import os
import uuid
import pandas as pd

from flask import render_template, request, send_file
from common.logger import system_logger


BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))

UPLOAD_FOLDER = os.path.join(BASE_DIR, "uploads")
OUTPUT_FOLDER = os.path.join(BASE_DIR, "output")

os.makedirs(UPLOAD_FOLDER, exist_ok=True)
os.makedirs(OUTPUT_FOLDER, exist_ok=True)


# =========================
# 1. 读取文件（CSV/TXT/Excel）
# =========================
def read_any(file_path):

    ext = file_path.lower().split(".")[-1]

    # Excel
    if ext in ["xls", "xlsx"]:
        df = pd.read_excel(file_path, dtype=str)
        return df

    # CSV / TXT
    if ext in ["csv", "txt"]:

        seps = [",", "|", "\t", " "]

        for sep in seps:
            try:
                df = pd.read_csv(
                    file_path,
                    sep=sep,
                    engine="python",
                    dtype=str,
                    encoding="utf-8"
                )

                if df.shape[1] > 1:
                    return df

            except:
                continue

        # fallback GBK
        for sep in seps:
            try:
                df = pd.read_csv(
                    file_path,
                    sep=sep,
                    engine="python",
                    dtype=str,
                    encoding="gbk"
                )

                if df.shape[1] > 1:
                    return df

            except:
                continue

        raise Exception("无法解析TXT/CSV结构")

    raise Exception("不支持的文件类型")


# =========================
# 2. 转换核心
# =========================
def convert_file(df, target):

    out_name = f"convert_{uuid.uuid4().hex}"

    # Excel
    if target == "excel":
        path = os.path.join(OUTPUT_FOLDER, out_name + ".xlsx")
        df.to_excel(path, index=False)

    # CSV
    elif target == "csv":
        path = os.path.join(OUTPUT_FOLDER, out_name + ".csv")
        df.to_csv(path, index=False, encoding="utf-8-sig")

    # TXT（默认 tab）
    elif target == "txt":
        path = os.path.join(OUTPUT_FOLDER, out_name + ".txt")
        df.to_csv(path, index=False, sep="\t", encoding="utf-8")

    else:
        raise Exception("未知转换类型")

    return path, os.path.basename(path)


# =========================
# 3. 页面
# =========================
def file_convert_page():

    preview = None
    download_file = None
    message = None

    if request.method == "POST":

        try:
            file = request.files.get("file")
            target = request.form.get("target")

            if not file or not file.filename:
                raise Exception("请选择文件")

            filename = f"{uuid.uuid4()}_{file.filename}"
            path = os.path.join(UPLOAD_FOLDER, filename)
            file.save(path)

            df = read_any(path)

            preview = df.head(100).fillna("").to_html(
                classes="table table-dark table-hover",
                index=False
            )

            out_path, download_file = convert_file(df, target)

            message = f"转换成功：{len(df)} 行"

            system_logger.info(
                f"[FileConvert] {file.filename} -> {target}"
            )

        except Exception as e:
            message = str(e)
            system_logger.exception("[FileConvert ERROR]")

    return render_template(
        "file_convert.html",
        preview=preview,
        download_file=download_file,
        message=message
    )


# =========================
# download
# =========================
def file_convert_download(filename):

    path = os.path.join(OUTPUT_FOLDER, filename)

    system_logger.info(f"[FileConvertDownload] {filename}")

    return send_file(path, as_attachment=True)