import json
from pathlib import Path
from typing import Any

from config import MCPBundle
from mcp.server.fastmcp import FastMCP


class MCPServer:
    """MCP server serving a pre-built documentation bundle."""

    def __init__(self, bundle: MCPBundle) -> None:
        self.mcp_root = bundle.root
        self.app = FastMCP(
            name=f"{bundle.name}-mcp",
            host="0.0.0.0",
            port=bundle.port,
        )
        self._register_resources()
        self._register_tools()

    # ------------------------------------------------------------------
    # Helpers
    # ------------------------------------------------------------------

    def _read_json(self, path: Path) -> Any:
        if not path.exists():
            return {"error": "not_found", "path": str(path)}
        return json.loads(path.read_text(encoding="utf-8"))

    # ------------------------------------------------------------------
    # MCP resources
    # ------------------------------------------------------------------

    def _register_resources(self) -> None:
        @self.app.resource("doc://index")
        def index():
            return self._read_json(self.mcp_root / "index.json")

        @self.app.resource("doc://nav")
        def nav():
            return self._read_json(self.mcp_root / "nav.json")

        @self.app.resource("doc://modules/{module}")
        def module(module: str):
            return self._read_json(self.mcp_root / "modules" / f"{module}.json")

    # ------------------------------------------------------------------
    # MCP tools
    # ------------------------------------------------------------------

    def _register_tools(self) -> None:
        @self.app.tool()
        def ping() -> str:
            return "pong"

    # ------------------------------------------------------------------
    # ASGI exposure
    # ------------------------------------------------------------------

    @property
    def asgi(self):
        return self.app