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Chat service for conversation and message management.
Per @specs/001-chatbot-mcp/plan.md and @specs/001-chatbot-mcp/data-model.md
"""
from sqlmodel import Session, select
from typing import List, Optional
from datetime import datetime
from uuid import UUID, uuid4
import re
import logging
from models.conversation import ConversationTable
from models.message import MessageTable, MessageRole
from config import engine
logger = logging.getLogger(__name__)
class ChatService:
"""
Service for chat business logic.
Handles conversation creation, message storage, history retrieval,
and input sanitization per @specs/001-chatbot-mcp/plan.md.
"""
@staticmethod
def create_conversation(session: Session, user_id: UUID, title: Optional[str] = None) -> ConversationTable:
"""
Create a new conversation for a user.
Args:
session: Database session
user_id: Owner's user ID (from JWT)
title: Optional conversation title
Returns:
Created conversation with user_id set
"""
conversation = ConversationTable(
id=uuid4(),
user_id=user_id,
title=title,
created_at=datetime.utcnow(),
updated_at=datetime.utcnow()
)
session.add(conversation)
session.commit()
session.refresh(conversation)
logger.info(f"Created conversation {conversation.id} for user {user_id}")
return conversation
@staticmethod
def get_conversation(session: Session, conversation_id: UUID, user_id: UUID) -> Optional[ConversationTable]:
"""
Retrieve a conversation if it belongs to the user.
Critical for security - enforces user ownership check.
Per @specs/001-chatbot-mcp/data-model.md data isolation requirements.
Args:
session: Database session
conversation_id: Conversation ID to retrieve
user_id: User requesting the conversation (for ownership verification)
Returns:
Conversation if found and owned by user, None otherwise
"""
return session.query(ConversationTable).filter(
ConversationTable.id == conversation_id,
ConversationTable.user_id == user_id # Critical for security
).first()
@staticmethod
def store_message(
session: Session,
conversation_id: UUID,
role: MessageRole,
content: str,
metadata: Optional[dict] = None
) -> MessageTable:
"""
Store a message in the conversation.
Args:
session: Database session
conversation_id: ID of the conversation
role: Message role (user or assistant)
content: Message content
metadata: Optional metadata for tool calls, token usage, etc.
Returns:
Created message
"""
message = MessageTable(
id=uuid4(),
conversation_id=conversation_id,
role=role,
content=content,
created_at=datetime.utcnow(),
tool_metadata=metadata
)
session.add(message)
# Update conversation's updated_at timestamp
conversation = session.get(ConversationTable, conversation_id)
if conversation:
conversation.updated_at = datetime.utcnow()
session.commit()
session.refresh(message)
logger.debug(f"Stored {role.value} message in conversation {conversation_id}")
return message
@staticmethod
def get_conversation_history(
session: Session,
conversation_id: UUID,
user_id: UUID,
limit: int = 100
) -> List[MessageTable]:
"""
Get message history for a conversation.
Enforces user ownership check before returning messages.
Per @specs/001-chatbot-mcp/plan.md stateless architecture requirements.
Args:
session: Database session
conversation_id: ID of the conversation
user_id: User requesting the history (for ownership verification)
limit: Maximum number of messages to return (default: 100)
Returns:
List of messages in chronological order, empty list if not found
Raises:
ValueError: If conversation doesn't belong to user
"""
# First verify user owns the conversation
conversation = ChatService.get_conversation(session, conversation_id, user_id)
if not conversation:
logger.warning(f"User {user_id} attempted to access conversation {conversation_id}")
return []
# Get messages ordered by created_at
statement = (
select(MessageTable)
.where(MessageTable.conversation_id == conversation_id)
.order_by(MessageTable.created_at.asc())
.limit(limit)
)
messages = session.exec(statement).all()
logger.info(f"Retrieved {len(messages)} messages for conversation {conversation_id}")
return messages
@staticmethod
def get_user_conversations(
session: Session,
user_id: UUID,
limit: int = 20
) -> List[ConversationTable]:
"""
Get all conversations for a user, ordered by updated_at desc.
Args:
session: Database session
user_id: User's ID
limit: Maximum number of conversations to return
Returns:
List of conversations, most recently updated first
"""
statement = (
select(ConversationTable)
.where(ConversationTable.user_id == user_id)
.order_by(ConversationTable.updated_at.desc())
.limit(limit)
)
return session.exec(statement).all()
@staticmethod
def sanitize_user_input(user_input: str) -> str:
"""
Sanitize user input to prevent prompt injection attacks.
Per @specs/001-chatbot-mcp/plan.md security requirements.
Removes or escapes potentially dangerous patterns.
Args:
user_input: Raw user input
Returns:
Sanitized input safe for use in AI prompts
"""
if not user_input:
return ""
# Remove null bytes
sanitized = user_input.replace("\x00", "")
# Limit length to prevent DoS
max_length = 5000
if len(sanitized) > max_length:
sanitized = sanitized[:max_length]
logger.warning(f"Truncated user input from {len(user_input)} to {max_length} chars")
# Remove excessive whitespace
sanitized = re.sub(r"\s+", " ", sanitized).strip()
# Check for obvious prompt injection patterns
injection_patterns = [
r"ignore\s+(all\s+)?(previous|above)",
r"disregard\s+(all\s+)?(previous|above)",
r"forget\s+(everything|all\s+instructions)",
r"<\|.*?\|>", # Special delimiter patterns
r"<<.*?>>", # Another delimiter pattern
]
for pattern in injection_patterns:
if re.search(pattern, sanitized, re.IGNORECASE):
logger.warning(f"Detected potential prompt injection: {pattern}")
# Don't block, but could add additional monitoring here
return sanitized
@staticmethod
def format_messages_for_openai(messages: List[MessageTable]) -> List[dict]:
"""
Format database messages for OpenAI API.
Converts MessageTable objects to OpenAI message format.
Args:
messages: List of MessageTable objects
Returns:
List of message dicts in OpenAI format
"""
formatted = []
for msg in messages:
formatted.append({
"role": msg.role.value, # "user" or "assistant"
"content": msg.content
})
return formatted
# Singleton instance for convenience
chat_service = ChatService()
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