3 files changed, 181 insertions, 0 deletions
diff --git a/web/src/math/Coord.ts b/web/src/math/Coord.ts
new file mode 100644
index 0000000..db7ee6d
--- /dev/null
+++ b/web/src/math/Coord.ts
@@ -0,0 +1,23 @@
+/** A coord on a grid whose origin is in the top left. */
+export default class Coord {
+  private readonly _x: number;
+  private readonly _y: number;
+
+  constructor(x: number, y: number) {
+    this._x = x;
+    this._y = y;
+  }
+
+  get x(): number {
+    return this._x;
+  }
+
+  get y(): number {
+    return this._y;
+  }
+
+  /** Get the squared distance of this point from the origin. */
+  squaredDistanceFromOrigin(): number {
+    return this._x * this._x + this._y * this._y;
+  }
+}
diff --git a/web/src/math/Ratio.ts b/web/src/math/Ratio.ts
new file mode 100644
index 0000000..4973ff4
--- /dev/null
+++ b/web/src/math/Ratio.ts
@@ -0,0 +1,61 @@
+/** Serializable representation of a ratio. */
+export type RatioData = [numerator: number, denominator: number];
+
+/** Representation of a ratio for performing fractional artithmetic. */
+export default class Ratio {
+  private readonly _numerator: number;
+  private readonly _denominator: number;
+
+  get numerator(): number {
+    return this._numerator;
+  }
+
+  get denominator(): number {
+    return this._denominator;
+  }
+
+  constructor(numerator: number, denominator: number) {
+    if (!Number.isInteger(numerator) || !Number.isInteger(denominator)) {
+      throw new TypeError(
+        `Ratio must have integer parts: ${numerator} / ${denominator}`,
+      );
+    }
+
+    if (denominator === 0) {
+      throw new RangeError("Ratio demnominator cannot be zero");
+    }
+
+    this._numerator = numerator;
+    this._denominator = denominator;
+  }
+
+  multiplyRatio(other: Ratio): Ratio {
+    return new Ratio(
+      this.numerator * other.numerator,
+      this.denominator * other.denominator,
+    );
+  }
+
+  divideRatio(other: Ratio): Ratio {
+    return new Ratio(
+      this.numerator * other.denominator,
+      this.denominator * other.numerator,
+    );
+  }
+
+  toNumber(): number {
+    return this.numerator / this.denominator;
+  }
+
+  static fromInteger(n: number): Ratio {
+    return new Ratio(n, 1);
+  }
+
+  toData(): RatioData {
+    return [this.numerator, this.denominator];
+  }
+
+  static fromData(ratio: RatioData): Ratio {
+    return new Ratio(ratio[0], ratio[1]);
+  }
+}
diff --git a/web/src/math/Rect.ts b/web/src/math/Rect.ts
new file mode 100644
index 0000000..e26fbae
--- /dev/null
+++ b/web/src/math/Rect.ts
@@ -0,0 +1,97 @@
+import Coord from "./Coord";
+
+/** A rectangle on a grid whose origin is in the top left. */
+export default class Rect {
+  private readonly _topLeft: Coord;
+  private readonly _width: number;
+  private readonly _height: number;
+
+  constructor(
+    topLeftX: number,
+    topLeftY: number,
+    width: number,
+    height: number,
+  ) {
+    this._topLeft = new Coord(topLeftX, topLeftY);
+    this._width = width;
+    this._height = height;
+  }
+
+  /** Width of this rectangle. */
+  get width(): number {
+    return this._width;
+  }
+
+  /** Height of this rectangle. */
+  get height(): number {
+    return this._height;
+  }
+
+  /** Coord of the top-left point of this rectangle. */
+  get topLeft(): Coord {
+    return this._topLeft;
+  }
+
+  /** Coord of the bottom-right point of this rectangle. */
+  get bottomRight(): Coord {
+    return new Coord(
+      this._topLeft.x + this._width,
+      this._topLeft.y + this._height,
+    );
+  }
+
+  /** Determine if this rectangle contains the point at `coord`. */
+  containsCoord(coord: Coord): boolean {
+    return (
+      this.topLeft.x <= coord.x &&
+      coord.x <= this.bottomRight.x &&
+      this.topLeft.y <= coord.y &&
+      coord.y <= this.bottomRight.y
+    );
+  }
+
+  verticallyContainsCoord(coord: Coord): boolean {
+    return this.topLeft.y <= coord.y && coord.y <= this.bottomRight.y;
+  }
+
+  horizontallyContainsCoord(coord: Coord): boolean {
+    return this.topLeft.x <= coord.x && coord.x <= this.bottomRight.x;
+  }
+
+  extend(other: Rect): Rect {
+    const topLeftX = Math.min(
+      this.topLeft.x,
+      this.bottomRight.x,
+      other.topLeft.x,
+      other.bottomRight.x,
+    );
+
+    const topLeftY = Math.min(
+      this.topLeft.y,
+      this.bottomRight.y,
+      other.topLeft.y,
+      other.bottomRight.y,
+    );
+
+    const bottomRightX = Math.max(
+      this.topLeft.x,
+      this.bottomRight.x,
+      other.topLeft.x,
+      other.bottomRight.x,
+    );
+
+    const bottomRightY = Math.max(
+      this.topLeft.y,
+      this.bottomRight.y,
+      other.topLeft.y,
+      other.bottomRight.y,
+    );
+
+    return new Rect(
+      topLeftX,
+      topLeftY,
+      bottomRightX - topLeftX,
+      bottomRightY - topLeftY,
+    );
+  }
+}