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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
const proposed = {x: entity.components.gridPosition.x + momentumVector.dx, y: entity.components.gridPosition.y + momentumVector.dy}
const entitiesInCell = entitiesGrid[proposed.x][proposed.y];
for (let id in entitiesInCell) {
if (entitiesInCell[id].hasComponent("pushable")) {
entitiesInCell[id].addComponent(game.components.Momentum({...momentumVector}));
}
}
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 };
};
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