import { describe, it, expect } from 'vitest';
import protobuf from 'protobufjs';
import {
  decodeValue,
  encodeValue,
  decodeDouble,
  decodeFloat,
  decodeSint32,
  decodeUint32,
  decodeUint64,
  decodeBool,
  decodeString,
  decodeBytes,
  decodeList,
  decodeTuple,
  decodeDictionary,
  decodeKrpcList,
} from '../src/decoder.js';
import { TypeCode, type KrpcType } from '../src/types.js';
import { MESSAGE_TYPES, KRPC } from '../src/schema.js';

const T = (t: Partial<KrpcType>): KrpcType => ({
  code: t.code ?? 0,
  service: t.service ?? '',
  name: t.name ?? '',
  types: t.types ?? [],
});

// We need a small fake "TYPE" registry for the tests so the decoder
// can find List / Tuple / Dictionary / Status by name. We can use the
// real MESSAGE_TYPES for the actual system messages.
const REG = MESSAGE_TYPES;

describe('primitive decoders', () => {
  it('decodes a double (8-byte little-endian)', () => {
    expect(decodeDouble(new Uint8Array(new Float64Array([3.14]).buffer))).toBeCloseTo(3.14, 10);
    expect(decodeDouble(new Uint8Array(new Float64Array([-0]).buffer))).toBe(-0);
    expect(decodeDouble(new Uint8Array(new Float64Array([0]).buffer))).toBe(0);
    expect(decodeDouble(new Uint8Array(new Float64Array([1e30]).buffer))).toBe(1e30);
  });

  it('decodes a float (4-byte little-endian)', () => {
    expect(decodeFloat(new Uint8Array(new Float32Array([2.5]).buffer))).toBeCloseTo(2.5, 5);
  });

  it('decodes a sint32 (zigzag varint)', () => {
    // 0 -> 0, 1 -> 2, -1 -> 1, 2 -> 4, -2 -> 3
    expect(decodeSint32(new Uint8Array([0]))).toBe(0);
    expect(decodeSint32(new Uint8Array([2]))).toBe(1);
    expect(decodeSint32(new Uint8Array([1]))).toBe(-1);
    expect(decodeSint32(new Uint8Array([4]))).toBe(2);
    expect(decodeSint32(new Uint8Array([3]))).toBe(-2);
  });

  it('decodes a uint32 (varint)', () => {
    expect(decodeUint32(new Uint8Array([0]))).toBe(0);
    expect(decodeUint32(new Uint8Array([0x7f]))).toBe(127);
    expect(decodeUint32(new Uint8Array([0x80, 0x01]))).toBe(128);
  });

  it('decodes a uint64 to BigInt (preserves > 2^53)', () => {
    // 2^53 + 1 exceeds Number.MAX_SAFE_INTEGER. Verify the decoder
    // produces the exact BigInt. Hand-varint for 2^53+1:
    //   7-bit groups, LSB first: 0x01 0x00 0x00 0x00 0x00 0x00 0x00 0x10
    //   (bit 53 = position 4 in the last group = 0b0010000 = 0x10)
    const big = 0x20_0000_0000_0001n; // 2^53 + 1
    const bytes = new Uint8Array([0x81, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x10]);
    expect(decodeUint64(bytes)).toBe(big);
  });

  it('decodes a bool', () => {
    expect(decodeBool(new Uint8Array([0]))).toBe(false);
    expect(decodeBool(new Uint8Array([1]))).toBe(true);
    expect(decodeBool(new Uint8Array([0xff]))).toBe(true);
  });

  it('decodes a string', () => {
    const utf8 = new TextEncoder().encode('Kerbin');
    const buf = new Uint8Array([utf8.length, ...utf8]);
    expect(decodeString(buf)).toBe('Kerbin');
  });

  it('decodes a string with non-ASCII characters', () => {
    const utf8 = new TextEncoder().encode('日本語');
    const buf = new Uint8Array([utf8.length, ...utf8]);
    expect(decodeString(buf)).toBe('日本語');
  });

  it('decodes bytes', () => {
    const payload = new Uint8Array([0xde, 0xad, 0xbe, 0xef]);
    const buf = new Uint8Array([payload.length, ...payload]);
    expect(decodeBytes(buf)).toEqual(payload);
  });
});

describe('decodeValue dispatcher', () => {
  it('decodes DOUBLE', () => {
    const bytes = new Uint8Array(new Float64Array([2.71828]).buffer);
    const out = decodeValue(T({ code: TypeCode.DOUBLE }), bytes);
    expect(out).toBeCloseTo(2.71828, 5);
  });

  it('decodes STRING', () => {
    const utf8 = new TextEncoder().encode('Mun');
    const bytes = new Uint8Array([utf8.length, ...utf8]);
    expect(decodeValue(T({ code: TypeCode.STRING }), bytes)).toBe('Mun');
  });

  it('decodes CLASS object id (non-null)', () => {
    // 42 as varint
    const id = decodeValue(T({ code: TypeCode.CLASS, service: 'SpaceCenter', name: 'Vessel' }), new Uint8Array([42]));
    expect(id).toBe(42n);
  });

  it('decodes CLASS object id (null when 0)', () => {
    expect(
      decodeValue(
        T({ code: TypeCode.CLASS, service: 'SpaceCenter', name: 'Vessel' }),
        new Uint8Array([0]),
      ),
    ).toBeNull();
  });

  it('decodes ENUMERATION as a sint32', () => {
    expect(
      decodeValue(
        T({ code: TypeCode.ENUMERATION, service: 'SpaceCenter', name: 'VesselType' }),
        new Uint8Array([0]), // Ship
      ),
    ).toBe(0);
  });

  it('decodes NONE as null', () => {
    expect(decodeValue(T({ code: TypeCode.NONE }), new Uint8Array(0))).toBeNull();
  });

  it('throws on unknown type code', () => {
    expect(() => decodeValue(T({ code: 9999 }), new Uint8Array(0))).toThrow(/unknown TypeCode/);
  });
});

describe('collection decoders', () => {
  it('decodes a list of doubles', () => {
    // Construct a KRPC.List message manually:
    //   items[0] = 8 bytes for double 1.0
    //   items[1] = 8 bytes for double 2.5
    const d1 = new Uint8Array(new Float64Array([1.0]).buffer);
    const d2 = new Uint8Array(new Float64Array([2.5]).buffer);
    const listMsg = KRPC.List.create({ items: [d1, d2] });
    const listBytes = KRPC.List.encode(listMsg).finish();
    const out = decodeList(
      T({ code: TypeCode.LIST, types: [T({ code: TypeCode.DOUBLE })] }),
      listBytes,
      REG,
    );
    expect(out).toEqual([1.0, 2.5]);
  });

  it('decodes a list of strings', () => {
    const enc = (s: string): Uint8Array => {
      const utf8 = new TextEncoder().encode(s);
      return new Uint8Array([utf8.length, ...utf8]);
    };
    const listMsg = KRPC.List.create({ items: [enc('Kerbin'), enc('Mun')] });
    const listBytes = KRPC.List.encode(listMsg).finish();
    const out = decodeList(
      T({ code: TypeCode.LIST, types: [T({ code: TypeCode.STRING })] }),
      listBytes,
      REG,
    );
    expect(out).toEqual(['Kerbin', 'Mun']);
  });

  it('decodes an empty list', () => {
    const listMsg = KRPC.List.create({ items: [] });
    const listBytes = KRPC.List.encode(listMsg).finish();
    const out = decodeList(
      T({ code: TypeCode.LIST, types: [T({ code: TypeCode.STRING })] }),
      listBytes,
      REG,
    );
    expect(out).toEqual([]);
  });

  it('decodes a null list as null', () => {
    const out = decodeList(
      T({ code: TypeCode.LIST, types: [T({ code: TypeCode.STRING })] }),
      new Uint8Array([0]),
      REG,
    );
    expect(out).toBeNull();
  });

  it('decodes a list of CLASS as a bigint array', () => {
    // items[0] = 7, items[1] = 0 (null)
    const listMsg = KRPC.List.create({ items: [new Uint8Array([7]), new Uint8Array([0])] });
    const listBytes = KRPC.List.encode(listMsg).finish();
    const out = decodeList(
      T({
        code: TypeCode.LIST,
        types: [T({ code: TypeCode.CLASS, service: 'SpaceCenter', name: 'CelestialBody' })],
      }),
      listBytes,
      REG,
    );
    expect(out).toEqual([7n, null]);
  });

  it('decodes a tuple of mixed types', () => {
    // tuple: (string "Kerbin", double 0.5)
    const utf8 = new TextEncoder().encode('Kerbin');
    const sBytes = new Uint8Array([utf8.length, ...utf8]);
    const dBytes = new Uint8Array(new Float64Array([0.5]).buffer);
    const tupleMsg = KRPC.Tuple.create({ items: [sBytes, dBytes] });
    const tupleBytes = KRPC.Tuple.encode(tupleMsg).finish();
    const out = decodeTuple(
      T({
        code: TypeCode.TUPLE,
        types: [T({ code: TypeCode.STRING }), T({ code: TypeCode.DOUBLE })],
      }),
      tupleBytes,
      REG,
    );
    expect(out).toEqual(['Kerbin', 0.5]);
  });

  it('decodes a dictionary of string -> double', () => {
    const utf8 = new TextEncoder().encode('mu');
    const sBytes = new Uint8Array([utf8.length, ...utf8]);
    const dBytes = new Uint8Array(new Float64Array([3.53e12]).buffer);
    const dictMsg = KRPC.Dictionary.create({
      entries: [{ key: sBytes, value: dBytes }],
    });
    const dictBytes = KRPC.Dictionary.encode(dictMsg).finish();
    const out = decodeDictionary(
      T({
        code: TypeCode.DICTIONARY,
        types: [T({ code: TypeCode.STRING }), T({ code: TypeCode.DOUBLE })],
      }),
      dictBytes,
      REG,
    );
    expect(out.get('mu')).toBe(3.53e12);
  });

  it('decodes a null dictionary as null', () => {
    const out = decodeDictionary(
      T({
        code: TypeCode.DICTIONARY,
        types: [T({ code: TypeCode.STRING }), T({ code: TypeCode.DOUBLE })],
      }),
      new Uint8Array([0]),
      REG,
    );
    expect(out).toBeNull();
  });

  it('exposes a low-level decodeKrpcList for testing', () => {
    const listMsg = KRPC.List.create({ items: [new Uint8Array([1, 2, 3])] });
    const bytes = KRPC.List.encode(listMsg).finish();
    const out = decodeKrpcList(bytes, KRPC.List);
    // protobufjs returns Node Buffers (which extend Uint8Array). Compare
    // the underlying bytes so this works regardless of wrapper class.
    expect(out).toHaveLength(1);
    expect(Array.from(out[0] as Uint8Array)).toEqual([1, 2, 3]);
  });
});

describe('encodeValue (round-trips)', () => {
  it('encodes a double', () => {
    const bytes = encodeValue(T({ code: TypeCode.DOUBLE }), 1.5);
    expect(decodeValue(T({ code: TypeCode.DOUBLE }), bytes)).toBe(1.5);
  });

  it('encodes a string', () => {
    const bytes = encodeValue(T({ code: TypeCode.STRING }), 'Kerbol');
    expect(decodeValue(T({ code: TypeCode.STRING }), bytes)).toBe('Kerbol');
  });

  it('encodes a CLASS object id', () => {
    const bytes = encodeValue(
      T({ code: TypeCode.CLASS, service: 'SpaceCenter', name: 'Vessel' }),
      42n,
    );
    expect(decodeValue(T({ code: TypeCode.CLASS, service: 'SpaceCenter', name: 'Vessel' }), bytes)).toBe(42n);
  });

  it('encodes a null CLASS as id=0', () => {
    const bytes = encodeValue(
      T({ code: TypeCode.CLASS, service: 'SpaceCenter', name: 'Vessel' }),
      null,
    );
    expect(bytes).toEqual(new Uint8Array([0]));
  });

  it('encodes an ENUMERATION', () => {
    const bytes = encodeValue(
      T({ code: TypeCode.ENUMERATION, service: 'SpaceCenter', name: 'VesselType' }),
      3, // Probe
    );
    expect(
      decodeValue(
        T({ code: TypeCode.ENUMERATION, service: 'SpaceCenter', name: 'VesselType' }),
        bytes,
      ),
    ).toBe(3);
  });

  it('encodes a list of doubles', () => {
    const bytes = encodeValue(
      T({ code: TypeCode.LIST, types: [T({ code: TypeCode.DOUBLE })] }),
      [1.0, 2.0, 3.0],
      REG,
    );
    const out = decodeValue(
      T({ code: TypeCode.LIST, types: [T({ code: TypeCode.DOUBLE })] }),
      bytes,
      REG,
    );
    expect(out).toEqual([1.0, 2.0, 3.0]);
  });

  it('encodes a uint64 BigInt', () => {
    const id = 0x1_0000_0000n; // 2^32
    const bytes = encodeValue(T({ code: TypeCode.UINT64 }), id);
    expect(decodeValue(T({ code: TypeCode.UINT64 }), bytes)).toBe(id);
  });

  it('encodes a bool', () => {
    expect(decodeValue(T({ code: TypeCode.BOOL }), encodeValue(T({ code: TypeCode.BOOL }), true))).toBe(true);
    expect(decodeValue(T({ code: TypeCode.BOOL }), encodeValue(T({ code: TypeCode.BOOL }), false))).toBe(false);
  });

  it('rejects SET (not implemented)', () => {
    expect(() =>
      encodeValue(T({ code: TypeCode.SET, types: [T({ code: TypeCode.STRING })] }), new Set(), REG),
    ).toThrow(/SET not implemented/);
  });
});

// Suppress unused-warning for the TYPE const helper by using it once.
const _checkTypeHelper: KrpcType = T({ code: TypeCode.STRING });
void _checkTypeHelper;
// Also pin the protobufjs default import to confirm we still have it.
const _pb: typeof protobuf = protobuf;
void _pb;