"""OpenAI-compatible HTTP client for a vLLM server.

The wire format uses the standard OpenAI ``/v1/chat/completions`` schema.
Frames are sent inline as base64 ``data:`` URLs.
"""
from __future__ import annotations

import json
import time
from typing import Any, Optional

import requests


class VLLMClient:
    """OpenAI-compatible client backed by a vLLM server."""

    def __init__(
        self,
        base_url: str,
        model_name: str,
        api_key: str = "EMPTY",
        max_tokens: int = 2048,
        temperature: float = 0.0,
        top_p: Optional[float] = None,
        request_interval: float = 0.0,
        max_retries: int = 3,
        retry_base_delay: float = 2.0,
        request_timeout: int = 300,
    ) -> None:
        base_url = (base_url or "").rstrip("/")
        if not base_url.endswith("/v1"):
            base_url = f"{base_url}/v1"
        self.base_url = base_url
        self.model_name = model_name
        self.max_tokens = int(max_tokens)
        self.temperature = float(temperature)
        self.top_p = top_p
        self.request_interval = float(request_interval)
        self.max_retries = int(max_retries)
        self.retry_base_delay = float(retry_base_delay)
        self.request_timeout = int(request_timeout)
        self.headers = {
            "Content-Type": "application/json",
            "Authorization": f"Bearer {api_key or 'EMPTY'}",
        }

    # ------------------------------------------------------------------
    # Public inference entry points
    # ------------------------------------------------------------------

    def infer_text_only(
        self,
        user_text: str,
        system_text: Optional[str] = None,
    ) -> str:
        messages = self._build_messages(
            user_content=[{"type": "text", "text": user_text}],
            system_text=system_text,
        )
        return self._infer(messages)

    def infer_with_frames(
        self,
        user_text: str,
        frame_b64_list: list[str],
        system_text: Optional[str] = None,
    ) -> str:
        content_parts: list[dict[str, Any]] = []
        for frame_b64 in frame_b64_list:
            content_parts.append(
                {
                    "type": "image_url",
                    "image_url": {"url": f"data:image/jpeg;base64,{frame_b64}"},
                }
            )
        content_parts.append({"type": "text", "text": user_text})
        messages = self._build_messages(
            user_content=content_parts, system_text=system_text
        )
        return self._infer(messages)

    # ------------------------------------------------------------------
    # Internal helpers
    # ------------------------------------------------------------------

    @staticmethod
    def _build_messages(
        user_content: list[dict[str, Any]],
        system_text: Optional[str],
    ) -> list[dict[str, Any]]:
        messages: list[dict[str, Any]] = []
        if system_text and system_text.strip():
            messages.append(
                {
                    "role": "system",
                    "content": [{"type": "text", "text": system_text}],
                }
            )
        messages.append({"role": "user", "content": user_content})
        return messages

    def _infer(self, messages: list[dict[str, Any]]) -> str:
        url = f"{self.base_url}/chat/completions"
        payload: dict[str, Any] = {
            "model": self.model_name,
            "messages": messages,
            "max_tokens": self.max_tokens,
            "temperature": self.temperature,
        }
        if self.top_p is not None:
            payload["top_p"] = self.top_p

        resp = self._post_with_retry(url, payload)
        data = resp.json()
        if data.get("error"):
            raise RuntimeError(f"vLLM API error: {data['error']}")

        choices = data.get("choices", [])
        if not choices:
            raise RuntimeError(
                "vLLM API returned no choices: "
                f"{json.dumps(data, ensure_ascii=False)[:500]}"
            )

        content = choices[0].get("message", {}).get("content", "")
        if isinstance(content, str) and content.strip():
            return content
        if isinstance(content, list):
            text_parts = [
                part.get("text", "")
                for part in content
                if isinstance(part, dict)
            ]
            text = "\n".join(p for p in text_parts if p)
            if text.strip():
                return text

        raise RuntimeError(
            "No text found in vLLM response: "
            f"{json.dumps(data, ensure_ascii=False)[:500]}"
        )

    def _post_with_retry(
        self, url: str, payload: dict[str, Any]
    ) -> requests.Response:
        last_exc: Optional[Exception] = None
        for attempt in range(self.max_retries):
            try:
                resp = requests.post(
                    url,
                    headers=self.headers,
                    json=payload,
                    timeout=self.request_timeout,
                )
                resp.raise_for_status()
                return resp
            except Exception as exc:  # noqa: BLE001
                last_exc = exc
                if attempt < self.max_retries - 1:
                    delay = self.retry_base_delay * (2 ** attempt)
                    print(
                        f"  [vllm retry] attempt {attempt + 1}/"
                        f"{self.max_retries} failed: {exc}; sleep {delay:.1f}s"
                    )
                    time.sleep(delay)
        raise RuntimeError(
            f"vLLM request failed after {self.max_retries} attempts: {last_exc}"
        )