"""Tests for FallbackProvider model failover."""

from __future__ import annotations

from typing import Any
from unittest.mock import MagicMock

import pytest

from nanobot.providers.base import LLMProvider, LLMResponse
from nanobot.providers.fallback_provider import FallbackProvider


def _make_response(
    content: str = "ok",
    finish_reason: str = "stop",
    *,
    error_kind: str | None = None,
) -> LLMResponse:
    return LLMResponse(content=content, finish_reason=finish_reason, error_kind=error_kind)


def _error_response(content: str = "api error") -> LLMResponse:
    return _make_response(content, finish_reason="error", error_kind="server_error")


class _FakeProvider(LLMProvider):
    """Fake provider for testing."""

    def __init__(self, name: str = "fake", response: LLMResponse | None = None):
        super().__init__()
        self.name = name
        self._response = response or _make_response()
        self.chat_calls: list[dict[str, Any]] = []
        self.chat_stream_calls: list[dict[str, Any]] = []

    def get_default_model(self) -> str:
        return f"{self.name}/model"

    async def chat(self, **kwargs: Any) -> LLMResponse:
        self.chat_calls.append(dict(kwargs))
        return self._response

    async def chat_stream(self, **kwargs: Any) -> LLMResponse:
        self.chat_stream_calls.append(dict(kwargs))
        on_delta = kwargs.get("on_content_delta")
        if on_delta and self._response.content:
            await on_delta(self._response.content)
        return self._response


# -- config-level tests --


def test_fallback_models_default_empty() -> None:
    from nanobot.config.schema import ModelPresetConfig
    p = ModelPresetConfig(model="test/model")
    assert p.fallback_models == []


def test_fallback_models_accepts_list() -> None:
    from nanobot.config.schema import ModelPresetConfig
    p = ModelPresetConfig(model="test/primary", fallback_models=["test/a", "test/b"])
    assert p.fallback_models == ["test/a", "test/b"]


def test_fallback_models_from_camel_case() -> None:
    from nanobot.config.schema import ModelPresetConfig
    p = ModelPresetConfig.model_validate({
        "model": "test/primary",
        "fallbackModels": ["test/a"],
    })
    assert p.fallback_models == ["test/a"]


# -- FallbackProvider tests --


class TestNoFallbackWhenPrimarySucceeds:
    @pytest.mark.asyncio
    async def test(self) -> None:
        primary = _FakeProvider("primary", _make_response("primary ok"))
        factory = MagicMock()
        fb = FallbackProvider(
            primary=primary,
            fallback_models=["fallback-a"],
            provider_factory=factory,
        )

        result = await fb.chat(messages=[{"role": "user", "content": "hi"}])
        assert result.content == "primary ok"
        assert result.finish_reason == "stop"
        factory.assert_not_called()


class TestFallbackOnPrimaryError:
    @pytest.mark.asyncio
    async def test_first_fallback_succeeds(self) -> None:
        primary = _FakeProvider("primary", _error_response())
        fallback = _FakeProvider("fallback", _make_response("fallback ok"))
        factory = MagicMock(return_value=fallback)

        fb = FallbackProvider(
            primary=primary,
            fallback_models=["fallback-a"],
            provider_factory=factory,
        )

        result = await fb.chat(messages=[{"role": "user", "content": "hi"}], model="primary-model")
        assert result.content == "fallback ok"
        assert result.finish_reason == "stop"
        factory.assert_called_once_with("fallback-a")
        assert primary.chat_calls[0]["model"] == "primary-model"
        assert fallback.chat_calls[0]["model"] == "fallback-a"


class TestNoFallbackWhenContentStreamed:
    @pytest.mark.asyncio
    async def test(self) -> None:
        primary = _FakeProvider("primary", _error_response())
        factory = MagicMock()
        fb = FallbackProvider(
            primary=primary,
            fallback_models=["fallback-a"],
            provider_factory=factory,
        )

        async def _delta(text: str) -> None:
            pass

        result = await fb.chat_stream(
            messages=[{"role": "user", "content": "hi"}],
            on_content_delta=_delta,
        )
        # Primary returns error but content was "streamed" (FakeProvider calls delta)
        # so failover should be skipped
        assert result.finish_reason == "error"
        factory.assert_not_called()


class TestFailoverOnTransientError:
    @pytest.mark.asyncio
    async def test_rate_limit(self) -> None:
        primary = _FakeProvider("primary", _error_response("rate limit exceeded"))
        fallback = _FakeProvider("fallback", _make_response("fallback ok"))
        factory = MagicMock(return_value=fallback)
        fb = FallbackProvider(
            primary=primary,
            fallback_models=["fallback-a"],
            provider_factory=factory,
        )

        result = await fb.chat(messages=[{"role": "user", "content": "hi"}])
        assert result.content == "fallback ok"
        assert result.finish_reason == "stop"
        factory.assert_called_once_with("fallback-a")

    @pytest.mark.asyncio
    async def test_timeout(self) -> None:
        primary = _FakeProvider(
            "primary",
            _make_response("timed out", finish_reason="error", error_kind="timeout"),
        )
        fallback = _FakeProvider("fallback", _make_response("fallback ok"))
        factory = MagicMock(return_value=fallback)
        fb = FallbackProvider(
            primary=primary,
            fallback_models=["fallback-a"],
            provider_factory=factory,
        )

        result = await fb.chat(messages=[{"role": "user", "content": "hi"}])
        assert result.content == "fallback ok"
        assert result.finish_reason == "stop"
        factory.assert_called_once_with("fallback-a")


class TestFallbackTriesModelsInOrder:
    @pytest.mark.asyncio
    async def test(self) -> None:
        primary = _FakeProvider("primary", _error_response("primary fail"))
        fallback_a = _FakeProvider("a", _error_response("a fail"))
        fallback_b = _FakeProvider("b", _make_response("b ok"))
        factory = MagicMock(side_effect=[fallback_a, fallback_b])

        fb = FallbackProvider(
            primary=primary,
            fallback_models=["fallback-a", "fallback-b"],
            provider_factory=factory,
        )

        result = await fb.chat(messages=[{"role": "user", "content": "hi"}])
        assert result.content == "b ok"
        assert factory.call_count == 2
        factory.assert_any_call("fallback-a")
        factory.assert_any_call("fallback-b")


class TestAllFallbacksFail:
    @pytest.mark.asyncio
    async def test(self) -> None:
        primary = _FakeProvider("primary", _error_response("primary fail"))
        fallback = _FakeProvider("fallback", _error_response("all fail"))
        factory = MagicMock(return_value=fallback)

        fb = FallbackProvider(
            primary=primary,
            fallback_models=["fallback-a"],
            provider_factory=factory,
        )

        result = await fb.chat(messages=[{"role": "user", "content": "hi"}])
        assert result.finish_reason == "error"
        assert "all fail" in result.content


class TestFactoryExceptionSkipsModel:
    @pytest.mark.asyncio
    async def test(self) -> None:
        primary = _FakeProvider("primary", _error_response())
        fallback_b = _FakeProvider("b", _make_response("b ok"))
        factory = MagicMock(side_effect=[ValueError("no key"), fallback_b])

        fb = FallbackProvider(
            primary=primary,
            fallback_models=["fallback-a", "fallback-b"],
            provider_factory=factory,
        )

        result = await fb.chat(messages=[{"role": "user", "content": "hi"}])
        assert result.content == "b ok"
        assert factory.call_count == 2


class TestFallbackModelParameter:
    @pytest.mark.asyncio
    async def test(self) -> None:
        """Fallback calls should use the fallback model name."""
        primary = _FakeProvider("primary", _error_response())
        fallback = _FakeProvider("fallback", _make_response("ok"))
        factory = MagicMock(return_value=fallback)

        fb = FallbackProvider(
            primary=primary,
            fallback_models=["fallback-model"],
            provider_factory=factory,
        )

        await fb.chat(messages=[{"role": "user", "content": "hi"}], model="primary-model")
        assert fallback.chat_calls[0]["model"] == "fallback-model"


class TestNoFallbackWhenEmptyList:
    @pytest.mark.asyncio
    async def test(self) -> None:
        primary = _FakeProvider("primary", _error_response())
        factory = MagicMock()

        fb = FallbackProvider(
            primary=primary,
            fallback_models=[],
            provider_factory=factory,
        )

        result = await fb.chat(messages=[{"role": "user", "content": "hi"}])
        assert result.finish_reason == "error"
        factory.assert_not_called()


class TestChatStreamFailover:
    @pytest.mark.asyncio
    async def test_fallback_succeeds(self) -> None:
        # Use empty content so on_content_delta is not triggered on the error
        primary = _FakeProvider("primary", _error_response(""))
        fallback = _FakeProvider("fallback", _make_response("stream ok"))
        factory = MagicMock(return_value=fallback)

        fb = FallbackProvider(
            primary=primary,
            fallback_models=["fallback-a"],
            provider_factory=factory,
        )

        result = await fb.chat_stream(messages=[{"role": "user", "content": "hi"}])
        assert result.content == "stream ok"
        assert result.finish_reason == "stop"


class TestGetDefaultModel:
    def test(self) -> None:
        primary = _FakeProvider("primary")
        fb = FallbackProvider(
            primary=primary,
            fallback_models=["a"],
            provider_factory=MagicMock(),
        )
        assert fb.get_default_model() == "primary/model"


class TestCircuitBreaker:
    @pytest.mark.asyncio
    async def test_skips_primary_after_three_failures(self) -> None:
        primary = _FakeProvider("primary", _error_response())
        fallback = _FakeProvider("fallback", _make_response("fallback ok"))
        factory = MagicMock(return_value=fallback)
        fb = FallbackProvider(
            primary=primary,
            fallback_models=["fallback-a"],
            provider_factory=factory,
        )

        # 3 failures — primary should still be called each time
        for _ in range(3):
            result = await fb.chat(messages=[{"role": "user", "content": "hi"}])
            assert result.content == "fallback ok"

        assert len(primary.chat_calls) == 3

        # 4th call — primary circuit is open, should be skipped
        primary.chat_calls.clear()
        result = await fb.chat(messages=[{"role": "user", "content": "hi"}])
        assert result.content == "fallback ok"
        assert len(primary.chat_calls) == 0

    @pytest.mark.asyncio
    async def test_resets_on_success(self) -> None:
        primary = _FakeProvider("primary", _error_response())
        fallback = _FakeProvider("fallback", _make_response("fallback ok"))
        factory = MagicMock(return_value=fallback)
        fb = FallbackProvider(
            primary=primary,
            fallback_models=["fallback-a"],
            provider_factory=factory,
        )

        # 2 failures
        for _ in range(2):
            await fb.chat(messages=[{"role": "user", "content": "hi"}])

        # 3rd call: primary succeeds — circuit resets
        primary._response = _make_response("primary ok")
        result = await fb.chat(messages=[{"role": "user", "content": "hi"}])
        assert result.content == "primary ok"

        # 4th call: primary fails again — should still be called (counter reset)
        primary._response = _error_response()
        primary.chat_calls.clear()
        result = await fb.chat(messages=[{"role": "user", "content": "hi"}])
        assert result.content == "fallback ok"
        assert len(primary.chat_calls) == 1


class TestGenerationForwarded:
    def test(self) -> None:
        from nanobot.providers.base import GenerationSettings
        primary = _FakeProvider("primary")
        primary.generation = GenerationSettings(temperature=0.5, max_tokens=1024)
        fb = FallbackProvider(
            primary=primary,
            fallback_models=["a"],
            provider_factory=MagicMock(),
        )
        assert fb.generation.temperature == 0.5
        assert fb.generation.max_tokens == 1024