# MongoDB Multi-Tenant Support Module

from typing import Any, Dict, List, Tuple


class MongoTenantHelper:
    """Helper class for MongoDB multi-tenant operations"""
    
    @staticmethod
    def add_tenant_fields(data: Dict[str, Any], tenant_id: str, kb_id: str) -> Dict[str, Any]:
        """Add tenant_id and kb_id fields to a document"""
        data["tenant_id"] = tenant_id
        data["kb_id"] = kb_id
        return data
    
    @staticmethod
    def get_tenant_filter(tenant_id: str, kb_id: str, additional_filter: Dict = None) -> Dict:
        """Build a MongoDB filter for tenant and KB"""
        filter_dict = {
            "tenant_id": tenant_id,
            "kb_id": kb_id
        }
        if additional_filter:
            filter_dict.update(additional_filter)
        return filter_dict
    
    @staticmethod
    def create_tenant_indexes(collection_name: str) -> List[Dict[str, str]]:
        """Get recommended indexes for tenant isolation"""
        return [
            {
                "name": f"idx_{collection_name}_tenant_kb",
                "keys": [("tenant_id", 1), ("kb_id", 1)]
            },
            {
                "name": f"idx_{collection_name}_tenant_kb_id",
                "keys": [("tenant_id", 1), ("kb_id", 1), ("_id", 1)]
            },
        ]
    
    @staticmethod
    def build_upsert_with_tenant(
        filter_dict: Dict,
        update_dict: Dict,
        tenant_id: str,
        kb_id: str
    ) -> Tuple[Dict, Dict]:
        """Build filter and update dictionaries for upsert operations"""
        filter_dict["tenant_id"] = tenant_id
        filter_dict["kb_id"] = kb_id
        
        update_dict["$set"]["tenant_id"] = tenant_id
        update_dict["$set"]["kb_id"] = kb_id
        
        return filter_dict, update_dict

# ============================================================================
# MIGRATION HELPER FOR EXISTING MONGODB COLLECTIONS
# ============================================================================

async def add_tenant_fields_to_collection(
    db,
    collection_name: str,
    default_tenant_id: str = "default",
    default_kb_id: str = "default"
):
    """
    Add tenant_id and kb_id fields to existing MongoDB collection.
    
    This is a one-time migration operation that adds the new fields
    to all documents in the collection with default values.
    """
    collection = db[collection_name]
    
    # Check if any document already has tenant_id field
    sample = await collection.find_one({"tenant_id": {"$exists": True}})
    
    if not sample:
        # Perform bulk update to add tenant fields to all documents
        result = await collection.update_many(
            {"tenant_id": {"$exists": False}},
            {
                "$set": {
                    "tenant_id": default_tenant_id,
                    "kb_id": default_kb_id
                }
            }
        )
        return {
            "modified": result.modified_count,
            "status": "migration_completed"
        }
    else:
        return {"status": "already_migrated"}


async def create_tenant_indexes_on_collection(db, collection_name: str):
    """Create multi-tenant indexes on a MongoDB collection"""
    collection = db[collection_name]
    
    # Create indexes
    indexes = MongoTenantHelper.create_tenant_indexes(collection_name)
    
    for index in indexes:
        try:
            await collection.create_index(
                index["keys"],
                name=index["name"],
                background=True
            )
        except Exception as e:
            print(f"Warning: Could not create index {index['name']}: {e}")