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astar.go

@@ -7,6 +7,9 @@ import (
 	"time"
 )
 
+// parentNone marks cells with no predecessor; must not collide with 0–3 (cardinal directions).
+const parentNone byte = 0xff
+
 type Item struct {
 	index    int     // index of the cell in the grid (y * width + x)
 	priority float32 // f = g + h
@@ -71,6 +74,9 @@ func (a *AStar) Init(width int, height int) {
 	for i := range a.gScores {
 		a.gScores[i] = math.MaxFloat32
 	}
+	for i := range a.parents {
+		a.parents[i] = parentNone
+	}
 }
 
 func (a *AStar) ResetGrid(withTypes bool) {
@@ -79,7 +85,7 @@ func (a *AStar) ResetGrid(withTypes bool) {
 			a.gridTypes[i] = 0
 		}
 		a.gScores[i] = math.MaxFloat32
-		a.parents[i] = 0
+		a.parents[i] = parentNone
 		a.closedSet[i] = false
 	}
 	a.openSet = a.openSet[:0]
@@ -93,6 +99,9 @@ func (a *AStar) RebuildGrid(width int, height int) {
 	a.closedSet = make([]bool, width*height)
 	a.width = width
 	a.height = height
+	for i := range a.parents {
+		a.parents[i] = parentNone
+	}
 }
 
 func (a *AStar) SetHeuristic(heuristic int32) {
@@ -162,21 +171,30 @@ func (a *AStar) GetParent(x int, y int) byte {
 	return a.parents[y*a.width+x]
 }
 
+func (a *AStar) GetParents() []byte {
+	return a.parents
+}
+
 func (a *AStar) ParentIndexToXY(childx int, childy int, parent byte) (int, int) {
-	if parent == 0 {
+	switch parent {
+	case 0:
 		return childx - 1, childy // parent left
-	} else if parent == 1 {
+	case 1:
 		return childx, childy - 1 // parent above
-	} else if parent == 2 {
+	case 2:
 		return childx + 1, childy // parent right
-	} else if parent == 3 {
+	case 3:
 		return childx, childy + 1 // parent below
+	default:
+		return -1, -1
 	}
-	return childx, childy
 }
 
 func (a *AStar) ParentIndexToXYIndex(childx int, childy int, parent byte) int {
 	x, y := a.ParentIndexToXY(childx, childy, parent)
+	if x < 0 || y < 0 || x >= a.width || y >= a.height {
+		return -1
+	}
 	return y*a.width + x
 }
 
@@ -235,9 +253,15 @@ func (a *AStar) CalculatePath(startX int, startY int, endX int, endY int) [][]in
 			// We've found the goal!
 			fmt.Println("Found the goal!")
 			path := make([][]int, 0)
-			for currentIndex := current.index; currentIndex != startIndex; currentIndex = a.ParentIndexToXYIndex(currentIndex%a.width, currentIndex/a.width, a.parents[currentIndex]) {
-				x, y := a.ParentIndexToXY(currentIndex%a.width, currentIndex/a.width, a.parents[currentIndex])
+			for currentIndex := current.index; currentIndex != startIndex; {
+				p := a.parents[currentIndex]
+				next := a.ParentIndexToXYIndex(currentIndex%a.width, currentIndex/a.width, p)
+				if next < 0 {
+					break
+				}
+				x, y := a.ParentIndexToXY(currentIndex%a.width, currentIndex/a.width, p)
 				path = append(path, []int{x, y})
+				currentIndex = next
 			}
 			return path
 		}
@@ -264,3 +288,60 @@ func (a *AStar) CalculatePath(startX int, startY int, endX int, endY int) [][]in
 	}
 	return make([][]int, 0)
 }
+
+func (a *AStar) CalculatePathLive(startX int, startY int, endX int, endY int, updateChan chan int) [][]int {
+	timer := time.Now()
+	defer func() {
+		a.timeTaken = time.Since(timer)
+	}()
+	startIndex := startY*a.width + startX
+	endIndex := endY*a.width + endX
+	a.gScores[startIndex] = 0
+	startF := a.heuristic(startX, startY, endX, endY)
+	heap.Push(&a.openSet, &Item{index: startIndex, priority: startF, gScore: 0})
+
+	for a.openSet.Len() > 0 {
+		current := heap.Pop(&a.openSet).(*Item)
+		if a.closedSet[current.index] {
+			continue
+		}
+		if current.index == endIndex {
+			// We've found the goal!
+			fmt.Println("Found the goal!")
+			path := make([][]int, 0)
+			for currentIndex := current.index; currentIndex != startIndex; {
+				p := a.parents[currentIndex]
+				next := a.ParentIndexToXYIndex(currentIndex%a.width, currentIndex/a.width, p)
+				if next < 0 {
+					break
+				}
+				x, y := a.ParentIndexToXY(currentIndex%a.width, currentIndex/a.width, p)
+				path = append(path, []int{x, y})
+				currentIndex = next
+			}
+			return path
+		}
+
+		a.closedSet[current.index] = true
+		updateChan <- current.index
+
+		for _, neighborIndex := range a.GetNeighbors(current.index%a.width, current.index/a.width) {
+			if a.closedSet[neighborIndex] {
+				continue
+			}
+			if a.gridTypes[neighborIndex] == 1 {
+				a.gScores[neighborIndex] = math.MaxFloat32
+				continue
+			}
+			terrainCost := a.GetTerrainCost(neighborIndex%a.width, neighborIndex/a.width)
+			tentativeGScore := a.gScores[current.index] + terrainCost
+			if tentativeGScore < a.gScores[neighborIndex] {
+				a.SetParent(neighborIndex%a.width, neighborIndex/a.width, current.index%a.width, current.index/a.width)
+				a.gScores[neighborIndex] = tentativeGScore
+				priority := tentativeGScore + a.heuristic(neighborIndex%a.width, neighborIndex/a.width, endX, endY)
+				heap.Push(&a.openSet, &Item{index: neighborIndex, priority: priority, gScore: tentativeGScore})
+			}
+		}
+	}
+	return make([][]int, 0)
+}

main.go

@@ -315,11 +315,16 @@ func main() {
 	defer rl.UnloadTexture(mapTexture)
 	defer rl.UnloadImage(mapImage)
 
+	updateChan := make(chan int, 100000)
+
 	autoCompute := false
 
 	astar := AStar{}
 	astar.Init(width, height)
 
+	// Above the channel loop
+	lastEvaluatedNode := -1 // Track the "tip of the spear"
+
 	for !rl.WindowShouldClose() {
 		screenWidth := float32(rl.GetScreenWidth())
 		screenHeight := float32(rl.GetScreenHeight())
@@ -459,6 +464,30 @@ func main() {
 			}
 			lastMousePos = rl.NewVector2(-1, -1)
 		}
+		updatesProcessed := 0
+	DrainLoop: // Use a label so we can break out of the infinite 'for' loop
+		for {
+			select {
+			case nodeIndex := <-updateChan:
+				x := nodeIndex % width
+				y := nodeIndex / width
+				if x != int(startPos.X) || y != int(startPos.Y) {
+					// Bake the blue pixel into the image
+					rl.ImageDrawPixel(mapImage, int32(x), int32(y), rl.NewColor(0, 0, 255, 255))
+					tex.markRegion(x, y, x, y, width, height)
+				}
+
+				lastEvaluatedNode = nodeIndex // Save the absolute latest node
+				updatesProcessed++
+
+				if updatesProcessed > 50000 {
+					break DrainLoop
+				}
+			default:
+				// Channel is empty
+				break DrainLoop
+			}
+		}
 
 		// --- DRAWING ---
 		rl.BeginDrawing()
@@ -475,6 +504,42 @@ func main() {
 			cellSize,            // Scale factor
 			rl.White,            // Tint (White means no tint)
 		)
+
+		// 2. Trace parent chain and draw a yellow polyline (cell centers) each frame.
+		if lastEvaluatedNode != -1 {
+			startIndex := int(startPos.Y)*width + int(startPos.X)
+			parents := astar.GetParents()
+			pathThickness := float32(10.0) / (camera.Zoom / 0.75)
+			if pathThickness < 1 {
+				pathThickness = 1
+			}
+			pathColor := rl.NewColor(255, 255, 0, 255)
+
+			var centers []rl.Vector2
+			for idx := lastEvaluatedNode; idx >= 0 && idx < width*height && idx != startIndex; {
+				cx := (float32(idx%width) + 0.5) * cellSize
+				cy := (float32(idx/width) + 0.5) * cellSize
+				centers = append(centers, rl.NewVector2(cx, cy))
+
+				if idx == startIndex {
+					break
+				}
+				p := parents[idx]
+				if p == parentNone {
+					break
+				}
+				next := astar.ParentIndexToXYIndex(idx%width, idx/width, p)
+				if next < 0 || next == idx {
+					break
+				}
+				idx = next
+			}
+
+			for i := 0; i < len(centers)-1; i++ {
+				rl.DrawLineEx(centers[i], centers[i+1], pathThickness, pathColor)
+			}
+		}
+
 		drawInfiniteGridLines(camera, canvasWidth, screenHeight, cellSize, width, height)
 		rl.EndMode2D()
 		rl.EndScissorMode()
@@ -550,6 +615,7 @@ func main() {
 		if !toolDropdownOpen && !heuristicDropdownOpen {
 			if rg.Button(rl.NewRectangle(sidebarX+(10*scale), (200*scale), (180*scale), (30*scale)), "Reset Visualization") {
 				astar.ResetGrid(false) // keep grid types, otherwise it will delete the board before simulating
+				lastEvaluatedNode = -1
 				gridTypes := astar.GetGridTypes()
 				for i, gridType := range gridTypes {
 					// reset the map image
@@ -568,6 +634,34 @@ func main() {
 			}
 		}
 
+		if rg.Button(rl.NewRectangle(sidebarX+(10*scale), (screenHeight-(80*scale)), (180*scale), (30*scale)), "Calculate Path (Live)") {
+			if int(startPos.X) < 0 || int(startPos.X) >= width || int(startPos.Y) < 0 || int(startPos.Y) >= height || int(endPos.X) < 0 || int(endPos.X) >= width || int(endPos.Y) < 0 || int(endPos.Y) >= height {
+				posError = true
+			} else {
+				astar.ResetGrid(false) // keep grid types, otherwise it will delete the board before simulating
+				astar.SetHeuristic(activeHeuristic)
+				lastEvaluatedNode = -1
+				gridTypes := astar.GetGridTypes()
+				for i, gridType := range gridTypes {
+					// reset the map image
+					switch gridType {
+					case 0:
+						rl.ImageDrawPixel(mapImage, int32(i%width), int32(i/width), rl.NewColor(240, 240, 240, 255))
+					case 1:
+						rl.ImageDrawPixel(mapImage, int32(i%width), int32(i/width), rl.NewColor(0, 0, 0, 255))
+					case 2:
+						rl.ImageDrawPixel(mapImage, int32(i%width), int32(i/width), rl.NewColor(0, 255, 0, 255))
+					case 3:
+						rl.ImageDrawPixel(mapImage, int32(i%width), int32(i/width), rl.NewColor(255, 0, 0, 255))
+					}
+				}
+				tex.markFull()
+				go func() {
+					astar.CalculatePathLive(int(startPos.X), int(startPos.Y), int(endPos.X), int(endPos.Y), updateChan)
+				}()
+			}
+		}
+
 		// AutoCompute
 		autoCompute = rg.CheckBox(rl.NewRectangle(sidebarX+(160*scale), (screenHeight-(40*scale)), (30*scale), (30*scale)), "", autoCompute) // no title because it would overlap the button
 
@@ -578,6 +672,7 @@ func main() {
 			} else {
 				astar.ResetGrid(false) // keep grid types, otherwise it will delete the board before simulating
 				astar.SetHeuristic(activeHeuristic)
+				lastEvaluatedNode = -1
 				gridTypes := astar.GetGridTypes()
 				for i, gridType := range gridTypes {
 					// reset the map image