//! Public dispatch for the `maestro` CLI subcommands.
//!
//! Extracted from the per-binary `main.rs` (NAP-245) so the umbrella `maestro`
//! binary can dispatch to the same logic.
//!
//! ## Transport (NAP-244)
//!
//! The CLI talks to its **home daemon** (`[cli].home_daemon_url`, default
//! `http://127.0.0.1:7070`) and lets the daemon broker the rest:
//!
//! * `list` reads the daemon's local catalog mirror (own ∪ peer sessions).
//! * `spawn` / `kill` hit the daemon's local session endpoints.
//! * `attach` opens the daemon's `WS /api/attach/:id` broker, which picks the
//!   transport and enforces `allow_inbound` on the target side.
//!
//! If the home daemon is **unreachable** (connection refused / not running),
//! every command falls back to the legacy registry path (registry HTTP +
//! direct WS) with a one-line stderr warning, so migration is painless. A few
//! operations the daemon can't yet satisfy locally (cross-daemon spawn → 501,
//! cross-daemon kill → 404) also fall back to the registry, which forwards
//! them the old way. The fallback is removed in a future ticket.

use std::path::{Path, PathBuf};

use crate::attach::{broker_attach_url, parse_detach_key, run_attach, run_attach_url};
use crate::cli::{AttachArgs, Command, KillArgs, ListArgs, PolicyCmd, SetRegistryArgs, SpawnArgs};
use crate::config::{default_config_path, CliConfig, ConfigError};
use crate::http::{HttpError, RegistryClient};
use crate::policy::{run_reload as run_policy_reload, run_show as run_policy_show};
use crate::sessions::{fetch_connect_info, run_kill, run_list, run_spawn};

#[derive(Debug, thiserror::Error)]
#[allow(clippy::result_large_err)]
pub enum CliError {
    #[error("config: {0}")]
    Config(#[from] ConfigError),
    #[error("{0}")]
    Http(#[from] crate::http::HttpError),
    #[error("{0}")]
    Attach(#[from] crate::attach::AttachError),
    #[error("{0}")]
    Io(#[from] std::io::Error),
    #[error("{0}")]
    Policy(#[from] crate::policy::PolicyError),
}

/// Dispatch a parsed top-level subcommand. The umbrella binary passes the
/// global flags (`--config`, `--registry-url`, `--home-daemon-url`) in
/// alongside the variant.
#[allow(clippy::result_large_err)]
pub async fn dispatch(
    command: Command,
    config: Option<PathBuf>,
    registry_url_override: Option<String>,
    home_daemon_url_override: Option<String>,
) -> Result<(), CliError> {
    let config_path = match config {
        Some(p) => p,
        None => default_config_path()?,
    };

    match command {
        Command::SetRegistry(args) => set_registry(&config_path, args),
        Command::Policy(sub) => policy(&config_path, sub).await,
        Command::List(args) => {
            list(
                &config_path,
                registry_url_override,
                home_daemon_url_override,
                args,
            )
            .await
        }
        Command::Spawn(args) => {
            spawn(
                &config_path,
                registry_url_override,
                home_daemon_url_override,
                args,
            )
            .await
        }
        Command::Attach(args) => {
            attach(
                &config_path,
                registry_url_override,
                home_daemon_url_override,
                args,
            )
            .await
        }
        Command::Kill(args) => {
            kill(
                &config_path,
                registry_url_override,
                home_daemon_url_override,
                args,
            )
            .await
        }
    }
}

#[allow(clippy::result_large_err)]
fn set_registry(config_path: &Path, args: SetRegistryArgs) -> Result<(), CliError> {
    let url = args.url.trim_end_matches('/');
    CliConfig::save_registry_url(config_path, url)?;
    println!("registry URL saved to {}", config_path.display());
    Ok(())
}

#[allow(clippy::result_large_err)]
async fn policy(config_path: &Path, sub: PolicyCmd) -> Result<(), CliError> {
    let mut stdout = std::io::stdout().lock();
    match sub {
        PolicyCmd::Reload => run_policy_reload(config_path, &mut stdout).await?,
        PolicyCmd::Show { json } => run_policy_show(config_path, json, &mut stdout).await?,
    }
    Ok(())
}

#[allow(clippy::result_large_err)]
async fn list(
    config_path: &Path,
    registry_url_override: Option<String>,
    home_daemon_url_override: Option<String>,
    args: ListArgs,
) -> Result<(), CliError> {
    let cfg = CliConfig::load(config_path)?;
    let home_url = cfg.resolve_home_daemon_url(home_daemon_url_override);
    let daemon = daemon_client(&home_url, config_path);
    let mut stdout = std::io::stdout().lock();

    match run_list(&daemon, &args, &mut stdout).await {
        Ok(()) => Ok(()),
        Err(e) if e.is_unreachable() => {
            warn_fallback(&home_url, &e);
            let registry = registry_client(registry_url_override, &cfg, config_path)?;
            run_list(&registry, &args, &mut stdout).await?;
            Ok(())
        }
        Err(e) => Err(e.into()),
    }
}

#[allow(clippy::result_large_err)]
async fn spawn(
    config_path: &Path,
    registry_url_override: Option<String>,
    home_daemon_url_override: Option<String>,
    args: SpawnArgs,
) -> Result<(), CliError> {
    let cfg = CliConfig::load(config_path)?;
    let home_url = cfg.resolve_home_daemon_url(home_daemon_url_override.clone());
    let daemon = daemon_client(&home_url, config_path);
    let attach_after = args.attach;
    // `spawn --attach` has no detach-key flag; use the attach default (Ctrl-q).
    let detach_key = 0x11;

    // Cross-daemon create isn't brokered by the local daemon yet (501), so we
    // fall back to the registry on that as well as on unreachable.
    let session = match run_spawn(&daemon, args.clone()).await {
        Ok(s) => s,
        Err(e) if e.is_unreachable() || e.is_remote_op_unsupported() => {
            warn_fallback(&home_url, &e);
            let registry = registry_client(registry_url_override.clone(), &cfg, config_path)?;
            run_spawn(&registry, args).await?
        }
        Err(e) => return Err(e.into()),
    };
    println!("spawned {}", session.id);

    if attach_after {
        attach_session(
            &home_url,
            registry_url_override,
            &cfg,
            config_path,
            session.id,
            detach_key,
        )
        .await?;
    }
    Ok(())
}

#[allow(clippy::result_large_err)]
async fn attach(
    config_path: &Path,
    registry_url_override: Option<String>,
    home_daemon_url_override: Option<String>,
    args: AttachArgs,
) -> Result<(), CliError> {
    let cfg = CliConfig::load(config_path)?;
    let home_url = cfg.resolve_home_daemon_url(home_daemon_url_override);
    let detach = parse_detach_key(&args.detach_key)?;
    attach_session(
        &home_url,
        registry_url_override,
        &cfg,
        config_path,
        args.session_id,
        detach,
    )
    .await
}

#[allow(clippy::result_large_err)]
async fn kill(
    config_path: &Path,
    registry_url_override: Option<String>,
    home_daemon_url_override: Option<String>,
    args: KillArgs,
) -> Result<(), CliError> {
    let cfg = CliConfig::load(config_path)?;
    let home_url = cfg.resolve_home_daemon_url(home_daemon_url_override);
    let daemon = daemon_client(&home_url, config_path);

    // The local daemon only kills sessions it owns (peer sessions → 404); the
    // registry forwards cross-daemon kills, so fall back on 404 too.
    match run_kill(&daemon, &args).await {
        Ok(()) => {}
        Err(e) if e.is_unreachable() || e.is_not_found() => {
            warn_fallback(&home_url, &e);
            let registry = registry_client(registry_url_override, &cfg, config_path)?;
            run_kill(&registry, &args).await?;
        }
        Err(e) => return Err(e.into()),
    }
    println!("killed {}", args.session_id);
    Ok(())
}

/// Attach to `session_id` through the home-daemon broker, falling back to the
/// registry's connect-info + direct WS path if the daemon is unreachable.
#[allow(clippy::result_large_err)]
async fn attach_session(
    home_url: &str,
    registry_url_override: Option<String>,
    cfg: &CliConfig,
    config_path: &Path,
    session_id: uuid::Uuid,
    detach: u8,
) -> Result<(), CliError> {
    let broker_url = broker_attach_url(home_url, session_id)?;
    match run_attach_url(&broker_url, detach).await {
        Ok(()) => Ok(()),
        Err(e) if e.is_unreachable() => {
            eprintln!(
                "[maestro] home daemon at {home_url} unreachable; \
                 falling back to the registry (legacy direct attach)"
            );
            let registry = registry_client(registry_url_override, cfg, config_path)?;
            let info = fetch_connect_info(&registry, session_id).await?;
            run_attach(info, session_id, detach).await?;
            Ok(())
        }
        Err(e) => Err(e.into()),
    }
}

/// HTTP client pointed at the home daemon's local API. The daemon's local
/// surface needs no auth (same-trust as `bind_addr`), so no cookie is sent.
fn daemon_client(home_url: &str, config_path: &Path) -> RegistryClient {
    RegistryClient::new(home_url.to_string(), None, config_path.to_path_buf())
}

/// HTTP client pointed at the registry (legacy / fallback path).
#[allow(clippy::result_large_err)]
fn registry_client(
    override_url: Option<String>,
    cfg: &CliConfig,
    config_path: &Path,
) -> Result<RegistryClient, CliError> {
    let url = override_url
        .or_else(|| cfg.registry_url.clone())
        .ok_or(ConfigError::NoRegistryUrl)?;
    Ok(RegistryClient::new(
        url,
        cfg.cookie.clone(),
        config_path.to_path_buf(),
    ))
}

fn warn_fallback(home_url: &str, err: &HttpError) {
    eprintln!(
        "[maestro] home daemon at {home_url} unavailable ({err}); \
         falling back to the registry"
    );
}