import { describe, expect, it } from "vitest";
import {
	compactRelativeTime,
	formatCount,
	formatDate,
	formatDateTime,
	formatDuration,
	relativeTime,
	uniquePrefixLength
} from "#lib/format.ts";

describe("formatCount", () => {
	it("leaves counts under a thousand alone", () => {
		expect(formatCount(0)).toBe("0");
		expect(formatCount(1)).toBe("1");
		expect(formatCount(999)).toBe("999");
	});

	it("abbreviates thousands, dropping a trailing zero decimal", () => {
		expect(formatCount(1000)).toBe("1k");
		expect(formatCount(1200)).toBe("1.2k");
		expect(formatCount(12_345)).toBe("12.3k");
		expect(formatCount(999_000)).toBe("999k");
	});

	it("truncates instead of rounding, so a count never overflows its unit", () => {
		expect(formatCount(1299)).toBe("1.2k");
		expect(formatCount(999_999)).toBe("999.9k");
		expect(formatCount(1_999_999)).toBe("1.9m");
	});

	it("abbreviates millions", () => {
		expect(formatCount(1_000_000)).toBe("1m");
		expect(formatCount(2_500_000)).toBe("2.5m");
		expect(formatCount(1_200_000_000)).toBe("1200m");
	});

	it("renders nothing for a missing count", () => {
		expect(formatCount(undefined)).toBe("");
		expect(formatCount(null)).toBe("");
	});
});

describe("formatDuration", () => {
	it("reads 0s under a second, so an instant run differs from one that never ran", () => {
		expect(formatDuration(0)).toBe("0s");
		expect(formatDuration(999)).toBe("0s");
	});

	it("joins only the non-zero chunks", () => {
		expect(formatDuration(45_000)).toBe("45s");
		expect(formatDuration(90_000)).toBe("1m 30s");
		expect(formatDuration(3_600_000)).toBe("1h");
		expect(formatDuration(90_061_000)).toBe("1d 1h 1m 1s");
	});

	it("rejects negative and non-finite input", () => {
		expect(formatDuration(-1)).toBe("");
		expect(formatDuration(Number.NaN)).toBe("");
		expect(formatDuration(Number.POSITIVE_INFINITY)).toBe("");
	});
});

describe("relativeTime", () => {
	const now = new Date("2026-08-18T12:00:00Z");

	it("describes the past, and the future as now", () => {
		expect(relativeTime("2026-08-18T11:59:30Z", now)).toBe("30 seconds ago");
		expect(relativeTime("2026-08-18T09:00:00Z", now)).toBe("3 hours ago");
		expect(relativeTime("2026-08-15T12:00:00Z", now)).toBe("3 days ago");
		expect(relativeTime("2026-08-18T14:00:00Z", now)).toBe("now");
	});

	it("falls back to years past the largest division", () => {
		expect(relativeTime("2020-08-18T12:00:00Z", now)).toBe("6 years ago");
	});

	it("accepts a Date and renders nothing for an unparseable string", () => {
		expect(relativeTime(new Date("2026-08-17T12:00:00Z"), now)).toBe("yesterday");
		expect(relativeTime("not a date", now)).toBe("");
	});
});

describe("compactRelativeTime", () => {
	const now = new Date("2026-08-18T12:00:00Z");

	it("truncates to the largest whole unit that fits", () => {
		expect(compactRelativeTime("2026-08-18T11:59:59Z", now)).toBe("1s ago");
		expect(compactRelativeTime("2026-08-18T11:30:00Z", now)).toBe("30m ago");
		expect(compactRelativeTime("2026-08-18T02:00:00Z", now)).toBe("10h ago");
		expect(compactRelativeTime("2026-08-15T12:00:00Z", now)).toBe("3d ago");
		expect(compactRelativeTime("2026-08-01T12:00:00Z", now)).toBe("2w ago");
		expect(compactRelativeTime("2026-05-18T12:00:00Z", now)).toBe("3mo ago");
		expect(compactRelativeTime("2020-08-18T12:00:00Z", now)).toBe("6y ago");
	});

	it("reads future timestamps as now", () => {
		expect(compactRelativeTime("2026-08-18T12:00:00Z", now)).toBe("now");
		expect(compactRelativeTime("2026-08-18T12:00:30Z", now)).toBe("now");
		expect(compactRelativeTime("2026-08-20T12:00:00Z", now)).toBe("now");
	});

	it("renders nothing for an unparseable string", () => {
		expect(compactRelativeTime("not a date", now)).toBe("");
	});
});

describe("formatDate", () => {
	it("renders a short month-day-year", () => {
		expect(formatDate(new Date(2026, 7, 18, 12))).toBe("Aug 18, 2026");
	});

	it("renders nothing for an unparseable string", () => {
		expect(formatDate("not a date")).toBe("");
	});
});

describe("formatDateTime", () => {
	it("appends a time and zone to the date", () => {
		// zone abbreviation depends on the runner's timezone, so match the shape
		expect(formatDateTime(new Date(2026, 7, 18, 15, 4))).toMatch(/^Aug 18, 2026, 3:04 PM .+$/);
	});

	it("renders nothing for an unparseable string", () => {
		expect(formatDateTime("not a date")).toBe("");
	});
});

describe("uniquePrefixLength", () => {
	const ids = ["abc1", "abd2", "x9", "abc1"];

	it("stops one character past the longest prefix shared with another id", () => {
		expect(uniquePrefixLength("abc1", ids)).toBe(3);
		expect(uniquePrefixLength("abd2", ids)).toBe(3);
		expect(uniquePrefixLength("x9", ids)).toBe(1);
	});

	it("never runs past the id itself", () => {
		expect(uniquePrefixLength("ab", ["ab", "abc"])).toBe(2);
	});
});