import os
import uvicorn
import inspect

from mcp.server.fastmcp import FastMCP
from starlette.requests import Request
from starlette.responses import PlainTextResponse, JSONResponse

from langchain_community.utilities import SQLDatabase
from langchain_community.tools.sql_database.tool import QuerySQLCheckerTool
from langchain_openai import ChatOpenAI

llm = ChatOpenAI(
    api_key=os.environ.get('OPENAI_API_KEY', None),
    base_url=os.environ['OPENAI_BASE_URL'],
    model='gpt-4o-mini',
    temperature=0
)

# Create an MCP server and the tool registry
mcp = FastMCP("Credit Card Database Server")
tool_registry = []

def register_tool(fn):
    """Decorator to register tool metadata and with MCP."""
    # Register with MCP
    mcp.tool()(fn)
    # Save metadata
    sig = inspect.signature(fn)
    params = [
        {
            "name": param.name,
            "type": str(param.annotation) if param.annotation is not inspect._empty else "Any",
            "default": param.default if param.default is not inspect._empty else None,
        }
        for param in sig.parameters.values()
    ]
    tool_registry.append({
        "name": fn.__name__,
        "description": fn.__doc__.strip() if fn.__doc__ else "",
        "parameters": params,
    })
    return fn

credit_card_db = SQLDatabase.from_uri(r"sqlite:///data/ccms.db")
query_checker_tool = QuerySQLCheckerTool(db=credit_card_db, llm=llm)

@mcp.custom_route("/", methods=["GET"])
async def home(request: Request) -> PlainTextResponse:
    return PlainTextResponse(
        """
        Credit Card Database MCP Server
        ----
        Use the following URL to connect with this server
        https://pgurazada1-credit-card-database-mcp-server.hf.space/mcp/
        
        Access the following URL for a list of tools and their documentation.
        https://pgurazada1-credit-card-database-mcp-server.hf.space/tools/
        """
    )

@register_tool
def sql_db_list_tables():
    """
    Returns a comma-separated list of table names in the database.
    """
    return credit_card_db.get_usable_table_names()

@register_tool
def sql_db_schema(table_names: list[str]) -> str:
    """
    Input 'table_names_str' is a comma-separated string of table names.
    Returns the DDL SQL schema for these tables.
    """
    return credit_card_db.get_table_info(table_names)

@register_tool
def sql_db_query_checker(query: str) -> str:
    """
    Input 'query' is a SQL query string.
    Checks if the query is valid.
    If the query is valid, it returns the original query.
    If the query is not valid, it returns the corrected query.
    This tool is used to ensure the query is valid before executing it.
    """
    return query_checker_tool.run(query)

@register_tool
def sql_db_query(query: str) -> str:
    """
    Input 'query' is a SQL query string.
    Executes the query (SELECT only) and returns the result.
    """
    return credit_card_db.run(query)

@mcp.custom_route("/tools", methods=["GET"])
async def list_tools(request: Request) -> JSONResponse:
    """Return all registered tool metadata as JSON."""
    return JSONResponse(tool_registry)

if __name__ == "__main__":
    uvicorn.run(mcp.streamable_http_app, host="0.0.0.0", port=8000)