"""
向量化服务：对文档/查询文本生成向量。

优先级：
1. 若配置了环境变量 EMBEDDING_API_URL，则调用第三方「OpenAI 兼容」的 /embeddings 接口
   （需配置 EMBEDDING_API_KEY、EMBEDDING_MODEL，默认 text-embedding-3-small）。
2. 否则使用本地「哈希 TF 嵌入」兜底，使向量检索在无外部依赖时也能端到端跑通，
   且相似文本（共享词汇）会得到更高余弦相似度，便于演示召回效果。
"""
import os
import re
import math
import json
import hashlib
import urllib.request

EMBED_DIM = 256
MODEL = os.getenv("EMBEDDING_MODEL", "mock-hash-embed-v1")


def _tokenize(text):
    text = (text or "").lower()
    # 英文/数字按词，CJK 逐字（中文无空格，需拆到字级才能命中子词）
    tokens = re.findall(r"[a-z0-9]+", text)
    tokens += re.findall(r"[一-鿿]", text)
    return tokens


def _hash_embedding(texts, dim=EMBED_DIM):
    vecs = []
    for text in texts:
        vec = [0.0] * dim
        tokens = _tokenize(text)
        if not tokens:
            tokens = list(text or "")
        for tok in tokens:
            h = int(hashlib.md5(tok.encode("utf-8")).hexdigest(), 16)
            vec[h % dim] += 1.0
        norm = math.sqrt(sum(v * v for v in vec))
        if norm > 0:
            vec = [v / norm for v in vec]
        vecs.append(vec)
    return vecs


def embed(texts):
    """返回 list[list[float]]，与输入顺序一致。"""
    if not texts:
        return []
    api_url = os.getenv("EMBEDDING_API_URL")
    if api_url:
        api_key = os.getenv("EMBEDDING_API_KEY", "")
        model = os.getenv("EMBEDDING_MODEL", "text-embedding-3-small")
        payload = json.dumps({"input": texts, "model": model}).encode("utf-8")
        req = urllib.request.Request(
            api_url,
            data=payload,
            headers={
                "Content-Type": "application/json",
                "Authorization": f"Bearer {api_key}" if api_key else "",
            },
            method="POST",
        )
        with urllib.request.urlopen(req, timeout=30) as resp:
            data = json.loads(resp.read().decode("utf-8"))
        items = data["data"]
        if items and "index" in items[0]:
            items = sorted(items, key=lambda x: x["index"])
        return [item["embedding"] for item in items]
    return _hash_embedding(texts)


def cosine(a, b):
    dot = sum(x * y for x, y in zip(a, b))
    na = math.sqrt(sum(x * x for x in a))
    nb = math.sqrt(sum(y * y for y in b))
    if na == 0 or nb == 0:
        return 0.0
    return dot / (na * nb)


def chunk_text(text, size=400, overlap=50):
    text = (text or "").strip()
    if not text:
        return []
    if len(text) <= size:
        return [text]
    chunks = []
    start = 0
    while start < len(text):
        end = min(start + size, len(text))
        chunks.append(text[start:end])
        if end == len(text):
            break
        start = end - overlap
    return chunks


def extract_text(path, ext):
    """抽取文档纯文本；未知格式拒绝，已知格式解析失败时保留占位文本。"""
    if ext not in {".txt", ".md", ".docx", ".xlsx", ".pdf", ".doc"}:
        raise ValueError(f"unsupported file extension: {ext}")
    try:
        if ext in {".txt", ".md"}:
            with open(path, "r", encoding="utf-8", errors="replace") as f:
                return f.read()
        if ext == ".docx":
            from docx import Document

            doc = Document(path)
            return "\n".join(p.text for p in doc.paragraphs)
        if ext == ".xlsx":
            import openpyxl

            wb = openpyxl.load_workbook(path, data_only=True, read_only=True)
            rows = []
            for ws in wb.worksheets:
                for row in ws.iter_rows(values_only=True):
                    cells = [str(c) for c in row if c is not None]
                    if cells:
                        rows.append(" ".join(cells))
            return "\n".join(rows)
        if ext == ".pdf":
            try:
                from pypdf import PdfReader
            except ImportError:
                from PyPDF2 import PdfReader
            reader = PdfReader(path)
            return "\n".join((p.extract_text() or "") for p in reader.pages)
        if ext == ".doc":
            with open(path, "rb") as f:
                raw = f.read().decode("utf-8", errors="ignore")
            return re.sub(r"[\x00-\x08\x0b\x0c\x0e-\x1f]+", " ", raw)
    except Exception as e:  # 解析失败时回退
        print("extract_text failed:", e)
    return f"文档：{os.path.basename(path)} 类型 {ext}"