/**
 * DMP-08 — Advertisement bitset length invariant.
 *
 * In `ChunkAdvertisePayload`, the bit-length of `presence` MUST equal
 * `totalChunks`; padding bits in the final byte MUST be zero. The codec
 * rejects mismatched bitset wires with either
 * `DMP.BITSET_LENGTH_MISMATCH` or `DMP.BITSET_PADDING_NONZERO`.
 */

import { describe, expect, it } from "@suaveplan/testing/runner";
import {
    BITSET_MAGIC,
    chunkIdsToRawBitset,
    DMP_CODES,
    DmpError,
    decodeAdvertisePayload,
    encodeAdvertisePayload,
    encodeFramedBitset,
} from "../src/index.js";

const FILE_ID = "b".repeat(64);

function makeAdvertise(presence: Uint8Array, totalChunks: number) {
    return encodeAdvertisePayload({
        fileId: FILE_ID,
        presence,
        totalChunks,
        generation: 1,
        timestamp: 0,
    });
}

function makeFramedBitset(ids: number[], bitLength: number) {
    return encodeFramedBitset(chunkIdsToRawBitset(ids, bitLength), bitLength);
}

describe("DMP-08 — bitset length invariant", () => {
    it("advertisement with presence.length ≠ totalChunks rejected", {
        timeout: 5000,
    }, () => {
        const presence = makeFramedBitset([0, 5], 16);
        try {
            makeAdvertise(presence, 32);
            throw new Error("expected mismatch rejection");
        } catch (err) {
            expect(err).toBeInstanceOf(DmpError);
            expect((err as DmpError).code).toBe(
                DMP_CODES.BITSET_LENGTH_MISMATCH
            );
        }
    });

    it("valid advertisement (bitLength == totalChunks) round-trips", {
        timeout: 5000,
    }, () => {
        const presence = makeFramedBitset([0, 5, 7], 8);
        const wire = makeAdvertise(presence, 8);
        const decoded = decodeAdvertisePayload(wire);
        expect(decoded.totalChunks).toBe(8);
        expect(decoded.presence).toEqual(presence);
    });

    it("non-zero padding bits rejected", { timeout: 5000 }, () => {
        // Hand-build a framed bitset with bitLength=10 (so high bits 10..15
        // must be zero) but flip bit 14 to violate padding zeroing.
        const raw = new Uint8Array([0x01, 0xff]);
        // Build the wire envelope by hand.
        const wire = new Uint8Array(12 + raw.length);
        wire.set(BITSET_MAGIC, 0);
        const view = new DataView(
            wire.buffer,
            wire.byteOffset,
            wire.byteLength
        );
        view.setUint32(4, 10, false);
        view.setUint32(8, raw.length, false);
        wire.set(raw, 12);
        try {
            makeAdvertise(wire, 10);
            throw new Error("expected padding-nonzero rejection");
        } catch (err) {
            expect(err).toBeInstanceOf(DmpError);
            expect((err as DmpError).code).toBe(
                DMP_CODES.BITSET_PADDING_NONZERO
            );
        }
    });
});