import { describe, expect, it } from "vitest";
import { deepestSoFar, lengthAtDepth } from "./thread";

describe("deepestSoFar", () => {
  it("keeps the lowest point the line has reached at each sample", () => {
    // The line goes down, loops back up, and goes down again.
    expect(deepestSoFar([10, 5, 20, 15, 30])).toEqual([10, 10, 20, 20, 30]);
  });

  it("is empty for an empty line", () => {
    expect(deepestSoFar([])).toEqual([]);
  });

  it("works above the top of the page", () => {
    expect(deepestSoFar([-20, -30, -10])).toEqual([-20, -20, -10]);
  });
});

describe("lengthAtDepth", () => {
  const depths = [10, 10, 20, 20, 30];

  it("draws nothing above the start of the line", () => {
    expect(lengthAtDepth(depths, 8, 9)).toBe(0);
  });

  it("draws everything the line needed to reach that depth, loops included", () => {
    expect(lengthAtDepth(depths, 8, 10)).toBe(16);
    expect(lengthAtDepth(depths, 8, 19)).toBe(16);
    expect(lengthAtDepth(depths, 8, 20)).toBe(32);
  });

  it("draws the whole line below its end", () => {
    expect(lengthAtDepth(depths, 8, 1000)).toBe(40);
  });

  it("draws nothing of an empty line", () => {
    expect(lengthAtDepth([], 8, 1000)).toBe(0);
  });
});