//! 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::*` / `ManagerRequest::*` against
//! hyperhive's own per-container unix socket at `/run/hive/mcp.sock`.
//!
//! Two protocols, two surfaces:
//! - **hyperhive socket** at `/run/hive/mcp.sock` — JSON-line, our
//!   broker-routed protocol. Unaffected by this module.
//! - **MCP stdio** owned by this module — what claude actually speaks.
//!
//! Two server flavors:
//! - `AgentServer` — sub-agent tools (`send`, `recv`).
//! - `ManagerServer` — agent tools + lifecycle (`request_spawn`, `kill`,
//!   `request_apply_commit`).
//!
//! Both go through the same `run_tool_envelope` helper so logging + status
//! line stay uniform.

use std::future::Future;
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;

/// Wire-protocol-agnostic view of a hyperhive socket response. Both
/// `AgentResponse` and `ManagerResponse` convert into this so the tool
/// formatters can be shared between `AgentServer` and `ManagerServer`.
#[derive(Debug)]
pub enum SocketReply {
    Ok,
    Err(String),
    Message { from: String, body: String },
    Empty,
    Status(u64),
    QuestionQueued(i64),
    Recent(Vec<hive_sh4re::InboxRow>),
}

impl From<hive_sh4re::AgentResponse> for SocketReply {
    fn from(r: hive_sh4re::AgentResponse) -> Self {
        match r {
            hive_sh4re::AgentResponse::Ok => Self::Ok,
            hive_sh4re::AgentResponse::Err { message } => Self::Err(message),
            hive_sh4re::AgentResponse::Message { from, body } => Self::Message { from, body },
            hive_sh4re::AgentResponse::Empty => Self::Empty,
            hive_sh4re::AgentResponse::Status { unread } => Self::Status(unread),
            hive_sh4re::AgentResponse::Recent { rows } => Self::Recent(rows),
            hive_sh4re::AgentResponse::QuestionQueued { id } => Self::QuestionQueued(id),
        }
    }
}

impl From<hive_sh4re::ManagerResponse> for SocketReply {
    fn from(r: hive_sh4re::ManagerResponse) -> Self {
        match r {
            hive_sh4re::ManagerResponse::Ok => Self::Ok,
            hive_sh4re::ManagerResponse::Err { message } => Self::Err(message),
            hive_sh4re::ManagerResponse::Message { from, body } => Self::Message { from, body },
            hive_sh4re::ManagerResponse::Empty => Self::Empty,
            hive_sh4re::ManagerResponse::Status { unread } => Self::Status(unread),
            hive_sh4re::ManagerResponse::QuestionQueued { id } => Self::QuestionQueued(id),
            hive_sh4re::ManagerResponse::Recent { rows } => Self::Recent(rows),
        }
    }
}

/// Format helper for "send-like" tools (anything that expects an `Ok`).
/// `tool` and `ok_msg` only appear in the result string; they don't change
/// behavior.
pub fn format_ack(resp: Result<SocketReply, anyhow::Error>, tool: &str, ok_msg: String) -> String {
    match resp {
        Ok(SocketReply::Ok) => ok_msg,
        Ok(SocketReply::Err(m)) => format!("{tool} failed: {m}"),
        Ok(other) => format!("{tool} unexpected response: {other:?}"),
        Err(e) => format!("{tool} transport error: {e:#}"),
    }
}

/// Format helper for `recv` tools: `Message` → from + body block;
/// `Empty` → marker; anything else surfaces as an error.
pub fn format_recv(resp: Result<SocketReply, anyhow::Error>) -> String {
    match resp {
        Ok(SocketReply::Message { from, body }) => format!("from: {from}\n\n{body}"),
        Ok(SocketReply::Empty) => "(empty)".into(),
        Ok(SocketReply::Err(m)) => format!("recv failed: {m}"),
        Ok(other) => format!("recv unexpected response: {other:?}"),
        Err(e) => format!("recv transport error: {e:#}"),
    }
}

/// Common envelope around every MCP tool handler: pre-log → run →
/// post-log. The inbox-status hint used to be appended to every tool
/// result; that lives in the wake prompt + UI header now, so tool
/// results stay clean.
pub async fn run_tool_envelope<F>(tool: &'static str, args: String, body: F) -> String
where
    F: Future<Output = String>,
{
    tracing::info!(tool, %args, "tool: request");
    let result = body.await;
    tracing::info!(tool, result = %result, "tool: result");
    result
}

#[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 {
    /// How long to long-poll for a new message before returning the
    /// empty marker. Capped at 60s server-side. Default (None) is
    /// 30s. Useful when an agent wants to throttle wakes without
    /// actually napping — pick a longer wait to coalesce bursts.
    #[serde(default)]
    pub wait_seconds: Option<u64>,
}

/// 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 log = format!("{args:?}");
        let to = args.to.clone();
        if let Err(refusal) = check_send_allowed(&to) {
            return run_tool_envelope("send", log, async move { refusal }).await;
        }
        run_tool_envelope("send", log, async move {
            let resp = client::request::<_, hive_sh4re::AgentResponse>(
                &self.socket,
                &hive_sh4re::AgentRequest::Send {
                    to: args.to,
                    body: args.body,
                },
            )
            .await
            .map(SocketReply::from);
            format_ack(resp, "send", format!("sent to {to}"))
        })
        .await
    }

    #[tool(
        description = "Surface a question to the operator on the dashboard. Returns immediately \
        with a question id — do NOT wait inline. When the operator answers, a system message \
        with event `operator_answered { id, question, answer }` lands in your inbox; handle it \
        on a future turn. Use this when a decision needs human signal (ambiguous scope, \
        permission to do something risky, choosing between options). `options` is advisory: \
        pass a short fixed-choice list when applicable, otherwise leave empty for free text. \
        Set `multi: true` to let the operator pick multiple options (checkboxes); the answer \
        comes back as a comma-separated string. Set `ttl_seconds` to auto-cancel a \
        no-longer-relevant question — on expiry the answer is `[expired]` and the same \
        `operator_answered` event fires."
    )]
    async fn ask_operator(&self, Parameters(args): Parameters<AskOperatorArgs>) -> String {
        let log = format!("{args:?}");
        run_tool_envelope("ask_operator", log, async move {
            let resp = client::request::<_, hive_sh4re::AgentResponse>(
                &self.socket,
                &hive_sh4re::AgentRequest::AskOperator {
                    question: args.question,
                    options: args.options,
                    multi: args.multi,
                    ttl_seconds: args.ttl_seconds,
                },
            )
            .await
            .map(SocketReply::from);
            match resp {
                Ok(SocketReply::QuestionQueued(id)) => format!(
                    "question queued (id={id}); operator's answer will arrive as a system \
                     `operator_answered` event in your inbox"
                ),
                Ok(SocketReply::Err(m)) => format!("ask_operator failed: {m}"),
                Ok(other) => format!("ask_operator unexpected response: {other:?}"),
                Err(e) => format!("ask_operator transport error: {e:#}"),
            }
        })
        .await
    }

    #[tool(
        description = "Pop one message from this agent's inbox. Returns the sender and body, \
            or an empty marker if nothing is waiting. Without `wait_seconds` (or with 0) the \
            call returns immediately — a cheap 'anything pending?' peek. Pass a positive \
            `wait_seconds` (capped at 180) to park the turn waiting for new work — incoming \
            messages wake you instantly, otherwise the call returns empty at the timeout. \
            That's strictly better than a fixed shell `sleep`. Typical pattern: when you have \
            nothing else useful to do, call `recv(wait_seconds: 180)` to park until \
            something arrives."
    )]
    async fn recv(&self, Parameters(args): Parameters<RecvArgs>) -> String {
        let log = format!("{args:?}");
        run_tool_envelope("recv", log, async move {
            let resp = client::request::<_, hive_sh4re::AgentResponse>(
                &self.socket,
                &hive_sh4re::AgentRequest::Recv {
                    wait_seconds: args.wait_seconds,
                },
            )
            .await
            .map(SocketReply::from);
            format_recv(resp)
        })
        .await
    }
}

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

/// Run the manager MCP server over stdio. Same idea, different tool surface.
pub async fn serve_manager_stdio(socket: PathBuf) -> Result<()> {
    let server = ManagerServer::new(socket);
    let service = server.serve(stdio()).await?;
    service.waiting().await?;
    Ok(())
}

// -----------------------------------------------------------------------------
// Manager tool surface
// -----------------------------------------------------------------------------

#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
pub struct RequestSpawnArgs {
    /// New sub-agent name (≤9 chars). Queues a Spawn approval; the
    /// operator approves on the dashboard before the container is created.
    pub name: String,
}

#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
pub struct KillArgs {
    /// Sub-agent name (without the `h-` container prefix).
    pub name: String,
}

#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
pub struct StartArgs {
    /// Sub-agent name (without the `h-` container prefix).
    pub name: String,
}

#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
pub struct RestartArgs {
    /// Sub-agent name (without the `h-` container prefix).
    pub name: String,
}

#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
pub struct UpdateArgs {
    /// Sub-agent name (without the `h-` container prefix).
    pub name: String,
}

#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
pub struct AskOperatorArgs {
    /// The question to surface on the dashboard.
    pub question: String,
    /// Optional fixed-choice answers. The dashboard always renders a
    /// free-text fallback ("Other…") so the operator is never trapped
    /// by an incomplete list.
    #[serde(default)]
    pub options: Vec<String>,
    /// When true, options are rendered as checkboxes — operator can pick
    /// any subset. The answer comes back as a single string with
    /// selections joined by ", ". Ignored when `options` is empty.
    #[serde(default)]
    pub multi: bool,
    /// Optional auto-cancel after `ttl_seconds`. On expiry the question
    /// resolves with answer `[expired]` and the manager receives the
    /// usual `operator_answered` system event. `None` (default) =
    /// wait indefinitely.
    #[serde(default)]
    pub ttl_seconds: Option<u64>,
}

#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
pub struct RequestApplyCommitArgs {
    /// Agent whose config repo the commit lives in (use `"hm1nd"` for the
    /// manager's own config).
    pub agent: String,
    /// Git sha (full or short) pointing at the proposed `agent.nix`.
    pub commit_ref: String,
}

#[derive(Debug, Clone)]
pub struct ManagerServer {
    socket: PathBuf,
}

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

    /// Helper: issue any `ManagerRequest`, convert the reply through
    /// `SocketReply`. Manager tools that just need an `Ok` ack share this.
    async fn dispatch(
        &self,
        req: hive_sh4re::ManagerRequest,
    ) -> Result<SocketReply, anyhow::Error> {
        client::request::<_, hive_sh4re::ManagerResponse>(&self.socket, &req)
            .await
            .map(SocketReply::from)
    }
}

#[tool_router]
impl ManagerServer {
    #[tool(
        description = "Send a message to a sub-agent (by logical name), to another agent, \
        or to the operator (recipient `operator`, surfaces in the dashboard)."
    )]
    async fn send(&self, Parameters(args): Parameters<SendArgs>) -> String {
        let log = format!("{args:?}");
        let to = args.to.clone();
        run_tool_envelope("send", log, async move {
            let resp = self
                .dispatch(hive_sh4re::ManagerRequest::Send {
                    to: args.to,
                    body: args.body,
                })
                .await;
            format_ack(resp, "send", format!("sent to {to}"))
        })
        .await
    }

    #[tool(
        description = "Pop one message from the manager inbox. Returns sender + body, or \
        empty. Without `wait_seconds` (or 0) returns immediately — a cheap inbox peek. \
        Pass a positive value (capped at 180) to park until either a message arrives \
        or the timeout fires; prefer a long wait (120 or 180) over ending a turn \
        early when you have nothing else to do."
    )]
    async fn recv(&self, Parameters(args): Parameters<RecvArgs>) -> String {
        let log = format!("{args:?}");
        run_tool_envelope("recv", log, async move {
            let resp = self
                .dispatch(hive_sh4re::ManagerRequest::Recv {
                    wait_seconds: args.wait_seconds,
                })
                .await;
            format_recv(resp)
        })
        .await
    }

    #[tool(
        description = "Queue a Spawn approval for a brand-new sub-agent. The operator \
        approves on the dashboard before the container is actually created."
    )]
    async fn request_spawn(&self, Parameters(args): Parameters<RequestSpawnArgs>) -> String {
        let log = format!("{args:?}");
        let name = args.name.clone();
        run_tool_envelope("request_spawn", log, async move {
            let resp = self
                .dispatch(hive_sh4re::ManagerRequest::RequestSpawn { name: args.name })
                .await;
            format_ack(
                resp,
                "request_spawn",
                format!("spawn approval queued for {name}"),
            )
        })
        .await
    }

    #[tool(
        description = "Stop a sub-agent container (graceful). The state dir is kept; \
        recreating reuses prior config + Claude credentials. No approval required."
    )]
    async fn kill(&self, Parameters(args): Parameters<KillArgs>) -> String {
        let log = format!("{args:?}");
        let name = args.name.clone();
        run_tool_envelope("kill", log, async move {
            let resp = self
                .dispatch(hive_sh4re::ManagerRequest::Kill { name: args.name })
                .await;
            format_ack(resp, "kill", format!("killed {name}"))
        })
        .await
    }

    #[tool(
        description = "Start a stopped sub-agent container. No approval required — \
        lifecycle ops on existing containers are at the manager's discretion."
    )]
    async fn start(&self, Parameters(args): Parameters<StartArgs>) -> String {
        let log = format!("{args:?}");
        let name = args.name.clone();
        run_tool_envelope("start", log, async move {
            let resp = self
                .dispatch(hive_sh4re::ManagerRequest::Start { name: args.name })
                .await;
            format_ack(resp, "start", format!("started {name}"))
        })
        .await
    }

    #[tool(description = "Restart a sub-agent container (stop + start). No approval required.")]
    async fn restart(&self, Parameters(args): Parameters<RestartArgs>) -> String {
        let log = format!("{args:?}");
        let name = args.name.clone();
        run_tool_envelope("restart", log, async move {
            let resp = self
                .dispatch(hive_sh4re::ManagerRequest::Restart { name: args.name })
                .await;
            format_ack(resp, "restart", format!("restarted {name}"))
        })
        .await
    }

    #[tool(
        description = "Rebuild a sub-agent: re-applies the current hyperhive flake + agent.nix \
        and restarts the container. No approval required — idempotent. Use when you receive a \
        `needs_update` system event for an agent."
    )]
    async fn update(&self, Parameters(args): Parameters<UpdateArgs>) -> String {
        let log = format!("{args:?}");
        let name = args.name.clone();
        run_tool_envelope("update", log, async move {
            let resp = self
                .dispatch(hive_sh4re::ManagerRequest::Update { name: args.name })
                .await;
            format_ack(resp, "update", format!("updated {name}"))
        })
        .await
    }

    #[tool(
        description = "Surface a question to the operator on the dashboard. Returns immediately \
        with a question id — do NOT wait inline. When the operator answers, a system message \
        with event `operator_answered { id, question, answer }` lands in your inbox; handle it \
        on a future turn. Use this when a decision needs human signal (ambiguous sub-agent \
        request, policy call, scope clarification). `options` is advisory: pass a short \
        fixed-choice list when applicable, otherwise leave empty for free text. Set \
        `multi: true` to let the operator pick multiple options (checkboxes); the answer \
        comes back as a comma-separated string. Set `ttl_seconds` to auto-cancel a \
        no-longer-relevant question instead of blocking forever — on expiry the answer \
        is `[expired]` and the same `operator_answered` event fires."
    )]
    async fn ask_operator(&self, Parameters(args): Parameters<AskOperatorArgs>) -> String {
        let log = format!("{args:?}");
        run_tool_envelope("ask_operator", log, async move {
            let resp = self
                .dispatch(hive_sh4re::ManagerRequest::AskOperator {
                    question: args.question,
                    options: args.options,
                    multi: args.multi,
                    ttl_seconds: args.ttl_seconds,
                })
                .await;
            match resp {
                Ok(SocketReply::QuestionQueued(id)) => format!(
                    "question queued (id={id}); operator's answer will arrive as a system \
                     `operator_answered` event in your inbox"
                ),
                Ok(SocketReply::Err(m)) => format!("ask_operator failed: {m}"),
                Ok(other) => format!("ask_operator unexpected response: {other:?}"),
                Err(e) => format!("ask_operator transport error: {e:#}"),
            }
        })
        .await
    }

    #[tool(
        description = "Submit a config change for operator approval. Pass the agent name \
        (e.g. `alice` or `hm1nd` for the manager's own config) and a commit sha in that \
        agent's proposed config repo. On approval hive-c0re rebuilds the container."
    )]
    async fn request_apply_commit(
        &self,
        Parameters(args): Parameters<RequestApplyCommitArgs>,
    ) -> String {
        let log = format!("{args:?}");
        let agent = args.agent.clone();
        let commit_ref = args.commit_ref.clone();
        run_tool_envelope("request_apply_commit", log, async move {
            let resp = self
                .dispatch(hive_sh4re::ManagerRequest::RequestApplyCommit {
                    agent: args.agent,
                    commit_ref: args.commit_ref,
                })
                .await;
            format_ack(
                resp,
                "request_apply_commit",
                format!("apply approval queued for {agent} @ {commit_ref}"),
            )
        })
        .await
    }
}

#[tool_handler(
    instructions = "You are the hyperhive manager (hm1nd). You coordinate sub-agents and \
        relay between them and the operator. Use `send` to talk to agents/operator, `recv` \
        to drain your inbox. Privileged: `request_spawn` (new agent, gated on operator \
        approval), `kill` (graceful stop), `request_apply_commit` (config change for \
        any agent including yourself), `ask_operator` (block on a human answer via the \
        dashboard). The manager's own config lives at \
        `/agents/hm1nd/config/agent.nix`."
)]
impl ServerHandler for ManagerServer {}

/// 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", "Read", "TodoWrite", "Write"];

/// Which MCP tool surface to advertise via `--allowedTools`. The agent
/// list is the strict subset of the manager list, so we just thread the
/// flavor through.
#[derive(Debug, Clone, Copy)]
pub enum Flavor {
    Agent,
    Manager,
}

/// MCP tools claude is allowed to call without prompting. Mirrors the
/// hyperhive surface so a new tool added in the corresponding `#[tool_router]`
/// impl needs to be listed here too.
#[must_use]
pub fn allowed_mcp_tools(flavor: Flavor) -> Vec<String> {
    let names: &[&str] = match flavor {
        Flavor::Agent => &["send", "recv", "ask_operator"],
        Flavor::Manager => &[
            "send",
            "recv",
            "request_spawn",
            "kill",
            "start",
            "restart",
            "update",
            "request_apply_commit",
            "ask_operator",
        ],
    };
    let mut out: Vec<String> = names
        .iter()
        .map(|t| format!("mcp__{SERVER_NAME}__{t}"))
        .collect();
    // Extra MCP servers declared via `hyperhive.extraMcpServers` in
    // the agent's NixOS config. Each entry maps its `allowedTools`
    // pattern list to `mcp__<server>__<pattern>` so claude can call
    // them without per-tool operator approval. `["*"]` (the default)
    // expands to `mcp__<server>__*` — every tool from that server.
    for (server, spec) in load_extra_mcp() {
        if server == SERVER_NAME {
            continue;
        }
        for pat in spec.allowed_tools {
            out.push(format!("mcp__{server}__{pat}"));
        }
    }
    out
}

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

/// Where the NixOS module writes the per-agent extra-MCP spec (see
/// `nix/templates/harness-base.nix`). Each entry becomes an additional
/// `mcpServers.<key>` block in the rendered claude config + a
/// `mcp__<key>__<tool>` pattern in `--allowedTools`.
const EXTRA_MCP_PATH: &str = "/etc/hyperhive/extra-mcp.json";

/// Where the NixOS module writes the per-agent send allow-list (see
/// `nix/templates/harness-base.nix`). Empty list = unrestricted (the
/// default). Non-empty list constrains `mcp__hyperhive__send`'s `to`
/// field; the manager is always implicitly permitted regardless of
/// the list contents.
const SEND_ALLOW_PATH: &str = "/etc/hyperhive/send-allow.json";

/// Enforce the per-agent send allow-list. Returns `Ok` when the
/// recipient is permitted (no list configured, manager always
/// allowed, or `to` is in the list); returns `Err(refusal)` with a
/// claude-readable string when blocked — the harness surfaces the
/// refusal as the tool result so claude knows the message didn't
/// land and can react (e.g. route via the manager instead).
fn check_send_allowed(to: &str) -> Result<(), String> {
    if to == hive_sh4re::MANAGER_AGENT {
        // Always allow agents to talk to the manager — otherwise a
        // misconfigured allow-list could leave a sub-agent unable
        // to ask for help.
        return Ok(());
    }
    let Ok(raw) = std::fs::read_to_string(SEND_ALLOW_PATH) else {
        return Ok(()); // file missing → no policy configured → unrestricted
    };
    let allow: Vec<String> = match serde_json::from_str(&raw) {
        Ok(v) => v,
        Err(e) => {
            tracing::warn!(
                path = SEND_ALLOW_PATH,
                error = ?e,
                "send allow-list parse failed; falling back to unrestricted",
            );
            return Ok(());
        }
    };
    if allow.is_empty() {
        return Ok(()); // empty list = unrestricted (back-compat)
    }
    if allow.iter().any(|n| n == to) {
        return Ok(());
    }
    Err(format!(
        "send refused: recipient '{to}' not in hyperhive.allowedRecipients \
         (configured in agent.nix). Allowed: {allow:?}. The manager is \
         always reachable — route through `send(to: \"manager\", …)` if \
         you need to reach someone outside the allow-list."
    ))
}

#[derive(Debug, serde::Deserialize)]
struct ExtraMcpServer {
    command: String,
    #[serde(default)]
    args: Vec<String>,
    #[serde(default)]
    env: std::collections::BTreeMap<String, String>,
    #[serde(default = "default_allowed_tools")]
    #[serde(rename = "allowedTools")]
    allowed_tools: Vec<String>,
}

fn default_allowed_tools() -> Vec<String> {
    vec!["*".to_owned()]
}

/// Read + parse the extra-MCP spec. Returns an empty map on missing /
/// unparsable file (the agent has none configured, or the file is
/// malformed — both cases degrade to "no extra servers").
fn load_extra_mcp() -> std::collections::BTreeMap<String, ExtraMcpServer> {
    let Ok(raw) = std::fs::read_to_string(EXTRA_MCP_PATH) else {
        return std::collections::BTreeMap::new();
    };
    serde_json::from_str(&raw).unwrap_or_else(|e| {
        tracing::warn!(
            path = EXTRA_MCP_PATH,
            error = ?e,
            "extra-mcp spec parse failed; ignoring",
        );
        std::collections::BTreeMap::new()
    })
}

/// 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>`). Merges in
/// any extra MCP servers declared via `hyperhive.extraMcpServers` in the
/// agent's NixOS config.
#[must_use]
pub fn render_claude_config(agent_binary: &str, socket: &std::path::Path) -> String {
    let mut servers = serde_json::Map::new();
    servers.insert(
        SERVER_NAME.to_owned(),
        serde_json::json!({
            "command": agent_binary,
            "args": ["--socket", socket.display().to_string(), "mcp"],
            "env": {}
        }),
    );
    for (name, spec) in load_extra_mcp() {
        if name == SERVER_NAME {
            tracing::warn!(
                "extra MCP server name `{SERVER_NAME}` collides with the built-in surface; ignoring",
            );
            continue;
        }
        servers.insert(
            name,
            serde_json::json!({
                "command": spec.command,
                "args": spec.args,
                "env": spec.env,
            }),
        );
    }
    let config = serde_json::json!({ "mcpServers": servers });
    serde_json::to_string_pretty(&config).unwrap_or_else(|_| "{}".into())
}