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package physics
import (
"fmt"
"math"
"age_of_empires/ecs"
"golang.org/x/exp/slices"
"golang.org/x/exp/slog"
)
const MOVE_SPEED = 10.0
type Path []Point
func (p Path) String() string {
return fmt.Sprintf("%s -> %s", p[0].String(), p[len(p)-1].String())
}
type Move struct {
IsActive bool
Origin Point
Destination Point
Path Path
}
type Node struct {
CostFromOrigin int
CostToDestination int
Parent Point
}
func (n Node) Cost() int {
return n.CostFromOrigin + n.CostToDestination
}
type MoveMap struct {
Width int
Height int
Blocked map[Point]bool
}
type PathSearch struct {
origin Point
destination Point
openList map[Point]Node
closedList map[Point]Node
moveMap MoveMap
}
func SearchPath(origin Point, destination Point, moveMap MoveMap) (Path, bool) {
search := PathSearch{
origin: origin,
destination: destination,
openList: map[Point]Node{},
closedList: map[Point]Node{},
moveMap: moveMap,
}
return search.search()
}
var neighborsDirectionsDiagonal = []Point{
{X: -100, Y: 0}, // left
{X: 100, Y: 0}, // right
{X: 0, Y: -100}, // up
{X: 0, Y: 100}, // down
{X: -100, Y: -100}, // top-left
{X: 100, Y: -100}, // top-right
{X: -100, Y: 100}, // bottom-left
{X: 100, Y: 100}, // bottom-right
}
// Add neighbors to the open list
// Choose neighborsDirections
func (s *PathSearch) addNeighbors(point Point) {
for _, dir := range neighborsDirectionsDiagonal {
neighbor := Point{X: point.X + dir.X, Y: point.Y + dir.Y}
if neighbor.X >= 0 && neighbor.X <= s.moveMap.Width-100 &&
neighbor.Y >= 0 && neighbor.Y <= s.moveMap.Height-100 {
s.consider(neighbor, point)
}
}
}
func (s *PathSearch) consider(neighbor Point, point Point) {
if s.moveMap.Blocked[neighbor] {
return
}
if _, ok := s.closedList[neighbor]; !ok {
node := Node{
CostFromOrigin: s.closedList[point].CostFromOrigin + int(Distance(point, neighbor)),
CostToDestination: int(Distance(neighbor, s.destination)),
Parent: point,
}
existing, ok := s.openList[neighbor]
if !ok || existing.Cost() > node.Cost() {
s.openList[neighbor] = node
}
}
}
// openList must not be empty
func (s *PathSearch) bestOpenNode() (Point, Node) {
bestPoint := Point{X: 0, Y: 0}
bestNode := Node{}
bestCost := math.MaxInt32
for point, node := range s.openList {
if cost := node.Cost(); cost < bestCost {
bestPoint = point
bestNode = node
bestCost = cost
}
}
return bestPoint, bestNode
}
func (s *PathSearch) buildPath() Path {
point := s.destination
path := Path{s.destination}
node := s.closedList[s.destination]
for point != s.origin {
point = node.Parent
path = append(path, point)
node = s.closedList[point]
}
slices.Reverse(path)
return path
}
func (s *PathSearch) search() (Path, bool) {
s.openList[s.origin] = Node{CostFromOrigin: 0, CostToDestination: int(Distance(s.origin, s.destination)), Parent: s.origin}
point := s.origin
var node Node
for point != s.destination && len(s.openList) > 0 {
point, node = s.bestOpenNode()
s.closedList[point] = node
delete(s.openList, point)
s.addNeighbors(point)
}
if point == s.destination {
return s.buildPath(), true
}
return Path{}, false
}
func NewMove(origin Point, destination Point, moveMap MoveMap) Move {
current := Point{
X: origin.X / 100 * 100,
Y: origin.Y / 100 * 100,
}
path, ok := SearchPath(current, destination, moveMap)
if !ok {
slog.Info("no path found", slog.String("destination", destination.String()))
return Move{IsActive: false}
}
return Move{IsActive: true, Origin: origin, Destination: destination, Path: path[1:]}
}
func (p *Path) isValid(moveMap MoveMap) bool {
for _, point := range *p {
if moveMap.Blocked[point] {
return false
}
}
return true
}
func moveToward(position Point, destination Point) Point {
remainingMove := destination.Sub(position)
delta := remainingMove.Mul(MOVE_SPEED).Div(int(Length(remainingMove)))
return position.Add(delta)
}
func UpdateMoveSystem(moveMap MoveMap, masks []ecs.Mask, moves []Move, positions []Point) {
required := ecs.CM_Position | ecs.CM_Move
for i, mask := range masks {
if mask&required != required {
continue
}
move := &moves[i]
position := &positions[i]
if !move.IsActive {
continue
}
if len(move.Path) == 0 {
move.IsActive = false
continue
}
next := move.Path[0]
if Distance(*position, next) >= MOVE_SPEED {
*position = moveToward(*position, next)
continue
}
// About to snap to next cell — check it's still free
if moveMap.Blocked[next] {
slog.Info("cell blocked on arrival, repathing", slog.String("next", next.String()))
path, ok := SearchPath(*position, move.Destination, moveMap)
if !ok {
slog.Info("no path found", slog.String("destination", move.Destination.String()))
move.IsActive = false
continue
}
move.Path = path[1:]
continue
}
oldCell := Point{X: position.X / 100 * 100, Y: position.Y / 100 * 100}
*position = next
moveMap.Blocked[next] = true
delete(moveMap.Blocked, oldCell)
remainingPath := move.Path[1:]
if next == move.Destination {
move.IsActive = false
slog.Info("move finished", slog.String("destination", move.Destination.String()))
continue
}
if remainingPath.isValid(moveMap) {
move.Path = remainingPath
continue
}
// Here maybe the destination has to change
path, ok := SearchPath(next, move.Destination, moveMap)
if !ok {
slog.Info("no path found", slog.String("destination", move.Destination.String()))
move.IsActive = false
continue
}
move.Path = path[1:]
}
}
|
