infinite-grid.js

class InfiniteGrid {
	constructor({ defaultFactory = (x, y) => 0, string_map = {} } = {}) {
		this.defaultFactory = defaultFactory;
		this.string_map = string_map;
		this.grid = new Map();
		this.max_x = -Infinity;
		this.min_x = Infinity;
		this.max_y = -Infinity;
		this.min_y = Infinity;
	}

	static toId(x, y) {
		return `${x},${y}`;
	}

	set(x, y, value) {
		if (typeof x !== 'number' || typeof y !== 'number') {
			throw new Error(
				`x and y must be numbers, got (${typeof x})${x} and (${typeof y})${y}`
			);
		}
		if (x < this.min_x) this.min_x = x;
		if (x > this.max_x) this.max_x = x;
		if (y < this.min_y) this.min_y = y;
		if (y > this.max_y) this.max_y = y;
		const id = InfiniteGrid.toId(x, y);
		this.grid.set(id, value);
	}

	get(x, y) {
		const id = InfiniteGrid.toId(x, y);
		if (!this.grid.has(id)) {
			this.set(x, y, this.defaultFactory(x, y));
		}
		return this.grid.get(id);
	}

	toGrid() {
		let grid = [];
		for (let y = this.min_y; y <= this.max_y; y++) {
			let row = [];
			for (let x = this.min_x; x <= this.max_x; x++) {
				let cell = this.get(x, y);
				row.push(cell);
			}
			grid.push(row);
		}

		return grid;
	}

	sum() {
		let sum = 0;
		for (let value of this.grid.values()) {
			sum += value;
		}

		return sum;
	}

	toString() {
		let grid = this.toGrid();
		let rows = '';
		for (let y = 0; y < grid.length; y++) {
			let row = '';
			for (let x = 0; x < grid[y].length; x++) {
				let cell = grid[y][x];
				let cell_string =
					cell in this.string_map ? this.string_map[cell] : String(cell);
				row += cell_string;
			}
			rows += rows.length ? '\n' + row : row;
		}

		return rows;
	}
}

module.exports = {
	InfiniteGrid,
};