//! Embedded MCP server. Claude Code (running inside the agent container)
//! launches this as a stdio child via `--mcp-config`; tool calls land here
//! and are translated to `AgentRequest::Send`/`Recv` against hyperhive's
//! own per-agent unix socket at `/run/hive/mcp.sock`.
//!
//! Two protocols, two surfaces:
//! - **hyperhive socket** at `/run/hive/mcp.sock` — JSON-line, our
//!   broker-routed Send/Recv. Unaffected by this module.
//! - **MCP stdio** owned by this module — what claude actually speaks.
//!
//! The agent surface today is intentionally tiny (send/recv); the manager
//! surface (Phase 8 follow-up) will add `request_spawn`, `request_kill`,
//! `request_apply_commit`.

use std::path::PathBuf;

use anyhow::Result;
use rmcp::{
    ServerHandler, ServiceExt,
    handler::server::wrapper::Parameters,
    schemars, tool, tool_handler, tool_router,
    transport::stdio,
};

use crate::client;

#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
pub struct SendArgs {
    /// Logical agent name to deliver the message to (e.g. `"manager"`,
    /// `"alice"`, or the literal `"operator"` for the dashboard's T4LK box).
    pub to: String,
    /// Message body. Plain text; the broker doesn't parse it.
    pub body: String,
}

#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
pub struct RecvArgs {}

/// Per-agent tool surface. Holds the socket path so each tool call doesn't
/// re-derive it; the socket itself is the per-container `/run/hive/mcp.sock`.
#[derive(Debug, Clone)]
pub struct AgentServer {
    socket: PathBuf,
}

impl AgentServer {
    #[must_use]
    pub fn new(socket: PathBuf) -> Self {
        Self { socket }
    }
}

#[tool_router]
impl AgentServer {
    #[tool(
        description = "Send a message to another hyperhive agent (or to the operator). \
            Use this to talk to peers or to surface output for the human at the dashboard."
    )]
    async fn send(&self, Parameters(args): Parameters<SendArgs>) -> String {
        let req = hive_sh4re::AgentRequest::Send {
            to: args.to.clone(),
            body: args.body,
        };
        match client::request::<_, hive_sh4re::AgentResponse>(&self.socket, &req).await {
            Ok(hive_sh4re::AgentResponse::Ok) => format!("sent to {}", args.to),
            Ok(hive_sh4re::AgentResponse::Err { message }) => format!("send failed: {message}"),
            Ok(other) => format!("send unexpected response: {other:?}"),
            Err(e) => format!("send transport error: {e:#}"),
        }
    }

    #[tool(
        description = "Pop one message from this agent's inbox. Returns the sender and body, \
            or an empty marker if nothing is waiting."
    )]
    async fn recv(&self, Parameters(_): Parameters<RecvArgs>) -> String {
        let req = hive_sh4re::AgentRequest::Recv;
        match client::request::<_, hive_sh4re::AgentResponse>(&self.socket, &req).await {
            Ok(hive_sh4re::AgentResponse::Message { from, body }) => {
                format!("from: {from}\n\n{body}")
            }
            Ok(hive_sh4re::AgentResponse::Empty) => "(empty)".into(),
            Ok(hive_sh4re::AgentResponse::Err { message }) => format!("recv failed: {message}"),
            Ok(other) => format!("recv unexpected response: {other:?}"),
            Err(e) => format!("recv transport error: {e:#}"),
        }
    }
}

#[tool_handler(
    instructions = "You are a hyperhive agent. Use `send` to talk to peers (by their logical \
        name) or to the operator (recipient `operator`). Use `recv` to drain your inbox one \
        message at a time."
)]
impl ServerHandler for AgentServer {}

/// Run the MCP server over stdio. Returns when the client disconnects.
pub async fn serve_stdio(socket: PathBuf) -> Result<()> {
    let server = AgentServer::new(socket);
    let service = server.serve(stdio()).await?;
    service.waiting().await?;
    Ok(())
}

/// Name of the hyperhive MCP server inside claude's view. Claude prefixes
/// tools as `mcp__<this>__<tool>` (e.g. `mcp__hyperhive__send`).
pub const SERVER_NAME: &str = "hyperhive";

/// Built-in claude tools the turn loop enables via `--tools`. Anything not
/// in this list literally doesn't exist in the session (claude won't even
/// try to call it). Web egress (`WebFetch`/`WebSearch`) and nested agents
/// (`Task`) are intentionally omitted for now; `Bash` is allowed pending a
/// finer-grained allow-list system for shell command patterns. Edit later
/// as our trust model evolves.
pub const ALLOWED_BUILTIN_TOOLS: &[&str] = &[
    "Bash",
    "Edit",
    "Glob",
    "Grep",
    "NotebookEdit",
    "Read",
    "TodoWrite",
    "Write",
];

/// MCP tools claude is allowed to call without prompting. Mirrors the
/// hyperhive surface so a new tool added below propagates to claude's
/// allow-list automatically.
#[must_use]
pub fn allowed_mcp_tools() -> Vec<String> {
    ["send", "recv"]
        .iter()
        .map(|t| format!("mcp__{SERVER_NAME}__{t}"))
        .collect()
}

/// Combined allow-list passed to `--allowedTools` (auto-approve) — covers
/// both the built-ins and the MCP surface.
#[must_use]
pub fn allowed_tools_arg() -> String {
    let mut all: Vec<String> = ALLOWED_BUILTIN_TOOLS.iter().map(|s| (*s).to_owned()).collect();
    all.extend(allowed_mcp_tools());
    all.join(",")
}

/// Built-in tools list for `--tools` (which built-ins exist in this
/// session). Same as `ALLOWED_BUILTIN_TOOLS` but joined comma-separated.
#[must_use]
pub fn builtin_tools_arg() -> String {
    ALLOWED_BUILTIN_TOOLS.join(",")
}

/// Render the MCP config blob claude reads from `--mcp-config <path>`.
/// `agent_binary` is the path (or PATH-resolvable name) of the `hive-ag3nt`
/// executable; `socket` is the hyperhive per-agent socket bind-mounted into
/// the container (forwarded to the child as `--socket <path>`).
#[must_use]
pub fn render_claude_config(agent_binary: &str, socket: &std::path::Path) -> String {
    let config = serde_json::json!({
        "mcpServers": {
            SERVER_NAME: {
                "command": agent_binary,
                "args": ["--socket", socket.display().to_string(), "mcp"],
                "env": {}
            }
        }
    });
    serde_json::to_string_pretty(&config).unwrap_or_else(|_| "{}".into())
}