"""
Streamlit File Extension Renamer
--------------------------------
A lightweight Streamlit app intended for deployment on Hugging Face Spaces.
The app lets users upload one or more files and rename (not convert) their
extensions to any common file-type extension the user selects. Executable
and binary files are blocked for security reasons.
"""

from __future__ import annotations

import os, pathlib
# 1️⃣ give Streamlit a real home BEFORE importing it
os.environ.setdefault("STREAMLIT_HOME", "/tmp/.streamlit")
pathlib.Path(os.environ["STREAMLIT_HOME"]).mkdir(parents=True, exist_ok=True)

import streamlit as st

import zipfile
from datetime import datetime
from pathlib import Path



# -----------------------------------------------------------------------------
# Configuration
# -----------------------------------------------------------------------------
# List of target extensions displayed to the user. Extend this list as needed.
ALLOWED_TARGET_EXTS: list[str] = [
    ".txt",
    ".pdf",
    ".doc",
    ".docx",
    ".json",
    ".csv",
    ".xml",
    ".html",
    ".css",
    ".js",
    ".md",
    ".jpg",
    ".jpeg",
    ".png",
    ".gif",
    ".bmp",
    ".tiff",
    ".svg",
    ".ico",
    ".mp3",
    ".wav",
    ".mp4",
    ".avi",
    ".mkv",
    ".mov",
    ".zip",
    ".tar",
    ".gz",
    ".7z",
]

# Source‐file extensions that are disallowed (will be skipped if uploaded).
DISALLOWED_SOURCE_EXTS: set[str] = {".exe", ".bin"}

# -----------------------------------------------------------------------------
# UI helpers
# -----------------------------------------------------------------------------

def make_sidebar() -> str:
    """Return the user-chosen target extension from sidebar controls."""
    st.sidebar.header("Settings")
    target_ext = st.sidebar.selectbox(
        label="Target extension (applied to **all** uploaded files)",
        options=ALLOWED_TARGET_EXTS,
        index=ALLOWED_TARGET_EXTS.index(".pdf"),
    )

    st.sidebar.markdown(
        """❗ **Note**: This tool only renames the file extension. It does **not**
        convert the underlying file format. Opening a renamed file with an
        incompatible program may fail or lead to data corruption."""
    )
    return target_ext


def make_uploader():
    """Return the list of files uploaded by the user."""
    return st.file_uploader(
        "Upload one or more files",
        accept_multiple_files=True,
        type=[ext.lstrip(".") for ext in ALLOWED_TARGET_EXTS],
        help="Drag-and-drop or browse for files to rename.",
    )


# -----------------------------------------------------------------------------
# Core logic
# -----------------------------------------------------------------------------

def write_zip(uploaded_files: list[st.runtime.uploaded_file_manager.UploadedFile], target_ext: str) -> io.BytesIO:
    """Return an in-memory ZIP archive of the uploaded files with the new extension."""
    buffer = io.BytesIO()
    with zipfile.ZipFile(buffer, "w", zipfile.ZIP_DEFLATED) as zf:
        for file in uploaded_files:
            orig_path = Path(file.name)
            if orig_path.suffix.lower() in DISALLOWED_SOURCE_EXTS:
                st.warning(f"⏭️  Skipping disallowed file: **{orig_path.name}**")
                continue

            renamed = orig_path.with_suffix(target_ext)
            zf.writestr(renamed.name, file.read())
            st.success(f"✅ Renamed **{orig_path.name}** → **{renamed.name}**")

    buffer.seek(0)
    return buffer


# -----------------------------------------------------------------------------
# Main app
# -----------------------------------------------------------------------------

def main() -> None:
    st.set_page_config("Extension Renamer", page_icon="📄", layout="centered")
    st.title("📄 Universal File-Extension Renamer")
    st.write(
        "Upload files, choose a new extension, and download them renamed in a single ZIP archive."
    )

    target_ext = make_sidebar()
    uploaded_files = make_uploader()

    if uploaded_files and st.button("🔄 Rename & Package"):
        zip_buffer = write_zip(uploaded_files, target_ext)
        timestamp = datetime.utcnow().strftime("%Y%m%dT%H%M%SZ")
        st.download_button(
            label="⬇️ Download ZIP",
            data=zip_buffer,
            file_name=f"renamed_{timestamp}.zip",
            mime="application/zip",
        )

    st.caption("© 2025 File-Extension Renamer • Built with Streamlit • Deployed on Hugging Face Spaces")


if __name__ == "__main__":
    main()