1 files changed, 91 insertions, 0 deletions
diff --git a/selection/selection.go b/selection/selection.go
new file mode 100644
index 0000000..2755110
--- /dev/null
+++ b/selection/selection.go
@@ -0,0 +1,91 @@
+package selection
+
+import (
+	"age_of_empires/ecs"
+	"age_of_empires/physics"
+	"math"
+
+	"github.com/hajimehoshi/ebiten/v2"
+)
+
+const HALO_WIDTH = 10
+
+type Priority int
+
+const (
+	Unit Priority = iota
+	Building
+)
+
+type GlobalSelection struct {
+	IsActive bool
+	Start    physics.Point
+}
+
+type Selection struct {
+	IsSelected bool
+	Halo       *ebiten.Image
+	Priority   Priority
+}
+
+type Multiple struct {
+	Bounds      physics.Rectangle
+	Preselected []*ecs.Component[Selection]
+}
+
+func NewMultiple(start physics.Point, end physics.Point) Multiple {
+	return Multiple{
+		Bounds:      physics.Rectangle{Min: start, Max: end}.Canon(),
+		Preselected: []*ecs.Component[Selection]{},
+	}
+}
+
+func (m *Multiple) Preselect(position ecs.Component[physics.Point], bounds physics.Rectangle, selection *ecs.Component[Selection]) {
+	if !selection.IsEnabled {
+		return
+	}
+	selection.Value.IsSelected = false
+	if m.Bounds.Overlaps(bounds) {
+		m.Preselected = append(m.Preselected, selection)
+	}
+}
+
+func (m *Multiple) Select() {
+	if len(m.Preselected) == 0 {
+		return
+	}
+	highestPriority := Priority(math.MaxInt)
+	for _, selection := range m.Preselected {
+		if selection.Value.Priority < highestPriority {
+			highestPriority = selection.Value.Priority
+		}
+	}
+	for _, selection := range m.Preselected {
+		if selection.Value.Priority == highestPriority {
+			selection.Value.IsSelected = true
+		}
+	}
+}
+
+type Single struct {
+	Cursor      physics.Point
+	HasSelected bool
+}
+
+func NewSingle(cursor physics.Point) Single {
+	return Single{
+		Cursor:      cursor,
+		HasSelected: false,
+	}
+}
+
+func (s *Single) Select(position ecs.Component[physics.Point], bounds physics.Rectangle, selection *ecs.Component[Selection]) {
+	if !selection.IsEnabled {
+		return
+	}
+	selection.Value.IsSelected = false
+	if s.HasSelected || !s.Cursor.In(bounds) {
+		return
+	}
+	selection.Value.IsSelected = true
+}