from __future__ import annotations

import uuid
from dataclasses import dataclass


@dataclass
class ExtractedFile:
    doc_id: str
    source_label: str
    text: str
    warning: str | None = None


def _safe_decode(data: bytes) -> str:
    for enc in ("utf-8", "utf-8-sig", "gbk"):
        try:
            return data.decode(enc)
        except UnicodeDecodeError:
            continue
    return data.decode("utf-8", errors="replace")


def extract_text_from_upload(*, filename: str, data: bytes) -> ExtractedFile:
    name = (filename or "upload").strip() or "upload"
    lower = name.lower()
    doc_id = f"file-{uuid.uuid4().hex[:12]}"

    if lower.endswith(".pdf"):
        try:
            from io import BytesIO

            from pypdf import PdfReader

            reader = PdfReader(BytesIO(data))
            parts: list[str] = []
            for page in reader.pages:
                t = page.extract_text()
                if t:
                    parts.append(t)
            text = "\n".join(parts).strip()
            warn = None
            if not text:
                warn = "PDF 未解析出文本（可能为扫描件，需先 OCR）"
            return ExtractedFile(
                doc_id=doc_id, source_label=name, text=text or "", warning=warn
            )
        except Exception as e:  # noqa: BLE001
            return ExtractedFile(
                doc_id=doc_id,
                source_label=name,
                text="",
                warning=f"PDF 解析失败: {e}",
            )

    text = _safe_decode(data).strip()
    return ExtractedFile(doc_id=doc_id, source_label=name, text=text)