"""
Tests for response mode switching based on Accept header.
[AC-AISVC-06] Tests for automatic switching between JSON and SSE streaming modes.
"""

import pytest
from fastapi.testclient import TestClient
from httpx import AsyncClient

from app.main import app


class TestAcceptHeaderSwitching:
    """
    [AC-AISVC-06] Test cases for Accept header based response mode switching.
    """

    @pytest.fixture
    def client(self):
        return TestClient(app)

    @pytest.fixture
    def valid_request_body(self):
        return {
            "sessionId": "test_session_001",
            "currentMessage": "Hello, how are you?",
            "channelType": "wechat",
        }

    @pytest.fixture
    def valid_headers(self):
        return {"X-Tenant-Id": "tenant_001"}

    def test_json_response_with_default_accept(
        self, client: TestClient, valid_request_body: dict, valid_headers: dict
    ):
        """
        [AC-AISVC-06] Test that default Accept header returns JSON response.
        """
        response = client.post(
            "/ai/chat",
            json=valid_request_body,
            headers=valid_headers,
        )

        assert response.status_code == 200
        assert response.headers["content-type"] == "application/json"

        data = response.json()
        assert "reply" in data
        assert "confidence" in data
        assert "shouldTransfer" in data

    def test_json_response_with_application_json_accept(
        self, client: TestClient, valid_request_body: dict, valid_headers: dict
    ):
        """
        [AC-AISVC-06] Test that Accept: application/json returns JSON response.
        """
        headers = {**valid_headers, "Accept": "application/json"}

        response = client.post(
            "/ai/chat",
            json=valid_request_body,
            headers=headers,
        )

        assert response.status_code == 200
        assert response.headers["content-type"] == "application/json"

        data = response.json()
        assert "reply" in data
        assert "confidence" in data
        assert "shouldTransfer" in data

    def test_sse_response_with_text_event_stream_accept(
        self, client: TestClient, valid_request_body: dict, valid_headers: dict
    ):
        """
        [AC-AISVC-06] Test that Accept: text/event-stream returns SSE response.
        """
        headers = {**valid_headers, "Accept": "text/event-stream"}

        response = client.post(
            "/ai/chat",
            json=valid_request_body,
            headers=headers,
        )

        assert response.status_code == 200
        assert "text/event-stream" in response.headers["content-type"]

        content = response.text
        assert "event: message" in content
        assert "event: final" in content

    def test_sse_response_event_sequence(
        self, client: TestClient, valid_request_body: dict, valid_headers: dict
    ):
        """
        [AC-AISVC-07, AC-AISVC-08] Test that SSE events follow proper sequence.
        message* -> final -> close
        """
        headers = {**valid_headers, "Accept": "text/event-stream"}

        response = client.post(
            "/ai/chat",
            json=valid_request_body,
            headers=headers,
        )

        content = response.text

        assert "event:message" in content or "event: message" in content, f"Expected message event in: {content[:500]}"
        assert "event:final" in content or "event: final" in content, f"Expected final event in: {content[:500]}"

        message_idx = content.find("event:message")
        if message_idx == -1:
            message_idx = content.find("event: message")
        final_idx = content.find("event:final")
        if final_idx == -1:
            final_idx = content.find("event: final")

        assert final_idx > message_idx, "final event should come after message events"

    def test_missing_tenant_id_returns_400(
        self, client: TestClient, valid_request_body: dict
    ):
        """
        [AC-AISVC-12] Test that missing X-Tenant-Id returns 400 error.
        """
        response = client.post(
            "/ai/chat",
            json=valid_request_body,
        )

        assert response.status_code == 400

        data = response.json()
        assert data["code"] == "MISSING_TENANT_ID"
        assert "message" in data

    def test_invalid_channel_type_returns_400(
        self, client: TestClient, valid_headers: dict
    ):
        """
        [AC-AISVC-03] Test that invalid channel type returns 400 error.
        """
        invalid_body = {
            "sessionId": "test_session_001",
            "currentMessage": "Hello",
            "channelType": "invalid_channel",
        }

        response = client.post(
            "/ai/chat",
            json=invalid_body,
            headers=valid_headers,
        )

        assert response.status_code == 400

    def test_missing_required_fields_returns_400(
        self, client: TestClient, valid_headers: dict
    ):
        """
        [AC-AISVC-03] Test that missing required fields return 400 error.
        """
        incomplete_body = {
            "sessionId": "test_session_001",
        }

        response = client.post(
            "/ai/chat",
            json=incomplete_body,
            headers=valid_headers,
        )

        assert response.status_code == 400


class TestHealthEndpoint:
    """
    [AC-AISVC-20] Test cases for health check endpoint.
    """

    @pytest.fixture
    def client(self):
        return TestClient(app)

    def test_health_check_returns_200(self, client: TestClient):
        """
        [AC-AISVC-20] Test that health check returns 200 with status.
        """
        response = client.get("/ai/health")

        assert response.status_code == 200
        data = response.json()
        assert data["status"] == "healthy"


class TestSSEStateMachine:
    """
    [AC-AISVC-08, AC-AISVC-09] Test cases for SSE state machine.
    """

    @pytest.mark.asyncio
    async def test_state_transitions(self):
        from app.core.sse import SSEState, SSEStateMachine

        state_machine = SSEStateMachine()

        assert state_machine.state == SSEState.INIT

        success = await state_machine.transition_to_streaming()
        assert success is True
        assert state_machine.state == SSEState.STREAMING

        assert state_machine.can_send_message() is True

        success = await state_machine.transition_to_final()
        assert success is True
        assert state_machine.state == SSEState.FINAL_SENT

        assert state_machine.can_send_message() is False

        await state_machine.close()
        assert state_machine.state == SSEState.CLOSED

    @pytest.mark.asyncio
    async def test_error_transition_from_streaming(self):
        from app.core.sse import SSEState, SSEStateMachine

        state_machine = SSEStateMachine()
        await state_machine.transition_to_streaming()

        success = await state_machine.transition_to_error()
        assert success is True
        assert state_machine.state == SSEState.ERROR_SENT

    @pytest.mark.asyncio
    async def test_cannot_transition_to_final_from_init(self):
        from app.core.sse import SSEStateMachine

        state_machine = SSEStateMachine()

        success = await state_machine.transition_to_final()
        assert success is False


class TestMiddleware:
    """
    [AC-AISVC-10, AC-AISVC-12] Test cases for middleware.
    """

    @pytest.fixture
    def client(self):
        return TestClient(app)

    def test_tenant_context_extraction(
        self, client: TestClient
    ):
        """
        [AC-AISVC-10] Test that X-Tenant-Id is properly extracted and used.
        """
        headers = {"X-Tenant-Id": "tenant_test_123"}
        body = {
            "sessionId": "session_001",
            "currentMessage": "Test message",
            "channelType": "wechat",
        }

        response = client.post("/ai/chat", json=body, headers=headers)

        assert response.status_code == 200

    def test_health_endpoint_bypasses_tenant_check(
        self, client: TestClient
    ):
        """
        Test that health endpoint doesn't require X-Tenant-Id.
        """
        response = client.get("/ai/health")

        assert response.status_code == 200