import streamlit as st
import os
import zipfile
from pathlib import Path
import tempfile
import shutil

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"""
    # Remove the dot if user includes it
    if new_extension.startswith('.'):
        new_extension = new_extension[1:]
    
    # Get the base name without extension
    base_name = Path(original_name).stem
    
    # Create new filename
    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"""
    # Create a temporary directory
    with tempfile.TemporaryDirectory() as temp_dir:
        zip_path = os.path.join(temp_dir, "converted_files.zip")
        
        with zipfile.ZipFile(zip_path, 'w') as zipf:
            for filename, content in files_data:
                zipf.writestr(filename, content)
        
        # Read the zip file content
        with open(zip_path, 'rb') as f:
            zip_content = f.read()
    
    return zip_content

def main():
    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:
        # Validate 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")
            return
        
        st.success(f"✅ Converting to: **{full_extension}**")
        
        # Process files
        converted_files = []
        results_data = []
        
        st.header("📁 Conversion Results")
        
        for uploaded_file in uploaded_files:
            original_name = uploaded_file.name
            file_content = uploaded_file.read()
            
            # Convert extension
            new_filename, new_content = change_file_extension(
                file_content, original_name, new_extension
            )
            
            converted_files.append((new_filename, new_content))
            
            # Display result
            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()
        
        # Download options
        st.header("💾 Download")
        
        if len(converted_files) == 1:
            # Single file download
            filename, content = converted_files[0]
            st.download_button(
                label=f"📥 Download {filename}",
                data=content,
                file_name=filename,
                mime="application/octet-stream"
            )
        else:
            # Multiple files - create zip
            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")
    
    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")
    
    # Footer
    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)

if __name__ == "__main__":
    main()