import { describe, it, expect } from 'vitest';
import { schemaRegistry as analyzeSource } from '../upstream/schema';
import { generateCode } from '../../src/codegen/generator';
import { protobuf_getUnknownFieldMetadata } from '../../src/runtime';
import { loadFixture } from '../helpers';

/** Analyze fixture → generate → eval → return encode/decode pair */
function makeRoundTrip(fixtureName: string, msgName: string) {
    return makeRoundTripFromSchema(loadFixture(fixtureName), msgName);
}

function makeRoundTripFromSchema(schema: string, msgName: string) {
    const gen = generateCode(analyzeSource(schema, `${msgName}.ts`));
    return new Function(
        gen + `\nreturn { enc: protobuf_encode_${msgName}, dec: protobuf_decode_${msgName} };`,
    )() as {
        enc: (obj: unknown) => Uint8Array;
        dec: (data: Uint8Array) => any;
    };
}

function encodeVarint32(value: number): number[] {
    const bytes: number[] = [];
    let remaining = value >>> 0;

    do {
        let byte = remaining & 0x7f;
        remaining >>>= 7;

        if (remaining !== 0) {
            byte |= 0x80;
        }

        bytes.push(byte);
    } while (remaining !== 0);

    return bytes;
}

describe('code generator', () => {
    it.each([
        [0, []],
        [1, [0x08, 0x01]],
        [127, [0x08, 0x7f]],
        [128, [0x08, 0x80, 0x01]],
        [300, [0x08, 0xac, 0x02]],
        [16384, [0x08, 0x80, 0x80, 0x01]],
        [0xffffffff, [0x08, 0xff, 0xff, 0xff, 0xff, 0x0f]],
    ] as const)('encodes and decodes uint32 wire fixture %i', (value, bytes) => {
        const { enc, dec } = makeRoundTrip('simple.ts', 'SimpleMsg');
        expect([...enc({ value })]).toEqual(bytes);
        expect(dec(Uint8Array.from(bytes)).value).toBe(value);
    });

    it.each([
        [0x10, 0xac, 0x02],
        [0x12, 0x03, 0x41, 0x42, 0x43],
        [0x15, 0, 0, 0, 0],
        [0x11, 0, 0, 0, 0, 0, 0, 0, 0],
    ])('skips an unknown wire field before a known field (%j)', (...bytes) => {
        const { dec } = makeRoundTrip('simple.ts', 'SimpleMsg');
        expect(dec(Uint8Array.from([...bytes, 0x08, 42])).value).toBe(42);
    });

    it('generates encode/decode for simple uint_32', () => {
        const gen = generateCode(analyzeSource(loadFixture('simple.ts'), 't.ts'));
        expect(gen).toContain('function protobuf_encode_SimpleMsg(obj)');
        expect(gen).toContain('function protobuf_decode_SimpleMsg(data');
        // Tag for field 1, varint should be pre-computed as 0x08
        expect(gen).toContain('buf[offset++] = 8;');
    });

    it('generates nested message code', () => {
        const gen = generateCode(analyzeSource(loadFixture('nested.ts'), 't.ts'));
        expect(gen).toContain('__write_Inner(');
        expect(gen).toContain('protobuf_decode_Inner(data, offset, offset + _len)');
    });

    it('round-trip uint_32', () => {
        const { enc, dec } = makeRoundTrip('simple.ts', 'SimpleMsg');
        expect(dec(enc({ value: 42 })).value).toBe(42);
    });

    it('round-trip nested message', () => {
        const { enc, dec } = makeRoundTrip('nested.ts', 'Outer');
        expect(dec(enc({ inner: { value: 999 } })).inner.value).toBe(999);
    });

    it('round-trip string', () => {
        const { enc, dec } = makeRoundTrip('string-msg.ts', 'StringMsg');
        expect(dec(enc({ text: 'hello world' })).text).toBe('hello world');
    });

    it('round-trip unicode string', () => {
        const { enc, dec } = makeRoundTrip('string-msg.ts', 'StringMsg');
        expect(dec(enc({ text: '你好，protobuf🚀' })).text).toBe('你好，protobuf🚀');
    });

    it('round-trip bool', () => {
        const { enc, dec } = makeRoundTrip('bool-msg.ts', 'BoolMsg');
        expect(dec(enc({ active: true })).active).toBe(true);
        const empty = enc({ active: false });
        expect(empty.length).toBe(0);
        expect(dec(empty).active).toBe(false);
    });

    it('proto3 default encoding (0 → empty)', () => {
        const { enc } = makeRoundTrip('simple.ts', 'SimpleMsg');
        expect(enc({ value: 0 }).length).toBe(0);
    });

    it('round-trip repeated uint_32', () => {
        const { enc, dec } = makeRoundTrip('repeated.ts', 'RepeatedMsg');
        const result = dec(enc({ ids: [10, 20, 30], names: [] }));
        expect(result.ids).toEqual([10, 20, 30]);
        expect(result.names).toEqual([]);
    });

    it('round-trip repeated string', () => {
        const { enc, dec } = makeRoundTrip('repeated.ts', 'RepeatedMsg');
        const result = dec(enc({ ids: [], names: ['hello', 'world'] }));
        expect(result.ids).toEqual([]);
        expect(result.names).toEqual(['hello', 'world']);
    });

    it('repeated empty arrays round-trip', () => {
        const { enc, dec } = makeRoundTrip('repeated.ts', 'RepeatedMsg');
        const result = dec(enc({ ids: [], names: [] }));
        expect(result.ids).toEqual([]);
        expect(result.names).toEqual([]);
    });

    it('round-trip bigint-backed 64-bit integers', () => {
        const schema = `
interface BigIntMsg {
  unsigned: pb<1, uint_64>;
  signed: pb<2, int_64>;
  zigzag: pb<3, sint_64>;
  fixed: pb<4, fixed_64>;
  sfixed: pb<5, sfixed_64>;
  ids: pb_repeated<6, uint_64>;
}`;
        const { enc, dec } = makeRoundTripFromSchema(schema, 'BigIntMsg');
        const input = {
            unsigned: 18446744073709551615n,
            signed: -1n,
            zigzag: -1234567890123456789n,
            fixed: 0x0102030405060708n,
            sfixed: -0x0102030405060708n,
            ids: [1n, 2n, 9007199254740993n],
        };
        expect(dec(enc(input))).toEqual(input);
    });

    it('round-trip sint_32 with negative values', () => {
        const schema = `
interface Sint32Msg {
  value: pb<1, sint_32>;
  values: pb_repeated<2, sint_32>;
}`;
        const { enc, dec } = makeRoundTripFromSchema(schema, 'Sint32Msg');
        const input = { value: -789, values: [-1, 0, 1, -789, 2147483647, -2147483648] };
        expect(dec(enc(input))).toEqual(input);
    });

    it('preserves legacy outbound int_32 bytes while accepting canonical negative varints', () => {
        const schema = `
interface Int32Msg {
  value: pb<1, int_32>;
  values: pb_repeated<2, int_32>;
  forced: pb_optional<3, int_32>;
}`;
        const { enc, dec } = makeRoundTripFromSchema(schema, 'Int32Msg');
        const input = {
            value: -1,
            values: [-2147483648, -1, 0, 1, 2147483647],
            forced: -2147483648,
        };
        const encoded = enc(input);

        // Keep SnowLuma's established five-byte negative int32 encoding on the
        // outbound path until QQ interoperability is verified on a live account.
        // The decoder remains liberal and accepts protobuf's canonical ten-byte
        // negative form below.
        expect(Array.from(encoded.slice(0, 6))).toEqual([0x08, 0xff, 0xff, 0xff, 0xff, 0x0f]);
        expect(dec(encoded)).toEqual(input);
        expect(
            dec(Uint8Array.from([0x08, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x01]))
                .value,
        ).toBe(-1);
    });

    it('retains the low 32 bits of extended uint_32 field varints', () => {
        const { dec } = makeRoundTripFromSchema(
            `interface Uint32Msg { value: pb<1, uint_32>; }`,
            'Uint32Msg',
        );

        // QQ sometimes serializes a signed 32-bit source into a schema slot that
        // clients expose as uint32. Protobuf readers consume the full ten-byte
        // varint and retain its low 32 bits for wire compatibility.
        expect(
            dec(Uint8Array.from([0x08, 0xfe, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x01]))
                .value,
        ).toBe(0xfffffffe);

        // QQ-compatible uint32 readers consume up to a full 64-bit varint and
        // retain its low 32 bits. Some push-envelope sequences use that wire
        // representation, so values with non-zero high bits must remain decodable.
        expect(dec(Uint8Array.from([0x08, 0x80, 0x80, 0x80, 0x80, 0x10])).value).toBe(0);
        expect(dec(Uint8Array.from([0x08, 0x87, 0x80, 0x80, 0x80, 0x10])).value).toBe(7);

        // Compatibility applies only to complete uint64 varints. Truncated input
        // and values wider than 64 bits must still fail loudly.
        expect(() => dec(Uint8Array.from([0x08, 0x80]))).toThrow(/[Tt]runcated.*varint/);
        expect(() =>
            dec(
                Uint8Array.from([0x08, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x02]),
            ),
        ).toThrow(/Invalid protobuf varint/);
    });

    it('rejects malformed length-delimited fields without leaving parent bounds', () => {
        const schema = `interface BytesMsg { data: pb<1, bytes>; }`;
        const { dec } = makeRoundTripFromSchema(schema, 'BytesMsg');

        expect(() => dec(Uint8Array.from([0x0a, 0x80]))).toThrow(/[Tt]runcated.*varint/);
        expect(() => dec(Uint8Array.from([0x0a, 0x80, 0x80, 0x80, 0x80, 0x10]))).toThrow(
            /Invalid protobuf varint/,
        );
    });

    it('skips unknown groups without decoding their fields into the parent', () => {
        const schema = `
interface Text { str: pb<1, string>; }
interface Elem { text: pb<1, Text>; }
`;
        const { dec } = makeRoundTripFromSchema(schema, 'Elem');
        const decoded = dec(
            Uint8Array.from([
                0x7b, 0x0a, 0x08, 0x0a, 0x06, 0x66, 0x6f, 0x72, 0x67, 0x65, 0x64, 0x7c,
            ]),
        );

        expect(decoded.text).toBeNull();
        expect(protobuf_getUnknownFieldMetadata(decoded).fields).toMatchObject([
            { fieldNumber: 15, wireType: 3 },
        ]);
    });

    it('aggregates repeated unknown fields instead of retaining every occurrence', () => {
        const { dec } = makeRoundTripFromSchema(
            `interface UnknownMsg { known: pb<1, uint_32>; }`,
            'UnknownMsg',
        );
        const wire: number[] = [];
        const tag = encodeVarint32((60 << 3) | 0);

        for (let index = 0; index < 1_000; index++) {
            wire.push(...tag, 0);
        }

        const metadata = protobuf_getUnknownFieldMetadata(dec(Uint8Array.from(wire)));
        expect(metadata).toEqual({
            fields: [{ fieldNumber: 60, wireType: 0, count: 1_000, totalByteLength: 1_000 }],
            totalOccurrences: 1_000,
            omittedOccurrences: 0,
            omittedByteLength: 0,
        });
    });

    it('caps retained unknown field kinds and summarizes overflow', () => {
        const { dec } = makeRoundTripFromSchema(
            `interface UnknownKindsMsg { known: pb<1, uint_32>; }`,
            'UnknownKindsMsg',
        );
        const wire: number[] = [];

        for (let fieldNumber = 2; fieldNumber <= 66; fieldNumber++) {
            wire.push(...encodeVarint32((fieldNumber << 3) | 0), 0);
        }

        const metadata = protobuf_getUnknownFieldMetadata(dec(Uint8Array.from(wire)));
        expect(metadata.fields).toHaveLength(64);
        expect(metadata.totalOccurrences).toBe(65);
        expect(metadata.omittedOccurrences).toBe(1);
        expect(metadata.omittedByteLength).toBe(1);
    });

    it('round-trip double as ieee754 number', () => {
        const schema = `
interface DoubleMsg {
  value: pb<1, double>;
  values: pb_repeated<2, double>;
}`;
        const { enc, dec } = makeRoundTripFromSchema(schema, 'DoubleMsg');
        const result = dec(enc({ value: Math.PI, values: [Math.E, -0.5] }));
        expect(result.value).toBeCloseTo(Math.PI);
        expect(result.values[0]).toBeCloseTo(Math.E);
        expect(result.values[1]).toBeCloseTo(-0.5);
    });
});

describe('pb_optional explicit presence', () => {
    it('serialises a zero scalar (where pb<> would omit it)', () => {
        const { enc, dec } = makeRoundTripFromSchema(
            `interface OptMsg { forced: pb_optional<1, uint_32>; }`,
            'OptMsg',
        );
        // field 1, varint, value 0 → tag 0x08 then payload 0x00 (NOT empty).
        expect(Array.from(enc({ forced: 0 }))).toEqual([0x08, 0x00]);
        expect(dec(enc({ forced: 0 })).forced).toBe(0);
    });

    it('still omits the field when the value is absent (undefined)', () => {
        const { enc } = makeRoundTripFromSchema(
            `interface OptMsg2 { forced: pb_optional<1, uint_32>; }`,
            'OptMsg2',
        );
        expect(enc({}).length).toBe(0);
    });

    it('does not change a sibling plain pb<> field (it still omits its zero)', () => {
        const { enc, dec } = makeRoundTripFromSchema(
            `interface MixMsg { plain: pb<1, uint_32>; forced: pb_optional<2, uint_32>; }`,
            'MixMsg',
        );
        // plain=0 omitted (unchanged); only forced=0 is emitted (field 2 → tag 0x10).
        expect(Array.from(enc({ plain: 0, forced: 0 }))).toEqual([0x10, 0x00]);
        expect(dec(enc({ plain: 7, forced: 9 }))).toEqual({ plain: 7, forced: 9 });
    });

    it('forces a false bool onto the wire', () => {
        const { enc, dec } = makeRoundTripFromSchema(
            `interface BoolOpt { flag: pb_optional<1, bool>; }`,
            'BoolOpt',
        );
        expect(Array.from(enc({ flag: false }))).toEqual([0x08, 0x00]);
        expect(dec(enc({ flag: false })).flag).toBe(false);
        expect(Array.from(enc({ flag: true }))).toEqual([0x08, 0x01]);
    });
});