"""Export Utilities - CSV, Excel, and REAL Power BI export"""

import pandas as pd
import io
import json
from datetime import datetime

class ExportUtils:
    def __init__(self, df):
        self.df = df
        
    def to_csv(self):
        """Export to CSV"""
        return self.df.to_csv(index=False).encode('utf-8')
    
    def to_excel(self):
        """Export to Excel with formatting"""
        output = io.BytesIO()
        with pd.ExcelWriter(output, engine='openpyxl') as writer:
            # Write main data
            self.df.to_excel(writer, sheet_name='Data', index=False)
            
            # Add summary sheet
            numeric_cols = self.df.select_dtypes(include=['number']).columns
            if len(numeric_cols) > 0:
                summary = self.df[numeric_cols].describe()
                summary.to_excel(writer, sheet_name='Summary', index=True)
            
            # Add column info sheet
            col_info = pd.DataFrame({
                'Column': self.df.columns,
                'Type': self.df.dtypes.astype(str),
                'Nulls': self.df.isnull().sum(),
                'Unique': self.df.nunique()
            })
            col_info.to_excel(writer, sheet_name='Column Info', index=False)
        
        output.seek(0)
        return output.getvalue()
    
    def to_powerbi_ready(self):
        """Prepare data for Power BI - Creates CSV optimized for Power BI"""
        df_powerbi = self.df.copy()
        
        # Clean column names (Power BI friendly)
        df_powerbi.columns = [col.replace(' ', '_').replace('-', '_').replace('/', '_') for col in df_powerbi.columns]
        
        # Clean datetime columns for Power BI
        for col in df_powerbi.columns:
            if 'datetime' in col.lower() or 'date' in col.lower() or 'time' in col.lower():
                try:
                    df_powerbi[col] = pd.to_datetime(df_powerbi[col])
                except:
                    pass
        
        # Convert to CSV for Power BI import
        return df_powerbi.to_csv(index=False).encode('utf-8')
    
    def to_powerbi_with_metadata(self):
        """Export to Power BI with metadata file"""
        # Main data CSV
        data_csv = self.to_powerbi_ready()
        
        # Create metadata JSON
        numeric_cols = self.df.select_dtypes(include=['number']).columns
        categorical_cols = self.df.select_dtypes(include=['object']).columns
        date_cols = self.df.select_dtypes(include=['datetime64']).columns
        
        metadata = {
            'export_date': datetime.now().isoformat(),
            'table_name': 'Cleaned_Data',
            'row_count': len(self.df),
            'column_count': len(self.df.columns),
            'columns': list(self.df.columns),
            'numeric_columns': list(numeric_cols),
            'categorical_columns': list(categorical_cols),
            'date_columns': list(date_cols),
            'recommended_measures': {},
            'recommended_visuals': []
        }
        
        # Add recommended measures
        for col in numeric_cols[:10]:
            metadata['recommended_measures'][f'Total_{col}'] = f'SUM(Cleaned_Data[{col}])'
            metadata['recommended_measures'][f'Average_{col}'] = f'AVERAGE(Cleaned_Data[{col}])'
        
        # Add recommended visuals
        if len(categorical_cols) > 0 and len(numeric_cols) > 0:
            metadata['recommended_visuals'].append({
                'type': 'bar_chart',
                'category': categorical_cols[0],
                'value': numeric_cols[0],
                'title': f'{numeric_cols[0]} by {categorical_cols[0]}'
            })
        
        if len(date_cols) > 0 and len(numeric_cols) > 0:
            metadata['recommended_visuals'].append({
                'type': 'line_chart',
                'date': date_cols[0],
                'value': numeric_cols[0],
                'title': f'{numeric_cols[0]} Over Time'
            })
        
        metadata_json = json.dumps(metadata, indent=2).encode('utf-8')
        
        return {
            'data': data_csv,
            'metadata': metadata_json,
            'instructions': self._get_powerbi_instructions()
        }
    
    def _get_powerbi_instructions(self):
        """Get step-by-step Power BI import instructions"""
        instructions = """
=== POWER BI IMPORT INSTRUCTIONS ===

METHOD 1: Direct Import (Recommended)
1. Open Power BI Desktop
2. Click "Get Data" → "Text/CSV"
3. Select the exported CSV file
4. Click "Load"
5. Power BI will auto-detect data types

METHOD 2: Advanced Import
1. Click "Get Data" → "More..."
2. Search for "CSV" or "Text"
3. Select your file
4. Configure:
   - First row as headers: YES
   - Data type detection: Based on first 200 rows
5. Click "Load"

=== AFTER IMPORT ===

Recommended DAX Measures to Create:

"""
        return instructions
    
    def to_powerbi_zip(self):
        """Create a zip file with all Power BI resources"""
        import zipfile
        
        output = io.BytesIO()
        with zipfile.ZipFile(output, 'w', zipfile.ZIP_DEFLATED) as zipf:
            #Add data CSV
            data_csv = self.to_powerbi_ready()
            zipf.writestr('data.csv', data_csv)
            
            #Add metadata
            powerbi_data = self.to_powerbi_with_metadata()
            zipf.writestr('metadata.json', powerbi_data['metadata'])
            
            #Add instructions
            zipf.writestr('instructions.txt', powerbi_data['instructions'])
            
            #Add sample DAX file
            dax_content = self._generate_dax_file()
            zipf.writestr('measures.dax', dax_content)
        
        output.seek(0)
        return output.getvalue()
    
    def _generate_dax_file(self):
        """Generate DAX file for Power BI"""
        numeric_cols = self.df.select_dtypes(include=['number']).columns
        
        dax = f"""// DAX Measures for Power BI
// Generated on: {datetime.now().strftime('%Y-%m-%d %H:%M:%S')}
// Table Name: Cleaned_Data

// ============ BASIC MEASURES ============

Total Records = COUNTROWS(Cleaned_Data)

"""
        
        for col in numeric_cols[:15]:
            dax += f"""
// {col} Measures
Total {col} = SUM(Cleaned_Data[{col}])
Average {col} = AVERAGE(Cleaned_Data[{col}])
Min {col} = MIN(Cleaned_Data[{col}])
Max {col} = MAX(Cleaned_Data[{col}])

"""
        
        dax += """
// ============ HOW TO USE ============
// 1. In Power BI, go to "Modeling" tab
// 2. Click "New Measure"
// 3. Copy-paste any measure above
// 4. Press Enter to save

// ============ EXAMPLE VISUALS ============
// - Card Visual: Total Records
// - Bar Chart: Category vs Total Sales
// - Line Chart: Date vs Average Value
"""
        
        return dax
    
    def to_json(self):
        """Export to JSON"""
        return self.df.to_json(orient='records', indent=2).encode('utf-8')
    
    def get_powerbi_template(self):
        """Get Power BI DAX template (legacy - kept for compatibility)"""
        numeric_cols = self.df.select_dtypes(include=['number']).columns
        categorical_cols = self.df.select_dtypes(include=['object']).columns
        
        template = f"""// Power BI DAX Template for your data
// Generated on: {datetime.now().strftime('%Y-%m-%d %H:%M:%S')}
// Table name: Cleaned_Data

// ============ BASIC MEASURES ============

Total Records = COUNTROWS(Cleaned_Data)

"""
        
        for col in numeric_cols[:10]:
            template += f"""
Total {col} = SUM(Cleaned_Data[{col}])
Average {col} = AVERAGE(Cleaned_Data[{col}])
"""
        
        template += """
// ============ HOW TO USE ============
// 1. Export your data as CSV first
// 2. In Power BI: Get Data → CSV → Select your file
// 3. Go to Modeling tab → New Measure
// 4. Copy and paste any measure above
// 5. Drag measures to visuals

// ============ RECOMMENDED VISUALS ============
"""
        
        if len(categorical_cols) > 0 and len(numeric_cols) > 0:
            template += f"""
- Bar Chart: {categorical_cols[0]} vs {numeric_cols[0]}
"""
        
        if len(self.df.select_dtypes(include=['datetime64']).columns) > 0:
            template += f"""
- Line Chart: Date vs {numeric_cols[0] if len(numeric_cols) > 0 else 'Value'}
"""
        
        return template