from typing import List
import time
import logging
from langchain_core.embeddings import Embeddings
from openai import OpenAI, RateLimitError
from app.config import settings

logger = logging.getLogger(__name__)


class SiliconFlowEmbeddings(Embeddings):
    """OpenAI 兼容 embeddings 直连客户端（绕开 langchain tiktoken token 化）

    langchain 的 OpenAIEmbeddings 默认 tiktoken_enabled=True，会把文本编码成
    整数 token 数组发送给 API（OpenAI 官方接受，但 siliconflow 等第三方网关
    只接受字符串 input，导致 400 code:20015 parameter invalid）。
    本类直接用 openai SDK 发送字符串数组，兼容 siliconflow 等网关。

    内置 429 TPM 指数退避重试：SiliconFlow 全量同步易触 TPM 限额，429 是
    临时性状态，退避重试能自动恢复完成，避免 sync 整段中断。
    """

    _BATCH_SIZE = 32
    _THROTTLE_SECONDS = 0.02
    _MAX_RETRY = 3
    _INITIAL_RETRY_SECONDS = 2.0

    def __init__(self, model: str, api_key: str, base_url: str):
        self.model = model
        self.client = OpenAI(api_key=api_key, base_url=base_url)

    def _call_with_retry(self, batch):
        wait = self._INITIAL_RETRY_SECONDS
        for attempt in range(self._MAX_RETRY + 1):
            try:
                return self.client.embeddings.create(model=self.model, input=batch)
            except RateLimitError as e:
                if attempt == self._MAX_RETRY:
                    raise
                logger.warning("embeddings 429 TPM 限制，%.0fs 后重试 (%d/%d)", wait, attempt + 1, self._MAX_RETRY)
                time.sleep(wait)
                wait = min(wait * 2, 30.0)
        raise RuntimeError("unreachable")

    def embed_documents(self, texts: List[str]) -> List[List[float]]:
        result = []
        for i in range(0, len(texts), self._BATCH_SIZE):
            batch = texts[i:i + self._BATCH_SIZE]
            resp = self._call_with_retry(batch)
            result.extend(d.embedding for d in resp.data)
            if i + self._BATCH_SIZE < len(texts):
                time.sleep(self._THROTTLE_SECONDS)
        return result

    def embed_query(self, text: str) -> List[float]:
        resp = self._call_with_retry([text])
        return resp.data[0].embedding


_embeddings = None


def get_embeddings():
    global _embeddings
    if _embeddings is None:
        _embeddings = SiliconFlowEmbeddings(
            model=settings.embedding_model,
            api_key=settings.effective_embedding_api_key,
            base_url=settings.effective_embedding_base_url,
        )
    return _embeddings