From 06e89cbc5035de86351477828e4c22468d98a4a0 Mon Sep 17 00:00:00 2001
From: "Juan J. Martinez" <jjm@usebox.net>
Date: Mon, 18 Jul 2022 12:58:44 +0100
Subject: One more example with structs

---
 examples/entities.micro | 156 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 156 insertions(+)
 create mode 100644 examples/entities.micro

diff --git a/examples/entities.micro b/examples/entities.micro
new file mode 100644
index 0000000..63f719f
--- /dev/null
+++ b/examples/entities.micro
@@ -0,0 +1,156 @@
+//
+// Example of an entity system
+//
+
+const MAX_ENTS number = 10;
+
+const UNUSED number = 0;
+const QUEUED number = 1;
+const ACTIVE number = 2;
+
+const PLAYER number = 0;
+const ENEMY number = 1;
+const ITEM number = 2;
+
+def Entity {
+    var id number;
+
+    var used number;
+    var type number;
+    var x number;
+    var y number;
+    var frame number;
+    var delay number;
+
+    var lives number;
+    var score number;
+
+    def update() {
+        println("updating player");
+    }
+
+    def erase() {
+        println(id, " -> erase x:", x, " y:", y, " f:", frame);
+    }
+
+    def draw() {
+        println(id, " -> read bg x:", x, " y:", y);
+
+        println(id, " -> blit x:", x, " y:", y, " f:", frame);
+    }
+
+    def destroy() {
+        used = UNUSED;
+    }
+
+    def test(other Entity) bool {
+        // TODO
+        return false;
+    }
+
+    def enemyUpdate() {
+        println(id, " -> updating enemy ", used);
+    }
+
+    def enemy() {
+        type = ENEMY;
+        update = enemyUpdate;
+    }
+}
+
+def Game {
+    var ents [10]Entity;
+    var next number;
+
+    def spawn(x number, y number) Entity {
+        var start number = next;
+        for {
+            if !ents[next].used {
+                ents[next].used = QUEUED;
+                ents[next].x = x;
+                ents[next].y = y;
+                ents[next].frame = 0;
+                ents[next].delay = 0;
+                ents[next].id = next;
+                return ents[next];
+            }
+            next = (next + 1) % MAX_ENTS;
+            if next == start {
+                panic("out of ents :(");
+            }
+        }
+    }
+
+    var player Entity = spawn(1, 1);
+
+    def erase() {
+        for e in ents {
+            if e.used == ACTIVE {
+                e.erase();
+            }
+        }
+    }
+
+    def draw() {
+        for e in ents {
+            if e.used == ACTIVE {
+                e.draw();
+            }
+        }
+    }
+
+    def update() {
+        for e in ents {
+            if e.used == ACTIVE {
+                e.update();
+                if e.type != PLAYER && e.test(player) {
+                    if e.type == ENEMY {
+                        player.lives = player.lives - 1;
+                        continue;
+                    }
+                    if e.type == ITEM {
+                        player.score = player.score + 10;
+                        e.destroy();
+                        continue;
+                    }
+                }
+                continue;
+            }
+            if e.used == QUEUED {
+                e.used = ACTIVE;
+            }
+        }
+    }
+
+    def run() {
+        var loops number;
+        for loops < 10 {
+            erase();
+            update();
+            draw();
+
+            // buffer SWAP
+
+            if player.lives == 0 {
+                println("game over");
+                break;
+            }
+
+            loops = loops + 1;
+        }
+
+        if loops == 10 {
+            println("out of rounds");
+        }
+    }
+}
+
+var game Game;
+game.player.lives = 10;
+
+game.spawn(1, 2).enemy();
+game.spawn(2, 2).enemy();
+game.spawn(2, 2).enemy();
+game.spawn(2, 2).enemy();
+
+game.run();
-- 
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