import { describe, expect, it } from "vitest";
import { discoveredPageCount, offsetFor, pageCount, pageParam } from "$lib/pagination";

describe("pagination helpers", () => {
	describe("pageParam", () => {
		it("defaults to 1 when missing", () => {
			expect(pageParam(new URL("https://tangled.org/repo"))).toBe(1);
		});

		it("parses valid positive page numbers", () => {
			expect(pageParam(new URL("https://tangled.org/repo?page=3"))).toBe(3);
		});

		it("falls back to 1 for invalid or zero pages", () => {
			expect(pageParam(new URL("https://tangled.org/repo?page=0"))).toBe(1);
			expect(pageParam(new URL("https://tangled.org/repo?page=-5"))).toBe(1);
			expect(pageParam(new URL("https://tangled.org/repo?page=abc"))).toBe(1);
		});
	});

	describe("offsetFor", () => {
		it("returns undefined for page 1", () => {
			expect(offsetFor(1, 30)).toBeUndefined();
		});

		it("returns correct offset for pages > 1", () => {
			expect(offsetFor(2, 30)).toBe(30);
			expect(offsetFor(3, 30)).toBe(60);
		});
	});

	describe("pageCount", () => {
		it("returns 1 for 0 items", () => {
			expect(pageCount(0, 30)).toBe(1);
		});

		it("calculates ceiling pages correctly", () => {
			expect(pageCount(30, 30)).toBe(1);
			expect(pageCount(31, 30)).toBe(2);
			expect(pageCount(90, 30)).toBe(3);
		});
	});

	describe("discoveredPageCount", () => {
		it("increments page when hasNext is true", () => {
			expect(discoveredPageCount(1, true)).toBe(2);
			expect(discoveredPageCount(5, true)).toBe(6);
		});

		it("stays on current page when hasNext is false", () => {
			expect(discoveredPageCount(1, false)).toBe(1);
			expect(discoveredPageCount(5, false)).toBe(5);
		});
	});
});