import pytest
import boto3
from moto import mock_aws
from unittest.mock import patch, MagicMock
from unittest import TestCase
from src.extract_lambda import list_existing_s3_files, connect_to_database, DBConnectionException, lambda_handler, process_and_upload_tables
import os 
import logging
import json

@pytest.fixture(scope='class')
def mock_config():
    env_vars = {
        "host": "abc",
        "port": "5432",
        "user": "def",
        "password": "password",
        "database": "db",
    }
    with patch("src.extract_lambda.get_config", return_value=env_vars) as mock_config:
        yield mock_config


@pytest.fixture(scope='class')
def aws_credentials():
    os.environ["AWS_ACCESS_KEY_ID"] = 'testing'
    os.environ["AWS_SECRET_ACCESS_KEY"] = 'testing'
    os.environ["AWS_SECURIT_TOKEN"] = 'testing'
    os.environ["AWS_SESSION_TOKEN"] = 'testing'
    os.environ["AWS_DEFAULT_REGION"]= 'eu-west-2'

@pytest.fixture(scope='class')
def s3_client(aws_credentials):
    with mock_aws():
        yield boto3.client('s3')

class TestLambdaHandler:
    def test_lambda_handler_files_processed_and_uploaded_successfully(self, mocker):
        mock_db = MagicMock()
        mock_db.run.side_effect = [
            [['Fruits']],  
            [['Vegetable', 'Sour', 'Green'], ['Berry', 'Sweet', 'Red']],  
            [['Food_type'], ['Flavour'], ['Colour']]  
        ]
        mock_db.columns.return_value = [{'name': 'Food_type'}, {'name': 'Flavour'}, {'name': 'Colour'}]
        with patch("src.extract_lambda.connect_to_database", return_value=mock_db):
            mock_process_and_upload_tables = mocker.patch("src.extract_lambda.process_and_upload_tables", return_value=mock_db)
            mock_list_existing_s3_files = mocker.patch("src.extract_lambda.list_existing_s3_files", return_value={})
            event = {}
            context = {}
            response = lambda_handler(event, context)
            assert response['statusCode'] == 200
            assert json.loads(response['body']) == 'CSV files processed and uploaded successfully.'
            mock_list_existing_s3_files.assert_called_once()
            mock_process_and_upload_tables.assert_called_once_with(mock_db, {})
            mock_db.close.assert_called_once()

    def test_lambda_handler_no_changes_detected_no_files_uploaded(self, mocker):
        mock_db = MagicMock()
        mock_db.run.side_effect = [
            [['Fruits']],
            [['Vegetable', 'Sour', 'Green'], ['Berry', 'Sweet', 'Red']],
            [['Food_type'], ['Flavour'], ['Colour']]
        ]
        mock_db.columns.return_value = [{'name': 'Food_type'}, {'name': 'Flavour'}, {'name': 'Colour'}]

        with patch("src.extract_lambda.connect_to_database", return_value=mock_db):
            mock_process_and_upload_tables = mocker.patch("src.extract_lambda.process_and_upload_tables", return_value=False)
            mock_list_existing_s3_files = mocker.patch("src.extract_lambda.list_existing_s3_files", return_value={})
            event = {}
            context = {}
            response = lambda_handler(event, context)
            assert response['statusCode'] == 200
            assert json.loads(response['body']) == 'No changes detected, no CSV files were uploaded.'
            mock_list_existing_s3_files.assert_called_once()
            mock_process_and_upload_tables.assert_called_once_with(mock_db, {})
            mock_db.close.assert_called_once()

    def test_lambda_handler_exception_error(self, mocker):
        with patch("src.extract_lambda.connect_to_database", side_effect=Exception("Database connection error")):
            mock_process_and_upload_tables = mocker.patch("src.extract_lambda.process_and_upload_tables")
            mock_list_existing_s3_files = mocker.patch("src.extract_lambda.list_existing_s3_files")
            event = {}
            context = {}
            response = lambda_handler(event, context)
            assert response['statusCode'] == 500
            assert json.loads(response['body']) == 'Internal server error.'
            mock_list_existing_s3_files.assert_not_called()
            mock_process_and_upload_tables.assert_not_called()        

class TestListExistingS3Files:
    def test_error_if_no_bucket(self, s3_client, caplog):

        logger = logging.getLogger()
        logger.info('Testing now.')
        caplog.set_level(logging.ERROR)
        list_existing_s3_files(client=s3_client)
        assert 'Error listing S3 objects' in caplog.text

    def test_error_if_bucket_is_empty(self, s3_client, caplog):

        s3_client.create_bucket(Bucket='extract_bucket', 
                                CreateBucketConfiguration={
                                    'LocationConstraint': 'eu-west-2'
                                })
        list_existing_s3_files(client=s3_client)
        assert 'The bucket is empty' in caplog.text 

    def test_error_retrieving_object(self, s3_client, caplog):
        s3_client.upload_file('tests/dummy.txt', 'extract_bucket', 'dummy.txt')
        list_existing_s3_files(bucket_name='test_bucket', client=s3_client)

        assert 'Error retrieving S3 object ' in caplog.text

    def test_retrieves_file_content(self, s3_client, caplog):
        result = list_existing_s3_files(client=s3_client)

        assert list(result.values()) == ['This is a test file.'] 

class TestConnectToDatabase:
    def test_connect_to_database(mock_conn, mock_config):
        with patch("src.extract_lambda.Connection", autospec=True) as mock_conn:  
            connect_to_database()
            mock_conn.assert_called_with(
            host="abc", user="def", port="5432", password="password", database="db"
            )

    def test_database_error(self, mock_config):
        with pytest.raises(DBConnectionException):
            connect_to_database()

    def test_logs_interface_error(self, caplog):
        logger = logging.getLogger()
        logger.info('Testing now.')
        caplog.set_level(logging.ERROR)
        with pytest.raises(DBConnectionException):
            connect_to_database()
        assert 'Interface error' in caplog.text
'''
class TestProcessAndUploadTables:
    def test_error_process_and_upload_tables(mock_conn, mock_config, s3_client, caplog):
        logger = logging.getLogger()
        logger.info('Testing now.')
        caplog.set_level(logging.ERROR)
        ####
        queries = ["SELECT table_name FROM information_schema.tables WHERE table_schema='public' AND table_type='BASE TABLE';",
                    "SELECT * FROM Fruits;",
                    "SELECT column_name FROM INFORMATION_SCHEMA.COLUMNS where table_name = 'Fruits'"]
        return_values = [[['Fruits']],
                        [['Vegetable','Sour','Green'],['Berry','Sweet','Red']],
                        [['Food_type'],['Flavour'],['Colour']]]
        vals = dict(zip(queries,return_values))

        ####
        with patch('src.extract_lambda.connect_to_database') as mock_db:
            mock_db().run.side_effects = return_values
            s3_key = 'Fruits/2024/08/15/Fruits_16:46:30.csv'
            existing_files = {s3_key: 'Food_type,Flavour,Colour\nFruit,Sour,Green\nBerry,Sweet,Red'}
            s3_client.create_bucket(Bucket='extract_bucket', 
                        CreateBucketConfiguration={'LocationConstraint': 'eu-west-2'})
            s3_client.upload_file('tests/dummy_identical.csv', 'extract_bucket', s3_key)
            process_and_upload_tables(mock_db(), existing_files, client=s3_client)
            assert 'No new data.' in caplog.text
'''