import { describe, expect, it } from "@suaveplan/testing/runner";
import fc from "fast-check";

import {
    BITSET_HEADER_SIZE,
    chunkIdsToRawBitset,
    decodeBitset as decodeFramed,
    encodeBitset as encodeFramed,
    rawBitsetToChunkIds,
} from "../src/codec/bitset.js";
import { DMP_CODES, DmpError } from "../src/error-codes.js";
import {
    decodeBitsetToChunkIds as decodeBitset,
    encodeBitsetFromChunkIds as encodeBitset,
    SELECT_FORM_BITSET_THRESHOLD,
    selectForm,
    selectWhole,
} from "../src/select/form.js";

describe("@suaveplan/drive-mesh-protocol — selectForm", () => {
    it("rejects empty needed list with EMPTY_REQUEST", {
        timeout: 5000,
    }, () => {
        expect(() => selectForm([])).toThrow(DmpError);
        try {
            selectForm([]);
        } catch (err) {
            expect(err).toBeInstanceOf(DmpError);
            expect((err as DmpError).code).toBe(DMP_CODES.EMPTY_REQUEST);
        }
    });

    it("returns kind:'specific' for ≤ threshold counts", {
        timeout: 5000,
    }, () => {
        const result = selectForm([0, 5, 17]);
        expect(result.kind).toBe("specific");
        if (result.kind === "specific") {
            expect(result.chunkIds).toEqual([0, 5, 17]);
        }
    });

    it("returns kind:'specific' at exactly threshold", {
        timeout: 5000,
    }, () => {
        const ids = Array.from(
            { length: SELECT_FORM_BITSET_THRESHOLD },
            (_, i) => i
        );
        const result = selectForm(ids);
        expect(result.kind).toBe("specific");
    });

    it("returns kind:'bitset' for > threshold counts", {
        timeout: 5000,
    }, () => {
        const ids = Array.from(
            { length: SELECT_FORM_BITSET_THRESHOLD + 1 },
            (_, i) => i
        );
        const result = selectForm(ids);
        expect(result.kind).toBe("bitset");
        if (result.kind === "bitset") {
            expect(result.bytes).toBeInstanceOf(Uint8Array);
            expect(result.bytes.length).toBeGreaterThan(BITSET_HEADER_SIZE);
        }
    });

    it("honors a caller-supplied threshold override", { timeout: 5000 }, () => {
        const result = selectForm([0, 1, 2], { threshold: 2 });
        expect(result.kind).toBe("bitset");
    });

    it("threshold is exposed as the documented 64", { timeout: 5000 }, () => {
        expect(SELECT_FORM_BITSET_THRESHOLD).toBe(64);
    });
});

describe("@suaveplan/drive-mesh-protocol — selectWhole", () => {
    it("returns the canonical whole form", { timeout: 5000 }, () => {
        expect(selectWhole()).toEqual({ kind: "whole" });
    });
});

describe("@suaveplan/drive-mesh-protocol — chunkIdsToRawBitset / rawBitsetToChunkIds", () => {
    it("encodes a single bit", { timeout: 5000 }, () => {
        const raw = chunkIdsToRawBitset([0], 1);
        expect(raw.length).toBe(1);
        expect(raw[0]).toBe(0b00000001);
    });

    it("encodes bits across byte boundaries", { timeout: 5000 }, () => {
        const raw = chunkIdsToRawBitset([0, 7, 8, 15], 16);
        expect(raw.length).toBe(2);
        expect(raw[0]).toBe(0b10000001);
        expect(raw[1]).toBe(0b10000001);
    });

    it("rejects negative chunk ids", { timeout: 5000 }, () => {
        expect(() => chunkIdsToRawBitset([-1], 8)).toThrow(DmpError);
    });

    it("rejects ids past bitLength", { timeout: 5000 }, () => {
        expect(() => chunkIdsToRawBitset([10], 8)).toThrow(DmpError);
    });

    it("decodes returns indexes in ascending order", { timeout: 5000 }, () => {
        const raw = chunkIdsToRawBitset([10, 3, 17, 0], 18);
        expect(rawBitsetToChunkIds(raw, 18)).toEqual([0, 3, 10, 17]);
    });
});

describe("@suaveplan/drive-mesh-protocol — encodeBitset / decodeBitset (framed)", () => {
    it("framed bytes carry the magic prefix", { timeout: 5000 }, () => {
        const bytes = encodeBitset([0, 5, 17]);
        expect(bytes[0]).toBe(0x44); // 'D'
        expect(bytes[1]).toBe(0x4d); // 'M'
        expect(bytes[2]).toBe(0x50); // 'P'
        expect(bytes[3]).toBe(0x42); // 'B'
    });

    it("decode honours the embedded bit-length", { timeout: 5000 }, () => {
        const framed = encodeFramed(chunkIdsToRawBitset([0, 5, 17], 18), 18);
        const round = decodeFramed(framed);
        expect(round.bitLength).toBe(18);
    });

    it("roundtrip property: decode(encode(x)) preserves the sorted set", {
        timeout: 5000,
    }, () => {
        fc.assert(
            fc.property(
                fc
                    .array(fc.integer({ min: 0, max: 1023 }), {
                        minLength: 1,
                        maxLength: 64,
                    })
                    .map((arr) => Array.from(new Set(arr))),
                (input) => {
                    const sorted = [...input].sort((a, b) => a - b);
                    const framed = encodeBitset(sorted);
                    const recovered = decodeBitset(framed);
                    expect(recovered).toEqual(sorted);
                }
            ),
            { numRuns: 50 }
        );
    });
});