import { describe, expect, it } from "vitest";
import { curtainEdge, curtainPolygon } from "./curtain";

const ROWS = Array.from({ length: 30 }, (_, row) => row);

describe("curtainEdge", () => {
  it("is fully closed at progress 0 and fully open at progress 1, in every row", () => {
    for (const row of ROWS) {
      expect(curtainEdge(row, 0)).toBe(0);
      expect(curtainEdge(row, 1)).toBe(1);
    }
  });

  it("never moves backwards as progress grows", () => {
    for (const row of ROWS) {
      let last = 0;
      for (let step = 0; step <= 20; step++) {
        const edge = curtainEdge(row, step / 20);
        expect(edge).toBeGreaterThanOrEqual(last);
        last = edge;
      }
    }
  });

  it("is ragged: rows are at different places half way through", () => {
    const places = new Set(ROWS.map((row) => curtainEdge(row, 0.5).toFixed(3)));
    expect(places.size).toBeGreaterThan(10);
  });

  it("stays within 0..1 and clamps progress outside 0..1", () => {
    expect(curtainEdge(3, -1)).toBe(0);
    expect(curtainEdge(3, 2)).toBe(1);
  });

  it("is deterministic per row", () => {
    expect(curtainEdge(7, 0.4)).toBe(curtainEdge(7, 0.4));
  });
});

describe("curtainPolygon", () => {
  const box = { width: 200, height: 40, cell: 20 };

  it("covers nothing at progress 0 and the whole box at progress 1 (behind the edge)", () => {
    expect(curtainPolygon("behind", 0, box)).toBe("polygon(0px 0px, 0px 0px, 0px 20px, 0px 20px, 0px 40px, 0px 40px)");
    expect(curtainPolygon("behind", 1, box)).toBe(
      "polygon(0px 0px, 200px 0px, 200px 20px, 200px 20px, 200px 40px, 0px 40px)",
    );
  });

  it("is the complement ahead of the edge", () => {
    expect(curtainPolygon("ahead", 1, box)).toBe(
      "polygon(200px 0px, 200px 0px, 200px 20px, 200px 20px, 200px 40px, 200px 40px)",
    );
    expect(curtainPolygon("ahead", 0, box)).toBe(
      "polygon(200px 0px, 0px 0px, 0px 20px, 0px 20px, 0px 40px, 200px 40px)",
    );
  });

  it("adds a row for a height that is not a multiple of the cell", () => {
    const points = curtainPolygon("behind", 1, { width: 100, height: 50, cell: 20 }).split(",");
    // Two corner points plus two per row, for three rows.
    expect(points).toHaveLength(8);
  });
});