1 files changed, 71 insertions, 0 deletions
diff --git a/invaders/arena.go b/invaders/arena.go
new file mode 100644
index 0000000..440db57
--- /dev/null
+++ b/invaders/arena.go
@@ -0,0 +1,71 @@
+package invaders
+
+import (
+	tl "github.com/JoelOtter/termloop"
+	"github.com/afagundes/go-invaders/invaders/utils"
+)
+
+type Arena struct {
+	*tl.Entity
+	Init int
+	End  int
+}
+
+const (
+	ArenaMaxWidth  = 100
+	ArenaMaxHeight = 37
+)
+
+func newArena(screenWidth int, screenHeight int) *Arena {
+	width := utils.ValueMinusPercent(screenWidth, 0.40)
+	height := utils.ValueMinusPercent(screenHeight, 0.15)
+
+	if width > ArenaMaxWidth {
+		width = ArenaMaxWidth
+	}
+
+	if height > ArenaMaxHeight {
+		height = ArenaMaxHeight
+	}
+
+	centerX := screenWidth/2 - width/2
+	centerY := screenHeight/2 - height/2
+	init := centerX + 1
+	end := centerX + width
+
+	return &Arena{tl.NewEntityFromCanvas(centerX, centerY, createArena(width, height)), init, end}
+}
+
+func createArena(width, height int) tl.Canvas {
+	canvas := tl.NewCanvas(width, height)
+
+	for x, cell := range canvas {
+		for y := range cell {
+			fillTopBottom(x, y, height, canvas)
+			fillSides(x, y, width, canvas)
+		}
+	}
+
+	createCell(0, 0, canvas, '┌')
+	createCell(width-1, 0, canvas, '┐')
+	createCell(0, height-1, canvas, '└')
+	createCell(width-1, height-1, canvas, '┘')
+
+	return canvas
+}
+
+func fillTopBottom(x, y, height int, canvas tl.Canvas) {
+	if x > 0 && (y == 0 || y == height-1) {
+		createCell(x, y, canvas, '─')
+	}
+}
+
+func fillSides(x, y, width int, canvas tl.Canvas) {
+	if x == 0 || x == width-1 {
+		createCell(x, y, canvas, '│')
+	}
+}
+
+func createCell(x, y int, canvas tl.Canvas, ch rune) {
+	canvas[x][y] = tl.Cell{Bg: tl.ColorBlack, Fg: tl.ColorWhite, Ch: ch}
+}