"""Tests for QR bundle encoding/decoding."""

import hashlib
import pytest

from radicle_reticulum.git_bundle import GitBundle, BundleMetadata, BundleType
from radicle_reticulum.qr import (
    encode_bundle_to_qr,
    decode_bundle_from_qr_data,
    BundleTooLargeForQR,
    QR_MAX_BYTES,
    QR_MAGIC,
)


def make_small_bundle(data: bytes = b"tiny git bundle data") -> GitBundle:
    """Create a minimal GitBundle for testing."""
    metadata = BundleMetadata(
        bundle_type=BundleType.INCREMENTAL,
        repository_id="rad:z3test",
        source_node="did:key:z6Mktest",
        timestamp=1000,
        refs_included=["refs/heads/main"],
        prerequisites=["abc123"],
        size_bytes=len(data),
        checksum=hashlib.sha256(data).digest(),
    )
    return GitBundle(metadata=metadata, data=data)


class TestQRPayloadRoundtrip:
    """Test the binary payload encode/decode without QR rendering."""

    def _encode_payload(self, bundle: GitBundle) -> bytes:
        """Extract the raw bytes that would be put into a QR code."""
        import struct
        bundle_bytes = bundle.encode()
        checksum = hashlib.sha256(bundle_bytes).digest()
        length_prefix = len(bundle_bytes).to_bytes(4, "big")
        return QR_MAGIC + length_prefix + checksum + bundle_bytes

    def test_decode_roundtrip(self):
        bundle = make_small_bundle()
        payload = self._encode_payload(bundle)
        decoded = decode_bundle_from_qr_data(payload)
        assert decoded.metadata.repository_id == bundle.metadata.repository_id
        assert decoded.data == bundle.data

    def test_decode_rejects_wrong_magic(self):
        bundle = make_small_bundle()
        payload = b"WRONGMAGIC" + self._encode_payload(bundle)[len(QR_MAGIC):]
        with pytest.raises(ValueError, match="Not a Radicle QR payload"):
            decode_bundle_from_qr_data(payload)

    def test_decode_detects_corruption(self):
        bundle = make_small_bundle()
        payload = bytearray(self._encode_payload(bundle))
        payload[-1] ^= 0xFF  # flip last bit of bundle data
        with pytest.raises(ValueError, match="checksum mismatch"):
            decode_bundle_from_qr_data(bytes(payload))

    def test_decode_rejects_truncated_payload(self):
        bundle = make_small_bundle()
        payload = self._encode_payload(bundle)
        # Truncate the bundle data portion
        truncated = payload[:-10]
        with pytest.raises(ValueError, match="Truncated"):
            decode_bundle_from_qr_data(truncated)


class TestBundleTooLarge:
    def test_oversized_bundle_raises(self):
        large_data = b"x" * (QR_MAX_BYTES + 1)
        bundle = make_small_bundle(data=large_data)
        with pytest.raises(BundleTooLargeForQR, match="QR capacity"):
            encode_bundle_to_qr(bundle)

    def test_exact_limit_would_include_overhead(self):
        # QR_MAX_BYTES is the limit for the serialised bundle, including metadata.
        # A bundle with data just under the limit should still fail due to metadata overhead.
        # This test verifies the check catches realistic oversized bundles.
        oversized_data = b"a" * QR_MAX_BYTES
        bundle = make_small_bundle(data=oversized_data)
        with pytest.raises(BundleTooLargeForQR):
            encode_bundle_to_qr(bundle)


class TestQREncodeOutput:
    """Test QR rendering (requires qrcode package)."""

    def test_encode_returns_ascii_art(self):
        bundle = make_small_bundle()
        result = encode_bundle_to_qr(bundle)
        assert isinstance(result, str)
        assert len(result) > 0
        # ASCII art QR codes use block characters
        assert any(c in result for c in ("█", "░", " ", "\n"))

    def test_encode_small_bundle_succeeds(self):
        bundle = make_small_bundle(b"small")
        result = encode_bundle_to_qr(bundle)
        assert result  # non-empty

    def test_error_correction_levels(self):
        bundle = make_small_bundle()
        for level in ("L", "M", "Q", "H"):
            result = encode_bundle_to_qr(bundle, error_correction=level)
            assert isinstance(result, str)