"""Connection verification, model discovery, and capability probing."""

from __future__ import annotations

import contextlib
import logging
from dataclasses import dataclass
from typing import Any

import anyio
import httpx
import litellm

from app.db import Connection, Model, ModelSource
from app.services.model_resolver import ensure_v1, to_litellm
from app.services.openrouter_model_normalizer import normalize_openrouter_models
from app.services.provider_registry import Transport, provider_label, spec_for

logger = logging.getLogger(__name__)

VERIFY_TIMEOUT_SECONDS = 8.0
DISCOVERY_TIMEOUT_SECONDS = 15.0
TEST_TIMEOUT_SECONDS = 30.0


@dataclass(frozen=True)
class VerifyResult:
    status: str
    ok: bool
    message: str = ""


class ModelDiscoveryError(Exception):
    """User-correctable discovery failure for provider configuration issues."""


def _auth_headers(conn: Connection) -> dict[str, str]:
    if not conn.api_key:
        return {}
    return {"Authorization": f"Bearer {conn.api_key}"}


def _anthropic_headers(conn: Connection) -> dict[str, str]:
    headers = {"anthropic-version": "2023-06-01"}
    if conn.api_key:
        headers["x-api-key"] = conn.api_key
    return headers


def _base_url_or_default(conn: Connection) -> str | None:
    if conn.base_url:
        return conn.base_url.rstrip("/")
    if conn.provider == "openai":
        return "https://api.openai.com/v1"
    if conn.provider == "anthropic":
        return "https://api.anthropic.com/v1"
    return spec_for(conn.provider).default_base_url


def _docker_hint(url: str | None, exc_or_status: Any) -> str:
    raw = str(exc_or_status)
    if not url:
        return raw
    if "localhost" in url or "127.0.0.1" in url:
        return (
            f"{raw}. The backend is running inside Docker; localhost means the "
            "backend container. Use host.docker.internal and make sure the model "
            "server listens on 0.0.0.0."
        )
    if "host.docker.internal" in url and (
        "refused" in raw.lower() or "connect" in raw.lower()
    ):
        return (
            f"{raw}. The host is reachable only if your local model server is "
            "listening on 0.0.0.0. On Linux Docker, add "
            "`host.docker.internal:host-gateway` to extra_hosts."
        )
    return raw


def _model_test_error(conn: Connection, model_id: str, exc: Exception) -> VerifyResult:
    provider_name = provider_label(conn.provider)
    raw = str(exc)
    normalized = raw.lower()
    exc_name = exc.__class__.__name__.lower()
    status_code = getattr(exc, "status_code", None)

    logger.info(
        "Model test failed for provider=%s model=%s: %s",
        conn.provider,
        model_id,
        raw,
    )

    if status_code in (401, 403) or "authentication" in exc_name or "401" in normalized:
        return VerifyResult(
            "AUTH_FAILED",
            False,
            f"Authentication failed. Check your {provider_name} credentials and try again.",
        )

    if status_code == 404 or "notfound" in exc_name or "not found" in normalized:
        if conn.provider == "azure":
            message = (
                "Azure OpenAI deployment was not found. Check the deployment name, "
                "API version, and endpoint."
            )
        else:
            message = f"Model '{model_id}' was not found on {provider_name}."
        return VerifyResult("NOT_FOUND", False, message)

    if status_code == 429 or "ratelimit" in exc_name or "rate limit" in normalized:
        return VerifyResult(
            "RATE_LIMITED",
            False,
            f"{provider_name} rate limited the model test. Try again later.",
        )

    if "timeout" in exc_name or "timed out" in normalized:
        return VerifyResult(
            "TIMEOUT",
            False,
            f"{provider_name} did not respond in time. Check the endpoint and try again.",
        )

    if "connection" in exc_name or "connect" in normalized:
        return VerifyResult(
            "UNREACHABLE",
            False,
            _docker_hint(
                _base_url_or_default(conn),
                f"Could not reach {provider_name}. Check the endpoint and try again.",
            ),
        )

    return VerifyResult(
        "UNREACHABLE",
        False,
        f"Could not test model '{model_id}' on {provider_name}. Check the credentials, endpoint, and model name.",
    )


async def verify_connection(conn: Connection) -> VerifyResult:
    spec = spec_for(conn.provider)
    base_url = _base_url_or_default(conn)
    if spec.base_url_required and not base_url:
        return VerifyResult("UNREACHABLE", False, "Base URL is required.")

    if spec.transport == Transport.OLLAMA and base_url:
        url = f"{base_url.rstrip('/')}/api/version"
    elif spec.discovery in {"openai_models", "openrouter"} and base_url:
        url = f"{ensure_v1(base_url)}/models"
    elif spec.discovery == "anthropic_models" and base_url:
        url = f"{base_url.rstrip('/')}/models"
    else:
        return VerifyResult(
            "OK", True, "Connection uses provider-native authentication."
        )

    try:
        async with httpx.AsyncClient(timeout=VERIFY_TIMEOUT_SECONDS) as client:
            headers = (
                _anthropic_headers(conn)
                if spec.auth_style == "x-api-key"
                else _auth_headers(conn)
            )
            response = await client.get(url, headers=headers)
        if response.status_code in (401, 403):
            return VerifyResult("AUTH_FAILED", False, "Authentication failed.")
        if response.status_code == 404:
            if spec.transport == Transport.OLLAMA and url.endswith("/v1/models"):
                message = "Ollama native API should not use /v1."
            elif spec.transport == Transport.OPENAI_COMPATIBLE:
                message = "OpenAI-compatible servers should expose /v1/models."
            else:
                message = "Endpoint returned 404."
            return VerifyResult("NOT_FOUND", False, message)
        response.raise_for_status()
        return VerifyResult("OK", True, "Connection verified.")
    except httpx.ConnectError as exc:
        return VerifyResult("UNREACHABLE", False, _docker_hint(base_url, exc))
    except httpx.TimeoutException as exc:
        return VerifyResult("UNREACHABLE", False, f"Connection timed out: {exc}")
    except httpx.HTTPError as exc:
        return VerifyResult("UNREACHABLE", False, _docker_hint(base_url, exc))


def _discovery_error_message(conn: Connection, exc: httpx.HTTPError) -> str:
    base_url = _base_url_or_default(conn)
    if isinstance(exc, httpx.HTTPStatusError):
        status_code = exc.response.status_code
        if status_code in (401, 403):
            return "Authentication failed while discovering models."
        if status_code == 404:
            spec = spec_for(conn.provider)
            if spec.transport == Transport.OPENAI_COMPATIBLE:
                return "OpenAI-compatible servers should expose /v1/models."
            return "Model discovery endpoint returned 404."
        return f"Model discovery failed with HTTP {status_code}."
    if isinstance(exc, httpx.TimeoutException):
        return f"Model discovery timed out: {exc}"
    return _docker_hint(base_url, exc)


def _allowlist(conn: Connection) -> set[str]:
    raw = (conn.extra or {}).get("model_ids") or []
    return {str(item).strip() for item in raw if str(item).strip()}


def _litellm_info(model_string: str, model_id: str) -> dict[str, Any]:
    with contextlib.suppress(Exception):
        info = litellm.get_model_info(model=model_string)
        if isinstance(info, dict):
            return info
    return (
        litellm.model_cost.get(model_string) or litellm.model_cost.get(model_id) or {}
    )


def _classify_from_litellm(model_string: str, model_id: str) -> dict[str, Any]:
    info = _litellm_info(model_string, model_id)
    mode = info.get("mode")
    supports_image_input = False
    supports_tools = False
    with contextlib.suppress(Exception):
        supports_image_input = bool(litellm.supports_vision(model=model_string))
    with contextlib.suppress(Exception):
        supports_tools = bool(litellm.supports_function_calling(model=model_string))
    return {
        "supports_chat": mode in (None, "chat", "completion", "responses"),
        "max_input_tokens": info.get("max_input_tokens") or info.get("max_tokens"),
        "supports_image_input": supports_image_input,
        "supports_tools": supports_tools,
        "supports_image_generation": mode
        in {"image_generation", "image_generation_model"},
    }


def derive_capabilities(
    conn: Connection, model_id: str, metadata: dict | None = None
) -> dict[str, Any]:
    metadata = metadata or {}
    spec = spec_for(conn.provider)
    model_string, _ = to_litellm(conn, model_id)
    facts = _classify_from_litellm(model_string, model_id)
    if spec.transport == Transport.OLLAMA:
        caps = set(metadata.get("capabilities") or [])
        details = metadata.get("details") or {}
        facts.update(
            {
                "supports_chat": "embedding" not in caps,
                "supports_image_input": "vision" in caps
                or facts["supports_image_input"],
                "supports_tools": "tools" in caps or facts["supports_tools"],
                "supports_image_generation": False,
                "max_input_tokens": metadata.get("context_length")
                or metadata.get("num_ctx")
                or details.get("context_length")
                or facts["max_input_tokens"],
            }
        )
    return facts


async def _discover_openai_shaped_models(
    conn: Connection, base_url: str | None
) -> list[dict[str, Any]]:
    resolved_base_url = base_url or _base_url_or_default(conn)
    if not resolved_base_url:
        return []

    url = f"{ensure_v1(resolved_base_url)}/models"
    async with httpx.AsyncClient(timeout=DISCOVERY_TIMEOUT_SECONDS) as client:
        response = await client.get(url, headers=_auth_headers(conn))
    response.raise_for_status()

    results: list[dict[str, Any]] = []
    for item in response.json().get("data", []):
        model_id = item.get("id")
        if not model_id:
            continue
        results.append(
            {
                "model_id": model_id,
                "display_name": item.get("name") or model_id,
                "source": ModelSource.DISCOVERED,
                **derive_capabilities(conn, model_id, item),
                "metadata": item,
            }
        )
    return results


async def _discover_anthropic_models(conn: Connection) -> list[dict[str, Any]]:
    base_url = _base_url_or_default(conn)
    if not base_url:
        return []

    url = f"{base_url.rstrip('/')}/models"
    async with httpx.AsyncClient(timeout=DISCOVERY_TIMEOUT_SECONDS) as client:
        response = await client.get(url, headers=_anthropic_headers(conn))
    response.raise_for_status()

    results: list[dict[str, Any]] = []
    for item in response.json().get("data", []):
        model_id = item.get("id")
        if not model_id:
            continue
        results.append(
            {
                "model_id": model_id,
                "display_name": item.get("display_name") or model_id,
                "source": ModelSource.DISCOVERED,
                **derive_capabilities(conn, model_id, item),
                "metadata": item,
            }
        )
    return results


async def _ollama_tags_then_show(conn: Connection) -> list[dict[str, Any]]:
    if not conn.base_url:
        return []

    base_url = conn.base_url.rstrip("/")
    async with httpx.AsyncClient(timeout=DISCOVERY_TIMEOUT_SECONDS) as client:
        response = await client.get(f"{base_url}/api/tags", headers=_auth_headers(conn))
        response.raise_for_status()
        models = response.json().get("models", [])
        results: list[dict[str, Any]] = []
        for item in models:
            model_id = item.get("model") or item.get("name")
            if not model_id:
                continue
            metadata = dict(item)
            with contextlib.suppress(Exception):
                show_response = await client.post(
                    f"{base_url}/api/show",
                    json={"model": model_id},
                    headers=_auth_headers(conn),
                )
                show_response.raise_for_status()
                metadata.update(show_response.json())
            results.append(
                {
                    "model_id": model_id,
                    "display_name": item.get("name") or model_id,
                    "source": ModelSource.DISCOVERED,
                    **derive_capabilities(conn, model_id, metadata),
                    "metadata": metadata,
                }
            )
    return results


async def _openrouter_models(conn: Connection) -> list[dict[str, Any]]:
    base_url = _base_url_or_default(conn) or "https://openrouter.ai/api/v1"
    async with httpx.AsyncClient(timeout=DISCOVERY_TIMEOUT_SECONDS) as client:
        response = await client.get(
            f"{ensure_v1(base_url)}/models", headers=_auth_headers(conn)
        )
    response.raise_for_status()
    return normalize_openrouter_models(response.json().get("data", []))


def _litellm_static_models(conn: Connection) -> list[dict[str, Any]]:
    provider = conn.provider
    prefix = spec_for(provider).litellm_prefix or provider
    results: list[dict[str, Any]] = []
    for model_string, metadata in litellm.model_cost.items():
        if not isinstance(model_string, str) or not model_string.startswith(
            f"{prefix}/"
        ):
            continue
        model_id = model_string.split("/", 1)[1]
        results.append(
            {
                "model_id": model_id,
                "display_name": metadata.get("display_name") or model_id,
                "source": ModelSource.DISCOVERED,
                **_classify_from_litellm(model_string, model_id),
                "metadata": metadata,
            }
        )
    return results


async def _discover_bedrock_models(conn: Connection) -> list[dict[str, Any]]:
    params = (conn.extra or {}).get("litellm_params", {})
    region_name = params.get("aws_region_name")
    if not region_name:
        return []

    def list_models() -> list[dict[str, Any]]:
        import os

        import boto3

        if bearer_token := params.get("aws_bearer_token_bedrock"):
            try:
                os.environ["AWS_BEARER_TOKEN_BEDROCK"] = bearer_token
                client = boto3.client("bedrock", region_name=region_name)
            finally:
                os.environ.pop("AWS_BEARER_TOKEN_BEDROCK", None)
        else:
            client_kwargs: dict[str, str] = {"region_name": region_name}
            if params.get("aws_access_key_id"):
                client_kwargs["aws_access_key_id"] = params["aws_access_key_id"]
            if params.get("aws_secret_access_key"):
                client_kwargs["aws_secret_access_key"] = params["aws_secret_access_key"]
            client = boto3.client("bedrock", **client_kwargs)

        response = client.list_foundation_models()
        results: list[dict[str, Any]] = []
        for item in response.get("modelSummaries", []):
            model_id = item.get("modelId")
            if not model_id:
                continue
            input_modalities = set(item.get("inputModalities") or [])
            output_modalities = set(item.get("outputModalities") or [])
            results.append(
                {
                    "model_id": model_id,
                    "display_name": item.get("modelName") or model_id,
                    "source": ModelSource.DISCOVERED,
                    "supports_chat": "TEXT" in input_modalities
                    and "TEXT" in output_modalities,
                    "supports_image_input": "IMAGE" in input_modalities,
                    "supports_tools": None,
                    "supports_image_generation": "IMAGE" in output_modalities,
                    "max_input_tokens": None,
                    "metadata": item,
                }
            )
        return results

    return await anyio.to_thread.run_sync(list_models)


async def discover_models(conn: Connection) -> list[dict[str, Any]]:
    allowlist = _allowlist(conn)
    spec = spec_for(conn.provider)

    try:
        if spec.discovery == "ollama":
            results = await _ollama_tags_then_show(conn)
        elif spec.discovery == "openrouter":
            results = await _openrouter_models(conn)
        elif spec.discovery == "anthropic_models":
            results = await _discover_anthropic_models(conn)
        elif spec.discovery == "openai_models":
            results = await _discover_openai_shaped_models(conn, conn.base_url)
        elif spec.discovery == "bedrock_models":
            results = await _discover_bedrock_models(conn)
        elif spec.discovery == "static":
            results = _litellm_static_models(conn)
        else:
            results = []
    except httpx.HTTPError as exc:
        raise ModelDiscoveryError(_discovery_error_message(conn, exc)) from exc

    if allowlist:
        results = [item for item in results if item["model_id"] in allowlist]
    return results


async def test_model(conn: Connection, model: Model) -> VerifyResult:
    model_string, kwargs = to_litellm(conn, model.model_id)
    try:
        await litellm.acompletion(
            model=model_string,
            messages=[{"role": "user", "content": "Hello"}],
            timeout=TEST_TIMEOUT_SECONDS,
            **kwargs,
        )
    except Exception as exc:
        return _model_test_error(conn, model.model_id, exc)

    model.supports_chat = True
    return VerifyResult("OK", True, "Model test succeeded.")


__all__ = [
    "ModelDiscoveryError",
    "VerifyResult",
    "derive_capabilities",
    "discover_models",
    "test_model",
    "verify_connection",
]