {
				return
			}
			if waterMask != nil && waterMask.GetXY(x, y) {
				return
			}
			for dy := -radius; dy <= radius; dy++ {
				yy := y + dy
				if yy < 0 || yy >= wallMask.Height {
					continue
				}
				for dx := -radius; dx <= radius; dx++ {
					if dx*dx+dy*dy > radius*radius {
						continue
					}
					xx := x + dx
					if xx < 0 || xx >= wallMask.Width {
						continue
					}
					if waterMask != nil && waterMask.GetXY(xx, yy) {
						continue
					}
					wallMask.SetXY(xx, yy)
					if len(wallIDByPixel) == wallMask.Width*wallMask.Height {
						wallIDByPixel[yy*wallMask.Width+xx] = wallID
					}
					img.Set(xx, yy, col)
					idx := yy*wallMask.Width + xx
					if !seen[idx] {
						seen[idx] = true
						pixels = append(pixels, image.Point{X: xx, Y: yy})
					}
				}
			}
		})
	}

	return pixels
}

// bresenhamPoints returns all pixels on a line from a to b using Bresenham's algorithm.
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, x1, y1 := a.X, a.Y, 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
		}
	}
}

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)
			}
		}
	}
}

func GenerateTurrets(
	img *image.RGBA,
	width, height int,
	settings *Settings,
	layout *FortificationLayout,
	waterMask, roadMask *PixelMask,
	roads []*Road,
) *PixelMask {
	mask := NewPixelMask(width, height)
	if !settings.ShowTurrets || layout == nil || layout.Mask == nil || len(layout.WallIDByPixel) != width*height {
		return mask
	}
	if img == nil {
		img = image.NewRGBA(image.Rect(0, 0, width, height))
	}
	if waterMask == nil {
		waterMask = NewPixelMask(width, height)
	}
	if roadMask == nil {
		roadMask = NewPixelMask(width, height)
	}

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

	wallPoints := make(map[int][]image.Point)
	waterMeetPoints := make(map[int][]image.Point)
	for y := 0; y < height; y++ {
		row := y * width
		for x := 0; x < width; x++ {
			wid := layout.WallIDByPixel[row+x]
			if wid <= 0 {
				continue
			}
			if !isBoundaryWallPixel(x, y, layout.Mask) {
				continue
			}
			p := image.Point{X: x, Y: y}
			wallPoints[wid] = append(wallPoints[wid], p)
			if touchesWater(x, y, waterMask) {
				waterMeetPoints[wid] = append(waterMeetPoints[wid], p)
			}
		}
	}

	occupied := make(map[int]bool)
	addTurret := func(center image.Point) {
		snapped, ok := snapPointToWallCenter(center, layout.Mask, max(3, radius*4))
		if !ok {
			return
		}
		if nearbyTurretExists(mask, snapped, max(2, radius)) {
			return
		}
		key := snapped.Y*width + snapped.X
		if occupied[key] {
			return
		}
		occupied[key] = true
		drawTurret(img, mask, snapped, radius, shape, colorRed)
	}

	// Base spacing turrets along each wall ring.
	for wid, pts := range wallPoints {
		if len(pts) == 0 {
			continue
		}
		centroid := averagePoint(pts)
		sort.Slice(pts, func(i, j int) bool {
			ai := math.Atan2(float64(pts[i].Y-centroid.Y), float64(pts[i].X-centroid.X))
			aj := math.Atan2(float64(pts[j].Y-centroid.Y), float64(pts[j].X-centroid.X))
			return ai < aj
		})
		// Spacing is "distance along wall as % of wall circumference", independent of turret size.
		spacingPct := clamp(settings.TurretSpacing, 0, 100)
		step := int(math.Round((spacingPct / 100.0) * float64(len(pts))))
		if step < 1 {
			step = 1
		}
		if step > len(pts) {
			step = len(pts)
		}
		for i := 0; i < len(pts); i += step {
			addTurret(pts[i])
		}

		// Always place turrets where wall meets water.
		for _, p := range waterMeetPoints[wid] {
			addTurret(p)
		}
	}

	// Gate turrets: one on each side of each road crossing, spacing = 3x road width.
	for _, r := range roads {
		if r == nil || len(r.Points) < 2 {
			continue
		}
		gates := roadGateCentersForRoad(r, layout)
		if len(gates) == 0 {
			continue
		}
		for _, g := range gates {
			tx, ty, ok := estimateWallTangent(g, layout.Mask)
			if !ok {
				continue
			}
			offset := 1.5 * float64(max(1, r.Width))
			left := image.Point{
				X: int(math.Round(float64(g.X) + tx*offset)),
				Y: int(math.Round(float64(g.Y) + ty*offset)),
			}
			right := image.Point{
				X: int(math.Round(float64(g.X) - tx*offset)),
				Y: int(math.Round(float64(g.Y) - ty*offset)),
			}
			addTurret(left)
			addTurret(right)
		}
	}

	// Always redraw gate turrets from layout.Gates last so they appear on top of roads.
	// (Gate turrets were first drawn during fortification generation but roads paint over them.)
	if len(layout.Gates) > 0 {
		for _, gate := range layout.Gates {
			drawTurret(img, mask, gate.LeftTurret, radius, shape, colorRed)
			drawTurret(img, mask, gate.RightTurret, radius, shape, colorRed)
		}
	}

	return mask
}

func isBoundaryWallPixel(x, y int, wallMask *PixelMask) bool {
	if wallMask == nil || !wallMask.GetXY(x, y) {
		return false
	}
	for dy := -1; dy <= 1; dy++ {
		for dx := -1; dx <= 1; dx++ {
			if dx == 0 && dy == 0 {
				continue
			}
			nx, ny := x+dx, y+dy
			if !wallMask.InBounds(nx, ny) || !wallMask.GetXY(nx, ny) {
				return true
			}
		}
	}
	return false
}

func touchesWater(x, y int, waterMask *PixelMask) bool {
	if waterMask == nil {
		return false
	}
	for dy := -1; dy <= 1; dy++ {
		for dx := -1; dx <= 1; dx++ {
			nx, ny := x+dx, y+dy
			if waterMask.GetXY(nx, ny) {
				return true
			}
		}
	}
	return false
}

func drawTurret(img *image.RGBA, mask *PixelMask, center image.Point, radius int, shape string, col color.RGBA) {
	for dy := -radius; dy <= radius; dy++ {
		for dx := -radius; dx <= radius; dx++ {
			if shape == "circular" && dx*dx+dy*dy > radius*radius {
				continue
			}
			x, y := center.X+dx, center.Y+dy
			if !mask.InBounds(x, y) {
				continue
			}
			mask.SetXY(x, y)
			img.Set(x, y, col)
		}
	}
}

func nearbyTurretExists(mask *PixelMask, center image.Point, radius int) bool {
	if mask == nil {
		return false
	}
	for dy := -radius; dy <= radius; dy++ {
		for dx := -radius; dx <= radius; dx++ {
			if dx*dx+dy*dy > radius*radius {
				continue
			}
			if mask.GetXY(center.X+dx, center.Y+dy) {
				return true
			}
		}
	}
	return false
}

// snapPointToWallCenter finds the medial center of the wall at the given hint point.
// It finds the nearest boundary pixel, then walks inward (toward the wall interior)
// to find the midpoint between the two opposite boundary edges — the wall's center line.
// Falls back to snapPointToWall if the wall is too thin to measure.
func snapPointToWallCenter(hint image.Point, wallMask *PixelMask, maxRadius int) (image.Point, bool) {
	if wallMask == nil {
		return image.Point{}, false
	}

	// First, snap hint to a wall pixel at all.
	start, ok := snapPointToWall(hint, wallMask, maxRadius)
	if !ok {
		return image.Point{}, false
	}

	// Walk in 8 directions from start to find the two farthest boundary pixels;
	// their midpoint is the wall center.
	type ray struct{ dx, dy float64 }
	rays := []ray{
		{1, 0}, {-1, 0}, {0, 1}, {0, -1},
		{1, 1}, {-1, 1}, {1, -1}, {-1, -1},
	}

	// For each direction, walk until we exit the wall, record the last wall pixel.
	wallEdges := make([]image.Point, 0, 8)
	for _, r := range rays {
		prev := start
		for s := 1; s <= maxRadius*2; s++ {
			nx := int(math.Round(float64(start.X) + r.dx*float64(s)))
			ny := int(math.Round(float64(start.Y) + r.dy*float64(s)))
			if !wallMask.InBounds(nx, ny) {
				break
			}
			if !wallMask.GetXY(nx, ny) {
				// prev was last wall pixel in this direction
				wallEdges = append(wallEdges, prev)
				break
			}
			prev = image.Point{X: nx, Y: ny}
		}
	}

	if len(wallEdges) < 2 {
		return start, true // wall too thin, just use the snapped point
	}

	// Average all edge points — this approximates the medial center well enough.
	sx, sy := 0, 0
	for _, e := range wallEdges {
		sx += e.X
		sy += e.Y
	}
	cx := sx / len(wallEdges)
	cy := sy / len(wallEdges)
	center := image.Point{X: cx, Y: cy}

	// Make sure the result is actually inside the wall mask.
	if wallMask.GetXY(cx, cy) {
		return center, true
	}
	// Snap it back if it drifted outside (can happen on very thin walls).
	return snapPointToWall(center, wallMask, max(3, maxRadius/2))
}

func snapPointToWall(center image.Point, wallMask *PixelMask, maxRadius int) (image.Point, bool) {
	if wallMask == nil {
		return image.Point{}, false
	}
	if wallMask.GetXY(center.X, center.Y) {
		return center, true
	}
	if maxRadius < 1 {
		maxRadius = 1
	}
	best := image.Point{}
	bestD2 := math.MaxInt
	found := false
	for r := 1; r <= maxRadius; r++ {
		minX := center.X - r
		maxX := center.X + r
		minY := center.Y - r
		maxY := center.Y + r
		for y := minY; y <= maxY; y++ {
			for x := minX; x <= maxX; x++ {
				if x != minX && x != maxX && y != minY && y != maxY {
					continue
				}
				if !wallMask.GetXY(x, y) {
					continue
				}
				dx := x - center.X
				dy := y - center.Y
				d2 := dx*dx + dy*dy
				if d2 < bestD2 {
					bestD2 = d2
					best = image.Point{X: x, Y: y}
					found = true
				}
			}
		}
		if found {
			return best, true
		}
	}
	return image.Point{}, false
}

func roadGateCentersForRoad(r *Road, layout *FortificationLayout) []image.Point {
	out := make([]image.Point, 0, 2)
	if r == nil || layout == nil || layout.Mask == nil || len(r.Points) < 2 {
		return out
	}
	prevID := 0
	if layout.Mask.InBounds(r.Points[0].Point.X, r.Points[0].Point.Y) {
		prevID = layout.WallIDByPixel[r.Points[0].Point.Y*layout.Mask.Width+r.Points[0].Point.X]
	}
	for i := 1; i < len(r.Points); i++ {
		p := r.Points[i].Point
		currID := 0
		if layout.Mask.InBounds(p.X, p.Y) {
			currID = layout.WallIDByPixel[p.Y*layout.Mask.Width+p.X]
		}
		if (prevID == 0 && currID > 0) || (prevID > 0 && currID == 0) {
			out = append(out, p)
		}
		prevID = currID
	}
	return out
}