"""OpenAI-compatible chat-completions backend.

Covers OpenAI / Azure OpenAI / DeepSeek / Moonshot / Qwen-cloud / Ollama /
vLLM / LM Studio — anything that exposes `POST {endpoint}/chat/completions`.

We avoid the openai SDK to keep the plugin's dependency surface to stdlib +
pyyaml. Uses urllib so even environments without `requests` work.
"""
from __future__ import annotations
import json
import urllib.error
import urllib.request
from dataclasses import dataclass


@dataclass
class OpenAICompatibleBackend:
    cfg: dict

    @property
    def endpoint(self) -> str:
        return self.cfg["endpoint"].rstrip("/")

    @property
    def model(self) -> str:
        return self.cfg["model"]

    @property
    def api_key(self) -> str:
        return self.cfg.get("api_key") or "missing-key"

    @property
    def max_output_tokens(self) -> int:
        return int(self.cfg.get("max_output_tokens", 4000))

    @property
    def timeout(self) -> int:
        return int(self.cfg.get("timeout_seconds", 60))

    def summarise(self, system_prompt: str, conversation_text: str) -> str:
        url = f"{self.endpoint}/chat/completions"
        body = {
            "model": self.model,
            "max_tokens": self.max_output_tokens,
            "temperature": 0.2,
            "messages": [
                {"role": "system", "content": system_prompt},
                {"role": "user", "content": conversation_text},
            ],
        }
        data = json.dumps(body).encode("utf-8")
        req = urllib.request.Request(
            url,
            data=data,
            headers={
                "Content-Type": "application/json",
                "Authorization": f"Bearer {self.api_key}",
            },
            method="POST",
        )
        try:
            with urllib.request.urlopen(req, timeout=self.timeout) as resp:
                payload = json.loads(resp.read().decode("utf-8"))
        except urllib.error.HTTPError as e:
            detail = e.read().decode("utf-8", errors="replace")[:500]
            raise RuntimeError(f"LLM HTTP {e.code}: {detail}") from e
        except urllib.error.URLError as e:
            raise RuntimeError(f"LLM connection failed: {e.reason}") from e

        choices = payload.get("choices") or []
        if not choices:
            raise RuntimeError(f"LLM returned no choices: {payload}")
        msg = choices[0].get("message") or {}
        content = msg.get("content")
        if not isinstance(content, str) or not content.strip():
            raise RuntimeError(f"LLM returned empty content: {payload}")
        return content.strip()