"""Tests for VersionService.

This file demonstrates the testing patterns for Phase 2 service layer.
Tests are organized by functionality and cover success paths, error paths,
edge cases, and permission enforcement.
"""

from unittest.mock import MagicMock

import pytest

from nexus.bricks.versioning.version_service import VersionService


class TestVersionServiceInit:
    """Test VersionService initialization."""

    def test_init_minimal(self, mock_metadata_store, mock_cas_store):
        """Test service initialization with minimal dependencies."""
        service = VersionService(
            metadata_store=mock_metadata_store,
            cas_store=mock_cas_store,
        )

        assert service.metadata == mock_metadata_store
        assert service.cas == mock_cas_store
        assert service._permission_enforcer is None
        assert service._enforce_permissions is True

    def test_init_with_permissions(
        self, mock_metadata_store, mock_cas_store, mock_permission_enforcer
    ):
        """Test service initialization with permission enforcer."""
        service = VersionService(
            metadata_store=mock_metadata_store,
            cas_store=mock_cas_store,
            permission_enforcer=mock_permission_enforcer,
        )

        assert service._permission_enforcer == mock_permission_enforcer

    def test_init_disable_permissions(self, mock_metadata_store, mock_cas_store):
        """Test service initialization with permissions disabled."""
        service = VersionService(
            metadata_store=mock_metadata_store,
            cas_store=mock_cas_store,
            enforce_permissions=False,
        )

        assert service._enforce_permissions is False


class TestVersionServiceGetVersion:
    """Test VersionService.get_version() method."""

    @pytest.fixture
    def service(self, mock_metadata_store, mock_cas_store):
        """Create service instance with mocked dependencies."""
        return VersionService(
            metadata_store=mock_metadata_store,
            cas_store=mock_cas_store,
            enforce_permissions=False,  # Disable for unit tests
        )

    @pytest.mark.asyncio
    async def test_get_version_not_found_without_session_factory(self, service, operation_context):
        """Test that get_version raises NexusFileNotFoundError when no session_factory."""
        from nexus.contracts.exceptions import NexusFileNotFoundError

        # Without session_factory, version_meta is None → NexusFileNotFoundError
        with pytest.raises(NexusFileNotFoundError):
            await service.get_version(
                path="/test.txt",
                version=1,
                context=operation_context,
            )

    # ========================================================================
    # Future Tests (After Implementation Extraction)
    # ========================================================================
    # These tests will be uncommented once implementation is extracted

    # @pytest.mark.asyncio
    # async def test_get_version_success(self, service, operation_context):
    #     """Test getting a specific version successfully."""
    #     # Arrange
    #     service.metadata.get_version_metadata.return_value = {
    #         "version": 2,
    #         "etag": "def456",
    #         "size": 2048,
    #     }
    #     service.cas.get.return_value = b"version 2 content"
    #
    #     # Act
    #     content = await service.get_version(
    #         path="/test.txt",
    #         version=2,
    #         context=operation_context,
    #     )
    #
    #     # Assert
    #     assert content == b"version 2 content"
    #     service.metadata.get_version_metadata.assert_called_once_with(
    #         "/test.txt", 2
    #     )
    #     service.cas.get.assert_called_once_with("def456")

    # @pytest.mark.asyncio
    # async def test_get_version_not_found(self, service, operation_context):
    #     """Test getting non-existent version."""
    #     # Arrange
    #     service.metadata.get_version_metadata.return_value = None
    #
    #     # Act & Assert
    #     with pytest.raises(FileNotFoundError, match="Version 99 not found"):
    #         await service.get_version(
    #             path="/test.txt",
    #             version=99,
    #             context=operation_context,
    #         )

    # @pytest.mark.asyncio
    # async def test_get_version_invalid_number(self, service, operation_context):
    #     """Test getting version with invalid version number."""
    #     with pytest.raises(ValueError, match="Version must be positive"):
    #         await service.get_version(
    #             path="/test.txt",
    #             version=0,  # Invalid
    #             context=operation_context,
    #         )

    # @pytest.mark.asyncio
    # async def test_get_version_with_permissions(
    #     self, mock_metadata_store, mock_cas_store, mock_permission_enforcer
    # ):
    #     """Test get_version with permission enforcement enabled."""
    #     # Arrange
    #     service = VersionService(
    #         metadata_store=mock_metadata_store,
    #         cas_store=mock_cas_store,
    #         permission_enforcer=mock_permission_enforcer,
    #         enforce_permissions=True,
    #     )
    #     mock_permission_enforcer.check_permission.return_value = False
    #     context = OperationContext(user_id="alice", groups=[])
    #
    #     # Act & Assert
    #     with pytest.raises(PermissionError, match="READ permission denied"):
    #         await service.get_version(
    #             path="/test.txt",
    #             version=1,
    #             context=context,
    #         )


class TestVersionServiceListVersions:
    """Test VersionService.list_versions() method."""

    @pytest.fixture
    def service(self, mock_metadata_store, mock_cas_store):
        """Create service instance."""
        return VersionService(
            metadata_store=mock_metadata_store,
            cas_store=mock_cas_store,
            enforce_permissions=False,
        )

    @pytest.mark.asyncio
    async def test_list_versions_without_session_factory(self, service, operation_context):
        """Test that list_versions returns empty list when no session_factory."""
        # Without session_factory, list_versions returns [] (no RecordStore to query)
        result = await service.list_versions(
            path="/test.txt",
            context=operation_context,
        )

        assert result == []

    # ========================================================================
    # Future Tests
    # ========================================================================

    # @pytest.mark.asyncio
    # async def test_list_versions_success(self, service, operation_context):
    #     """Test listing versions successfully."""
    #     # Arrange
    #     versions = [
    #         {"version": 3, "created_at": "2026-01-03", "size": 3000},
    #         {"version": 2, "created_at": "2026-01-02", "size": 2000},
    #         {"version": 1, "created_at": "2026-01-01", "size": 1000},
    #     ]
    #     service.metadata.list_versions.return_value = versions
    #
    #     # Act
    #     result = await service.list_versions(
    #         path="/test.txt",
    #         context=operation_context,
    #     )
    #
    #     # Assert
    #     assert len(result) == 3
    #     assert result[0]["version"] == 3  # Newest first
    #     assert result[-1]["version"] == 1  # Oldest last

    # @pytest.mark.asyncio
    # async def test_list_versions_empty(self, service, operation_context):
    #     """Test listing versions for file with no versions."""
    #     # Arrange
    #     service.metadata.list_versions.return_value = []
    #
    #     # Act
    #     result = await service.list_versions(
    #         path="/test.txt",
    #         context=operation_context,
    #     )
    #
    #     # Assert
    #     assert result == []

    # @pytest.mark.asyncio
    # async def test_list_versions_file_not_found(self, service, operation_context):
    #     """Test listing versions for non-existent file."""
    #     # Arrange
    #     service.metadata.list_versions.side_effect = FileNotFoundError()
    #
    #     # Act & Assert
    #     with pytest.raises(FileNotFoundError):
    #         await service.list_versions(
    #             path="/nonexistent.txt",
    #             context=operation_context,
    #         )


class TestVersionServiceRollback:
    """Test VersionService.rollback() method."""

    @pytest.fixture
    def service(self, mock_metadata_store, mock_cas_store):
        """Create service instance."""
        return VersionService(
            metadata_store=mock_metadata_store,
            cas_store=mock_cas_store,
            enforce_permissions=False,
        )

    @pytest.mark.asyncio
    async def test_rollback_requires_dlc(self, service, operation_context):
        """Test that rollback requires DLC to be configured."""
        with pytest.raises(RuntimeError, match="DLC not configured"):
            await service.rollback(
                path="/test.txt",
                version=2,
                context=operation_context,
            )

    # ========================================================================
    # Future Tests
    # ========================================================================

    # @pytest.mark.asyncio
    # async def test_rollback_success(self, service, operation_context):
    #     """Test rolling back to previous version."""
    #     # Arrange
    #     service.metadata.get_version_metadata.return_value = {
    #         "version": 2,
    #         "etag": "def456",
    #         "size": 2048,
    #     }
    #     service.metadata.get_latest_version.return_value = 3
    #
    #     # Act
    #     await service.rollback(
    #         path="/test.txt",
    #         version=2,
    #         context=operation_context,
    #     )
    #
    #     # Assert
    #     # Should create new version (v4) pointing to v2's content
    #     service.metadata.create_version.assert_called_once()
    #     call_args = service.metadata.create_version.call_args
    #     assert call_args[1]["is_rollback"] is True
    #     assert call_args[1]["rollback_from"] == 2

    # @pytest.mark.asyncio
    # async def test_rollback_to_current_version(self, service, operation_context):
    #     """Test that rolling back to current version raises error."""
    #     # Arrange
    #     service.metadata.get_latest_version.return_value = 3
    #
    #     # Act & Assert
    #     with pytest.raises(ValueError, match="Cannot rollback to current version"):
    #         await service.rollback(
    #             path="/test.txt",
    #             version=3,  # Current version
    #             context=operation_context,
    #         )

    # @pytest.mark.asyncio
    # async def test_rollback_permission_denied(
    #     self, mock_metadata_store, mock_cas_store, mock_permission_enforcer
    # ):
    #     """Test rollback with insufficient permissions."""
    #     # Arrange
    #     service = VersionService(
    #         metadata_store=mock_metadata_store,
    #         cas_store=mock_cas_store,
    #         permission_enforcer=mock_permission_enforcer,
    #         enforce_permissions=True,
    #     )
    #     mock_permission_enforcer.check_permission.return_value = False
    #     context = OperationContext(user_id="alice", groups=[])
    #
    #     # Act & Assert
    #     with pytest.raises(PermissionError, match="WRITE permission denied"):
    #         await service.rollback(
    #             path="/test.txt",
    #             version=2,
    #             context=context,
    #         )


class TestVersionServiceDiffVersions:
    """Test VersionService.diff_versions() method."""

    @pytest.fixture
    def service(self, mock_metadata_store, mock_cas_store):
        """Create service instance."""
        return VersionService(
            metadata_store=mock_metadata_store,
            cas_store=mock_cas_store,
            enforce_permissions=False,
        )

    @pytest.mark.asyncio
    async def test_diff_versions_requires_session_factory(self, service, operation_context):
        """Test that diff_versions raises RuntimeError without session_factory."""
        # Without session_factory, diff_versions raises RuntimeError
        with pytest.raises(RuntimeError, match="session_factory required"):
            await service.diff_versions(
                path="/test.txt",
                v1=1,
                v2=2,
                mode="metadata",
                context=operation_context,
            )

    # ========================================================================
    # Future Tests
    # ========================================================================

    # @pytest.mark.asyncio
    # async def test_diff_versions_metadata_mode(self, service, operation_context):
    #     """Test diff in metadata mode."""
    #     # Arrange
    #     v1_meta = {
    #         "version": 1,
    #         "size": 1000,
    #         "etag": "abc123",
    #         "created_at": "2026-01-01T00:00:00",
    #     }
    #     v2_meta = {
    #         "version": 2,
    #         "size": 2000,
    #         "etag": "def456",
    #         "created_at": "2026-01-02T00:00:00",
    #     }
    #     service.metadata.get_version_metadata.side_effect = [v1_meta, v2_meta]
    #
    #     # Act
    #     result = await service.diff_versions(
    #         path="/test.txt",
    #         v1=1,
    #         v2=2,
    #         mode="metadata",
    #         context=operation_context,
    #     )
    #
    #     # Assert
    #     assert result["v1"] == v1_meta
    #     assert result["v2"] == v2_meta
    #     assert result["size_delta"] == 1000
    #     assert result["same_content"] is False  # Different etags

    # @pytest.mark.asyncio
    # async def test_diff_versions_unified_mode(self, service, operation_context):
    #     """Test diff in unified mode (like git diff)."""
    #     # Arrange
    #     service.cas.get.side_effect = [
    #         b"line 1\nline 2\nline 3\n",  # v1 content
    #         b"line 1\nline 2 modified\nline 3\nline 4\n",  # v2 content
    #     ]
    #
    #     # Act
    #     result = await service.diff_versions(
    #         path="/test.txt",
    #         v1=1,
    #         v2=2,
    #         mode="unified",
    #         context=operation_context,
    #     )
    #
    #     # Assert
    #     assert isinstance(result, str)
    #     assert "-line 2" in result
    #     assert "+line 2 modified" in result
    #     assert "+line 4" in result

    # @pytest.mark.asyncio
    # async def test_diff_versions_invalid_mode(self, service, operation_context):
    #     """Test diff with invalid mode."""
    #     with pytest.raises(ValueError, match="Invalid mode"):
    #         await service.diff_versions(
    #             path="/test.txt",
    #             v1=1,
    #             v2=2,
    #             mode="invalid_mode",
    #             context=operation_context,
    #         )


class TestVersionServiceHelpers:
    """Test VersionService helper methods."""

    def test_validate_path_absolute(self):
        """Test path validation converts to absolute path."""
        service = VersionService(
            metadata_store=MagicMock(),
            cas_store=MagicMock(),
        )

        result = service._validate_path("test.txt")
        assert result == "/test.txt"

    def test_validate_path_trailing_slash(self):
        """Test path validation removes trailing slash."""
        service = VersionService(
            metadata_store=MagicMock(),
            cas_store=MagicMock(),
        )

        result = service._validate_path("/path/to/file/")
        assert result == "/path/to/file"

    def test_validate_path_root(self):
        """Test path validation preserves root path."""
        service = VersionService(
            metadata_store=MagicMock(),
            cas_store=MagicMock(),
        )

        result = service._validate_path("/")
        assert result == "/"


# =============================================================================
# Integration Test Examples (Commented out until implementation extracted)
# =============================================================================

# class TestVersionServiceIntegration:
#     """Integration tests with real database and CAS."""
#
#     @pytest.fixture
#     def metadata_store(self, isolated_db):
#         """Create real metadata store."""
#         from nexus.storage.raft_metadata_store import RaftMetadataStore
#
#         store = str(isolated_db).replace(".db", "-raft")
#         yield store
#         store.close()
#
#     @pytest.fixture
#     def cas_store(self, tmp_path):
#         """Create real CAS store."""
#         from nexus.storage.cas_store import CASStore
#
#         cas_path = tmp_path / "cas"
#         cas_path.mkdir()
#         return CASStore(cas_path=str(cas_path))
#
#     @pytest.fixture
#     def service(self, metadata_store, cas_store):
#         """Create service with real dependencies."""
#         return VersionService(
#             metadata_store=metadata_store,
#             cas_store=cas_store,
#             enforce_permissions=False,
#         )
#
#     @pytest.mark.asyncio
#     async def test_version_workflow_end_to_end(self, service, operation_context):
#         """Test complete version workflow with real components."""
#         # This would test the full workflow:
#         # 1. Create file (version 1)
#         # 2. Update file (version 2)
#         # 3. Update again (version 3)
#         # 4. List versions
#         # 5. Get specific version
#         # 6. Rollback to version 2
#         # 7. Diff between versions
#         pass
