"""
Main Import Service - coordinates all CSV importers
"""
from typing import Dict, List, Any, Optional, Union
import logging
from enum import Enum
from sqlalchemy.orm import Session

from .base import ImportResult
from .rolodex_importer import RolodexCSVImporter
from .phone_importer import PhoneCSVImporter
from .files_importer import FilesCSVImporter
from .ledger_importer import LedgerCSVImporter
from .qdros_importer import QdrosCSVImporter

logger = logging.getLogger(__name__)


class TableType(Enum):
    """Supported table types for import"""
    ROLODEX = "rolodex"
    PHONE = "phone"
    FILES = "files"
    LEDGER = "ledger"
    QDROS = "qdros"


class ImportService:
    """Main service for handling CSV imports"""
    
    def __init__(self, db_session: Session):
        self.db_session = db_session
        self._importers = {
            TableType.ROLODEX: RolodexCSVImporter,
            TableType.PHONE: PhoneCSVImporter,
            TableType.FILES: FilesCSVImporter,
            TableType.LEDGER: LedgerCSVImporter,
            TableType.QDROS: QdrosCSVImporter
        }
        
    def get_supported_tables(self) -> List[str]:
        """Get list of supported table names"""
        return [table.value for table in TableType]
        
    def get_table_schema(self, table_name: str) -> Optional[Dict[str, Any]]:
        """Get schema information for a table"""
        try:
            table_type = TableType(table_name.lower())
            importer_class = self._importers[table_type]
            temp_importer = importer_class(self.db_session, "temp_schema_check")
            
            return {
                "table_name": temp_importer.table_name,
                "required_fields": temp_importer.required_fields,
                "field_mapping": temp_importer.field_mapping,
                "sample_headers": list(temp_importer.field_mapping.keys())
            }
        except (ValueError, KeyError):
            return None
            
    def import_csv(
        self, 
        table_name: str, 
        csv_content: str, 
        encoding: str = "utf-8",
        import_id: Optional[str] = None
    ) -> ImportResult:
        """Import CSV data to specified table"""
        
        try:
            # Validate table name
            table_type = TableType(table_name.lower())
        except ValueError:
            result = ImportResult()
            result.add_error(f"Unsupported table: {table_name}")
            return result
            
        # Get appropriate importer
        importer_class = self._importers[table_type]
        importer = importer_class(self.db_session, import_id)
        
        logger.info(f"Starting CSV import for table: {table_name} (import_id: {importer.import_id})")
        
        try:
            # Process the CSV
            result = importer.process_csv_content(csv_content, encoding)
            
            if result.success:
                logger.info(
                    f"Successfully imported {result.imported_rows} rows to {table_name}"
                )
            else:
                logger.warning(
                    f"Import failed for {table_name}: {len(result.errors)} errors"
                )
                
            return result
            
        except Exception as e:
            logger.error(f"Unexpected error during import to {table_name}: {str(e)}")
            result = ImportResult()
            result.add_error(f"Unexpected error: {str(e)}")
            return result
            
    def batch_import(
        self, 
        imports: List[Dict[str, Any]]
    ) -> Dict[str, ImportResult]:
        """
        Import multiple CSV files in a batch
        
        Args:
            imports: List of dicts with keys: table_name, csv_content, encoding
            
        Returns:
            Dict mapping table names to ImportResult objects
        """
        results = {}
        
        # Recommended import order (dependencies first)
        import_order = [
            TableType.ROLODEX,  # No dependencies
            TableType.PHONE,    # Depends on ROLODEX
            TableType.FILES,    # Depends on ROLODEX
            TableType.LEDGER,   # Depends on FILES
            TableType.QDROS     # Depends on FILES
        ]
        
        # Group imports by table type
        imports_by_table = {}
        for import_data in imports:
            table_name = import_data["table_name"].lower()
            if table_name not in imports_by_table:
                imports_by_table[table_name] = []
            imports_by_table[table_name].append(import_data)
            
        # Process in dependency order
        for table_type in import_order:
            table_name = table_type.value
            if table_name in imports_by_table:
                table_imports = imports_by_table[table_name]
                
                for import_data in table_imports:
                    result = self.import_csv(
                        table_name,
                        import_data["csv_content"],
                        import_data.get("encoding", "utf-8")
                    )
                    
                    # Use a unique key if multiple imports for same table
                    key = table_name
                    counter = 1
                    while key in results:
                        counter += 1
                        key = f"{table_name}_{counter}"
                        
                    results[key] = result
                    
                    # Stop processing if critical import fails
                    if not result.success and table_type in [TableType.ROLODEX, TableType.FILES]:
                        logger.error(f"Critical import failed for {table_name}, stopping batch")
                        break
                        
        return results
        
    def validate_csv_headers(self, table_name: str, csv_content: str) -> ImportResult:
        """Validate CSV headers without importing data"""
        try:
            table_type = TableType(table_name.lower())
        except ValueError:
            result = ImportResult()
            result.add_error(f"Unsupported table: {table_name}")
            return result
            
        # Get appropriate importer
        importer_class = self._importers[table_type]
        importer = importer_class(self.db_session, "validation_check")
        
        # Parse headers only
        import csv
        import io
        
        try:
            delimiter = importer.detect_delimiter(csv_content)
            csv_reader = csv.DictReader(io.StringIO(csv_content), delimiter=delimiter)
            headers = csv_reader.fieldnames or []
            
            if not headers:
                result = ImportResult()
                result.add_error("No headers found in CSV file")
                return result
                
            # Validate headers
            result = ImportResult()
            is_valid = importer.validate_headers(headers)
            result.success = is_valid
            
            if is_valid:
                result.add_warning(f"Headers validated successfully for {table_name}")
                
            return result
            
        except Exception as e:
            result = ImportResult()
            result.add_error(f"Error validating headers: {str(e)}")
            return result