from __future__ import annotations

import re
import uuid
from pathlib import Path

from fastapi import HTTPException, UploadFile

from app import config

ALLOWED_EXTENSIONS = frozenset(
    {
        "png",
        "jpg",
        "jpeg",
        "gif",
        "webp",
        "svg",
        "txt",
        "md",
        "pdf",
        "doc",
        "docx",
        "xls",
        "xlsx",
        "ppt",
        "pptx",
        "csv",
        "zip",
        "7z",
        "tar",
        "gz",
        "rar",
        "json",
    }
)

_SAFE_NAME_RE = re.compile(r"[^A-Za-z0-9._-]+")


def _safe_original_name(filename: str | None) -> str:
    name = Path(filename or "file").name
    name = _SAFE_NAME_RE.sub("_", name).strip("._") or "file"
    return name[:255]


def _extension(filename: str) -> str:
    return Path(filename).suffix.lstrip(".").lower()


async def save_upload(file: UploadFile) -> tuple[str, int, str, str]:
    original = _safe_original_name(file.filename)
    ext = _extension(original)
    if ext not in ALLOWED_EXTENSIONS:
        raise HTTPException(status_code=400, detail="File type not allowed")

    max_bytes = config.settings.max_upload_mb * 1024 * 1024
    config.settings.uploads_dir.mkdir(parents=True, exist_ok=True)

    stored_name = f"{uuid.uuid4().hex}.{ext}"
    dest = config.settings.uploads_dir / stored_name
    size = 0
    try:
        with dest.open("wb") as out:
            while True:
                chunk = await file.read(1024 * 1024)
                if not chunk:
                    break
                size += len(chunk)
                if size > max_bytes:
                    raise HTTPException(status_code=413, detail="File too large")
                out.write(chunk)
    except HTTPException:
        dest.unlink(missing_ok=True)
        raise
    except Exception:
        dest.unlink(missing_ok=True)
        raise

    mime = file.content_type or "application/octet-stream"
    rel_path = f"uploads/{stored_name}"
    return rel_path, size, mime, original