import os
import streamlit as st
import pandas as pd
import numpy as np
from io import BytesIO
import tempfile

# Optional: PDF extraction if needed
try:
    import pdfplumber
except ImportError:
    pdfplumber = None

# FAISS for potential vector similarity (for future enhancement)
import faiss

# Groq API for LLM integration
from groq import Groq

# -------------------------------
# Initialize Groq Client
# -------------------------------
client = Groq(api_key=os.environ.get("GROQ_API_KEY"))

# -------------------------------
# Utility Functions
# -------------------------------

def load_ledger(file):
    """
    Load ledger from CSV, JSON, or PDF.
    """
    file_ext = os.path.splitext(file.name)[1].lower()
    if file_ext == ".csv":
        df = pd.read_csv(file)
    elif file_ext == ".json":
        df = pd.read_json(file)
    elif file_ext == ".pdf":
        if pdfplumber is None:
            st.error("Please install pdfplumber to process PDF files.")
            return None
        with pdfplumber.open(file) as pdf:
            page = pdf.pages[0]  # Assumes table on first page
            table = page.extract_table()
            df = pd.DataFrame(table[1:], columns=table[0])
    else:
        st.error("Unsupported file type!")
        return None
    return df

def preprocess_ledger(df):
    """
    Standardize date format and convert credit/debit to float.
    """
    df['date'] = pd.to_datetime(df['date'], errors='coerce')
    df['credit'] = pd.to_numeric(df['credit'], errors='coerce').fillna(0.0)
    df['debit'] = pd.to_numeric(df['debit'], errors='coerce').fillna(0.0)
    return df

def generate_suggestion(row):
    """
    Generate a reconciliation suggestion using Groq API.
    """
    prompt = (
        f"Ledger entry mismatch detected.\n"
        f"- Date: {row['date'].date() if pd.notnull(row['date']) else 'Unknown'}\n"
        f"- Credit: {row['credit']}\n"
        f"- Debit: {row['debit']}\n\n"
        "Please provide reconciliation suggestions in simple bullet points."
    )
    try:
        response = client.chat.completions.create(
            messages=[{"role": "user", "content": prompt}],
            model="llama-3.3-70b-versatile",
            stream=False,
        )
        suggestion = response.choices[0].message.content
    except Exception as e:
        suggestion = f"Error generating suggestion: {e}"
    return suggestion

def compare_ledgers(df_a, df_b):
    """
    Compare two ledger DataFrames row-by-row based on date, credit, and debit.
    """
    results = []
    df_b_copy = df_b.copy()

    # Compare each entry in Ledger A with Ledger B
    for idx, row in df_a.iterrows():
        # Match based on same date and nearly identical credit & debit amounts.
        match = df_b_copy[
            (df_b_copy['date'] == row['date']) &
            (np.isclose(df_b_copy['credit'], row['credit'])) &
            (np.isclose(df_b_copy['debit'], row['debit']))
        ]
        if not match.empty:
            status = "✅ Matched"
            suggestion = ""
            # Remove matched entry to prevent duplicate matching.
            df_b_copy = df_b_copy.drop(match.index[0])
        else:
            status = "❌ Mismatch"
            suggestion = generate_suggestion(row)
        results.append({
            "date": row['date'],
            "credit": row['credit'],
            "debit": row['debit'],
            "description": row.get("description", ""),
            "status": status,
            "suggestion": suggestion
        })

    # Any remaining entries in Ledger B are extra entries.
    for idx, row in df_b_copy.iterrows():
        results.append({
            "date": row['date'],
            "credit": row['credit'],
            "debit": row['debit'],
            "description": row.get("description", ""),
            "status": "❌ Mismatch (Extra in Ledger B)",
            "suggestion": "Review extra entry in Ledger B."
        })

    result_df = pd.DataFrame(results)
    return result_df

def calculate_totals(df_a, df_b):
    """
    Calculate totals and differences for credits and debits.
    """
    totals = {
        "ledger_a_credit": df_a['credit'].sum(),
        "ledger_a_debit": df_a['debit'].sum(),
        "ledger_b_credit": df_b['credit'].sum(),
        "ledger_b_debit": df_b['debit'].sum(),
        "credit_difference": df_a['credit'].sum() - df_b['credit'].sum(),
        "debit_difference": df_a['debit'].sum() - df_b['debit'].sum(),
    }
    return totals

def generate_excel_report(df):
    """
    Generate an Excel report from the reconciliation DataFrame.
    """
    output = BytesIO()
    with pd.ExcelWriter(output, engine='xlsxwriter') as writer:
        df.to_excel(writer, index=False, sheet_name="Reconciliation")
    processed_data = output.getvalue()
    return processed_data

# -------------------------------
# Streamlit User Interface
# -------------------------------

def main():
    st.title("📊 Finance Ledger Reconciliation App")
    st.markdown("Upload the ledger files to compare two opposite party records and get reconciliation suggestions.")

    col1, col2 = st.columns(2)
    with col1:
        ledger_a_file = st.file_uploader("Upload Ledger A (CSV/JSON/PDF)", type=["csv", "json", "pdf"], key="ledger_a")
    with col2:
        ledger_b_file = st.file_uploader("Upload Ledger B (CSV/JSON/PDF)", type=["csv", "json", "pdf"], key="ledger_b")

    if ledger_a_file and ledger_b_file:
        df_a = load_ledger(ledger_a_file)
        df_b = load_ledger(ledger_b_file)

        if df_a is not None and df_b is not None:
            st.subheader("Original Ledgers Preview")
            st.markdown("**Ledger A:**")
            st.write(df_a.head())
            st.markdown("**Ledger B:**")
            st.write(df_b.head())

            # Preprocess the data
            df_a = preprocess_ledger(df_a)
            df_b = preprocess_ledger(df_b)

            st.subheader("Processed Ledgers Preview")
            st.markdown("**Ledger A:**")
            st.write(df_a.head())
            st.markdown("**Ledger B:**")
            st.write(df_b.head())

            # Compare ledgers and calculate differences
            with st.spinner("Comparing ledgers..."):
                result_df = compare_ledgers(df_a, df_b)
                totals = calculate_totals(df_a, df_b)

            st.subheader("Reconciliation Results")
            st.write(result_df)

            st.markdown("### Totals & Differences")
            st.write(totals)

            # Download report button (Excel file)
            excel_data = generate_excel_report(result_df)
            st.download_button(label="Download Report as Excel",
                               data=excel_data,
                               file_name="reconciliation_report.xlsx",
                               mime="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")

            st.success("Reconciliation completed successfully!")

if __name__ == '__main__':
    main()