"""
Unit tests for MongoDB database connection module.

Tests the database connection functionality with mocking
to avoid requiring actual MongoDB instance during tests.
"""

import pytest
from unittest.mock import Mock, patch, MagicMock
from pymongo.errors import ConnectionFailure, ServerSelectionTimeoutError

from app.database.connection import (
  create_mongodb_client,
  get_database,
  close_database_connection,
  get_mongodb_client,
  test_database_connection
)


def test_i_can_get_database_connection():
  """Test successful database connection creation."""
  mock_client = Mock()
  mock_database = Mock()
  mock_client.__getitem__.return_value = mock_database
  
  with patch('app.database.connection.MongoClient', return_value=mock_client):
    with patch('app.database.connection.get_mongodb_url', return_value="mongodb://localhost:27017"):
      with patch('app.database.connection.get_mongodb_database_name', return_value="testdb"):
        # Reset global variables
        import app.database.connection
        app.database.connection._client = None
        app.database.connection._database = None
        
        result = get_database()
        
        assert result == mock_database
        mock_client.admin.command.assert_called_with('ping')


def test_i_cannot_connect_to_invalid_mongodb_url():
  """Test fail-fast behavior with invalid MongoDB URL."""
  mock_client = Mock()
  mock_client.admin.command.side_effect = ConnectionFailure("Connection failed")
  
  with patch('app.database.connection.MongoClient', return_value=mock_client):
    with patch('app.database.connection.get_mongodb_url', return_value="mongodb://invalid:27017"):
      with pytest.raises(SystemExit) as exc_info:
        create_mongodb_client()
      
      assert exc_info.value.code == 1


def test_i_cannot_connect_with_server_selection_timeout():
  """Test fail-fast behavior with server selection timeout."""
  mock_client = Mock()
  mock_client.admin.command.side_effect = ServerSelectionTimeoutError("Timeout")
  
  with patch('app.database.connection.MongoClient', return_value=mock_client):
    with patch('app.database.connection.get_mongodb_url', return_value="mongodb://timeout:27017"):
      with pytest.raises(SystemExit) as exc_info:
        create_mongodb_client()
      
      assert exc_info.value.code == 1


def test_i_cannot_connect_with_unexpected_error():
  """Test fail-fast behavior with unexpected connection error."""
  with patch('app.database.connection.MongoClient', side_effect=Exception("Unexpected error")):
    with patch('app.database.connection.get_mongodb_url', return_value="mongodb://error:27017"):
      with pytest.raises(SystemExit) as exc_info:
        create_mongodb_client()
      
      assert exc_info.value.code == 1


def test_i_can_get_database_singleton():
  """Test that get_database returns the same instance (singleton pattern)."""
  mock_client = Mock()
  mock_database = Mock()
  mock_client.__getitem__.return_value = mock_database
  
  with patch('app.database.connection.MongoClient', return_value=mock_client):
    with patch('app.database.connection.get_mongodb_url', return_value="mongodb://localhost:27017"):
      with patch('app.database.connection.get_mongodb_database_name', return_value="testdb"):
        # Reset global variables
        import app.database.connection
        app.database.connection._client = None
        app.database.connection._database = None
        
        # First call
        db1 = get_database()
        # Second call
        db2 = get_database()
        
        assert db1 is db2
        # MongoClient should be called only once
        assert mock_client.admin.command.call_count == 1


def test_i_can_close_database_connection():
  """Test closing database connection."""
  mock_client = Mock()
  mock_database = Mock()
  mock_client.__getitem__.return_value = mock_database
  
  with patch('app.database.connection.MongoClient', return_value=mock_client):
    with patch('app.database.connection.get_mongodb_url', return_value="mongodb://localhost:27017"):
      with patch('app.database.connection.get_mongodb_database_name', return_value="testdb"):
        # Reset global variables
        import app.database.connection
        app.database.connection._client = None
        app.database.connection._database = None
        
        # Create connection
        get_database()
        
        # Close connection
        close_database_connection()
        
        mock_client.close.assert_called_once()
        assert app.database.connection._client is None
        assert app.database.connection._database is None


def test_i_can_get_mongodb_client():
  """Test getting raw MongoDB client instance."""
  mock_client = Mock()
  mock_database = Mock()
  mock_client.__getitem__.return_value = mock_database
  
  with patch('app.database.connection.MongoClient', return_value=mock_client):
    with patch('app.database.connection.get_mongodb_url', return_value="mongodb://localhost:27017"):
      with patch('app.database.connection.get_mongodb_database_name', return_value="testdb"):
        # Reset global variables
        import app.database.connection
        app.database.connection._client = None
        app.database.connection._database = None
        
        # Create connection first
        get_database()
        
        # Get client
        result = get_mongodb_client()
        
        assert result == mock_client


def test_i_can_get_none_mongodb_client_when_not_connected():
  """Test getting MongoDB client returns None when not connected."""
  # Reset global variables
  import app.database.connection
  app.database.connection._client = None
  app.database.connection._database = None
  
  result = get_mongodb_client()
  assert result is None


def test_i_can_test_database_connection_success():
  """Test database connection health check - success case."""
  mock_database = Mock()
  mock_database.command.return_value = True
  
  with patch('app.database.connection.get_database', return_value=mock_database):
    result = test_database_connection()
    
    assert result is True
    mock_database.command.assert_called_with('ping')


def test_i_cannot_test_database_connection_failure():
  """Test database connection health check - failure case."""
  mock_database = Mock()
  mock_database.command.side_effect = Exception("Connection error")
  
  with patch('app.database.connection.get_database', return_value=mock_database):
    result = test_database_connection()
    
    assert result is False


def test_i_can_close_connection_when_no_client():
  """Test closing connection when no client exists (should not raise error)."""
  # Reset global variables
  import app.database.connection
  app.database.connection._client = None
  app.database.connection._database = None
  
  # Should not raise any exception
  close_database_connection()
  
  assert app.database.connection._client is None
  assert app.database.connection._database is None