app.py

# app.py
# Hugging Face Space: Gradio app that chats about Gradio docs via the Gradio Docs MCP server.
# Features:
#   • MCP tool-calling (connects to the official Gradio Docs MCP SSE server)
#   • Streaming responses with live tool logs
#   • Optional "Concise / Detailed" answer style
#   • Lightweight citations panel (summarizes MCP tool hits)
#
# Requirements (in requirements.txt):
#   gradio>=4.44.0
#   huggingface_hub>=0.24.0
#
# Space secrets needed:
#   - HUGGING_FACE_HUB_TOKEN or HF_TOKEN  (token must allow using the selected provider/model)
#
# Notes:
#   - The default model/provider below are known to work with chat + tool calling via the HF router.
#   - You can override via Space Secrets: CHAT_MODEL, CHAT_PROVIDER, GRADIO_DOCS_MCP_SSE.

import os
import asyncio
from typing import Any, Dict, Iterable, List, Optional, Tuple

import gradio as gr
from huggingface_hub import MCPClient

# ----------------------------
# Configuration
# ----------------------------
GRADIO_DOCS_MCP_SSE = os.environ.get(
    "GRADIO_DOCS_MCP_SSE",
    "https://gradio-docs-mcp.hf.space/gradio_api/mcp/sse",
)

# Use a router model that supports OpenAI-style chat + tool calling.
MODEL_ID = os.environ.get("CHAT_MODEL", "Qwen/Qwen2.5-7B-Instruct")
PROVIDER = os.environ.get("CHAT_PROVIDER", "hf-inference")  # router
HF_TOKEN = os.environ.get("HF_TOKEN") or os.environ.get("HUGGING_FACE_HUB_TOKEN")

BASE_SYSTEM_PROMPT = (
    "You are a helpful assistant that answers strictly using the Gradio documentation "
    "via the MCP tools provided by the Gradio Docs MCP server. Prefer the latest docs. "
    "Cite relevant class/function names (e.g., gr.Interface) and include short code examples when helpful."
)
CONCISE_SUFFIX = " Keep answers concise (3–6 sentences) unless code is necessary."
DETAILED_SUFFIX = " Provide a detailed, step-by-step answer with short code where helpful."

# ----------------------------
# MCP Client (lazy init, reconfigurable)
# ----------------------------
mcp_client: Optional[MCPClient] = None
_initialized = False
_init_lock = asyncio.Lock()

def _current_system_prompt(style: str) -> str:
    return BASE_SYSTEM_PROMPT + (CONCISE_SUFFIX if style == "Concise" else DETAILED_SUFFIX)

def _reset_client():
    """Reset the global client so a new one is created with updated env (if any)."""
    global mcp_client, _initialized
    mcp_client = None
    _initialized = False

def get_mcp_client(model_id: str, provider: str, api_key: Optional[str]) -> MCPClient:
    global mcp_client
    if mcp_client is None:
        mcp_client = MCPClient(model=model_id, provider=provider, api_key=api_key)
    return mcp_client

async def ensure_init(model_id: str, provider: str, api_key: Optional[str]):
    """Attach the Gradio Docs MCP server exactly once."""
    global _initialized
    if _initialized:
        return
    async with _init_lock:
        if _initialized:
            return
        client = get_mcp_client(model_id, provider, api_key)
        # add_mcp_server may be a coroutine; await to avoid warnings
        await client.add_mcp_server(
            type="sse",
            url=GRADIO_DOCS_MCP_SSE,
            timeout=45,
        )
        _initialized = True

# ----------------------------
# Message helpers
# ----------------------------
def to_llm_messages(history_msgs: List[Dict[str, Any]], user_msg: str, style: str) -> List[Dict[str, Any]]:
    """
    Convert Chatbot messages list (role/content dicts) to the LLM format,
    with a system message prepended and the new user message appended.
    """
    msgs: List[Dict[str, Any]] = [{"role": "system", "content": _current_system_prompt(style)}]
    for m in history_msgs or []:
        role = m.get("role")
        content = m.get("content")
        if role in ("user", "assistant") and isinstance(content, str):
            msgs.append({"role": role, "content": content})
    msgs.append({"role": "user", "content": user_msg})
    return msgs

# ----------------------------
# Streaming + side-panels (tool logs & citations)
# ----------------------------
def _append_log(log_lines: List[str], line: str, max_lines: int = 200) -> None:
    log_lines.append(line)
    if len(log_lines) > max_lines:
        del log_lines[: len(log_lines) - max_lines]

def _format_tool_log(log_lines: List[str]) -> str:
    if not log_lines:
        return "_No tool activity yet._"
    return "\n".join(log_lines)

def _format_citations(cites: List[Tuple[str, Optional[str]]]) -> str:
    if not cites:
        return "_No citations captured yet._"
    # Show up to the last 12 citations (tool name + optional URL/source)
    last = cites[-12:]
    lines = []
    for (label, url) in last:
        if url:
            lines.append(f"- **{label}** — {url}")
        else:
            lines.append(f"- **{label}**")
    return "\n".join(lines)

async def stream_answer(
    messages_for_llm: List[Dict[str, Any]],
    model_id: str,
    provider: str,
    api_key: Optional[str],
) -> Iterable[Dict[str, Any]]:
    """
    Stream deltas and tool logs from MCPClient.process_single_turn_with_tools.
    Yield dicts with partial text plus updated tool logs & citations so the UI can update three panels.
    """
    await ensure_init(model_id, provider, api_key)
    client = get_mcp_client(model_id, provider, api_key)

    tool_log: List[str] = []
    citations: List[Tuple[str, Optional[str]]] = []  # (label, url)

    # Early token check
    if not api_key:
        yield {
            "delta": (
                "⚠️ Missing token: set `HUGGING_FACE_HUB_TOKEN` or `HF_TOKEN` "
                "in your Space **Settings → Secrets** to authenticate model calls."
            ),
            "tool_log": _format_tool_log(tool_log),
            "citations": _format_citations(citations),
        }
        return

    try:
        async for chunk in client.process_single_turn_with_tools(messages_for_llm):
            if isinstance(chunk, dict):
                ctype = chunk.get("type")

                if ctype == "tool_log":
                    name = chunk.get("tool", "tool")
                    status = chunk.get("status", "")
                    _append_log(tool_log, f"- {name} **{status}**")
                    yield {"delta": "", "tool_log": _format_tool_log(tool_log), "citations": _format_citations(citations)}

                elif ctype == "text_delta":
                    yield {"delta": chunk.get("delta", ""), "tool_log": _format_tool_log(tool_log), "citations": _format_citations(citations)}

                elif ctype == "text":
                    yield {"delta": chunk.get("text", ""), "tool_log": _format_tool_log(tool_log), "citations": _format_citations(citations)}

                elif ctype == "tool_result":
                    tool_name = chunk.get("tool", "tool")
                    content = chunk.get("content")
                    url = None
                    if isinstance(content, dict):
                        url = content.get("url") or content.get("link")
                        title = content.get("title") or content.get("name")
                        label = title or tool_name
                    elif isinstance(content, str):
                        label = tool_name
                        if "http://" in content or "https://" in content:
                            start = content.find("http")
                            url = content[start : start + 200].split("\n")[0].strip()
                    else:
                        label = tool_name

                    citations.append((label, url))
                    _append_log(tool_log, f"  • {tool_name} returned result")
                    snippet = ""
                    if isinstance(content, str):
                        snippet = content.strip()
                        if len(snippet) > 700:
                            snippet = snippet[:700] + "…"
                        snippet = f"\n\n**Result (from {tool_name}):**\n{snippet}"
                    yield {
                        "delta": snippet,
                        "tool_log": _format_tool_log(tool_log),
                        "citations": _format_citations(citations),
                    }

            else:
                yield {"delta": str(chunk), "tool_log": _format_tool_log(tool_log), "citations": _format_citations(citations)}

    except Exception as e:
        msg = str(e)
        if "401" in msg or "Unauthorized" in msg:
            err = (
                "❌ Unauthorized (401). Ensure your token is set and permitted for the chosen model/provider.\n"
                f"- Model: `{model_id}`\n- Provider: `{provider}`\n"
            )
        else:
            err = f"❌ Error: {msg}"
        yield {"delta": err, "tool_log": _format_tool_log(tool_log), "citations": _format_citations(citations)}

# ----------------------------
# Gradio UI
# ----------------------------
with gr.Blocks(fill_height=True) as demo:
    gr.Markdown(
        "# 🤖 Gradio Docs Chat (MCP Client)\n"
        "Ask anything about **Gradio**. Answers are grounded in the official docs via MCP tools."
    )

    with gr.Row():
        with gr.Column(scale=7):
            chat = gr.Chatbot(
                label="Gradio Docs Assistant",
                height=520,
                type="messages",
            )
            with gr.Row():
                msg = gr.Textbox(
                    placeholder="e.g., How do I use gr.Interface with multiple inputs?",
                    scale=9,
                    autofocus=True,
                )
                send_btn = gr.Button("Send", scale=1, variant="primary")

            clear = gr.ClearButton(components=[chat, msg], value="Clear")

        with gr.Column(scale=5):
            with gr.Accordion("⚙️ Settings", open=False):
                style = gr.Radio(
                    label="Answer Style",
                    choices=["Concise", "Detailed"],
                    value="Detailed",
                )
                model_read = gr.Markdown(
                    f"**Model:** `{MODEL_ID}`  \n**Provider:** `{PROVIDER}`  \n"
                    "_(override via Space Secrets: `CHAT_MODEL`, `CHAT_PROVIDER`)_"
                )

            with gr.Accordion("🛠 Tool Activity (live)", open=True):
                tool_log_md = gr.Markdown("_No tool activity yet._")

            with gr.Accordion("📎 Citations (recent)", open=True):
                citations_md = gr.Markdown("_No citations captured yet._")

    async def on_submit(user_msg: str, history_msgs: List[Dict[str, Any]], style_choice: str):
        """
        Append the user's message, then stream the assistant reply while updating:
          - chat text
          - tool activity
          - citations
        """
        history_msgs = (history_msgs or []) + [{"role": "user", "content": user_msg}]
        history_msgs.append({"role": "assistant", "content": ""})
        yield history_msgs, gr.update(value="_No tool activity yet._"), gr.update(value="_No citations captured yet._")

        messages_for_llm = to_llm_messages(history_msgs[:-1], user_msg, style_choice)

        async for chunk in stream_answer(messages_for_llm, MODEL_ID, PROVIDER, HF_TOKEN):
            delta = chunk.get("delta", "")
            if delta:
                history_msgs[-1]["content"] += delta
            yield history_msgs, gr.update(value=chunk.get("tool_log", "")), gr.update(value=chunk.get("citations", ""))

    msg.submit(on_submit, inputs=[msg, chat, style], outputs=[chat, tool_log_md, citations_md], queue=True)
    send_btn.click(on_submit, inputs=[msg, chat, style], outputs=[chat, tool_log_md, citations_md], queue=True)

# ----------------------------
# Gradio runtime (queue + launch)
# ----------------------------
# IMPORTANT: assign the queued app back to 'demo' for older Gradio versions.
demo = demo.queue(max_size=32)

# Always launch; Spaces runs this script directly.
demo.launch(
    ssr_mode=False,       # disable SSR to avoid Node helper churn
    server_name="0.0.0.0",
    server_port=7860,
)