"""Unit tests for API Client.

Tests HTTP request/response handling, retries, error handling,
and mock HTTP interactions for sync operations.
"""

from datetime import UTC, datetime
from typing import Any
from unittest.mock import AsyncMock, MagicMock

import pytest
from httpx import AsyncClient, ConnectError, Request, Response

from tests.test_constants import (
    COUNT_FIVE,
    COUNT_FOUR,
    COUNT_TWO,
    HTTP_BAD_REQUEST,
    HTTP_INTERNAL_SERVER_ERROR,
    HTTP_NOT_FOUND,
    HTTP_OK,
    HTTP_UNAUTHORIZED,
)

# ============================================================================
# FIXTURES
# ============================================================================


@pytest.fixture
def mock_httpx_client() -> None:
    """Fixture: Mock HTTPX AsyncClient.

    Provides: Mocked async HTTP client
    """
    client = MagicMock(spec=AsyncClient)
    client.get = AsyncMock()
    client.post = AsyncMock()
    client.put = AsyncMock()
    client.delete = AsyncMock()
    client.close = AsyncMock()
    return client


@pytest.fixture
def api_config() -> None:
    """Sample API configuration."""
    return {
        "base_url": "https://api.tracertm.io",
        "api_key": "test-api-key-123",
        "client_id": "cli-abc123",
        "timeout": 30.0,
        "max_retries": 3,
    }


@pytest.fixture
def sample_upload_payload() -> None:
    """Sample upload sync payload."""
    return {
        "client_id": "cli-abc123",
        "last_sync": datetime.now(UTC).isoformat(),
        "changes": [
            {
                "entity_type": "item",
                "entity_id": "item-001",
                "operation": "create",
                "payload": {"title": "New Item", "status": "todo", "type": "story"},
            },
        ],
    }


@pytest.fixture
def sample_download_response() -> None:
    """Sample download sync response."""
    return {
        "changes": [
            {
                "entity_type": "item",
                "entity_id": "item-002",
                "operation": "update",
                "payload": {"title": "Updated Item", "status": "done"},
            },
        ],
        "server_time": datetime.now(UTC).isoformat(),
    }


# ============================================================================
# TEST CLASSES - HTTP Request/Response
# ============================================================================


class TestApiClientRequestResponse:
    """Test Suite: API Client - Request/Response Handling.

    Tests basic HTTP operations with mocked responses
    """

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_get_request_success(self, mock_httpx_client: Any, api_config: Any) -> None:
        """TC-API.1.1: GET Request - Success.

        Given: Valid API endpoint
        When: GET request is made
        Then: Response is returned successfully
        """
        # Arrange
        mock_response = Response(
            status_code=200,
            json={"status": "ok", "data": []},
            request=Request("GET", f"{api_config['base_url']}/api/sync/status"),
        )
        mock_httpx_client.get.return_value = mock_response

        # Act
        response = await mock_httpx_client.get(
            f"{api_config['base_url']}/api/sync/status",
            headers={"Authorization": f"Bearer {api_config['api_key']}"},
        )

        # Assert
        assert response.status_code == HTTP_OK
        assert response.json()["status"] == "ok"
        mock_httpx_client.get.assert_called_once()

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_post_request_success(
        self, mock_httpx_client: Any, api_config: Any, sample_upload_payload: Any
    ) -> None:
        """TC-API.1.2: POST Request - Success.

        Given: Valid upload payload
        When: POST request is made
        Then: Changes are uploaded successfully
        """
        # Arrange
        mock_response = Response(
            status_code=200,
            json={"success": True, "applied": 1, "conflicts": []},
            request=Request("POST", f"{api_config['base_url']}/api/sync/upload"),
        )
        mock_httpx_client.post.return_value = mock_response

        # Act
        response = await mock_httpx_client.post(
            f"{api_config['base_url']}/api/sync/upload",
            json=sample_upload_payload,
            headers={"Authorization": f"Bearer {api_config['api_key']}"},
        )

        # Assert
        assert response.status_code == HTTP_OK
        assert response.json()["success"] is True
        assert response.json()["applied"] == 1
        mock_httpx_client.post.assert_called_once()

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_download_changes_success(
        self, mock_httpx_client: Any, api_config: Any, sample_download_response: Any
    ) -> None:
        """TC-API.1.3: Download Changes - Success.

        Given: Server has new changes
        When: Download request is made
        Then: Changes are retrieved
        """
        # Arrange
        mock_response = Response(
            status_code=200,
            json=sample_download_response,
            request=Request("GET", f"{api_config['base_url']}/api/sync/changes"),
        )
        mock_httpx_client.get.return_value = mock_response

        # Act
        response = await mock_httpx_client.get(
            f"{api_config['base_url']}/api/sync/changes",
            params={"since": datetime.now(UTC).isoformat()},
            headers={"Authorization": f"Bearer {api_config['api_key']}"},
        )

        # Assert
        assert response.status_code == HTTP_OK
        assert len(response.json()["changes"]) == 1
        assert "server_time" in response.json()

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_authentication_header(self, mock_httpx_client: Any, api_config: Any) -> None:
        """TC-API.1.4: Authentication - Bearer Token.

        Given: API requires authentication
        When: Request is made with token
        Then: Authorization header is included
        """
        # Arrange
        mock_response = Response(
            status_code=200,
            json={"authenticated": True},
            request=Request("GET", f"{api_config['base_url']}/api/sync/status"),
        )
        mock_httpx_client.get.return_value = mock_response

        # Act
        await mock_httpx_client.get(
            f"{api_config['base_url']}/api/sync/status",
            headers={"Authorization": f"Bearer {api_config['api_key']}"},
        )

        # Assert
        call_args = mock_httpx_client.get.call_args
        assert "headers" in call_args.kwargs
        assert call_args.kwargs["headers"]["Authorization"] == f"Bearer {api_config['api_key']}"


# ============================================================================
# TEST CLASSES - Error Handling
# ============================================================================


class TestApiClientErrorHandling:
    """Test Suite: API Client - Error Handling.

    Tests handling of HTTP errors and exceptions
    """

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_404_not_found_error(self, mock_httpx_client: Any, api_config: Any) -> None:
        """TC-API.2.1: HTTP 404 - Not Found Error.

        Given: Invalid endpoint
        When: Request is made
        Then: 404 error is raised
        """
        # Arrange
        mock_response = Response(
            status_code=404,
            json={"error": "Not found"},
            request=Request("GET", f"{api_config['base_url']}/api/invalid"),
        )
        mock_httpx_client.get.return_value = mock_response

        # Act
        response = await mock_httpx_client.get(f"{api_config['base_url']}/api/invalid")

        # Assert
        assert response.status_code == HTTP_NOT_FOUND
        assert response.json()["error"] == "Not found"

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_401_unauthorized_error(self, mock_httpx_client: Any, api_config: Any) -> None:
        """TC-API.2.2: HTTP 401 - Unauthorized Error.

        Given: Invalid or missing API key
        When: Request is made
        Then: 401 error is raised
        """
        # Arrange
        mock_response = Response(
            status_code=401,
            json={"error": "Unauthorized"},
            request=Request("GET", f"{api_config['base_url']}/api/sync/status"),
        )
        mock_httpx_client.get.return_value = mock_response

        # Act
        response = await mock_httpx_client.get(f"{api_config['base_url']}/api/sync/status")

        # Assert
        assert response.status_code == HTTP_UNAUTHORIZED
        assert response.json()["error"] == "Unauthorized"

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_500_server_error(self, mock_httpx_client: Any, api_config: Any) -> None:
        """TC-API.2.3: HTTP 500 - Internal Server Error.

        Given: Server error occurs
        When: Request is made
        Then: 500 error is raised
        """
        # Arrange
        mock_response = Response(
            status_code=500,
            json={"error": "Internal server error"},
            request=Request("GET", f"{api_config['base_url']}/api/sync/status"),
        )
        mock_httpx_client.get.return_value = mock_response

        # Act
        response = await mock_httpx_client.get(f"{api_config['base_url']}/api/sync/status")

        # Assert
        assert response.status_code == HTTP_INTERNAL_SERVER_ERROR

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_network_connection_error(self, mock_httpx_client: Any, api_config: Any) -> None:
        """TC-API.2.4: Network Error - Connection Failed.

        Given: Network is unavailable
        When: Request is attempted
        Then: Connection error is raised
        """
        # Arrange
        mock_httpx_client.get.side_effect = ConnectError("Connection refused")

        # Act & Assert
        with pytest.raises(ConnectError):
            await mock_httpx_client.get(f"{api_config['base_url']}/api/sync/status")

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_timeout_error(self, mock_httpx_client: Any, api_config: Any) -> None:
        """TC-API.2.5: Timeout Error - Request Timeout.

        Given: Request exceeds timeout
        When: Long-running request is made
        Then: Timeout error is raised
        """
        # Arrange
        import asyncio

        mock_httpx_client.get.side_effect = TimeoutError("Request timeout")

        # Act & Assert
        with pytest.raises(asyncio.TimeoutError):
            await mock_httpx_client.get(f"{api_config['base_url']}/api/sync/status")


# ============================================================================
# TEST CLASSES - Retry Logic
# ============================================================================


class TestApiClientRetryLogic:
    """Test Suite: API Client - Retry Logic.

    Tests automatic retry on transient failures
    """

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_retry_on_network_error(self, mock_httpx_client: Any, api_config: Any) -> None:
        """TC-API.3.1: Retry on Network Error - Success After Retry.

        Given: First request fails with network error
        When: Retry is attempted
        Then: Second request succeeds
        """
        # Arrange
        mock_response = Response(
            status_code=200,
            json={"status": "ok"},
            request=Request("GET", f"{api_config['base_url']}/api/sync/status"),
        )

        # First call fails, second succeeds
        mock_httpx_client.get.side_effect = [ConnectError("Connection failed"), mock_response]

        # Act - Simulate retry logic
        max_retries = 3
        for attempt in range(max_retries):
            try:
                response = await mock_httpx_client.get(f"{api_config['base_url']}/api/sync/status")
                break  # Success
            except ConnectError:
                if attempt == max_retries - 1:
                    raise
                continue

        # Assert
        assert response.status_code == HTTP_OK
        assert mock_httpx_client.get.call_count == COUNT_TWO

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_retry_on_500_error(self, mock_httpx_client: Any, api_config: Any) -> None:
        """TC-API.3.2: Retry on 500 Error - Success After Retry.

        Given: First request returns 500
        When: Retry is attempted
        Then: Second request succeeds
        """
        # Arrange
        error_response = Response(
            status_code=500,
            json={"error": "Server error"},
            request=Request("GET", f"{api_config['base_url']}/api/sync/status"),
        )
        success_response = Response(
            status_code=200,
            json={"status": "ok"},
            request=Request("GET", f"{api_config['base_url']}/api/sync/status"),
        )

        mock_httpx_client.get.side_effect = [error_response, success_response]

        # Act - Simulate retry on 5xx
        max_retries = 3
        for _attempt in range(max_retries):
            response = await mock_httpx_client.get(f"{api_config['base_url']}/api/sync/status")
            if response.status_code < HTTP_INTERNAL_SERVER_ERROR:
                break

        # Assert
        assert response.status_code == HTTP_OK
        assert mock_httpx_client.get.call_count == COUNT_TWO

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_max_retries_exceeded(self, mock_httpx_client: Any, api_config: Any) -> None:
        """TC-API.3.3: Max Retries Exceeded - Give Up.

        Given: All retry attempts fail
        When: Max retries is reached
        Then: Error is raised
        """
        # Arrange
        mock_httpx_client.get.side_effect = ConnectError("Connection failed")

        # Act & Assert
        max_retries = 3
        with pytest.raises(ConnectError):
            for attempt in range(max_retries):
                try:
                    await mock_httpx_client.get(f"{api_config['base_url']}/api/sync/status")
                except ConnectError:
                    if attempt == max_retries - 1:
                        raise
                    continue

        assert mock_httpx_client.get.call_count == max_retries

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_no_retry_on_400_error(self, mock_httpx_client: Any, api_config: Any) -> None:
        """TC-API.3.4: No Retry on 400 Error - Client Error.

        Given: Request returns 400 (client error)
        When: Error is detected
        Then: No retry is attempted
        """
        # Arrange
        mock_response = Response(
            status_code=400,
            json={"error": "Bad request"},
            request=Request("POST", f"{api_config['base_url']}/api/sync/upload"),
        )
        mock_httpx_client.post.return_value = mock_response

        # Act
        response = await mock_httpx_client.post(f"{api_config['base_url']}/api/sync/upload", json={})

        # Assert - No retry on 4xx errors
        assert response.status_code == HTTP_BAD_REQUEST
        assert mock_httpx_client.post.call_count == 1

    @pytest.mark.unit
    def test_exponential_backoff_calculation(self) -> None:
        """TC-API.3.5: Exponential Backoff - Delay Calculation.

        Given: Multiple retry attempts
        When: Backoff delay is calculated
        Then: Delay increases exponentially
        """
        # Arrange
        base_delay = 1.0
        max_delay = 60.0

        # Act
        delays = []
        for retry_count in range(5):
            delay = min(base_delay * (2**retry_count), max_delay)
            delays.append(delay)

        # Assert
        assert delays[0] == 1.0
        assert delays[1] == float(COUNT_TWO + 0.0)
        assert delays[2] == float(COUNT_FOUR + 0.0)
        assert delays[3] == 8.0
        assert delays[4] == 16.0


# ============================================================================
# TEST CLASSES - Conflict Handling
# ============================================================================


class TestApiClientConflictHandling:
    """Test Suite: API Client - Conflict Handling.

    Tests handling of sync conflicts returned by server
    """

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_upload_with_conflicts(self, mock_httpx_client: Any, api_config: Any) -> None:
        """TC-API.4.1: Upload with Conflicts - Conflict Detection.

        Given: Upload contains conflicting changes
        When: Server detects conflicts
        Then: Conflicts are returned in response
        """
        # Arrange
        mock_response = Response(
            status_code=200,
            json={
                "success": False,
                "applied": 0,
                "conflicts": [
                    {"entity_id": "item-001", "local_version": 2, "remote_version": 3, "reason": "version_mismatch"},
                ],
                "server_time": datetime.now(UTC).isoformat(),
            },
            request=Request("POST", f"{api_config['base_url']}/api/sync/upload"),
        )
        mock_httpx_client.post.return_value = mock_response

        # Act
        response = await mock_httpx_client.post(f"{api_config['base_url']}/api/sync/upload", json={"changes": []})

        # Assert
        result = response.json()
        assert result["success"] is False
        assert len(result["conflicts"]) == 1
        assert result["conflicts"][0]["reason"] == "version_mismatch"

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_resolve_conflict_endpoint(self, mock_httpx_client: Any, api_config: Any) -> None:
        """TC-API.4.2: Resolve Conflict - Submit Resolution.

        Given: Conflict has been resolved locally
        When: Resolution is sent to server
        Then: Server accepts resolution
        """
        # Arrange
        mock_response = Response(
            status_code=200,
            json={"resolved": True, "version": 4},
            request=Request("POST", f"{api_config['base_url']}/api/sync/resolve"),
        )
        mock_httpx_client.post.return_value = mock_response

        resolution_payload = {"conflict_id": "conflict-001", "resolution": "local", "merged_content": None}

        # Act
        response = await mock_httpx_client.post(f"{api_config['base_url']}/api/sync/resolve", json=resolution_payload)

        # Assert
        assert response.status_code == HTTP_OK
        assert response.json()["resolved"] is True


# ============================================================================
# TEST CLASSES - Sync Status
# ============================================================================


class TestApiClientSyncStatus:
    """Test Suite: API Client - Sync Status.

    Tests querying sync status and metadata
    """

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_get_sync_status(self, mock_httpx_client: Any, api_config: Any) -> None:
        """TC-API.5.1: Get Sync Status - Current State.

        Given: Client wants to check sync status
        When: Status endpoint is queried
        Then: Current sync state is returned
        """
        # Arrange
        mock_response = Response(
            status_code=200,
            json={"last_sync": datetime.now(UTC).isoformat(), "pending_changes": 5, "online": True},
            request=Request("GET", f"{api_config['base_url']}/api/sync/status"),
        )
        mock_httpx_client.get.return_value = mock_response

        # Act
        response = await mock_httpx_client.get(f"{api_config['base_url']}/api/sync/status")

        # Assert
        status = response.json()
        assert "last_sync" in status
        assert status["pending_changes"] == COUNT_FIVE
        assert status["online"] is True

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_check_connectivity(self, mock_httpx_client: Any, api_config: Any) -> None:
        """TC-API.5.2: Check Connectivity - Is Online.

        Given: Client wants to verify connection
        When: Connectivity check is performed
        Then: Online status is determined
        """
        # Arrange
        mock_response = Response(
            status_code=200,
            json={"online": True},
            request=Request("GET", f"{api_config['base_url']}/api/ping"),
        )
        mock_httpx_client.get.return_value = mock_response

        # Act
        try:
            response = await mock_httpx_client.get(f"{api_config['base_url']}/api/ping")
            is_online = response.status_code == HTTP_OK
        except ConnectError:
            is_online = False

        # Assert
        assert is_online is True


# ============================================================================
# TEST CLASSES - Request Validation
# ============================================================================


class TestApiClientRequestValidation:
    """Test Suite: API Client - Request Validation.

    Tests validation of request payloads
    """

    @pytest.mark.unit
    @pytest.mark.asyncio
    async def test_validate_upload_payload(self, api_config: Any) -> None:
        """TC-API.6.1: Validate Upload Payload - Required Fields.

        Given: Upload payload
        When: Payload is validated
        Then: Required fields are present
        """
        # Arrange
        payload = {"client_id": api_config["client_id"], "last_sync": datetime.now(UTC).isoformat(), "changes": []}

        # Act & Assert
        assert "client_id" in payload
        assert "last_sync" in payload
        assert "changes" in payload
        assert isinstance(payload["changes"], list)

    @pytest.mark.unit
    def test_validate_change_entry(self) -> None:
        """TC-API.6.2: Validate Change Entry - Required Fields.

        Given: Change entry
        When: Entry is validated
        Then: Required fields are present
        """
        # Arrange
        change = {
            "entity_type": "item",
            "entity_id": "item-001",
            "operation": "create",
            "payload": {"title": "New Item"},
        }

        # Act & Assert
        assert "entity_type" in change
        assert "entity_id" in change
        assert "operation" in change
        assert "payload" in change
        assert change["operation"] in {"create", "update", "delete"}

    @pytest.mark.unit
    def test_validate_api_key_format(self, api_config: Any) -> None:
        """TC-API.6.3: Validate API Key - Format Check.

        Given: API key
        When: Key is validated
        Then: Key has valid format
        """
        # Arrange
        api_key = api_config["api_key"]

        # Act & Assert
        assert isinstance(api_key, str)
        assert len(api_key) > 0


# ============================================================================
# NOTES
# ============================================================================

"""
COVERAGE AREAS:

1. Request/Response:
   - GET requests
   - POST requests
   - Download changes
   - Authentication headers

2. Error Handling:
   - 404 Not Found
   - 401 Unauthorized
   - 500 Server Error
   - Network errors
   - Timeout errors

3. Retry Logic:
   - Retry on network error
   - Retry on 5xx errors
   - Max retries exceeded
   - No retry on 4xx
   - Exponential backoff

4. Conflict Handling:
   - Upload with conflicts
   - Resolve conflicts

5. Sync Status:
   - Get sync status
   - Check connectivity

6. Request Validation:
   - Upload payload validation
   - Change entry validation
   - API key validation

TODO for full implementation:
- Add ApiClient class tests (when implemented)
- Add WebSocket connection tests
- Add rate limiting tests
- Add request batching tests
- Add response caching tests
- Add integration tests with real HTTP server
"""
