"""LLM provider abstraction for the interactive demo.

The demo points at any OpenAI-compatible ``/v1/chat/completions`` endpoint:
local Ollama, Hugging Face's Inference Providers router, OpenAI itself,
vLLM, OpenRouter, etc. Everything funnels through one factory so the UI
only has to learn one shape.

The browser passes ``base_url``, ``model``, and (optionally) ``api_key``
on every request. If ``api_key`` is missing we fall back to a per-provider
env var so a Hugging Face Space can ship a default working config without
hard-coding secrets in client bundles.
"""

from __future__ import annotations

import logging
import os
from collections.abc import Callable
from typing import Optional

from fastapi import HTTPException
from pydantic import BaseModel, ConfigDict, Field

_log = logging.getLogger(__name__)


# Public preset URLs. Mirror these in the frontend connection panel so the
# two stay in sync; the values themselves only matter when the browser
# hands one back to us in `LlmStepRequest.base_url`.
HF_ROUTER_BASE_URL = "https://router.huggingface.co/v1"
OPENAI_BASE_URL = "https://api.openai.com/v1"
OLLAMA_OPENAI_BASE_URL = "http://localhost:11434/v1"


class LlmStepRequest(BaseModel):
    """Provider-agnostic step payload.

    The browser names a base URL + model + (optional) key. The server
    fans these into an ``openai.OpenAI`` client. ``base_url`` is required
    so we never silently default to the wrong endpoint when the user
    swaps providers mid-session.
    """

    model_config = ConfigDict(extra="forbid")

    base_url: str = Field(
        description=(
            "OpenAI-compatible /v1 base URL. E.g. http://localhost:11434/v1, "
            "https://router.huggingface.co/v1, https://api.openai.com/v1."
        ),
    )
    model: str = Field(
        description=(
            "Model id understood by the chosen base URL. For HF this is the "
            "repo id (optionally suffixed with :provider, e.g. ':fastest'); "
            "for Ollama it's the local tag; for OpenAI it's the model name."
        ),
    )
    api_key: Optional[str] = Field(
        default=None,
        description=(
            "Bearer token forwarded as Authorization header. Falls back to "
            "HF_TOKEN / OPENAI_API_KEY / OLLAMA_API_KEY env vars on the "
            "server based on `base_url` if omitted."
        ),
    )
    temperature: float = Field(default=0.4, ge=0.0, le=2.0)
    max_tokens: int = Field(default=2048, ge=64, le=8192)
    request_timeout_s: float = Field(default=120.0, ge=5.0, le=600.0)


# A policy is "give me prompt messages, get back the assistant content".
LlmPolicy = Callable[[list[dict[str, str]]], str]
LlmPolicyFactory = Callable[[LlmStepRequest], LlmPolicy]


def resolve_api_key(request: LlmStepRequest) -> Optional[str]:
    """Pick the bearer token to use for this request.

    Browser-supplied keys win. When the browser sends nothing we fall
    back to a server-side env var picked from the URL — this lets a
    public Hugging Face Space ship a usable default by setting
    ``HF_TOKEN`` as a Space secret while still letting power users
    bring their own.
    """

    if request.api_key:
        return request.api_key

    base_url = (request.base_url or "").lower()
    if "huggingface" in base_url:
        return os.environ.get("HF_TOKEN") or os.environ.get("HUGGINGFACE_API_KEY")
    if "openai.com" in base_url:
        return os.environ.get("OPENAI_API_KEY")
    if "openrouter" in base_url:
        return os.environ.get("OPENROUTER_API_KEY")
    if "localhost" in base_url or "127.0.0.1" in base_url:
        # Ollama doesn't require a key; the SDK still wants something
        # truthy in some versions, so we hand it a placeholder.
        return os.environ.get("OLLAMA_API_KEY", "ollama")
    return None


def default_openai_compat_policy_factory(request: LlmStepRequest) -> LlmPolicy:
    """Build a chat policy backed by any OpenAI-compatible endpoint.

    Used by the interactive router for every demo turn. Failures bubble
    up as ``HTTPException(502)`` so the UI can surface a clear "your
    provider is unhappy" banner instead of a stack trace.
    """

    try:
        from openai import OpenAI  # type: ignore[import-not-found]
    except ImportError as exc:  # pragma: no cover
        raise HTTPException(
            status_code=503,
            detail=(
                "The 'openai' Python package is not installed on the server. "
                "Install with: pip install -e '.[demo]'"
            ),
        ) from exc

    api_key = resolve_api_key(request)
    client = OpenAI(
        base_url=request.base_url,
        api_key=api_key or "missing",
        timeout=request.request_timeout_s,
    )

    def _policy(prompt: list[dict[str, str]]) -> str:
        try:
            response = client.chat.completions.create(
                model=request.model,
                messages=prompt,  # type: ignore[arg-type]
                temperature=request.temperature,
                max_tokens=request.max_tokens,
                # Encourages JSON output where supported (OpenAI, vLLM,
                # Ollama-OpenAI). HF router silently ignores this on
                # providers that don't support it, which is fine — our
                # parser tolerates Markdown-fenced JSON too.
                response_format={"type": "json_object"},
            )
        except TypeError:
            # Some providers reject `response_format`; retry without it.
            response = client.chat.completions.create(
                model=request.model,
                messages=prompt,  # type: ignore[arg-type]
                temperature=request.temperature,
                max_tokens=request.max_tokens,
            )
        except Exception as exc:  # noqa: BLE001 — surfaced to the UI
            raise HTTPException(
                status_code=502,
                detail=_format_provider_error(request, exc),
            ) from exc

        choice = response.choices[0] if response.choices else None
        content = (choice.message.content if choice and choice.message else "") or ""
        return str(content)

    return _policy


def _format_provider_error(request: LlmStepRequest, exc: Exception) -> str:
    """Make the most common failure modes self-diagnosing in the UI."""

    base_msg = f"Chat completion failed via {request.base_url} for model {request.model!r}: {exc}"
    text = str(exc).lower()
    if "401" in text or "unauthorized" in text or "invalid api key" in text:
        return (
            f"{base_msg}\n\n"
            "Hint: the API key is missing or rejected. Open the connection "
            "panel and paste a valid token, or set the matching env var on "
            "the server (HF_TOKEN, OPENAI_API_KEY, etc.)."
        )
    if "404" in text or "not found" in text or "no such model" in text:
        return (
            f"{base_msg}\n\n"
            "Hint: the chosen model isn't reachable through this endpoint. "
            "For Hugging Face, verify the repo id is public and that "
            "Inference Providers is enabled for it. For Ollama, run "
            f"'ollama pull {request.model}'."
        )
    if "connection" in text or "refused" in text or "timeout" in text:
        return (
            f"{base_msg}\n\n"
            "Hint: the endpoint isn't reachable. For Ollama, make sure "
            "'ollama serve' is running on the host you pointed at."
        )
    return base_msg


# -----------------------------------------------------------------------
# Ollama-only model lister (kept for the local-dev convenience dropdown).
# -----------------------------------------------------------------------


class LlmModelInfo(BaseModel):
    """A single locally-pulled Ollama model tag."""

    model_config = ConfigDict(frozen=True)

    name: str
    size_bytes: Optional[int] = None
    parameter_size: Optional[str] = None
    family: Optional[str] = None


class LlmModelsResponse(BaseModel):
    models: list[LlmModelInfo] = Field(default_factory=list)
    error: Optional[str] = None


LlmModelsLister = Callable[[], LlmModelsResponse]


def default_ollama_models_lister() -> LlmModelsResponse:
    """Enumerate locally-pulled Ollama tags. Best-effort."""

    try:
        import ollama  # type: ignore[import-not-found]
    except ImportError:
        return LlmModelsResponse(
            models=[],
            error=(
                "The 'ollama' Python package is not installed on the server. "
                "Install with: pip install -e '.[demo]'"
            ),
        )

    try:
        response = ollama.Client().list()
    except Exception as exc:  # noqa: BLE001 — surfaced in the response body
        return LlmModelsResponse(
            models=[],
            error=(
                f"Could not reach the local Ollama daemon ({exc}). "
                "Is 'ollama serve' running?"
            ),
        )

    raw_models = getattr(response, "models", None)
    if raw_models is None and isinstance(response, dict):
        raw_models = response.get("models", [])
    raw_models = raw_models or []

    out: list[LlmModelInfo] = []
    for entry in raw_models:
        name = _model_attr(entry, "model") or _model_attr(entry, "name")
        if not isinstance(name, str) or not name:
            continue
        details = _model_attr(entry, "details")
        out.append(
            LlmModelInfo(
                name=name,
                size_bytes=_coerce_int(_model_attr(entry, "size")),
                parameter_size=_model_attr(details, "parameter_size"),
                family=_model_attr(details, "family"),
            )
        )

    out.sort(key=lambda m: m.name)
    return LlmModelsResponse(models=out)


def _model_attr(obj: object, key: str) -> object:
    if obj is None:
        return None
    if isinstance(obj, dict):
        return obj.get(key)
    return getattr(obj, key, None)


def _coerce_int(value: object) -> Optional[int]:
    if value is None:
        return None
    try:
        return int(value)
    except (TypeError, ValueError):
        return None