import streamlit as st
from diff_match_patch import diff_match_patch
import re

def main():
    st.set_page_config(page_title="Text Comparison Tool", layout="wide")
    st.title("Text Comparison Tool")

    # Initialize session state
    if 'old_text' not in st.session_state:
        st.session_state.old_text = ""
    if 'new_text' not in st.session_state:
        st.session_state.new_text = ""

    # Create two columns for text areas
    col1, col2 = st.columns(2)

    with col1:
        st.session_state.old_text = st.text_area(
            "Old Text:",
            height=300,
            value=st.session_state.old_text,
            placeholder="Enter original text..."
        )

    with col2:
        # Display diffs directly in the New Text area
        new_text_display = st.empty()
        
        # Show either editable text area or diff result
        if 'show_diff' not in st.session_state or not st.session_state.show_diff:
            st.session_state.new_text = new_text_display.text_area(
                "New Text:",
                height=300,
                value=st.session_state.new_text,
                placeholder="Enter modified text...",
                key="new_text_editable"
            )
        else:
            new_text_display.markdown(
                st.session_state.diff_html, 
                unsafe_allow_html=True
            )

    # Button controls
    col_compare, col_clear, col_copy = st.columns([1, 1, 1])
    
    with col_compare:
        if st.button("Compare"):
            dmp = diff_match_patch()
            diffs = dmp.diff_main(st.session_state.old_text, st.session_state.new_text)
            dmp.diff_cleanupSemantic(diffs)

            html = []
            for op, text in diffs:
                text = text.replace("\n", "<br>")
                if op == 1:  # Insertion
                    html.append(f'<span style="background-color: #c8e6c9; border-radius: 4px; padding: 2px 4px;">{text}</span>')
                elif op == -1:  # Deletion
                    html.append(f'<span style="background-color: #ffcdd2; text-decoration: line-through; border-radius: 4px; padding: 2px 4px;">{text}</span>')
                else:
                    html.append(text)
            
            st.session_state.diff_html = "".join(html)
            st.session_state.show_diff = True
            st.rerun()

    with col_clear:
        if st.button("Clear"):
            st.session_state.old_text = ""
            st.session_state.new_text = ""
            st.session_state.show_diff = False
            st.rerun()

    # Copy functionality
    with col_copy:
        if st.button("Copy Result"):
            if 'diff_html' in st.session_state:
                clean_text = re.sub(r'<br>', '\n', st.session_state.diff_html)
                clean_text = re.sub(r'<[^>]+>', '', clean_text)
                
                try:
                    import pyperclip
                    pyperclip.copy(clean_text)
                    st.success("Result copied to clipboard!")
                except:
                    st.error("Clipboard access requires extra permissions. Please copy manually:")
                    st.code(clean_text)
            else:
                st.warning("No comparison result to copy")

if __name__ == "__main__":
    main()