Add World entry point

The World class is the entrypoint of the simulation program, where all
cells lives and states are calculated.

Signed-off-by: Nicolas Paul <n@nc0.fr>

3 files changed, 121 insertions, 7 deletions

diff --git a/life2/simulator/src/game/world.js b/life2/simulator/src/game/world.js
new file mode 100644
index 0000000..c22cb49
--- /dev/null
+++ b/life2/simulator/src/game/world.js
@@ -0,0 +1,121 @@
+// Copyright (c) 2024 The Life 2 Authors.  All rights reserved.
+
+/**
+ * The possible states of a cell in the world.
+ * @readonly
+ * @enum {string}
+ */
+export const CELL_STATES = {
+    /** The cell is empty, possible because it never was filled or it died. */
+    EMPTY: ".",
+    /** The cell is occupied by a member of team A. */
+    TEAM_A: "a",
+    /** The cell is occupied by a member of team B. */
+    TEAM_B: "b",
+    /** The cell is a barrier, and it cannot be occupied by any entity,
+     * nor can it be modified by rules. */
+    BARRIER: "#",
+};
+
+/**
+ * A board is an array of strings, where each string represents a row of the
+ * board, and each character in the string represents a cell in the row.
+ * @typedef {Array<CELL_STATES>} Board
+ */
+
+/**
+ * The representation of the world, where all the entities live, and where the
+ * simulation takes place.
+ */
+export class World {
+    /**
+     * Create a new world with the given width and height.
+     * @constructor
+     * @param {number} width - The width of the world.
+     * @param {number} height - The height of the world.
+     */
+    constructor(width, height) {
+        // TODO(nc0) Support different types of boards, not just 2D
+
+        /**
+         * The width of the world board.
+         * @type {number}
+         * @readonly
+         */
+        this.width = width;
+        /**
+         * The height of the world board.
+         * @type {number}
+         * @readonly
+         */
+        this.height = height;
+        /**
+         * The board of the world, where all the entities live.
+         * @type {Board}
+         * @private
+         */
+        this.board = this.newBoard(width, height);
+    }
+
+    /**
+     * Create a new board with the given width and height, initializing all
+     * the cells to be empty.
+     * @param {number} width - The width of the board.
+     * @param {number} height - The height of the board.
+     * @returns {Board} The new board.
+     */
+    newBoard(width, height) {
+        return new Array(width).fill(CELL_STATES.EMPTY.repeat(height));
+    }
+
+    /**
+     * Returns the cell at the given coordinates.
+     * @param {number} x - The x coordinate of the cell.
+     * @param {number} y - The y coordinate of the cell.
+     * @returns {CELL_STATES | null} The cell at the given coordinates,
+     * or null if the coordinates are out of bounds.
+     */
+    getCell(x, y) {
+        if (x < 0 || x > this.width ||
+            y < 0 || y > this.height) return null;
+
+        return this.board[x][y];
+    }
+
+    /**
+     * Returns the cells that are adjacent to the given coordinates.
+     * @param {number} x - The x coordinate of the cell.
+     * @param {number} y - The y coordinate of the cell.
+     * @returns {Array<(number, number)>} The cells that are adjacent to the given
+     * coordinates.
+     */
+    getNeighbors(x, y) {
+        // TODO(nc0): Avoid hardcoding the 8 neighbors, check the bounds, ...
+        return [(x - 1, y - 1), (x, y - 1), (x + 1, y - 1),
+                (x - 1, y),   /* (x, y) */  (x + 1, y),
+                (x - 1, y + 1), (x, y + 1), (x + 1, y + 1)]
+               .filter((x, y) => this.getCell(x, y) !== null);
+    }
+
+    /**
+     *
+     */
+    nextState() {
+        // TODO(nc0): Implement various rules for the next state
+        const newBoard = this.newBoard(this.width, this.height);
+
+        for (let x = 0; x < this.width; x++) {
+            for (let y = 0; y < this.height; y++) {
+                const cell = this.getCell(x, y);
+                const neighbors = this.getNeighbors(x, y);
+                neighbors;
+
+                // Apply the rules to the cell and its neighbors
+                // and update the new board
+                newBoard[x][y] = cell;
+            }
+        }
+
+        this.board = newBoard;
+    }
+}
diff --git a/life2/simulator/src/index.js b/life2/simulator/src/index.js
deleted file mode 100644
index 07b6a60..0000000
--- a/life2/simulator/src/index.js
+++ /dev/null
@@ -1,7 +0,0 @@
-<!DOCTYPE html>
-<title>Life 2 Simulator</title>
-<script src="./life2.js"></script>
-<header></header>
-<main></main>
-<aside></aside>
-<footer></footer>
diff --git a/life2/simulator/src/style.css b/life2/simulator/src/style.css
deleted file mode 100644
index e69de29..0000000
--- a/life2/simulator/src/style.css
+++ /dev/null