import { describe, expect, it } from "@suaveplan/testing/runner";
import { PseudoRandomError } from "../errors/pseudo-random-error.js";
import { Xoshiro256PlusPlusRng } from "./xoshiro256.js";

describe("Xoshiro256PlusPlusRng", () => {
    it("is deterministic", { timeout: 5000 }, () => {
        const a = new Xoshiro256PlusPlusRng(123);
        const b = new Xoshiro256PlusPlusRng(123);
        for (let i = 0; i < 64; i += 1) {
            expect(a.nextUint32()).toBe(b.nextUint32());
        }
    });

    it("produces uint32 in range", { timeout: 5000 }, () => {
        const r = new Xoshiro256PlusPlusRng("x");
        for (let i = 0; i < 500; i += 1) {
            const v = r.nextUint32();
            expect(v).toBeGreaterThanOrEqual(0);
            expect(v).toBeLessThan(2 ** 32);
        }
    });

    it("nextFloat in [0,1)", { timeout: 5000 }, () => {
        const r = new Xoshiro256PlusPlusRng("y");
        for (let i = 0; i < 200; i += 1) {
            const f = r.nextFloat();
            expect(f).toBeGreaterThanOrEqual(0);
            expect(f).toBeLessThan(1);
        }
    });

    it("jump decorrelates streams", { timeout: 5000 }, () => {
        const a = new Xoshiro256PlusPlusRng(1);
        const b = new Xoshiro256PlusPlusRng(1);
        b.jump();
        const av = [a.nextUint32(), a.nextUint32()];
        const bv = [b.nextUint32(), b.nextUint32()];
        expect(av).not.toEqual(bv);
    });

    it("checkpoint/restore round-trip", { timeout: 5000 }, () => {
        const r = new Xoshiro256PlusPlusRng(7);
        r.skip(5);
        const cp = r.checkpoint();
        const exp = [r.nextUint32(), r.nextUint32(), r.nextUint32()];
        r.restore(cp);
        expect([r.nextUint32(), r.nextUint32(), r.nextUint32()]).toEqual(exp);
    });

    it("at doesn't mutate self", { timeout: 5000 }, () => {
        const r = new Xoshiro256PlusPlusRng(8);
        const ahead = r.at(5);
        expect(r.position).toBe(0);
        expect(ahead.position).toBe(5);
    });

    it("fork is independent", { timeout: 5000 }, () => {
        const r = new Xoshiro256PlusPlusRng(9);
        const c = r.fork("a");
        expect(r.nextUint32()).not.toBe(c.nextUint32());
    });

    it("restore validates algorithm and state", { timeout: 5000 }, () => {
        const r = new Xoshiro256PlusPlusRng(10);
        expect(() =>
            r.restore({ algorithm: "sfc32", state: [0, 0, 0, 0], counter: 0 })
        ).toThrow(PseudoRandomError);
        expect(() =>
            r.restore({ algorithm: "xoshiro256++", state: [], counter: 0 })
        ).toThrow(PseudoRandomError);
        expect(() =>
            r.restore({
                algorithm: "xoshiro256++",
                state: [0, 0, 0, 0, 0, 0, 0, Number.NaN],
                counter: 0,
            })
        ).toThrow(PseudoRandomError);
    });

    it("rejects bad skip/at args", { timeout: 5000 }, () => {
        const r = new Xoshiro256PlusPlusRng(11);
        expect(() => r.skip(-1)).toThrow(PseudoRandomError);
        expect(() => r.at(-1)).toThrow(PseudoRandomError);
    });
});