"""embed.py —— ollama 嵌入调用封装（httpx，并发 ≤8，bge-m3 1024 维）。

- embed_batch(texts)：同步函数，分批并发调 POST {url}/api/embed
- 空文本返回零向量；维度不符抛 EmbedError
- 单元测试注入假 embed（monkeypatch），本模块不依赖真 ollama
"""
from __future__ import annotations

import logging
from concurrent.futures import ThreadPoolExecutor

import httpx

from .settings import (
    DEFAULT_EMBED_MODEL,
    DEFAULT_EMBED_URL,
    EMBED_CONCURRENCY,
    EMBED_DIM,
    EMBED_TIMEOUT,
    get_paths,
)

logger = logging.getLogger(__name__)


class EmbedError(Exception):
    """嵌入调用失败（服务不可达/维度不符/响应异常）。"""


def _zero_vector() -> list[float]:
    return [0.0] * EMBED_DIM


def _request_one(client: httpx.Client, url: str, model: str, text: str) -> list[float]:
    """单条嵌入请求。空文本返回零向量（不打上游）。"""
    if not text or not text.strip():
        return _zero_vector()
    try:
        resp = client.post(
            f"{url.rstrip('/')}/api/embed",
            json={"model": model, "input": text},
            timeout=EMBED_TIMEOUT,
        )
        resp.raise_for_status()
        payload = resp.json()
        embeddings = payload.get("embeddings")
        if not embeddings or not isinstance(embeddings[0], list):
            raise EmbedError(f"嵌入响应形态异常：{str(payload)[:200]}")
        vector = [float(v) for v in embeddings[0]]
        if len(vector) != EMBED_DIM:
            raise EmbedError(f"嵌入维度不符：期望 {EMBED_DIM}，实际 {len(vector)}")
        return vector
    except EmbedError:
        raise
    except (httpx.HTTPError, ValueError) as exc:
        raise EmbedError(f"嵌入服务调用失败：{exc}") from exc


def embed_batch(
    texts: list[str],
    url: str | None = None,
    model: str | None = None,
) -> list[list[float]]:
    """批量嵌入：线程池并发 ≤ EMBED_CONCURRENCY，保持输入顺序。

    url/model 缺省取 settings（VSTORE_EMBED_URL / VSTORE_EMBED_MODEL）。
    """
    if not texts:
        return []
    paths = get_paths()
    base_url = url or paths.embed_url or DEFAULT_EMBED_URL
    model_name = model or paths.embed_model or DEFAULT_EMBED_MODEL

    results: list[list[float] | None] = [None] * len(texts)
    with httpx.Client() as client:
        with ThreadPoolExecutor(max_workers=EMBED_CONCURRENCY) as pool:
            futures = {
                pool.submit(_request_one, client, base_url, model_name, text): idx
                for idx, text in enumerate(texts)
            }
            for future in futures:
                idx = futures[future]
                try:
                    results[idx] = future.result()
                except EmbedError as exc:
                    logger.warning("embed: 第 %d 条嵌入失败：%s", idx, exc)
                    results[idx] = None
                except Exception as exc:  # 线程池其他异常也降级为零向量
                    logger.warning("embed: 第 %d 条嵌入异常：%s", idx, exc)
                    results[idx] = None
    return [v if v is not None else _zero_vector() for v in results]