Grid system & simple physics

4 files changed, 93 insertions, 11 deletions

diff --git a/src/systems/gridSystem.js b/src/systems/gridSystem.js
new file mode 100644
index 0000000..05ce17e
--- /dev/null
+++ b/src/systems/gridSystem.js
@@ -0,0 +1,73 @@
+game.system.GridSystem = ({ xDim, yDim, canvasWidth, canvasHeight }) => {
+  const entitiesGrid = Array(yDim).fill(null).map(() => Array(xDim).fill(null).map(() => new Map()));
+
+  const gridWidth = canvasWidth / xDim;
+  const gridHeight = canvasHeight / yDim;
+
+  const gameCoordsToGrid = ({ x, y }) => {
+    return { x: Math.floor((x+gridWidth/2) / canvasWidth * xDim), y: Math.floor((y+gridHeight/2) / canvasHeight * yDim) };
+  };
+
+  const gridCoordsToGame = ({ x, y }) => {
+    return { x: x * gridWidth, y: y * gridHeight };
+  };
+
+  const rebuildGrid = (entities) => {
+    let changedIds = new Set();
+    entities.map(entity => {
+      const { x, y } = entity.components.gridPosition;
+      if (!entitiesGrid[y][x].has(entity.id)) {
+        changedIds.add(entity.id);
+      }
+    });
+    entitiesGrid.forEach((row) => row.forEach((entitiesInCell) => {
+      for (let id of entitiesInCell.keys()) {
+        if (changedIds.has(id)) {
+          entitiesInCell.delete(id);
+        }
+      }
+    }));
+    changedIds.forEach(id => {
+      const entity = entities[id];
+      const { x, y } = entity.components.gridPosition;
+      entitiesGrid[y][x].set(entity.id, entity);
+    });
+  }
+
+  const update = (_elapsedTime, entities) => {
+    const gridEntities = Object.keys(entities).filter((x) => entities[x].hasComponent("gridPosition")).map((x) => entities[x]);
+    rebuildGrid(gridEntities);
+    gridEntities.map((entity) => {
+      if (entity.hasComponent("appearance")) {
+        entity.components.appearance.width = canvasWidth / xDim;
+        entity.components.appearance.height = canvasHeight / yDim;
+      }
+      if (entity.hasComponent("position")) {
+        const newGridCoords = gameCoordsToGrid(entity.components.position);
+        const oldGridCoords = entity.components.gridPosition;
+        if (!equivalence(newGridCoords, oldGridCoords)) {
+          const momentumVector = unitize({ 
+            dx: newGridCoords.x - oldGridCoords.x,
+            dy: newGridCoords.y - oldGridCoords.y,
+          });
+
+          // TODO: Loop in momentum direction until we find an entity that does not have "push" component
+          entity.components.gridPosition.x = entity.components.gridPosition.x + momentumVector.dx;
+          entity.components.gridPosition.y = entity.components.gridPosition.y + momentumVector.dy;
+
+          entity.components.position = {
+            ...entity.components.position,
+            ...gridCoordsToGame(entity.components.gridPosition)
+          };
+
+          if (entity.hasComponent("momentum")) {
+            entity.components.momentum.dx = 0;
+            entity.components.momentum.dy = 0;
+          }
+        }
+      }
+    });
+  };
+
+  return { entitiesGrid, gameCoordsToGrid, gridCoordsToGame, update, gridWidth, gridHeight };
+};
\ No newline at end of file
diff --git a/src/systems/physics.js b/src/systems/physics.js
new file mode 100644
index 0000000..c9b6cf7
--- /dev/null
+++ b/src/systems/physics.js
@@ -0,0 +1,13 @@
+game.system.Physics = () => {
+  const update = (elapsedTime) => {
+    for (let id in game.entities) {
+      const entity = game.entities[id];
+      if (entity.hasComponent("momentum")) {
+        const {dx, dy} = entity.components.momentum;
+        entity.components.position.x += dx * elapsedTime;
+        entity.components.position.y += dy * elapsedTime;
+      }
+    }
+  }
+  return { update };
+}
\ No newline at end of file
diff --git a/src/systems/render.js b/src/systems/render.js
index c8eff4b..0a4c72d 100644
--- a/src/systems/render.js
+++ b/src/systems/render.js
@@ -1,18 +1,13 @@
-game.systems = {};
-game.systems.Render = ((graphics) => {
-  const renderEntities = (elapsedTime, entities) => {
+game.system.Render = (graphics) => {
+  const update = (elapsedTime, entities) => {
+    graphics.clear();
+
     for (let id in entities) {
       const entity = entities[id];
-      if (entity.sprite && entity.components.position && entity.components.appearance) {
-//        document.getElementById("game-canvas").getContext("2d").drawImage(game.assets.bigblue, 100, 100, 100, 100);
+      if (entity.sprite && entity.hasComponent("position") && entity.hasComponent("appearance")) {
         entity.sprite.draw(elapsedTime, {...entity.components.position, ...entity.components.appearance});
       }
     }
   }
-
-  const update = (elapsedTime) => {
-    graphics.clear();
-    renderEntities(elapsedTime, game.entities);
-  }
   return { update };
-})(game.graphics);
\ No newline at end of file
+};
\ No newline at end of file
diff --git a/src/systems/system.js b/src/systems/system.js
new file mode 100644
index 0000000..f331401
--- /dev/null
+++ b/src/systems/system.js
@@ -0,0 +1 @@
+game.system = {};
\ No newline at end of file