//! SSH-specific implementation of [`RemoteTransport`].
//!
//! [`SshTransport`] uses an existing SSH ControlMaster socket to check/install
//! the remote server binary and to launch the `remote-server-proxy` process
//! whose stdin/stdout become the protocol channel.
use std::fmt;
use std::future::Future;
use std::path::{Path, PathBuf};
use std::pin::Pin;
use std::sync::Arc;

use anyhow::Result;
use remote_server::auth::RemoteServerAuthContext;
use remote_server::client::RemoteServerClient;
use remote_server::manager::RemoteServerExitStatus;
use remote_server::setup::{
    parse_uname_output, remote_server_daemon_dir, PreinstallCheckResult, RemotePlatform,
};
use remote_server::ssh::ssh_args;
use remote_server::transport::{Connection, ControlPath, Error, InstallOutcome, RemoteTransport};
use warpui::r#async::executor;

#[path = "ssh_transport/installation.rs"]
pub(crate) mod installation;

/// SSH transport: connects via a ControlMaster socket.
///
/// `socket_path` is the local Unix socket created by the ControlMaster
/// process (`ssh -N -o ControlMaster=yes -o ControlPath=<path>`). All SSH
/// commands (binary check, install, proxy launch) are multiplexed through
/// this socket without re-authenticating.
#[derive(Clone)]
pub struct SshTransport {
    socket_path: PathBuf,
    auth_context: Arc<RemoteServerAuthContext>,
    /// Whether Warp owns the ControlMaster behind `socket_path`. `false`
    /// when the SSH wrapper attached to a master the user already had
    /// running, in which case Warp must not run `ssh -O exit` against it
    /// on teardown.
    warp_owns_control_master: bool,
}

impl fmt::Debug for SshTransport {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("SshTransport")
            .field("socket_path", &self.socket_path)
            .field("warp_owns_control_master", &self.warp_owns_control_master)
            .finish_non_exhaustive()
    }
}

impl SshTransport {
    pub fn new(
        socket_path: PathBuf,
        auth_context: Arc<RemoteServerAuthContext>,
        warp_owns_control_master: bool,
    ) -> Self {
        Self {
            socket_path,
            auth_context,
            warp_owns_control_master,
        }
    }

    pub fn socket_path(&self) -> &PathBuf {
        &self.socket_path
    }

    pub fn warp_owns_control_master(&self) -> bool {
        self.warp_owns_control_master
    }

    pub fn remote_daemon_socket_path(&self) -> String {
        format!(
            "{}/{}",
            remote_server_daemon_dir(&self.auth_context.remote_server_identity_key()),
            remote_server::setup::daemon_socket_name(),
        )
    }

    pub fn remote_daemon_pid_path(&self) -> String {
        format!(
            "{}/{}",
            remote_server_daemon_dir(&self.auth_context.remote_server_identity_key()),
            remote_server::setup::daemon_pid_name(),
        )
    }

    fn remote_proxy_command(&self) -> String {
        let binary = remote_server::setup::remote_server_binary();
        let identity_key = self.auth_context.remote_server_identity_key();
        let quoted_identity_key = shell_words::quote(&identity_key);
        format!("{binary} remote-server-proxy --identity-key {quoted_identity_key}")
    }
}

/// Runs `uname -sm` on the remote host via the ControlMaster socket and
/// parses the output into a [`RemotePlatform`].
async fn detect_remote_platform(socket_path: &Path) -> Result<RemotePlatform, Error> {
    let output = remote_server::ssh::run_ssh_command(
        socket_path,
        "uname -sm",
        remote_server::setup::CHECK_TIMEOUT,
    )
    .await?;
    if output.status.success() {
        let stdout = String::from_utf8_lossy(&output.stdout);
        parse_uname_output(&stdout)
    } else {
        let code = output.status.code().unwrap_or(-1);
        let stderr = String::from_utf8_lossy(&output.stderr);
        Err(Error::Other(anyhow::anyhow!(
            "uname -sm exited with code {code}: {stderr}"
        )))
    }
}

impl RemoteTransport for SshTransport {
    fn detect_platform(
        &self,
    ) -> Pin<Box<dyn Future<Output = Result<RemotePlatform, Error>> + Send>> {
        let socket_path = self.socket_path.clone();
        Box::pin(async move { detect_remote_platform(&socket_path).await })
    }

    fn run_preinstall_check(
        &self,
    ) -> Pin<Box<dyn Future<Output = Result<PreinstallCheckResult, Error>> + Send>> {
        let socket_path = self.socket_path.clone();
        Box::pin(async move {
            match remote_server::ssh::run_ssh_script(
                &socket_path,
                remote_server::setup::PREINSTALL_CHECK_SCRIPT,
                remote_server::setup::CHECK_TIMEOUT,
            )
            .await
            {
                Ok(output) if output.status.success() => {
                    let stdout = String::from_utf8_lossy(&output.stdout);
                    Ok(PreinstallCheckResult::parse(&stdout))
                }
                Ok(output) => {
                    let exit_code = output.status.code().unwrap_or(-1);
                    let stderr = String::from_utf8_lossy(&output.stderr).trim().to_string();
                    Err(Error::ScriptFailed { exit_code, stderr })
                }
                Err(e) => Err(e.into()),
            }
        })
    }

    fn check_binary(&self) -> Pin<Box<dyn Future<Output = Result<bool, Error>> + Send>> {
        let socket_path = self.socket_path.clone();
        Box::pin(async move {
            let binary = remote_server::setup::remote_server_binary();
            let expected_helper_version = if remote_server::setup::uses_static_linux_helper() {
                let platform = detect_remote_platform(&socket_path).await?;
                installation::local_helper_version(&platform).await
            } else {
                None
            };
            let cmd = match expected_helper_version {
                Some(version) => format!(
                    "{binary} --version >/dev/null && test \"$(cat {binary}.wormhole-version 2>/dev/null)\" = \"{version}\""
                ),
                None => remote_server::setup::binary_check_command(),
            };
            log::info!("Running binary check: {cmd}");
            let output = remote_server::ssh::run_ssh_command(
                &socket_path,
                &cmd,
                remote_server::setup::CHECK_TIMEOUT,
            )
            .await?;
            // `<binary> --version` exits 0 when present, executable, and
            // functional. Static helpers additionally compare their bundled
            // build marker, where exit 1 means the remote copy is stale.
            // Exit 127 means the binary was not found, and 126 means it exists
            // but is not executable. Any other non-zero exit (e.g. SSH exit
            // 255 for a dead connection, or signal termination) is treated as
            // a transport-level failure.
            let code = output.status.code();
            let stdout = String::from_utf8_lossy(&output.stdout);
            log::info!("Binary check result: exit={code:?} stdout={stdout}");
            match code {
                Some(0) => Ok(true),
                Some(1) | Some(126) | Some(127) => Ok(false),
                Some(code) => {
                    let stderr = String::from_utf8_lossy(&output.stderr);
                    Err(Error::Other(anyhow::anyhow!(
                        "binary check exited with code {code}: {stderr}"
                    )))
                }
                None => Err(Error::Other(anyhow::anyhow!(
                    "binary check terminated by signal"
                ))),
            }
        })
    }

    fn check_has_old_binary(&self) -> Pin<Box<dyn Future<Output = anyhow::Result<bool>> + Send>> {
        let socket_path = self.socket_path.clone();
        Box::pin(async move {
            // Treat the existence of the remote-server install directory
            // itself as evidence of a prior install. If `~/.warp-XX/remote-server`
            // exists, something was installed there before, so any mismatch
            // with the client's expected binary path should be auto-updated
            // rather than surfaced as a first-time install prompt.
            let cmd = format!("test -d {}", remote_server::setup::remote_server_dir());
            let output = remote_server::ssh::run_ssh_command(
                &socket_path,
                &cmd,
                remote_server::setup::CHECK_TIMEOUT,
            )
            .await?;
            // `test -d` exits 0 when present, 1 when missing.
            // Anything else is treated as a check failure.
            match output.status.code() {
                Some(0) => Ok(true),
                Some(1) => Ok(false),
                Some(code) => {
                    let stderr = String::from_utf8_lossy(&output.stderr);
                    Err(anyhow::anyhow!(
                        "remote-server dir check exited with code {code}: {stderr}"
                    ))
                }
                None => Err(anyhow::anyhow!(
                    "remote-server dir check terminated by signal"
                )),
            }
        })
    }

    fn install_binary(&self) -> Pin<Box<dyn Future<Output = InstallOutcome> + Send>> {
        let socket_path = self.socket_path.clone();
        Box::pin(async move { installation::install_binary(&socket_path).await })
    }

    fn connect(
        &self,
        executor: Arc<executor::Background>,
    ) -> Pin<Box<dyn Future<Output = Result<Connection>> + Send>> {
        let socket_path = self.socket_path.clone();
        let warp_owns_control_master = self.warp_owns_control_master;
        let remote_proxy_command = self.remote_proxy_command();
        Box::pin(async move {
            let mut args = ssh_args(&socket_path);
            args.push(remote_proxy_command);

            // `kill_on_drop(true)` pairs with ownership of the `Child` being
            // returned in the [`Connection`] below: the
            // [`RemoteServerManager`] holds the `Child` on its per-session
            // state, and dropping that state (on explicit teardown or
            // spontaneous disconnect) sends SIGKILL to this ssh process.
            let mut child = command::r#async::Command::new("ssh")
                .args(&args)
                .stdin(std::process::Stdio::piped())
                .stdout(std::process::Stdio::piped())
                .stderr(std::process::Stdio::piped())
                .kill_on_drop(true)
                .spawn()?;

            let stdin = child
                .stdin
                .take()
                .ok_or_else(|| anyhow::anyhow!("Failed to capture child stdin"))?;
            let stdout = child
                .stdout
                .take()
                .ok_or_else(|| anyhow::anyhow!("Failed to capture child stdout"))?;
            let stderr = child
                .stderr
                .take()
                .ok_or_else(|| anyhow::anyhow!("Failed to capture child stderr"))?;

            let (client, event_rx, failure_rx, host_response_rx, stderr_tail) =
                RemoteServerClient::from_child_streams(stdin, stdout, stderr, &executor);
            Ok(Connection {
                client,
                event_rx,
                failure_rx,
                host_response_rx,
                child,
                // Tag the socket with master ownership. Teardown only runs
                // `ssh -O exit` against Warp-managed masters; a user-owned
                // (external) master must be left running when the Warp
                // session exits.
                control_path: if warp_owns_control_master {
                    ControlPath::WarpManaged(socket_path)
                } else {
                    ControlPath::UserOwned(socket_path)
                },
                stderr_tail,
            })
        })
    }

    fn remove_remote_server_binary(
        &self,
    ) -> Pin<Box<dyn Future<Output = anyhow::Result<()>> + Send>> {
        let socket_path = self.socket_path.clone();
        Box::pin(async move {
            let cmd = remote_server::setup::remote_server_removal_command();
            log::info!("Removing stale remote server binary: {cmd}");
            let output = remote_server::ssh::run_ssh_command(
                &socket_path,
                &cmd,
                remote_server::setup::CHECK_TIMEOUT,
            )
            .await?;
            if output.status.success() {
                Ok(())
            } else {
                let stderr = String::from_utf8_lossy(&output.stderr);
                Err(anyhow::anyhow!("Failed to remove binary: {stderr}"))
            }
        })
    }

    /// SSH exit code 255 indicates a connection-level error (broken pipe,
    /// connection reset, host unreachable) — the ControlMaster's TCP
    /// connection is dead. A signal kill also suggests the transport was
    /// torn down. In either case, reconnecting through the same
    /// ControlMaster is futile.
    fn is_reconnectable(&self, exit_status: Option<&RemoteServerExitStatus>) -> bool {
        match exit_status {
            Some(s) => s.code != Some(255) && !s.signal_killed,
            // No exit status available — optimistically allow reconnect.
            None => true,
        }
    }
}

#[cfg(test)]
#[path = "ssh_transport_tests.rs"]
mod tests;