import csv
import io
import json
from pathlib import Path

import pandas as pd
from docx import Document

from services.minio_client import download_object_bytes, split_bucket_path

try:
    from pypdf import PdfReader
except Exception:  # pragma: no cover
    PdfReader = None


def _decode_text(content: bytes) -> str:
    for encoding in ("utf-8", "utf-8-sig", "gbk", "gb18030"):
        try:
            return content.decode(encoding)
        except Exception:
            continue
    return content.decode("utf-8", errors="ignore")


def _summarize_docx(content: bytes) -> str:
    doc = Document(io.BytesIO(content))
    texts = [paragraph.text.strip() for paragraph in doc.paragraphs if paragraph.text.strip()]
    return "\n".join(texts[:40])[:4000]


def _summarize_csv(content: bytes) -> str:
    text = _decode_text(content)
    reader = csv.reader(io.StringIO(text))
    rows = list(reader[:20])
    return "\n".join([" | ".join(row) for row in rows])[:4000]


def _summarize_excel(content: bytes, suffix: str) -> str:
    excel_buffer = io.BytesIO(content)
    sheet_map = pd.read_excel(excel_buffer, sheet_name=None) if suffix == ".xlsx" else pd.read_excel(excel_buffer, sheet_name=None, engine="xlrd")
    parts: list[str] = []
    for sheet_name, dataframe in list(sheet_map.items())[:5]:
        preview = dataframe.head(10).fillna("").astype(str)
        parts.append(f"[工作表] {sheet_name}")
        parts.append(preview.to_csv(index=False).strip())
    return "\n".join(parts)[:5000]


def _summarize_pdf(content: bytes) -> str:
    if PdfReader is None:
        return "当前环境未安装 PDF 文本解析依赖，无法提取 PDF 正文。"
    reader = PdfReader(io.BytesIO(content))
    texts: list[str] = []
    for page in reader.pages[:10]:
        texts.append((page.extract_text() or "").strip())
    return "\n".join(filter(None, texts))[:4000]


def summarize_file_bytes(file_name: str, content: bytes) -> str:
    suffix = Path(file_name).suffix.lower()
    if suffix in {".txt", ".md", ".json"}:
        return _decode_text(content)[:4000]
    if suffix == ".csv":
        return _summarize_csv(content)
    if suffix in {".xlsx", ".xls"}:
        return _summarize_excel(content, suffix)
    if suffix == ".docx":
        return _summarize_docx(content)
    if suffix == ".pdf":
        return _summarize_pdf(content)
    return f"暂不支持解析该文件内容：{file_name}"


def summarize_minio_files(file_paths: list[str]) -> list[dict]:
    summaries: list[dict] = []
    for file_path in file_paths:
        bucket, object_name = split_bucket_path(file_path)
        content = download_object_bytes(bucket, object_name)
        file_name = Path(object_name).name
        summaries.append(
            {
                "file_name": file_name,
                "file_path": file_path,
                "summary": summarize_file_bytes(file_name, content),
            }
        )
    return summaries