import pandas as pd
import io
from flask import send_file


def update_forecast_history(session, train_percent, test_percent, forecast_periods, model_type, metrics,
                            add_to_existing=False):
    new_entry = {
        'train_percent': train_percent * 100,
        'test_percent': test_percent * 100,
        'forecast_periods': forecast_periods,
        'mae': metrics['MAE'] if metrics else None,
        'mse': metrics['MSE'] if metrics else None,
        'rmse': metrics['RMSE'] if metrics else None,
        'model_type': model_type
    }
    forecast_history = session.get('forecast_history', [])
    if not any(entry['train_percent'] == new_entry['train_percent'] and
               entry['test_percent'] == new_entry['test_percent'] and
               entry['forecast_periods'] == new_entry['forecast_periods'] and
               entry['model_type'] == new_entry['model_type']
               for entry in forecast_history):
        forecast_history.append(new_entry)
        session['forecast_history'] = forecast_history
        if add_to_existing:
            session['selected_indices'] = session.get('selected_indices', []) + [len(forecast_history) - 1]
        else:
            session['selected_indices'] = [len(forecast_history) - 1]
        session.modified = True


def download_forecast_history(session):
    forecast_history = session.get('forecast_history', [])
    if not forecast_history:
        return None, 'No forecast history available'

    # Create DataFrame for forecast history
    df = pd.DataFrame(forecast_history)
    df = df.rename(columns={
        'train_percent': 'Train Percent (%)',
        'test_percent': 'Test Percent (%)',
        'forecast_periods': 'Forecast Periods',
        'mae': 'MAE',
        'mse': 'MSE',
        'rmse': 'RMSE',
        'model_type': 'Model'
    })
    df.insert(0, 'Run', range(1, len(df) + 1))

    # Save to Excel
    output = io.BytesIO()
    df.to_excel(output, index=False)
    output.seek(0)

    return send_file(output,
                     mimetype='application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
                     as_attachment=True,
                     download_name='forecast_history.xlsx'), None