"""Tests for binary codec."""

import pytest
from src.shared.binary_codec import BinaryCodec, FieldType, FieldID
from src.shared.models import Position, Snake


class TestPositionEncoding:
    """Test position encoding/decoding."""

    def test_encode_decode_position(self):
        """Test position round-trip."""
        positions = [
            Position(0, 0),
            Position(39, 29),  # Max grid position
            Position(20, 15),
            Position(1, 1),
        ]

        for pos in positions:
            encoded = BinaryCodec.encode_position(pos)
            decoded = BinaryCodec.decode_position(encoded)
            assert decoded.x == pos.x
            assert decoded.y == pos.y

    def test_packed_positions(self):
        """Test packed position encoding."""
        positions = [
            Position(0, 0),
            Position(1, 0),
            Position(2, 0),
            Position(3, 0),
            Position(3, 1),
        ]

        # Encode
        packed = BinaryCodec.encode_packed_positions(positions)

        # Decode
        decoded = BinaryCodec.decode_packed_positions(packed, len(positions))

        assert len(decoded) == len(positions)
        for orig, dec in zip(positions, decoded):
            assert dec.x == orig.x
            assert dec.y == orig.y

    def test_delta_encoding(self):
        """Test delta position encoding."""
        # Snake body (adjacent positions)
        positions = [
            Position(5, 5),
            Position(6, 5),  # Right
            Position(7, 5),  # Right
            Position(7, 6),  # Down
            Position(7, 7),  # Down
            Position(6, 7),  # Left
            Position(6, 6),  # Up
        ]

        # Encode
        encoded = BinaryCodec.encode_delta_positions(positions)

        # Decode
        decoded = BinaryCodec.decode_delta_positions(encoded, len(positions))

        assert len(decoded) == len(positions)
        for orig, dec in zip(positions, decoded):
            assert dec.x == orig.x
            assert dec.y == orig.y


class TestVarint:
    """Test variable-length integer encoding."""

    def test_small_values(self):
        """Test small varint values."""
        for value in [0, 1, 10, 127]:
            encoded = BinaryCodec.encode_varint(value)
            decoded, offset = BinaryCodec.decode_varint(encoded, 0)
            assert decoded == value
            assert offset == len(encoded)

    def test_large_values(self):
        """Test large varint values."""
        values = [128, 255, 1000, 10000, 65535, 1000000]

        for value in values:
            encoded = BinaryCodec.encode_varint(value)
            decoded, offset = BinaryCodec.decode_varint(encoded, 0)
            assert decoded == value

    def test_varint_size(self):
        """Test varint encoding size."""
        # Small values use 1 byte
        assert len(BinaryCodec.encode_varint(0)) == 1
        assert len(BinaryCodec.encode_varint(127)) == 1

        # Values >= 128 use 2+ bytes
        assert len(BinaryCodec.encode_varint(128)) == 2
        assert len(BinaryCodec.encode_varint(255)) == 2
        assert len(BinaryCodec.encode_varint(16383)) == 2
        assert len(BinaryCodec.encode_varint(16384)) == 3


class TestStringEncoding:
    """Test string encoding."""

    def test_short_strings(self):
        """Test encoding short strings."""
        strings = ["", "A", "Alice", "Player123"]

        for s in strings:
            encoded = BinaryCodec.encode_string_16(s)
            decoded, consumed = BinaryCodec.decode_string_16(encoded)
            assert decoded == s

    def test_max_length_string(self):
        """Test 16-character string."""
        s = "VeryLongUsername"
        assert len(s) == 16

        encoded = BinaryCodec.encode_string_16(s)
        decoded, consumed = BinaryCodec.decode_string_16(encoded)
        assert decoded == s

    def test_truncation(self):
        """Test string truncation."""
        s = "ThisIsAVeryLongUsernameThatExceedsLimit"
        encoded = BinaryCodec.encode_string_16(s)
        decoded, consumed = BinaryCodec.decode_string_16(encoded)

        # Should be truncated to 16 chars
        assert len(decoded) <= 16

    def test_unicode_strings(self):
        """Test Unicode string encoding."""
        strings = ["Hello世界", "Café", "🎮Player"]

        for s in strings:
            encoded = BinaryCodec.encode_string_16(s)
            decoded, consumed = BinaryCodec.decode_string_16(encoded)
            # Might be truncated due to UTF-8 byte limits
            assert decoded.startswith(s[:min(len(s), 10)])


class TestPlayerIdHash:
    """Test player ID hashing."""

    def test_consistent_hashing(self):
        """Test hash consistency."""
        player_id = "550e8400-e29b-41d4-a716-446655440000"

        hash1 = BinaryCodec.player_id_hash(player_id)
        hash2 = BinaryCodec.player_id_hash(player_id)

        assert hash1 == hash2

    def test_different_ids(self):
        """Test different IDs produce different hashes."""
        id1 = "550e8400-e29b-41d4-a716-446655440000"
        id2 = "550e8400-e29b-41d4-a716-446655440001"

        hash1 = BinaryCodec.player_id_hash(id1)
        hash2 = BinaryCodec.player_id_hash(id2)

        assert hash1 != hash2

    def test_hash_range(self):
        """Test hash is within uint32 range."""
        for i in range(100):
            player_id = f"player_{i}"
            hash_val = BinaryCodec.player_id_hash(player_id)
            assert 0 <= hash_val <= 0xFFFFFFFF


class TestCompression:
    """Test compression/decompression."""

    def test_compress_decompress(self):
        """Test compression round-trip."""
        data = b"This is test data that should compress well. " * 10

        compressed = BinaryCodec.compress(data)
        decompressed = BinaryCodec.decompress(compressed)

        assert decompressed == data
        assert len(compressed) < len(data)  # Should be smaller

    def test_small_data(self):
        """Test compression of small data."""
        data = b"short"

        compressed = BinaryCodec.compress(data)
        decompressed = BinaryCodec.decompress(compressed)

        assert decompressed == data
        # Small data might not compress well
        # Just verify round-trip works

    def test_empty_data(self):
        """Test compression of empty data."""
        data = b""

        compressed = BinaryCodec.compress(data)
        decompressed = BinaryCodec.decompress(compressed)

        assert decompressed == data


class TestPayloadDecoding:
    """Test payload field decoding."""

    def test_simple_payload(self):
        """Test decoding simple payload."""
        # Manually construct payload
        payload = bytearray()
        payload.append(BinaryCodec.VERSION)  # Version
        payload.append(2)  # Field count

        # Field 1: UPDATE_ID (uint16)
        payload.append(FieldID.UPDATE_ID)
        payload.append(FieldType.UINT16)
        payload.extend(BinaryCodec.encode_varint(2))  # Length
        payload.extend(b'\x00\x64')  # Value: 100

        # Field 2: GAME_RUNNING (uint8)
        payload.append(FieldID.GAME_RUNNING)
        payload.append(FieldType.UINT8)
        payload.extend(BinaryCodec.encode_varint(1))  # Length
        payload.append(1)  # True

        # Decode
        fields = self._decode_payload(bytes(payload))

        assert len(fields) >= 2
        # Check fields are present
        field_ids = [f[0] for f in fields]
        assert FieldID.UPDATE_ID in field_ids
        assert FieldID.GAME_RUNNING in field_ids

    def _decode_payload(self, payload: bytes):
        """Helper to decode payload."""
        if len(payload) < 2:
            return []

        version = payload[0]
        field_count = payload[1]
        fields = []
        offset = 2

        for _ in range(field_count):
            if offset + 2 > len(payload):
                break

            field_id = payload[offset]
            field_type = payload[offset + 1]
            offset += 2

            length, offset = BinaryCodec.decode_varint(payload, offset)

            if offset + length > len(payload):
                break

            field_data = payload[offset:offset + length]
            offset += length

            fields.append((field_id, field_type, field_data))

        return fields


class TestEdgeCases:
    """Test edge cases."""

    def test_max_grid_position(self):
        """Test maximum grid position (39, 29)."""
        pos = Position(39, 29)
        encoded = BinaryCodec.encode_position(pos)
        decoded = BinaryCodec.decode_position(encoded)
        assert decoded.x == 39
        assert decoded.y == 29

    def test_empty_position_list(self):
        """Test empty position list."""
        positions = []
        encoded = BinaryCodec.encode_packed_positions(positions)
        decoded = BinaryCodec.decode_packed_positions(encoded, 0)
        assert decoded == []

    def test_single_position(self):
        """Test single position."""
        positions = [Position(10, 10)]
        encoded = BinaryCodec.encode_delta_positions(positions)
        decoded = BinaryCodec.decode_delta_positions(encoded, 1)
        assert len(decoded) == 1
        assert decoded[0].x == 10
        assert decoded[0].y == 10


if __name__ == "__main__":
    pytest.main([__file__, "-v"])