import os
import streamlit as st
import zipfile
from pathlib import Path
import io

# Fix permission errors by setting environment variables BEFORE importing streamlit
os.environ["STREAMLIT_BROWSER_GATHER_USAGE_STATS"] = "false"
os.environ["STREAMLIT_SERVER_HEADLESS"] = "true"
os.environ["STREAMLIT_SERVER_ENABLE_CORS"] = "false"
os.environ["STREAMLIT_SERVER_ENABLE_XSRF_PROTECTION"] = "false"

def is_safe_extension(extension):
    """Check if the extension is safe to convert to"""
    dangerous_extensions = ['.exe', '.bin', '.bat', '.cmd', '.com', '.scr', '.pif', '.vbs', '.js']
    return extension.lower() not in dangerous_extensions

def change_file_extension(file_content, original_name, new_extension):
    """Change file extension and return new filename"""
    if new_extension.startswith('.'):
        new_extension = new_extension[1:]
    
    base_name = Path(original_name).stem
    new_filename = f"{base_name}.{new_extension}"
    
    return new_filename, file_content

def create_download_zip(files_data):
    """Create a zip file containing all converted files"""
    zip_buffer = io.BytesIO()
    
    with zipfile.ZipFile(zip_buffer, 'w', zipfile.ZIP_DEFLATED) as zipf:
        for filename, content in files_data:
            zipf.writestr(filename, content)
    
    zip_buffer.seek(0)
    return zip_buffer.getvalue()

# Configure page
st.set_page_config(
    page_title="File Extension Converter",
    page_icon="🔄",
    layout="wide"
)

st.title("🔄 File Extension Converter")
st.markdown("Convert any file extension to another (safely)")

# Sidebar with instructions
with st.sidebar:
    st.header("📋 Instructions")
    st.markdown("""
    1. Upload one or more files
    2. Enter the target extension
    3. Download converted files
    
    **Safety Note:** 
    - .exe and .bin files are blocked for security
    - Only the extension is changed, not the file content
    """)
    
    st.header("⚠️ Blocked Extensions")
    st.code(".exe, .bin, .bat, .cmd, .com, .scr, .pif, .vbs, .js")

# Main interface
col1, col2 = st.columns([2, 1])

with col1:
    st.header("Upload Files")
    uploaded_files = st.file_uploader(
        "Choose files to convert",
        accept_multiple_files=True,
        help="Upload any files you want to change the extension for"
    )

with col2:
    st.header("Target Extension")
    new_extension = st.text_input(
        "New extension",
        placeholder="e.g., txt, pdf, jpg",
        help="Enter the extension you want to convert to (without the dot)"
    ).strip()

if uploaded_files and new_extension:
    if new_extension.startswith('.'):
        new_extension = new_extension[1:]
    
    full_extension = f".{new_extension}"
    
    if not is_safe_extension(full_extension):
        st.error(f"❌ Extension '{full_extension}' is not allowed for security reasons")
        st.stop()
    
    st.success(f"✅ Converting to: **{full_extension}**")
    
    converted_files = []
    
    st.header("📁 Conversion Results")
    
    for uploaded_file in uploaded_files:
        original_name = uploaded_file.name
        file_content = uploaded_file.read()
        
        new_filename, new_content = change_file_extension(
            file_content, original_name, new_extension
        )
        
        converted_files.append((new_filename, new_content))
        
        col_orig, col_arrow, col_new = st.columns([3, 1, 3])
        with col_orig:
            st.text(f"📄 {original_name}")
        with col_arrow:
            st.text("➡️")
        with col_new:
            st.text(f"📄 {new_filename}")
    
    st.divider()
    
    st.header("💾 Download")
    
    if len(converted_files) == 1:
        filename, content = converted_files[0]
        st.download_button(
            label=f"📥 Download {filename}",
            data=content,
            file_name=filename,
            mime="application/octet-stream"
        )
    else:
        try:
            zip_content = create_download_zip(converted_files)
            st.download_button(
                label=f"📥 Download All Files ({len(converted_files)} files)",
                data=zip_content,
                file_name="converted_files.zip",
                mime="application/zip"
            )
            
            st.info(f"💡 {len(converted_files)} files will be downloaded as a ZIP archive")
        except Exception as e:
            st.error(f"Error creating ZIP file: {str(e)}")

elif uploaded_files and not new_extension:
    st.warning("⚠️ Please enter a target extension")
elif new_extension and not uploaded_files:
    st.warning("⚠️ Please upload files to convert")

st.divider()
st.markdown("""
<div style='text-align: center; color: #666; font-size: 0.8em;'>
    Built with Streamlit 🎈 | Safe file extension conversion
</div>
""", unsafe_allow_html=True)