fixed "Area" and tests

core/area.go

@@ -2,41 +2,45 @@ package core
 
 import "fmt"
 
-func NewArea(topLeft, bottomRight Point) Area {
-	a := Area{TopLeft: topLeft, BottomRight: bottomRight}
-	a.MaybeSwapPoints()
-	return a
+func NewArea(min, max Point) Area {
+	a := Area{Min: min, Max: max}
+	return a.Canon()
 }
 
-func NewAreaWH(topLeft Point, width, height int64) Area {
-	bottomRight := Point{X: topLeft.X + width, Y: topLeft.Y + height}
-	return NewArea(topLeft, bottomRight)
+func NewAreaWH(min Point, width, height int64) Area {
+	max := Point{X: min.X + width, Y: min.Y + height}
+	return NewArea(min, max)
 }
 
 type Area struct {
-	TopLeft     Point
-	BottomRight Point
+	Min Point
+	Max Point
+}
+
+func (area Area) Canon() Area {
+	area.MaybeSwapPoints()
+	return area
 }
 
 func (area *Area) MaybeSwapPoints() {
-	if area.TopLeft.X > area.BottomRight.X {
-		area.TopLeft.X, area.BottomRight.X = area.BottomRight.X, area.TopLeft.X
+	if area.Max.X < area.Min.X {
+		area.Min.X, area.Max.X = area.Max.X, area.Min.X
 	}
-	if area.TopLeft.Y > area.BottomRight.Y {
-		area.TopLeft.Y, area.BottomRight.Y = area.BottomRight.Y, area.TopLeft.Y
+	if area.Max.Y < area.Min.Y {
+		area.Min.Y, area.Max.Y = area.Max.Y, area.Min.Y
 	}
 }
 
 func (area Area) Equal(other Area) bool {
-	return area.TopLeft == other.TopLeft && area.BottomRight == other.BottomRight
+	return area.Min == other.Min && area.Max == other.Max
 }
 
 func (area Area) Height() int64 {
-	return Abs(area.TopLeft.Y-area.BottomRight.Y) + 1
+	return Abs(area.Min.Y-area.Max.Y) + 1
 }
 
 func (area Area) Width() int64 {
-	return Abs(area.TopLeft.X-area.BottomRight.X) + 1
+	return Abs(area.Min.X-area.Max.X) + 1
 }
 
 func (area Area) IsLandscape() bool {
@@ -48,43 +52,61 @@ func (area Area) IsPortrait() bool {
 }
 
 func (area Area) ContainsPoint(p Point) bool {
-	return p.X >= area.TopLeft.X && p.X <= area.BottomRight.X && p.Y >= area.TopLeft.Y && p.Y <= area.BottomRight.Y
+	return p.X >= area.Min.X && p.X <= area.Max.X && p.Y >= area.Min.Y && p.Y <= area.Max.Y
 }
 
 func (area Area) ContainsArea(a Area) bool {
-	return area.ContainsPoint(a.TopLeft) && area.ContainsPoint(a.BottomRight)
+	return area.ContainsPoint(a.Min) && area.ContainsPoint(a.Max)
 }
 
 func (area Area) IntersectsArea(a Area) bool {
-	return area.ContainsPoint(a.TopLeft) || area.ContainsPoint(a.BottomRight)
+	return area.ContainsPoint(a.Min) || area.ContainsPoint(a.Max)
+}
+
+// Intersect returns the largest rectangle contained by both r and s. If the
+// two rectangles do not overlap then the zero rectangle will be returned.
+func (r Area) Intersect(s Area) (Area, bool) {
+	if r.Min.X < s.Min.X {
+		r.Min.X = s.Min.X
+	}
+	if r.Min.Y < s.Min.Y {
+		r.Min.Y = s.Min.Y
+	}
+	if r.Max.X > s.Max.X {
+		r.Max.X = s.Max.X
+	}
+	if r.Max.Y > s.Max.Y {
+		r.Max.Y = s.Max.Y
+	}
+	return r, r.Min.X <= r.Max.X && r.Min.Y <= r.Max.Y
 }
 
 func (area Area) Surface() int64 {
 	return area.Height() * area.Width()
 }
 
 func (area Area) CountOverlappingPixels(other Area) int64 {
-	// Calculate the overlapping area
-	overlap := Area{
-		TopLeft: Point{
-			X: Max(area.TopLeft.X, other.TopLeft.X),
-			Y: Max(area.TopLeft.Y, other.TopLeft.Y),
-		},
-		BottomRight: Point{
-			X: Min(area.BottomRight.X, other.BottomRight.X),
-			Y: Min(area.BottomRight.Y, other.BottomRight.Y),
-		},
-	}
-
-	// If there is no overlap, return 0
-	if overlap.TopLeft.X >= overlap.BottomRight.X || overlap.TopLeft.Y >= overlap.BottomRight.Y {
+	is, does := area.Intersect(other)
+	if !does {
 		return 0
 	}
+	return is.Surface()
+
+	// // Calculate the overlapping area
+	// overlap := NewArea(
+	// 	NewPoint(Max(area.Min.X, other.Min.X), Max(area.Min.Y, other.Min.Y)),
+	// 	NewPoint(Min(area.Max.X, other.Max.X), Min(area.Max.Y, other.Max.Y)),
+	// )
+
+	// // If there is no overlap, return 0
+	// if overlap.Min.X >= overlap.Max.X || overlap.Min.Y >= overlap.Max.Y {
+	// 	return 0
+	// }
 
-	// Return the overlapping area's surface size
-	return overlap.Surface()
+	// // Return the overlapping area's surface size
+	// return overlap.Surface()
 }
 
 func (area Area) String() string {
-	return fmt.Sprintf("Area[TopLeft: %s, BottomRight: %s, Height: %d, Width: %d]", area.TopLeft, area.BottomRight, area.Height(), area.Width())
+	return fmt.Sprintf("Area[Min: %s, Max: %s, Height: %d, Width: %d]", area.Min, area.Max, area.Height(), area.Width())
 }