"""Unit tests for LlmConfigService (U5 — LLM provider/fallback CRUD).

Covers:
- Happy path: list → get → create → update → delete providers
- API key management: set_api_key writes to .env, masks in responses
- Fallback chain: get → set → delete
- Edge case: create duplicate provider → ValueError
- Edge case: update non-existent provider → ValueError
- Edge case: delete provider used in fallback → ValueError
- Edge case: delete non-existent provider → ValueError
- File locking: concurrent writes don't corrupt (sequential simulation)
- Singleton helpers (get/set_llm_config_service)
"""

from __future__ import annotations

import threading
from pathlib import Path
from typing import Any

import pytest
import yaml

from agentkit.server.admin.llm_config_service import (
    LlmConfigService,
    get_llm_config_service,
    set_llm_config_service,
)


# ---------------------------------------------------------------------------
# Fixtures
# ---------------------------------------------------------------------------


def _sample_config() -> dict[str, Any]:
    """A minimal agentkit.yaml-style config for testing."""
    return {
        "server": {"host": "0.0.0.0", "port": 8001},
        "llm": {
            "providers": {
                "openai": {
                    "type": "openai",
                    "api_key": "sk-test-12345678",
                    "base_url": "https://api.openai.com/v1",
                    "models": {"gpt-4o": {}},
                    "max_tokens": 4096,
                    "timeout": 120.0,
                },
            },
            "model_aliases": {"gpt4": "openai/gpt-4o"},
            "fallbacks": {},
        },
    }


@pytest.fixture
def config_path(tmp_path: Path) -> Path:
    """Create a temporary agentkit.yaml config file."""
    path = tmp_path / "agentkit.yaml"
    with open(path, "w", encoding="utf-8") as f:
        yaml.dump(_sample_config(), f, default_flow_style=False, allow_unicode=True)
    return path


@pytest.fixture
def service(config_path: Path) -> LlmConfigService:
    return LlmConfigService(config_path)


@pytest.fixture(autouse=True)
def _reset_singleton():
    """Reset the module singleton before and after each test."""
    set_llm_config_service(None)
    yield
    set_llm_config_service(None)


# ---------------------------------------------------------------------------
# Provider CRUD happy path
# ---------------------------------------------------------------------------


class TestProviderCrudHappyPath:
    def test_list_returns_existing_providers(self, service: LlmConfigService):
        providers = service.list_providers()
        assert len(providers) == 1
        assert providers[0]["name"] == "openai"
        assert providers[0]["type"] == "openai"

    def test_list_masks_api_keys(self, service: LlmConfigService):
        providers = service.list_providers()
        # API key should be masked: ****xxxx
        assert providers[0]["api_key"].startswith("****")
        # Should show only last 4 chars
        assert providers[0]["api_key"] == "****5678"

    def test_get_returns_provider_by_name(self, service: LlmConfigService):
        provider = service.get_provider("openai")
        assert provider is not None
        assert provider["name"] == "openai"
        assert provider["type"] == "openai"
        assert provider["base_url"] == "https://api.openai.com/v1"

    def test_get_returns_none_for_unknown(self, service: LlmConfigService):
        assert service.get_provider("nonexistent") is None

    def test_create_adds_provider_to_yaml(self, service: LlmConfigService, config_path: Path):
        created = service.create_provider(
            name="anthropic",
            provider_type="anthropic",
            api_key="sk-ant-test-abcd1234",
            base_url="https://api.anthropic.com",
            models={"claude-sonnet-4-20250514": {}},
            max_tokens=8192,
            timeout=90.0,
        )
        assert created["name"] == "anthropic"
        assert created["type"] == "anthropic"
        # API key should be masked in the response.
        assert created["api_key"].startswith("****")
        # Verify the YAML file was updated.
        with open(config_path, encoding="utf-8") as f:
            saved = yaml.safe_load(f)
        assert "anthropic" in saved["llm"]["providers"]
        # The YAML should store a ${VAR} reference, not the plaintext key.
        assert saved["llm"]["providers"]["anthropic"]["api_key"] == "${ANTHROPIC_API_KEY}"

    def test_create_writes_api_key_to_env_file(self, service: LlmConfigService, config_path: Path):
        service.create_provider(
            name="anthropic",
            provider_type="anthropic",
            api_key="sk-ant-test-abcd1234",
        )
        env_path = config_path.parent / ".env"
        assert env_path.exists()
        with open(env_path, encoding="utf-8") as f:
            content = f.read()
        assert "ANTHROPIC_API_KEY=sk-ant-test-abcd1234" in content

    def test_update_partial_only_changes_provided_fields(
        self, service: LlmConfigService, config_path: Path
    ):
        updated = service.update_provider("openai", max_tokens=2048)
        assert updated["max_tokens"] == 2048
        # Other fields should be preserved.
        assert updated["base_url"] == "https://api.openai.com/v1"
        assert updated["type"] == "openai"

    def test_update_with_masked_api_key_preserves_existing(
        self, service: LlmConfigService, config_path: Path
    ):
        """When user sends back a masked key (****xxxx), the real key should
        be preserved."""
        service.update_provider("openai", api_key="****5678")
        with open(config_path, encoding="utf-8") as f:
            saved = yaml.safe_load(f)
        # The original plaintext key should be preserved.
        assert saved["llm"]["providers"]["openai"]["api_key"] == "sk-test-12345678"

    def test_update_with_new_api_key_writes_to_env(
        self, service: LlmConfigService, config_path: Path
    ):
        service.update_provider("openai", api_key="sk-new-key-9999")
        env_path = config_path.parent / ".env"
        with open(env_path, encoding="utf-8") as f:
            content = f.read()
        assert "OPENAI_API_KEY=sk-new-key-9999" in content
        # YAML should now have a ${VAR} reference.
        with open(config_path, encoding="utf-8") as f:
            saved = yaml.safe_load(f)
        assert saved["llm"]["providers"]["openai"]["api_key"] == "${OPENAI_API_KEY}"

    def test_delete_removes_provider(self, service: LlmConfigService, config_path: Path):
        deleted = service.delete_provider("openai")
        assert deleted is True
        # Verify the YAML file was updated.
        with open(config_path, encoding="utf-8") as f:
            saved = yaml.safe_load(f)
        assert "openai" not in saved["llm"]["providers"]
        # list_providers should return empty.
        assert service.list_providers() == []


# ---------------------------------------------------------------------------
# Provider CRUD edge cases
# ---------------------------------------------------------------------------


class TestProviderCrudEdgeCases:
    def test_create_duplicate_raises_value_error(self, service: LlmConfigService):
        with pytest.raises(ValueError, match="already exists"):
            service.create_provider(
                name="openai",
                provider_type="openai",
                api_key="sk-duplicate",
            )

    def test_update_nonexistent_raises_value_error(self, service: LlmConfigService):
        with pytest.raises(ValueError, match="not found"):
            service.update_provider("nonexistent", max_tokens=2048)

    def test_delete_nonexistent_raises_value_error(self, service: LlmConfigService):
        with pytest.raises(ValueError, match="not found"):
            service.delete_provider("nonexistent")

    def test_delete_provider_used_in_fallback_raises_value_error(self, service: LlmConfigService):
        # Add a second provider and a fallback chain that references it.
        service.create_provider(
            name="anthropic",
            provider_type="anthropic",
            api_key="sk-ant-test",
        )
        service.set_fallback("gpt-4o", ["anthropic"])
        with pytest.raises(ValueError, match="used in fallback"):
            service.delete_provider("anthropic")


# ---------------------------------------------------------------------------
# API key management
# ---------------------------------------------------------------------------


class TestApiKeyManagement:
    def test_set_api_key_writes_to_env_file(self, service: LlmConfigService, config_path: Path):
        service.set_api_key("openai", "sk-brand-new-key-1234")
        env_path = config_path.parent / ".env"
        assert env_path.exists()
        with open(env_path, encoding="utf-8") as f:
            content = f.read()
        assert "OPENAI_API_KEY=sk-brand-new-key-1234" in content

    def test_set_api_key_updates_yaml_reference(self, service: LlmConfigService, config_path: Path):
        service.set_api_key("openai", "sk-brand-new-key-1234")
        with open(config_path, encoding="utf-8") as f:
            saved = yaml.safe_load(f)
        assert saved["llm"]["providers"]["openai"]["api_key"] == "${OPENAI_API_KEY}"

    def test_set_api_key_returns_masked_provider(self, service: LlmConfigService):
        result = service.set_api_key("openai", "sk-brand-new-key-1234")
        assert result["api_key"].startswith("****")
        # Should not contain the plaintext key.
        assert "sk-brand-new-key-1234" not in result["api_key"]

    def test_set_api_key_for_new_provider_creates_stub(
        self, service: LlmConfigService, config_path: Path
    ):
        """Setting an API key for a provider that doesn't yet exist in the
        YAML should create a stub entry."""
        result = service.set_api_key("gemini", "AIza-test-key-1234")
        assert result["name"] == "gemini"
        assert result["type"] == "openai"  # default type for stub
        assert result["api_key"].startswith("****")
        with open(config_path, encoding="utf-8") as f:
            saved = yaml.safe_load(f)
        assert "gemini" in saved["llm"]["providers"]
        assert saved["llm"]["providers"]["gemini"]["api_key"] == "${GEMINI_API_KEY}"


# ---------------------------------------------------------------------------
# Fallback chain management
# ---------------------------------------------------------------------------


class TestFallbackManagement:
    def test_get_fallbacks_returns_empty_when_none_configured(self, service: LlmConfigService):
        fallbacks = service.get_fallbacks()
        assert fallbacks == {}

    def test_set_fallback_adds_chain(self, service: LlmConfigService, config_path: Path):
        result = service.set_fallback("gpt-4o", ["openai", "anthropic"])
        assert result["model"] == "gpt-4o"
        assert result["chain"] == ["openai", "anthropic"]
        # Verify it was written to YAML.
        with open(config_path, encoding="utf-8") as f:
            saved = yaml.safe_load(f)
        assert saved["llm"]["fallbacks"]["gpt-4o"] == ["openai", "anthropic"]

    def test_get_fallbacks_returns_set_chain(self, service: LlmConfigService):
        service.set_fallback("gpt-4o", ["openai", "anthropic"])
        fallbacks = service.get_fallbacks()
        assert fallbacks == {"gpt-4o": ["openai", "anthropic"]}

    def test_set_fallback_overwrites_existing(self, service: LlmConfigService):
        service.set_fallback("gpt-4o", ["openai"])
        service.set_fallback("gpt-4o", ["anthropic", "gemini"])
        fallbacks = service.get_fallbacks()
        assert fallbacks["gpt-4o"] == ["anthropic", "gemini"]

    def test_delete_fallback_removes_chain(self, service: LlmConfigService):
        service.set_fallback("gpt-4o", ["openai"])
        deleted = service.delete_fallback("gpt-4o")
        assert deleted is True
        assert service.get_fallbacks() == {}

    def test_delete_fallback_returns_false_for_unset(self, service: LlmConfigService):
        deleted = service.delete_fallback("nonexistent")
        assert deleted is False


# ---------------------------------------------------------------------------
# File locking
# ---------------------------------------------------------------------------


class TestFileLocking:
    def test_concurrent_writes_do_not_corrupt(self, service: LlmConfigService, config_path: Path):
        """Simulate concurrent writes from multiple threads.

        Each thread creates a different provider. The file lock should
        serialize the writes so the final YAML is valid and contains
        all providers.
        """
        errors: list[Exception] = []

        def _create_provider(name: str, api_key: str) -> None:
            try:
                # Each thread needs its own service instance to avoid
                # sharing state, but they all point to the same file.
                svc = LlmConfigService(config_path)
                svc.create_provider(name=name, provider_type="openai", api_key=api_key)
            except Exception as exc:
                errors.append(exc)

        threads = [
            threading.Thread(
                target=_create_provider,
                args=(f"provider_{i}", f"sk-key-{i:04d}"),
            )
            for i in range(5)
        ]
        for t in threads:
            t.start()
        for t in threads:
            t.join()

        # No errors should have occurred.
        assert errors == [], f"Concurrent writes failed: {errors}"

        # The YAML file should be valid and contain all 5 new providers
        # plus the original "openai" provider.
        with open(config_path, encoding="utf-8") as f:
            saved = yaml.safe_load(f)
        providers = saved["llm"]["providers"]
        for i in range(5):
            assert f"provider_{i}" in providers
        assert "openai" in providers

    def test_lockfile_is_created(self, service: LlmConfigService, config_path: Path):
        """The lockfile should be created on the first write."""
        service.create_provider(
            name="anthropic",
            provider_type="anthropic",
            api_key="sk-ant-test",
        )
        lockfile = config_path.with_suffix(config_path.suffix + ".lock")
        assert lockfile.exists()


# ---------------------------------------------------------------------------
# Singleton helpers
# ---------------------------------------------------------------------------


class TestSingletonHelpers:
    def test_get_llm_config_service_requires_path_on_first_call(self):
        with pytest.raises(ValueError, match="config_path is required"):
            get_llm_config_service()

    def test_get_llm_config_service_returns_singleton(self, config_path: Path):
        svc1 = get_llm_config_service(config_path)
        svc2 = get_llm_config_service()  # subsequent call ignores path
        assert svc1 is svc2

    def test_set_llm_config_service_overrides_singleton(self, config_path: Path):
        custom = LlmConfigService(config_path)
        set_llm_config_service(custom)
        assert get_llm_config_service() is custom

    def test_set_llm_config_service_none_resets_singleton(self, config_path: Path):
        svc = get_llm_config_service(config_path)
        set_llm_config_service(None)
        # Next call should raise (no path provided after reset).
        with pytest.raises(ValueError, match="config_path is required"):
            get_llm_config_service()
        # The previously-created instance should still be usable.
        assert svc.list_providers() is not None


# ---------------------------------------------------------------------------
# Env var resolution
# ---------------------------------------------------------------------------


class TestEnvVarResolution:
    def test_list_providers_masks_env_var_referenced_keys(
        self, config_path: Path, monkeypatch: pytest.MonkeyPatch
    ):
        """When the YAML stores ``${VAR}``, the masked response should
        show the masked *resolved* env value, not the literal ``${VAR}``."""
        # Rewrite the config to use a ${VAR} reference.
        with open(config_path, "w", encoding="utf-8") as f:
            cfg = _sample_config()
            cfg["llm"]["providers"]["openai"]["api_key"] = "${TEST_OPENAI_KEY}"
            yaml.dump(cfg, f, default_flow_style=False, allow_unicode=True)
        # Set the env var so it can be resolved.
        monkeypatch.setenv("TEST_OPENAI_KEY", "sk-resolved-1234")
        svc = LlmConfigService(config_path)
        providers = svc.list_providers()
        assert providers[0]["api_key"] == "****1234"