import { describe, expect, it } from "vitest";
import { lineForTop, monotonic, topForLine } from "$lib/components/ui/markdownScroll";

const anchors = [
	{ line: 0, top: 0 },
	{ line: 4, top: 100 },
	{ line: 10, top: 400 }
];

describe("topForLine", () => {
	it("interpolates between the surrounding anchors", () => {
		expect(topForLine(anchors, 2)).toBe(50);
		expect(topForLine(anchors, 7)).toBe(250);
	});

	it("clamps past the last anchor", () => {
		expect(topForLine(anchors, 20)).toBe(400);
	});
});

describe("lineForTop", () => {
	it("inverts topForLine", () => {
		expect(lineForTop(anchors, 250)).toBe(7);
		expect(lineForTop(anchors, topForLine(anchors, 3.5))).toBe(3.5);
	});
});

describe("monotonic", () => {
	it("drops anchors that go back in lines or position", () => {
		expect(
			monotonic([
				{ line: 0, top: 0 },
				{ line: 2, top: 40 },
				{ line: 2, top: 60 },
				{ line: 1, top: 80 },
				{ line: 5, top: 30 },
				{ line: 6, top: 90 }
			])
		).toEqual([
			{ line: 0, top: 0 },
			{ line: 2, top: 40 },
			{ line: 6, top: 90 }
		]);
	});
});