"""
A low-level MCP Server exposing prompts over Streamable HTTP, without FastMCP or any frameowkrs
Note that SSE, Server-Sent Events, is depreciated by MCP now - it keeps the seesion alive and cost more in cloud deployment
Streamable HTTP is the new way to go

Example source :https://github.com/modelcontextprotocol/python-sdk/blob/main/examples/servers/simple-streamablehttp-stateless/mcp_simple_streamablehttp_stateless/server.py

Author: Alex Punnen
Status:  Demo
"""

from mcp.server.lowlevel import Server
from mcp.server.streamable_http_manager import StreamableHTTPSessionManager
from starlette.applications import Starlette
import uvicorn
from starlette.routing import Mount
from starlette.types import Receive, Scope, Send
from collections.abc import AsyncIterator
import contextlib
import mcp.types as types

def main(port: int = 4200) -> int:
    
    #---------------------------------------------------------------------------------------
    #   Define the MCP Application and add the artifacts to expose
    #   to the MCP Client . In this case it is just the prompts
    #   see - https://github.com/modelcontextprotocol/python-sdk/?tab=readme-ov-file#prompts
    #---------------------------------------------------------------------------------------

    app = Server("mcp-server")

    # Add an  tool
    @app.call_tool()
    async def add(name: str, arguments: dict) -> int:
        # see https://github.com/modelcontextprotocol/python-sdk/blob/6353dd192c41b891ef3bf1dfc093db46f6e2175a/examples/servers/simple-tool/mcp_simple_tool/server.py#L31
        """Add two numbers"""
        print(f"Server received: a={name} (type={type(name)}), arguments={arguments} (type={type(arguments)})") # 
        if name != "add":
            raise ValueError(f"Unknown tool: {name}")
        result =  int(arguments["a"]) + int(arguments["b"])
        return [types.TextContent(type='text', text=str(result))]

    @app.list_tools()
    async def list_tools() -> list[types.Tool]:
        return [
            types.Tool(
                name="add",
                description=(
                    "add two numbers and return the result. "
                    
                ),
                inputSchema={
                    "type": "object",
                    "required": ["a", "b"],
                    "properties": {
                        "a": {
                            "type": "integer",
                            "description": "The first number to add",
                        },
                        "b": {
                            "type": "integer",
                            "description": "The second number to add",
                        },
                    },
                },
            )
        ]
#---------------------------------------------------------------------------------------
#   ALL Boilerplate code below
#---------------------------------------------------------------------------------------

   # Create the session manager with true stateless mode
    session_manager = StreamableHTTPSessionManager(
        app=app,
        event_store=None,
        json_response=True,
        stateless=True,
    )

    async def handle_streamable_http(
        scope: Scope, receive: Receive, send: Send
    ) -> None:
        await session_manager.handle_request(scope, receive, send)

    @contextlib.asynccontextmanager
    async def lifespan(app: Starlette) -> AsyncIterator[None]:
        """Context manager for session manager."""
        async with session_manager.run():
            print("Application started with StreamableHTTP session manager!")
            try:
                yield
            
            finally:
                print("Application shutting down...")

    # Create an ASGI application using the transport
    starlette_app = Starlette(
        debug=True,
        routes=[
            Mount("/mcp", app=handle_streamable_http),
        ],
        lifespan=lifespan,
    )

    # 3) Launch via Uvicorn
    uvicorn.run(starlette_app, host="0.0.0.0", port=port)

    return 0

if __name__ == "__main__":
    main()