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package main
import (
"image/color"
"math"
"github.com/hajimehoshi/ebiten/v2"
"github.com/hajimehoshi/ebiten/v2/vector"
"golang.org/x/exp/slices"
"golang.org/x/exp/slog"
)
type Move struct {
IsActive bool
Origin Point
Destination Point
Path []Point
}
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) ([]Point, bool) {
search := PathSearch{
origin: origin,
destination: destination,
openList: map[Point]Node{},
closedList: map[Point]Node{},
moveMap: moveMap,
}
return search.search()
}
func (s *PathSearch) addNeighbours(point Point, node Node) {
if point.X >= 100 {
s.consider(Point{point.X - 100, point.Y}, point)
}
if point.X <= s.moveMap.Width-100 {
s.consider(Point{point.X + 100, point.Y}, point)
}
if point.Y >= 100 {
s.consider(Point{point.X, point.Y - 100}, point)
}
if point.Y <= s.moveMap.Height-100 {
s.consider(Point{point.X, point.Y + 100}, 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{}
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() []Point {
point := s.destination
path := []Point{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() ([]Point, 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.addNeighbours(point, node)
}
if point == s.destination {
return s.buildPath(), true
}
return []Point{}, false
}
func NewMove(origin Point, destination Point, moveMap MoveMap) Move {
current := Point{
origin.X / 100 * 100,
origin.Y / 100 * 100,
}
search, 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: search}
}
func (m *Move) Update(position Point, speed int) Point {
if !m.IsActive {
return position
}
next := m.Path[0]
if Distance(position, next) < float64(speed) {
if next == m.Destination {
m.IsActive = false
slog.Info("move finished", slog.String("destintation", m.Destination.String()))
} else {
m.Path = m.Path[1:]
}
return next
}
remainingMove := next.Sub(position)
delta := remainingMove.Mul(speed).Div(int(Length(remainingMove)))
return position.Add(delta)
}
func (e *Entity) StartMove(destination Point, moveMap MoveMap) {
if e.Move.IsEnabled && e.Position.IsEnabled && e.Selection.IsEnabled {
if e.Selection.Value.IsSelected {
e.Move.Value = NewMove(e.Position.Value, destination, moveMap)
slog.Info("entity starting move", slog.String("destination", destination.String()))
}
}
}
func (e *Entity) UpdateMove() {
if e.Move.IsEnabled && e.Position.IsEnabled {
e.Position.Value = e.Move.Value.Update(e.Position.Value, 10)
}
}
func DrawMove(screen *ebiten.Image, e *Entity) {
if e.Move.IsEnabled && e.Position.IsEnabled && e.Selection.IsEnabled {
if e.Selection.Value.IsSelected && e.Move.Value.IsActive {
last := e.Position.Value
dx := +e.Image.Value.Bounds().Dx() / 2
dy := +e.Image.Value.Bounds().Dy() / 2
for _, point := range e.Move.Value.Path {
vector.StrokeLine(screen, float32(last.X+dx), float32(last.Y+dy), float32(point.X+dx), float32(point.Y+dy), 10.0, color.RGBA{256 * 3 / 16, 256 * 3 / 16, 256 * 3 / 16, 256 / 4}, true)
last = point
}
}
}
}
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