//! Server rebuild and restart logic shared between the MCP tool and Matrix bot command.

use crate::agents::AgentPool;
use crate::slog;
use crate::chat::ChatTransport;
use std::path::Path;
use std::sync::Arc;

// ── Shutdown notification ────────────────────────────────────────────────

/// The reason the server is shutting down.
///
/// Used to select the appropriate shutdown message sent to active bot channels.
#[derive(Clone, Debug, PartialEq)]
pub enum ShutdownReason {
    /// The operator stopped the server manually (SIGINT / SIGTERM / ctrl-c).
    Manual,
    /// A rebuild-and-restart was requested (via MCP tool or bot command).
    Rebuild,
}

/// Sends a shutdown announcement to all configured bot channels.
///
/// Wraps a [`ChatTransport`] together with the list of channel/room IDs the
/// bot is active in.  Calling [`notify`] is best-effort — failures are logged
/// but never propagate, so shutdown is never blocked by a failed send.
pub struct BotShutdownNotifier {
    transport: Arc<dyn ChatTransport>,
    channels: Vec<String>,
    bot_name: String,
}

impl BotShutdownNotifier {
    pub fn new(
        transport: Arc<dyn ChatTransport>,
        channels: Vec<String>,
        bot_name: String,
    ) -> Self {
        Self {
            transport,
            channels,
            bot_name,
        }
    }

    /// Send a startup announcement to all configured channels.
    ///
    /// Called once per process start so users know the bot is online.
    /// Errors are logged and ignored — startup is never blocked by a failed send.
    pub async fn notify_startup(&self) {
        let msg = format!("{} is online.", self.bot_name);
        for channel in &self.channels {
            if let Err(e) = self.transport.send_message(channel, &msg, &msg).await {
                slog!("[startup] Failed to send startup message to {channel}: {e}");
            }
        }
    }

    /// Send a shutdown message to all configured channels.
    ///
    /// Errors from individual sends are logged and ignored so that a single
    /// failing channel does not prevent messages from reaching the rest.
    pub async fn notify(&self, reason: ShutdownReason) {
        let msg = match reason {
            ShutdownReason::Manual => {
                format!("{} is going offline (server stopped).", self.bot_name)
            }
            ShutdownReason::Rebuild => {
                format!(
                    "{} is going offline to pick up a new build.",
                    self.bot_name
                )
            }
        };
        for channel in &self.channels {
            if let Err(e) = self.transport.send_message(channel, &msg, &msg).await {
                slog!("[shutdown] Failed to send shutdown message to {channel}: {e}");
            }
        }
    }
}

// ── Rebuild ──────────────────────────────────────────────────────────────

/// Rebuild the server binary and re-exec.
///
/// 1. Gracefully stops all running agents (kills PTY children).
/// 2. Runs `cargo build [-p storkit]` from the workspace root, matching
///    the current build profile (debug or release).
/// 3. If the build fails, returns the build error (server stays up).
/// 4. If the build succeeds, sends a best-effort shutdown notification (if a
///    [`BotShutdownNotifier`] is provided), then re-execs the process with
///    the new binary via `std::os::unix::process::CommandExt::exec()`.
pub async fn rebuild_and_restart(
    agents: &AgentPool,
    project_root: &Path,
    notifier: Option<&BotShutdownNotifier>,
) -> Result<String, String> {
    slog!("[rebuild] Rebuild and restart requested");

    // 1. Gracefully stop all running agents.
    let running_count = agents
        .list_agents()
        .unwrap_or_default()
        .iter()
        .filter(|a| a.status == crate::agents::AgentStatus::Running)
        .count();
    if running_count > 0 {
        slog!("[rebuild] Stopping {running_count} running agent(s) before rebuild");
    }
    agents.kill_all_children();

    // 2. Find the workspace root (parent of the server binary's source).
    //    CARGO_MANIFEST_DIR at compile time points to the `server/` crate;
    //    the workspace root is its parent.
    let manifest_dir = std::path::Path::new(env!("CARGO_MANIFEST_DIR"));
    let workspace_root = manifest_dir
        .parent()
        .ok_or_else(|| "Cannot determine workspace root from CARGO_MANIFEST_DIR".to_string())?;

    slog!(
        "[rebuild] Building server from workspace root: {}",
        workspace_root.display()
    );

    // 3. Rebuild the frontend bundle so rust-embed picks up the latest assets.
    let frontend_dir = workspace_root.join("frontend");
    if frontend_dir.join("package.json").exists() {
        slog!("[rebuild] Building frontend");
        let fe_output = tokio::task::spawn_blocking({
            let frontend_dir = frontend_dir.clone();
            move || {
                std::process::Command::new("npm")
                    .args(["run", "build"])
                    .current_dir(&frontend_dir)
                    .output()
            }
        })
        .await
        .map_err(|e| format!("Frontend build task panicked: {e}"))?
        .map_err(|e| format!("Failed to run npm run build: {e}"))?;

        if !fe_output.status.success() {
            let stderr = String::from_utf8_lossy(&fe_output.stderr);
            slog!("[rebuild] Frontend build failed:\n{stderr}");
            return Err(format!("Frontend build failed:\n{stderr}"));
        }
        slog!("[rebuild] Frontend build succeeded");
    }

    // 4. Build the server binary, matching the current build profile so the
    //    re-exec via current_exe() picks up the new binary.
    let build_args: Vec<&str> = if cfg!(debug_assertions) {
        vec!["build", "-p", "storkit"]
    } else {
        vec!["build", "--release", "-p", "storkit"]
    };
    slog!("[rebuild] cargo {}", build_args.join(" "));
    let output = tokio::task::spawn_blocking({
        let workspace_root = workspace_root.to_path_buf();
        move || {
            std::process::Command::new("cargo")
                .args(&build_args)
                .current_dir(&workspace_root)
                .output()
        }
    })
    .await
    .map_err(|e| format!("Build task panicked: {e}"))?
    .map_err(|e| format!("Failed to run cargo build: {e}"))?;

    if !output.status.success() {
        let stderr = String::from_utf8_lossy(&output.stderr);
        slog!("[rebuild] Build failed:\n{stderr}");
        return Err(format!("Build failed:\n{stderr}"));
    }

    slog!("[rebuild] Build succeeded, re-execing with new binary");

    // 5. Send shutdown notification before replacing the process so that chat
    //    participants know the bot is going offline.  Best-effort only — we
    //    do not abort the rebuild if the send fails.
    if let Some(n) = notifier {
        n.notify(ShutdownReason::Rebuild).await;
    }

    // 6. Re-exec with the new binary.
    //    Use the cargo output path rather than current_exe() so that rebuilds
    //    inside Docker work correctly — the running binary may be installed at
    //    /usr/local/bin/storkit (read-only) while cargo writes the new binary
    //    to /app/target/release/storkit (a writable volume).
    let new_exe = if cfg!(debug_assertions) {
        workspace_root.join("target/debug/storkit")
    } else {
        workspace_root.join("target/release/storkit")
    };
    let args: Vec<String> = std::env::args().collect();

    // Remove the port file before re-exec so the new process can write its own.
    let port_file = project_root.join(".storkit_port");
    if port_file.exists() {
        let _ = std::fs::remove_file(&port_file);
    }
    // Also check cwd for port file.
    let cwd_port_file = std::path::Path::new(".storkit_port");
    if cwd_port_file.exists() {
        let _ = std::fs::remove_file(cwd_port_file);
    }

    // Use exec() to replace the current process.
    // This never returns on success.
    use std::os::unix::process::CommandExt;
    let err = std::process::Command::new(&new_exe)
        .args(&args[1..])
        .exec();

    // If we get here, exec() failed.
    Err(format!("Failed to exec new binary: {err}"))
}

// ── Tests ────────────────────────────────────────────────────────────────

#[cfg(test)]
mod tests {
    use super::*;
    use async_trait::async_trait;
    use crate::chat::MessageId;
    use std::sync::Mutex;

    /// In-memory transport that records sent messages.
    struct CapturingTransport {
        sent: Mutex<Vec<(String, String)>>,
        fail: bool,
    }

    impl CapturingTransport {
        fn new() -> Self {
            Self {
                sent: Mutex::new(Vec::new()),
                fail: false,
            }
        }

        fn failing() -> Self {
            Self {
                sent: Mutex::new(Vec::new()),
                fail: true,
            }
        }

        fn messages(&self) -> Vec<(String, String)> {
            self.sent.lock().unwrap().clone()
        }
    }

    #[async_trait]
    impl ChatTransport for CapturingTransport {
        async fn send_message(
            &self,
            room_id: &str,
            plain: &str,
            _html: &str,
        ) -> Result<MessageId, String> {
            if self.fail {
                return Err("send failed".to_string());
            }
            self.sent
                .lock()
                .unwrap()
                .push((room_id.to_string(), plain.to_string()));
            Ok("msg-id".to_string())
        }

        async fn edit_message(
            &self,
            _room_id: &str,
            _original_message_id: &str,
            _plain: &str,
            _html: &str,
        ) -> Result<(), String> {
            Ok(())
        }

        async fn send_typing(&self, _room_id: &str, _typing: bool) -> Result<(), String> {
            Ok(())
        }
    }

    #[tokio::test]
    async fn notify_manual_sends_to_all_channels() {
        let transport = Arc::new(CapturingTransport::new());
        let notifier = BotShutdownNotifier::new(
            Arc::clone(&transport) as Arc<dyn ChatTransport>,
            vec!["#channel1".to_string(), "#channel2".to_string()],
            "Timmy".to_string(),
        );

        notifier.notify(ShutdownReason::Manual).await;

        let msgs = transport.messages();
        assert_eq!(msgs.len(), 2);
        assert_eq!(msgs[0].0, "#channel1");
        assert_eq!(msgs[1].0, "#channel2");
        // Message must indicate manual stop.
        assert!(
            msgs[0].1.contains("offline"),
            "expected 'offline' in manual message: {}",
            msgs[0].1
        );
        assert!(
            msgs[0].1.contains("stopped") || msgs[0].1.contains("manual"),
            "expected reason in manual message: {}",
            msgs[0].1
        );
    }

    #[tokio::test]
    async fn notify_rebuild_sends_rebuild_reason() {
        let transport = Arc::new(CapturingTransport::new());
        let notifier = BotShutdownNotifier::new(
            Arc::clone(&transport) as Arc<dyn ChatTransport>,
            vec!["#general".to_string()],
            "Timmy".to_string(),
        );

        notifier.notify(ShutdownReason::Rebuild).await;

        let msgs = transport.messages();
        assert_eq!(msgs.len(), 1);
        // Message must indicate rebuild, not manual stop.
        assert!(
            msgs[0].1.contains("build") || msgs[0].1.contains("rebuild"),
            "expected rebuild reason in message: {}",
            msgs[0].1
        );
    }

    #[tokio::test]
    async fn notify_manual_and_rebuild_messages_are_distinct() {
        let transport_a = Arc::new(CapturingTransport::new());
        let notifier_a = BotShutdownNotifier::new(
            Arc::clone(&transport_a) as Arc<dyn ChatTransport>,
            vec!["C1".to_string()],
            "Bot".to_string(),
        );
        notifier_a.notify(ShutdownReason::Manual).await;

        let transport_b = Arc::new(CapturingTransport::new());
        let notifier_b = BotShutdownNotifier::new(
            Arc::clone(&transport_b) as Arc<dyn ChatTransport>,
            vec!["C1".to_string()],
            "Bot".to_string(),
        );
        notifier_b.notify(ShutdownReason::Rebuild).await;

        let manual_msg = &transport_a.messages()[0].1;
        let rebuild_msg = &transport_b.messages()[0].1;
        assert_ne!(manual_msg, rebuild_msg, "manual and rebuild messages must differ");
    }

    #[tokio::test]
    async fn notify_is_best_effort_failing_send_does_not_panic() {
        // A transport that always fails should not cause notify() to panic or
        // return an error — the failure is swallowed silently.
        let transport = Arc::new(CapturingTransport::failing());
        let notifier = BotShutdownNotifier::new(
            Arc::clone(&transport) as Arc<dyn ChatTransport>,
            vec!["#channel".to_string()],
            "Timmy".to_string(),
        );
        // Should complete without panicking.
        notifier.notify(ShutdownReason::Manual).await;
    }

    #[tokio::test]
    async fn notify_with_no_channels_is_noop() {
        let transport = Arc::new(CapturingTransport::new());
        let notifier = BotShutdownNotifier::new(
            Arc::clone(&transport) as Arc<dyn ChatTransport>,
            vec![],
            "Timmy".to_string(),
        );
        notifier.notify(ShutdownReason::Manual).await;
        assert!(transport.messages().is_empty());
    }

    // -- notify_startup -------------------------------------------------------

    #[tokio::test]
    async fn notify_startup_sends_online_message_to_all_channels() {
        let transport = Arc::new(CapturingTransport::new());
        let notifier = BotShutdownNotifier::new(
            Arc::clone(&transport) as Arc<dyn ChatTransport>,
            vec!["#channel1".to_string(), "#channel2".to_string()],
            "Timmy".to_string(),
        );

        notifier.notify_startup().await;

        let msgs = transport.messages();
        assert_eq!(msgs.len(), 2);
        assert_eq!(msgs[0].0, "#channel1");
        assert_eq!(msgs[1].0, "#channel2");
        assert!(
            msgs[0].1.contains("online"),
            "expected 'online' in startup message: {}",
            msgs[0].1
        );
        assert!(
            msgs[0].1.contains("Timmy"),
            "expected bot name in startup message: {}",
            msgs[0].1
        );
    }

    #[tokio::test]
    async fn notify_startup_message_uses_bot_name() {
        let transport = Arc::new(CapturingTransport::new());
        let notifier = BotShutdownNotifier::new(
            Arc::clone(&transport) as Arc<dyn ChatTransport>,
            vec!["#general".to_string()],
            "HAL".to_string(),
        );

        notifier.notify_startup().await;

        let msgs = transport.messages();
        assert_eq!(msgs[0].1, "HAL is online.");
    }

    #[tokio::test]
    async fn notify_startup_with_no_channels_is_noop() {
        let transport = Arc::new(CapturingTransport::new());
        let notifier = BotShutdownNotifier::new(
            Arc::clone(&transport) as Arc<dyn ChatTransport>,
            vec![],
            "Timmy".to_string(),
        );
        notifier.notify_startup().await;
        assert!(transport.messages().is_empty());
    }

    #[tokio::test]
    async fn notify_startup_is_best_effort_failing_send_does_not_panic() {
        let transport = Arc::new(CapturingTransport::failing());
        let notifier = BotShutdownNotifier::new(
            Arc::clone(&transport) as Arc<dyn ChatTransport>,
            vec!["#channel".to_string()],
            "Timmy".to_string(),
        );
        // Should complete without panicking.
        notifier.notify_startup().await;
    }

    #[tokio::test]
    async fn notify_startup_message_differs_from_shutdown_message() {
        let transport_start = Arc::new(CapturingTransport::new());
        let notifier_start = BotShutdownNotifier::new(
            Arc::clone(&transport_start) as Arc<dyn ChatTransport>,
            vec!["C1".to_string()],
            "Bot".to_string(),
        );
        notifier_start.notify_startup().await;

        let transport_stop = Arc::new(CapturingTransport::new());
        let notifier_stop = BotShutdownNotifier::new(
            Arc::clone(&transport_stop) as Arc<dyn ChatTransport>,
            vec!["C1".to_string()],
            "Bot".to_string(),
        );
        notifier_stop.notify(ShutdownReason::Manual).await;

        let startup_msg = &transport_start.messages()[0].1;
        let shutdown_msg = &transport_stop.messages()[0].1;
        assert_ne!(startup_msg, shutdown_msg, "startup and shutdown messages must differ");
    }
}