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game.system.GridSystem = ({ xDim, yDim }) => {
const entitiesGrid = Array(yDim).fill(null).map(() => Array(xDim).fill(null).map(() => new Map()));
let gridWidth = game.canvas.width / xDim;
let gridHeight = game.canvas.height / yDim;
const gameCoordsToGrid = ({ x, y }) => {
return { x: Math.floor((x+gridWidth/2) / game.canvas.width * xDim), y: Math.floor((y+gridHeight/2) / game.canvas.height * 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 = gridWidth;
entity.components.appearance.height = gridHeight;
}
if (entity.hasComponent("position")) {
let 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,
});
const proposed = {...newGridCoords};
if (entity.hasComponent("controllable")) {
let found = false;
do {
found = false;
const entitiesInCell = entitiesGrid[proposed.y][proposed.x];
for (let entity of entitiesInCell.values()) {
if (entity.hasComponent("pushable")) {
found = true;
entity.addComponent(game.components.Momentum({...momentumVector}));
}
}
proposed.x += momentumVector.dx;
proposed.y += momentumVector.dy;
const proposedClampedInBounds = clamp(proposed, xDim-1, yDim-1);
if (!equivalence(proposedClampedInBounds, proposed)) {
found = false;
}
} while (found);
}
if (entity.hasComponent("pushable") || entity.hasComponent("controllable")) {
for (let e of entitiesGrid[newGridCoords.y][newGridCoords.x].values()) {
if (e.hasComponent("stop")) {
newGridCoords = oldGridCoords;
break;
}
}
entity.addComponent(game.components.Momentum({...momentumVector}));
}
entity.components.gridPosition = {...entity.components.gridPosition, ...newGridCoords};
entity.components.position = {
...entity.components.position,
...gridCoordsToGame(entity.components.gridPosition)
};
if (entity.hasComponent("momentum")) {
entity.components.momentum.dx = 0;
entity.components.momentum.dy = 0;
}
}
} else {
entity.addComponent(game.components.Position({...gridCoordsToGame(entity.components.gridPosition)}));
};
});
};
return { entitiesGrid, gameCoordsToGrid, gridCoordsToGame, update, gridWidth, gridHeight };
};
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