#
# SPDX-FileCopyrightText: Hadad <hadad@linuxmail.org>
# SPDX-License-Identifier: Apache-2.0
#

# Import APIRouter and HTTPException classes from FastAPI framework
# APIRouter is used to create modular route handlers
# HTTPException is used to generate HTTP error responses with specific status codes and details
from fastapi import APIRouter, HTTPException

# Import Optional type hint from typing module
# Optional is used to indicate that a function parameter can be of a specified type or None
from typing import Optional

# Import session_store dictionary from the sessions module located in src.cores package
# session_store holds active session data keyed by session identifiers
from src.cores.sessions import session_store

# Create an instance of APIRouter to define routes related to session history
router = APIRouter()

# Define an asynchronous GET endpoint at path "/history" to retrieve chat history for a session
@router.get("/history")
async def get_history(session_id: Optional[str] = None):
    """
    This function handles GET requests to fetch the chat history for a specific session.

    Parameters:
    - session_id (Optional[str]): A string representing the unique identifier of the session.
      This parameter is optional in the function signature but required for successful retrieval.

    Returns:
    - A JSON object containing:
      - "session_id": The provided session identifier string.
      - "history": A list of past input-response pairs stored in the session.

    Raises:
    - HTTPException with status code 404 and a descriptive message if:
      - The session_id is not provided (None or empty).
      - The session_id does not exist in the session_store dictionary, indicating no active session.
    """

    # Check if session_id is missing or does not exist in the session_store dictionary
    if not session_id or session_id not in session_store:
        # Raise an HTTP 404 Not Found error with a clear message indicating the issue
        raise HTTPException(status_code=404, detail="Session not found or session_id missing.")

    # Retrieve the session data tuple from session_store using the session_id key
    # The tuple contains two elements; the first is ignored here, the second is the session data dictionary
    _, session_data = session_store[session_id]

    # Return a dictionary with the session_id and the chat history extracted from the session data
    # This dictionary will be automatically converted to JSON by FastAPI when sending the response
    return {"session_id": session_id, "history": session_data["history"]}