git-ark 0.6.0

//! `host add`: the SSH orchestration that wires the pure pieces in
//! `hostspec.rs`/`registry.rs` onto a real box.
//!
//! Everything here that actually talks to a host (`ssh_run`,
//! `ssh_pipe_file`, `ssh_append_unique`, `host_add`) is exercised end to end
//! by the controller against `docker/test-host`, not by a unit test — there
//! is no live host in CI. What IS unit-tested is every pure seam: parsing
//! `user@host`, building the `ssh` argument vector, the remote shell
//! commands those transport fns run, and the client-side path resolution
//! (keydir, registry path, `~/.ssh/config` upsert).

use crate::config::S3Config;
use crate::github;
use crate::hostspec::{
    assess, forced_command_line, parse_probe, per_host_prefix, render_config, render_secrets,
    ssh_config_block, PROBE_SCRIPT,
};
use crate::registry::{Host, Registry};
use crate::release;
use crate::repo_policy::read_repo_policy;
use crate::sshdiag::{classify_ssh_error, diagnosis_message, SshDiagnosis};
use anyhow::{anyhow, bail, Context, Result};
use std::collections::HashMap;
use std::io::Write;
use std::path::{Path, PathBuf};
use std::process::{Command, Stdio};

// ---------------------------------------------------------------------
// SSH transport
// ---------------------------------------------------------------------

/// The control-channel SSH target: the operator's interactive key, never the
/// forced-command key that `host add` goes on to install.
#[derive(Debug, Clone)]
pub struct SshSpec {
    pub user: String,
    pub host: String,
    pub port: Option<u16>,
    pub identity: Option<PathBuf>,
}

impl SshSpec {
    fn display(&self) -> String {
        format!("{}@{}", self.user, self.host)
    }
}

/// Split an ssh target `user@host` into `(user, host)`. git-ark hosts always
/// run under a dedicated user, so a bare hostname (no `@`) is rejected rather
/// than guessed at.
pub fn parse_target(target: &str) -> Result<(String, String)> {
    let (user, host) = target
        .split_once('@')
        .ok_or_else(|| anyhow::anyhow!("target must be `user@host` (got {target:?})"))?;
    if user.is_empty() || host.is_empty() {
        bail!("target must be `user@host` (got {target:?})");
    }
    Ok((user.to_string(), host.to_string()))
}

/// The `ssh` argument vector for `spec`, up to (not including) the trailing
/// remote command: `[-p <port>] [-i <identity>] -o StrictHostKeyChecking=accept-new
/// <user@host>`. `accept-new` trusts a host on first contact but still detects
/// a changed key on a later connection — the right default for boxes named
/// explicitly by the operator (this slice has no other host-identity check).
fn ssh_args(spec: &SshSpec) -> Vec<String> {
    let mut args = Vec::new();
    if let Some(port) = spec.port {
        args.push("-p".to_string());
        args.push(port.to_string());
    }
    if let Some(identity) = &spec.identity {
        args.push("-i".to_string());
        args.push(identity.display().to_string());
    }
    args.push("-o".to_string());
    args.push("StrictHostKeyChecking=accept-new".to_string());
    args.push(spec.display());
    args
}

fn ssh_command(spec: &SshSpec) -> Command {
    let mut cmd = Command::new("ssh");
    cmd.args(ssh_args(spec));
    cmd
}

/// Run `cmd` on `spec` over the control channel, returning stdout. Non-zero
/// exit is an error carrying stderr.
pub fn ssh_run(spec: &SshSpec, cmd: &str) -> Result<String> {
    let out = ssh_command(spec)
        .arg(cmd)
        .output()
        .with_context(|| format!("spawning ssh to {}", spec.display()))?;
    if !out.status.success() {
        bail!(
            "ssh {} failed: {}",
            spec.display(),
            String::from_utf8_lossy(&out.stderr).trim()
        );
    }
    Ok(String::from_utf8_lossy(&out.stdout).into_owned())
}

/// Like `ssh_run`, but writes `input` to the remote command's stdin before
/// waiting on it — the transport underneath `ssh_pipe_file` and
/// `ssh_append_unique`.
fn ssh_run_with_stdin(spec: &SshSpec, cmd: &str, input: &[u8]) -> Result<String> {
    let mut child = ssh_command(spec)
        .arg(cmd)
        .stdin(Stdio::piped())
        .stdout(Stdio::piped())
        .stderr(Stdio::piped())
        .spawn()
        .with_context(|| format!("spawning ssh to {}", spec.display()))?;
    child
        .stdin
        .take()
        .expect("stdin was piped")
        .write_all(input)
        .context("writing to ssh stdin")?;
    let out = child
        .wait_with_output()
        .with_context(|| format!("waiting on ssh to {}", spec.display()))?;
    if !out.status.success() {
        bail!(
            "ssh {} failed: {}",
            spec.display(),
            String::from_utf8_lossy(&out.stderr).trim()
        );
    }
    Ok(String::from_utf8_lossy(&out.stdout).into_owned())
}

/// The remote shell command `ssh_pipe_file` runs: capture stdin to a temp
/// file next to the target, `chmod` it, then atomically `mv` it into place —
/// so a connection dropped mid-transfer never leaves a partial file at
/// `remote_path`. `umask 077` makes the staged temp file private from the
/// moment it's created, rather than briefly world/group-readable under the
/// remote's default umask until the explicit `chmod` lands — belt-and-
/// suspenders for `secrets.toml`, harmless for the world-readable modes.
fn pipe_file_command(remote_path: &str, mode: u32) -> String {
    let tmp = format!("{remote_path}.uploading");
    let remote_q = shell_words::quote(remote_path);
    let tmp_q = shell_words::quote(&tmp);
    format!("umask 077; cat > {tmp_q} && chmod {mode:o} {tmp_q} && mv {tmp_q} {remote_q}")
}

/// Stream `bytes` to `remote_path` on the host, then `chmod mode`. Used for
/// the binary, `config.toml`, and `secrets.toml` — the proven pattern of
/// piping over the same control-channel `ssh` rather than requiring `scp`.
pub fn ssh_pipe_file(spec: &SshSpec, remote_path: &str, bytes: &[u8], mode: u32) -> Result<()> {
    ssh_run_with_stdin(spec, &pipe_file_command(remote_path, mode), bytes)?;
    Ok(())
}

/// The remote shell command `ssh_append_unique` runs: remove any existing
/// line containing `marker`, then append the line read from stdin — so
/// re-running `host add` with the *same* key is a no-op (removed, then
/// re-added, byte-identical) and re-running with a *rotated* key actually
/// replaces the stale line instead of silently keeping it (skip-on-marker
/// would leave a rotated forced-command key permanently unauthorized, since
/// `marker` — `install_dir` — is present regardless of which pubkey the line
/// carries). Backs `remote_file` up to `<remote_file>.bak` the first time
/// it's touched (never overwrites an existing backup).
///
/// `grep -v` exits 1 when it filters everything out of a file (e.g. the file
/// held only the stale line), so that step is deliberately decoupled from the
/// `&&` chain with `|| true` — otherwise the very rotation case this is meant
/// to fix would abort before the new line gets appended.
///
/// `remote_file` is interpolated unquoted (as a bare `sh` assignment) so a
/// leading `~` still tilde-expands — quoting it would suppress that. Every
/// call site in this file passes a fixed literal, never operator input, so
/// this is safe.
fn append_unique_script(remote_file: &str, marker: &str) -> String {
    let marker_q = shell_words::quote(marker);
    format!(
        "f={remote_file}; d=$(dirname \"$f\"); mkdir -p \"$d\" && touch \"$f\" && \
         line=\"$(cat)\" && {{ [ -f \"$f.bak\" ] || cp \"$f\" \"$f.bak\"; }} && \
         {{ grep -vF {marker_q} \"$f\" > \"$f.tmp\" 2>/dev/null || true; }} && \
         printf '%s\\n' \"$line\" >> \"$f.tmp\" && mv \"$f.tmp\" \"$f\""
    )
}

/// Append `line` to `remote_file` on the host, idempotently (see
/// `append_unique_script`).
pub fn ssh_append_unique(
    spec: &SshSpec,
    remote_file: &str,
    line: &str,
    marker: &str,
) -> Result<()> {
    ssh_run_with_stdin(
        spec,
        &append_unique_script(remote_file, marker),
        line.as_bytes(),
    )?;
    Ok(())
}

/// The remote selfcheck command: `<install_dir>/bin/git-ark selfcheck
/// --config <install_dir>/config.toml`, both paths shell-quoted like every
/// other remote command here — an unquoted `install_dir` containing a space
/// (a spaced remote `$HOME`) would otherwise split apart and false-abort an
/// otherwise-good host.
fn selfcheck_command(install_dir: &str) -> String {
    let bin_q = shell_words::quote(&format!("{install_dir}/bin/git-ark")).into_owned();
    let cfg_q = shell_words::quote(&format!("{install_dir}/config.toml")).into_owned();
    format!("{bin_q} selfcheck --config {cfg_q}")
}

/// `mkdir -p` one or more remote directories, each shell-quoted.
fn ssh_mkdir_p(spec: &SshSpec, dirs: &[String]) -> Result<()> {
    let quoted: Vec<String> = dirs
        .iter()
        .map(|d| shell_words::quote(d).into_owned())
        .collect();
    ssh_run(spec, &format!("mkdir -p {}", quoted.join(" ")))?;
    Ok(())
}

// ---------------------------------------------------------------------
// Client-side paths (keydir, registry, ~/.ssh/config)
// ---------------------------------------------------------------------

/// Client-side git-ark state directory — per-host forced-command keypairs,
/// and (absent a `GIT_ARK_HOSTS` override) the host registry. `~/.config/git-ark`:
/// colocated with the other client-side state (the age `identity.txt`), and
/// distinct from `~/.ssh` — a per-host key here is git-ark's own, not a
/// general-purpose SSH identity an operator would expect to find in `~/.ssh`.
fn client_dir(home: &Path) -> PathBuf {
    home.join(".config").join("git-ark")
}

fn home_dir() -> Result<PathBuf> {
    if let Ok(home) = std::env::var("HOME") {
        return Ok(PathBuf::from(home));
    }
    // Windows sets USERPROFILE, not HOME — the client (unlike the host) is
    // cross-platform, so fall back rather than erroring on every Windows run.
    std::env::var("USERPROFILE")
        .map(PathBuf::from)
        .context("neither HOME nor USERPROFILE is set")
}

pub fn client_keydir() -> Result<PathBuf> {
    Ok(client_dir(&home_dir()?))
}

pub fn client_ssh_config_path() -> Result<PathBuf> {
    Ok(home_dir()?.join(".ssh").join("config"))
}

/// The host registry path: `GIT_ARK_HOSTS` overrides (tests, alternate
/// profiles); else `<keydir>/hosts.toml`.
pub fn registry_path() -> Result<PathBuf> {
    if let Ok(p) = std::env::var("GIT_ARK_HOSTS") {
        return Ok(PathBuf::from(p));
    }
    Ok(client_keydir()?.join("hosts.toml"))
}

/// Drop the `Host git-ark-<name>` block from `existing`'s lines, keyed by its
/// `Host` line — every other block is preserved untouched, and trailing blank
/// lines are trimmed so callers control spacing after. Shared by
/// `upsert_ssh_config_block` (which re-appends a fresh block) and
/// `remove_ssh_config_block` (which doesn't).
fn drop_ssh_config_block<'a>(existing: &'a str, name: &str) -> Vec<&'a str> {
    let marker = format!("Host git-ark-{name}");
    let lines: Vec<&str> = existing.lines().collect();
    let mut kept: Vec<&str> = Vec::new();
    let mut i = 0;
    while i < lines.len() {
        if lines[i].trim() == marker {
            i += 1;
            // Drop the old block's body: everything up to the next `Host `
            // or `Match ` line — ssh_config stanzas are terminated by either
            // (the trailing space also keeps this from matching `HostName`).
            while i < lines.len()
                && !lines[i].trim_start().starts_with("Host ")
                && !lines[i].trim_start().starts_with("Match ")
            {
                i += 1;
            }
            continue;
        }
        kept.push(lines[i]);
        i += 1;
    }
    while matches!(kept.last(), Some(l) if l.trim().is_empty()) {
        kept.pop();
    }
    kept
}

/// Insert or replace the `Host git-ark-<name>` block within `existing` (the
/// current contents of `~/.ssh/config`), keyed by its `Host` line. Every
/// other block is preserved untouched; a prior block for this name is
/// replaced in place (idempotent re-runs of `host add`), otherwise the new
/// block is appended.
pub fn upsert_ssh_config_block(existing: &str, name: &str, block: &str) -> String {
    let kept = drop_ssh_config_block(existing, name);
    let mut out = kept.join("\n");
    if !out.is_empty() {
        out.push_str("\n\n");
    }
    out.push_str(block.trim_end());
    out.push('\n');
    out
}

/// Remove the `Host git-ark-<name>` block from `existing`, if present. Every
/// other block is preserved untouched. Used by `host remove` to drop the
/// client `~/.ssh/config` alias once a host leaves the registry.
pub fn remove_ssh_config_block(existing: &str, name: &str) -> String {
    let kept = drop_ssh_config_block(existing, name);
    if kept.is_empty() {
        return String::new();
    }
    let mut out = kept.join("\n");
    out.push('\n');
    out
}

/// The best `~/.ssh/config` alias that already reaches (`host`, `user`), for
/// recording as a host's push alias during adopt. Scans every `Host` stanza
/// (not just git-ark ones); a stanza matches when its `HostName` equals `host`
/// and, when `user` is given, its `User` equals `user` (a stanza with no `User`
/// line still matches — ssh falls through to the command-line user). Among the
/// matching stanzas' aliases, prefers an exact `git-ark-<name>`, then the first
/// beginning `git-ark`, then the first alias seen. `None` if nothing matches.
fn find_alias_for_target(
    ssh_config: &str,
    host: &str,
    user: Option<&str>,
    name: &str,
) -> Option<String> {
    let lines: Vec<&str> = ssh_config.lines().collect();
    let mut candidates: Vec<String> = Vec::new();
    let mut i = 0;
    while i < lines.len() {
        let mut head = lines[i].split_whitespace();
        if !matches!(head.next(), Some(k) if k.eq_ignore_ascii_case("Host")) {
            i += 1;
            continue;
        }
        let aliases: Vec<String> = head.map(|s| s.to_string()).collect();
        // Read the stanza body (until the next Host/Match) for HostName / User.
        i += 1;
        let mut hostname: Option<&str> = None;
        let mut block_user: Option<&str> = None;
        while i < lines.len() {
            let mut bt = lines[i].split_whitespace();
            match bt.next() {
                Some(k) if k.eq_ignore_ascii_case("Host") || k.eq_ignore_ascii_case("Match") => {
                    break
                }
                Some(k) if k.eq_ignore_ascii_case("HostName") => hostname = bt.next(),
                Some(k) if k.eq_ignore_ascii_case("User") => block_user = bt.next(),
                _ => {}
            }
            i += 1;
        }
        let host_matches = hostname == Some(host);
        let user_matches = match (user, block_user) {
            (None, _) | (Some(_), None) => true,
            (Some(u), Some(bu)) => u == bu,
        };
        if host_matches && user_matches {
            candidates.extend(aliases);
        }
    }
    let exact = format!("git-ark-{name}");
    candidates
        .iter()
        .find(|a| **a == exact)
        .or_else(|| candidates.iter().find(|a| a.starts_with("git-ark")))
        .or_else(|| candidates.first())
        .cloned()
}

/// Parse `key=value` lines (probe/selfcheck output shape) into a lookup map.
fn parse_kv(text: &str) -> std::collections::HashMap<String, String> {
    text.lines()
        .filter_map(|l| l.split_once('='))
        .map(|(k, v)| (k.to_string(), v.to_string()))
        .collect()
}

// ---------------------------------------------------------------------
// host add
// ---------------------------------------------------------------------

pub struct HostAddArgs {
    pub name: String,
    pub target: String,
    pub port: Option<u16>,
    pub identity: Option<PathBuf>,
    pub bucket: String,
    pub region: String,
    pub prefix: String,
    pub endpoint: Option<String>,
    pub recipient: String,
    /// Binary to ship to the host. `None` auto-fetches the matching release
    /// asset for this client's version (see `release::fetch_host_binary`).
    pub binary: Option<PathBuf>,
    /// Designate this host the GitHub mirror once it's wired and registered.
    /// Requires `GIT_ARK_GITHUB_TOKEN`; demotes whichever other host
    /// currently holds the mirror (see `designate_mirror`).
    pub mirror: bool,
}

/// Reject a `name` that isn't safe to use as a client keydir path component,
/// an ssh alias (`Host git-ark-<name>`), and a registry key. Checked before
/// any other work in `host_add` — unvalidated, `name` could walk
/// `keydir.join(name)` outside `~/.config/git-ark` (e.g. `../../foo`) or emit
/// a broken `Host git-ark-<name>` block.
fn validate_host_name(name: &str) -> Result<()> {
    let ok = !name.is_empty()
        && name != "."
        && name != ".."
        && name
            .chars()
            .all(|c| c.is_ascii_alphanumeric() || matches!(c, '.' | '_' | '-'));
    if !ok {
        bail!("host name {name:?} must match [A-Za-z0-9._-]+ (and not be `.` or `..`)");
    }
    Ok(())
}

/// Probe, wire, verify, and register a host. Fails before mutating anything
/// on the host if the probe/capability check doesn't pass; re-running for
/// the same `name` is idempotent (re-streams the binary/config, never
/// duplicates the `authorized_keys`/`~/.ssh/config` entries).
pub fn host_add(args: &HostAddArgs) -> Result<()> {
    validate_host_name(&args.name)?;

    // Host credentials, read first — before the probe or any ssh call — so a
    // missing/empty cred aborts with the host completely untouched, rather
    // than after dirs are created and the binary streamed.
    let key_id = std::env::var("GIT_ARK_HOST_S3_KEY_ID")
        .ok()
        .filter(|s| !s.is_empty());
    let secret = std::env::var("GIT_ARK_HOST_S3_SECRET")
        .ok()
        .filter(|s| !s.is_empty());
    let (key_id, secret) = match (key_id, secret) {
        (Some(k), Some(s)) => (k, s),
        _ => bail!(
            "GIT_ARK_HOST_S3_KEY_ID and GIT_ARK_HOST_S3_SECRET must both be set \
             (the host's write-only S3 credential); nothing was written to the host"
        ),
    };

    let (user, host) = parse_target(&args.target)?;
    let spec = SshSpec {
        user: user.clone(),
        host: host.clone(),
        port: args.port,
        identity: args.identity.clone(),
    };

    // 1. Probe + capability check. Nothing is written to the host until this
    // passes — a red probe leaves the box exactly as found.
    let probe_out = ssh_run(&spec, PROBE_SCRIPT)
        .inspect_err(|e| {
            // Diagnosis is a side note on the way to the same error, not a
            // replacement for it — `Other` prints nothing rather than
            // fabricate advice for an unrecognized failure.
            let diagnosis = classify_ssh_error(&e.to_string());
            if diagnosis != SshDiagnosis::Other {
                eprintln!(
                    "{}",
                    diagnosis_message(diagnosis, &spec.display(), args.port.unwrap_or(22))
                );
            }
        })
        .with_context(|| format!("probing {}", spec.display()))?;
    let facts = parse_probe(&probe_out);
    let plan = match assess(&facts) {
        Ok(plan) => plan,
        Err(reasons) => {
            eprintln!("✗ {} is not ready for git-ark:", spec.display());
            for r in &reasons {
                eprintln!("  - {r}");
            }
            bail!(
                "preflight probe failed ({} reason(s)); nothing was written to the host",
                reasons.len()
            );
        }
    };

    // 2. Resolve the binary. With `--binary`, read that path (a filename that
    // doesn't look like the target triple is a warning, not a hard stop — it
    // may be a renamed/symlinked binary that's still correct). Without it,
    // auto-fetch the matching release asset for the probed triple, verified
    // against the release SHA256SUMS.
    let binary_bytes = match &args.binary {
        Some(path) => {
            let bytes = std::fs::read(path)
                .with_context(|| format!("reading --binary {}", path.display()))?;
            if !path.to_string_lossy().contains(&plan.triple) {
                eprintln!(
                    "⚠ --binary {} doesn't look like it's built for {} (the probed host's triple) — continuing anyway",
                    path.display(),
                    plan.triple
                );
            }
            bytes
        }
        None => {
            println!(
                "• fetching git-ark v{} for {} from the release…",
                release::version(),
                plan.triple
            );
            release::fetch_host_binary(&plan.triple)?
        }
    };

    // 3. Forced-command keypair — generated client-side; only the public
    // half ever reaches the host. Skip if a key for this name already exists
    // (idempotent re-run).
    let keydir = client_keydir()?;
    std::fs::create_dir_all(&keydir).with_context(|| format!("creating {}", keydir.display()))?;
    let key_path = keydir.join(&args.name);
    let pub_path = keydir.join(format!("{}.pub", args.name));
    if !key_path.exists() {
        let status = Command::new("ssh-keygen")
            .args(["-t", "ed25519", "-N", "", "-q"])
            .arg("-f")
            .arg(&key_path)
            .arg("-C")
            .arg(format!("git-ark-{}", args.name))
            .status()
            .context("spawning ssh-keygen")?;
        if !status.success() {
            bail!("ssh-keygen failed generating {}", key_path.display());
        }
    }
    let pubkey = std::fs::read_to_string(&pub_path)
        .with_context(|| format!("reading {}", pub_path.display()))?
        .trim()
        .to_string();

    // 4. Remote install dirs.
    ssh_mkdir_p(
        &spec,
        &[
            format!("{}/bin", plan.install_dir),
            format!("{}/repos", plan.install_dir),
        ],
    )?;

    // 5. Stream the binary.
    ssh_pipe_file(
        &spec,
        &format!("{}/bin/git-ark", plan.install_dir),
        &binary_bytes,
        0o755,
    )?;

    // 6. Stream config.toml and secrets.toml. The host's write-only S3
    // credential was read from env at the top of this fn — never argv,
    // never printed. The rendered config's prefix is namespaced by host name
    // (per_host_prefix) so each host writes its own S3 subtree — the
    // registry keeps `args.prefix` as the shared base (see the `Host {..}`
    // below). No `--mirror` yet (Task 3); every host add is a plain,
    // non-mirror host until then.
    let s3 = S3Config {
        bucket: args.bucket.clone(),
        region: args.region.clone(),
        prefix: per_host_prefix(&args.prefix, &args.name),
        endpoint: args.endpoint.clone(),
    };
    let config_text = render_config(&plan.install_dir, &args.recipient, &s3, false);
    ssh_pipe_file(
        &spec,
        &format!("{}/config.toml", plan.install_dir),
        config_text.as_bytes(),
        0o644,
    )?;
    let secrets_text = render_secrets(&key_id, &secret, None);
    ssh_pipe_file(
        &spec,
        &format!("{}/secrets.toml", plan.install_dir),
        secrets_text.as_bytes(),
        0o600,
    )?;

    // 7. Install the forced-command key, replacing any existing line for
    // this install_dir (marker = install_dir, baked into the command= it's
    // paired with) — so a rotated/regenerated key replaces the stale one
    // instead of silently no-opping (see `append_unique_script`).
    let line = forced_command_line(&plan.install_dir, &pubkey);
    ssh_append_unique(&spec, "~/.ssh/authorized_keys", &line, &plan.install_dir)?;

    // 8. Verify. A failed/unhealthy selfcheck aborts here — the host is left
    // wired as-is (not rolled back) so the operator can inspect and re-run.
    let selfcheck_out = ssh_run(&spec, &selfcheck_command(&plan.install_dir))?;
    let selfcheck = parse_kv(&selfcheck_out);
    let config_valid = selfcheck.get("config_valid").map(String::as_str) == Some("true");
    let version = selfcheck.get("git_ark_version");
    if !config_valid || version.is_none() {
        bail!(
            "selfcheck did not report a healthy host (config_valid={:?}, git_ark_version={:?}); \
             the host has been wired, but `host add {}` should be re-run once fixed",
            selfcheck.get("config_valid"),
            version,
            args.name
        );
    }

    // 9. Client ~/.ssh/config alias, idempotent by `Host git-ark-<name>`.
    let port = args.port.unwrap_or(22);
    let block = ssh_config_block(
        &args.name,
        &host,
        port,
        &user,
        &key_path.display().to_string(),
    );
    let ssh_config_path = client_ssh_config_path()?;
    if let Some(parent) = ssh_config_path.parent() {
        std::fs::create_dir_all(parent)
            .with_context(|| format!("creating {}", parent.display()))?;
    }
    let existing = std::fs::read_to_string(&ssh_config_path).unwrap_or_default();
    let updated = upsert_ssh_config_block(&existing, &args.name, &block);
    std::fs::write(&ssh_config_path, updated)
        .with_context(|| format!("writing {}", ssh_config_path.display()))?;

    // 10. Register.
    let registry_path = registry_path()?;
    let mut registry = Registry::load(&registry_path)?;
    registry.upsert(Host {
        name: args.name.clone(),
        ssh_target: args.target.clone(),
        port,
        // The CONTROL-channel identity (the operator's interactive key), NOT the
        // forced-command key: management ops (apply_host_config / mirror set /
        // upgrade) run arbitrary commands and must use the control channel, or
        // they hit the git-only forced-command shim. The forced-command key is
        // used solely by the git-push ssh alias (`git-ark-<name>`).
        identity: args.identity.clone(),
        triple: plan.triple.clone(),
        install_dir: plan.install_dir.clone(),
        recipient: args.recipient.clone(),
        bucket: args.bucket.clone(),
        region: args.region.clone(),
        prefix: args.prefix.clone(),
        endpoint: args.endpoint.clone(),
        mirror: false,
        // Conventional host — the alias is `git-ark-<name>`, which host_add just
        // wrote. `None` resolves to exactly that; recording it would be noise.
        push_alias: None,
    });
    registry.save(&registry_path)?;

    println!(
        "✓ {} ready — git push git-ark-{}:<repo>",
        args.name, args.name
    );
    if let (Some(pct), Some(bytes)) = (
        selfcheck.get("disk_free_percent"),
        selfcheck.get("disk_free_bytes"),
    ) {
        println!("  disk: {pct}% free ({bytes} bytes)");
    }

    // 11. --mirror: designate this host the GitHub mirror now that it's
    // wired + registered. Reuses the `registry` already in scope (it holds
    // the just-upserted host, mirror=false) — `designate_mirror` re-renders
    // this host's config/secrets a second time (mirror=true, token written)
    // and, if some other host was the mirror, demotes it too.
    if args.mirror {
        let token = match std::env::var("GIT_ARK_GITHUB_TOKEN")
            .ok()
            .filter(|s| !s.is_empty())
        {
            Some(t) => t,
            None => bail!(
                "GIT_ARK_GITHUB_TOKEN must be set to add {} as the GitHub mirror (--mirror); \
                 the host was still added, just not designated the mirror \
                 (run `git-ark mirror set {}` once the token is set)",
                args.name,
                args.name
            ),
        };
        designate_mirror(&mut registry, &args.name, &token)?;
        println!("✓ {} designated the GitHub mirror", args.name);
    }

    Ok(())
}

// ---------------------------------------------------------------------
// host adopt — register an already-deployed host without touching it
// ---------------------------------------------------------------------

/// Inputs for `host adopt`.
pub struct HostAdoptArgs {
    pub name: String,
    pub target: String,
    pub port: Option<u16>,
    pub identity: Option<PathBuf>,
    /// Path to the host's `config.toml`; if omitted, adopt reads it from the
    /// git-ark forced-command line in the host's `authorized_keys`.
    pub config: Option<String>,
    /// The push alias to record, overriding discovery. Use when `~/.ssh/config`
    /// has several stanzas for this target, or none and you want to name it.
    pub push_alias: Option<String>,
}

/// Adopt an already-deployed host into the client registry — the recovery path
/// (a lost registry) and the way to bring in a host wired before the registry
/// existed. Reconstructs the registry entry from the host's deployed surface
/// over the control channel, verifies with `selfcheck`, and registers it.
///
/// It is **read-only on the host** and writes **nothing** to the client's ssh
/// config (no `git-ark-<name>` alias) — so existing remotes and aliases are
/// untouched. `status`/`upgrade` ride the control channel and need no alias.
pub fn host_adopt(args: &HostAdoptArgs) -> Result<()> {
    validate_host_name(&args.name)?;
    let (user, host) = parse_target(&args.target)?;
    let spec = SshSpec {
        user,
        host,
        port: args.port,
        identity: args.identity.clone(),
    };

    // 1. Where does git-ark live on the host? Explicit --config, else parse the
    //    forced-command line in authorized_keys.
    let config_path = match &args.config {
        Some(c) => c.clone(),
        None => {
            let ak = ssh_run(&spec, "cat ~/.ssh/authorized_keys 2>/dev/null || true")?;
            parse_forced_command_config(&ak).ok_or_else(|| {
                anyhow!(
                    "no git-ark forced-command line found in {}'s authorized_keys — \
                     pass --config <path-to-config.toml> to point me at it",
                    args.target
                )
            })?
        }
    };
    let install_dir = std::path::Path::new(&config_path)
        .parent()
        .and_then(|p| p.to_str())
        .ok_or_else(|| anyhow!("can't derive the install dir from {config_path}"))?
        .to_string();

    // 2. Triple from uname.
    let triple = triple_from_uname(&ssh_run(&spec, "uname -s; uname -m")?)?;

    // 3. Read the host's config.toml → the vault fields for a complete entry.
    let cfg_text = ssh_run(&spec, &format!("cat {}", shell_words::quote(&config_path)))?;
    let cfg: toml::Value =
        toml::from_str(&cfg_text).map_err(|e| anyhow!("parsing the host's config.toml: {e}"))?;
    let str_at = |v: Option<&toml::Value>| v.and_then(|x| x.as_str()).unwrap_or("").to_string();
    let s3 = cfg.get("s3");
    let recipient = str_at(cfg.get("age_recipient"));
    let bucket = str_at(s3.and_then(|v| v.get("bucket")));
    let region = str_at(s3.and_then(|v| v.get("region")));
    let prefix = str_at(s3.and_then(|v| v.get("prefix")));
    let endpoint = s3
        .and_then(|v| v.get("endpoint"))
        .and_then(|v| v.as_str())
        .map(str::to_string);
    let mirror = cfg.get("mirror").and_then(|v| v.as_bool()).unwrap_or(false);

    // 4. Verify with selfcheck (read-only). Use the exact config path found.
    let bin_q = shell_words::quote(&format!("{install_dir}/bin/git-ark")).into_owned();
    let cfg_q = shell_words::quote(&config_path).into_owned();
    let selfcheck = ssh_run(&spec, &format!("{bin_q} selfcheck --config {cfg_q}"))
        .context("running the host's git-ark selfcheck")?;
    if !selfcheck.contains("config_valid=true") {
        bail!(
            "selfcheck didn't confirm a working git-ark at {install_dir} on {}:\n{}",
            args.target,
            selfcheck.trim()
        );
    }
    let version = parse_kv(&selfcheck)
        .get("git_ark_version")
        .cloned()
        .unwrap_or_else(|| "?".into());

    // 5. Discover the push alias — an explicit --push-alias wins; else read the
    //    client's own ~/.ssh/config (still touching nothing) for a stanza that
    //    already reaches this target. `None` if there's nothing to discover:
    //    status/upgrade still work; push/route need an alias set later.
    let push_alias = args.push_alias.clone().or_else(|| {
        client_ssh_config_path()
            .ok()
            .and_then(|p| std::fs::read_to_string(p).ok())
            .and_then(|cfg| find_alias_for_target(&cfg, &spec.host, Some(&spec.user), &args.name))
    });

    // 6. Register — the ONLY thing written. No ssh alias, no host mutation.
    let registry_path = registry_path()?;
    let mut registry = Registry::load(&registry_path)?;
    registry.upsert(Host {
        name: args.name.clone(),
        ssh_target: args.target.clone(),
        port: args.port.unwrap_or(22),
        identity: args.identity.clone(),
        triple,
        install_dir,
        recipient,
        bucket,
        region,
        prefix,
        endpoint,
        mirror,
        push_alias: push_alias.clone(),
    });
    registry.save(&registry_path)?;

    println!(
        "✓ adopted '{}' (git-ark {version}) — registered from its deployed config; \
         nothing on the host or in your ssh config was touched",
        args.name
    );
    println!("  it now appears in `git-ark status` and can be `git-ark upgrade`d.");
    if mirror {
        println!("  (it holds the GitHub mirror.)");
    }
    match &push_alias {
        Some(alias) => println!("  push alias: {alias} — `git-ark route` and pushes will use it."),
        None => println!(
            "  no push alias found in ~/.ssh/config — status/upgrade work; set one with \
             `git-ark host adopt {} {} --push-alias <alias>` to enable push/route.",
            args.name, args.target
        ),
    }
    Ok(())
}

/// Extract the `--config <path>` from a git-ark forced-command line in an
/// `authorized_keys` body. The path ends at the first quote or whitespace.
pub fn parse_forced_command_config(authorized_keys: &str) -> Option<String> {
    for line in authorized_keys.lines() {
        if !line.contains("git-ark") {
            continue;
        }
        if let Some(idx) = line.find("--config ") {
            let rest = &line[idx + "--config ".len()..];
            let end = rest
                .find(|c: char| c == '"' || c.is_whitespace())
                .unwrap_or(rest.len());
            let path = &rest[..end];
            if !path.is_empty() {
                return Some(path.to_string());
            }
        }
    }
    None
}

/// Map `uname -s` / `uname -m` output (two lines) to a git-ark release triple.
pub fn triple_from_uname(uname: &str) -> Result<String> {
    let mut lines = uname.lines().map(str::trim);
    let os = lines.next().unwrap_or("");
    let arch = lines.next().unwrap_or("");
    match (os, arch) {
        ("Linux", "x86_64") => Ok("x86_64-unknown-linux-musl".to_string()),
        ("Linux", "aarch64" | "arm64") => Ok("aarch64-unknown-linux-musl".to_string()),
        _ => bail!("unsupported host {os}/{arch} — git-ark hosts are Linux x86_64 or aarch64"),
    }
}

// ---------------------------------------------------------------------
// host list / host remove
// ---------------------------------------------------------------------

/// Print the registry, one line per host as `name  ssh_target  triple`,
/// sorted by name. `Registry::list()` is in insertion order (only `save`
/// sorts on disk), so sort a copy here — an empty/missing registry prints
/// nothing.
pub fn host_list() -> Result<()> {
    let registry = Registry::load(&registry_path()?)?;
    let mut hosts: Vec<&Host> = registry.list().iter().collect();
    hosts.sort_by(|a, b| a.name.cmp(&b.name));
    for h in hosts {
        println!("{}  {}  {}", h.name, h.ssh_target, h.triple);
    }
    Ok(())
}

/// One host as clients see it over `host list --json`. `alias` is the RESOLVED
/// push alias (`Host::push_alias()`), never the raw `Option`, so a consumer
/// never re-derives it. The shape evolves additively: fields may be added; a
/// consumer tolerates unknown ones.
#[derive(Debug, serde::Serialize)]
struct HostRow<'a> {
    name: &'a str,
    alias: String,
    ssh_target: &'a str,
    port: u16,
    triple: &'a str,
    bucket: &'a str,
    region: &'a str,
    prefix: &'a str,
    endpoint: Option<&'a str>,
    mirror: bool,
}

/// The machine-readable fleet: one row per host, sorted by name. Pure over the
/// registry so it's unit-testable without touching disk.
fn host_rows(registry: &Registry) -> Vec<HostRow<'_>> {
    let mut hosts: Vec<&Host> = registry.list().iter().collect();
    hosts.sort_by(|a, b| a.name.cmp(&b.name));
    hosts
        .into_iter()
        .map(|h| HostRow {
            name: &h.name,
            alias: h.push_alias(),
            ssh_target: &h.ssh_target,
            port: h.port,
            triple: &h.triple,
            bucket: &h.bucket,
            region: &h.region,
            prefix: &h.prefix,
            endpoint: h.endpoint.as_deref(),
            mirror: h.mirror,
        })
        .collect()
}

/// `host list --json`: the client contract for resolving a host name to its
/// push alias and backend. Emits a flat JSON array of [`HostRow`].
pub fn host_list_json() -> Result<()> {
    let registry = Registry::load(&registry_path()?)?;
    let rows = host_rows(&registry);
    println!("{}", serde_json::to_string_pretty(&rows)?);
    Ok(())
}

/// Remove `name` from the registry and drop its `~/.ssh/config` alias block.
/// A name not in the registry is reported, not an error — there's nothing to
/// retry.
pub fn host_remove(name: &str) -> Result<()> {
    let registry_path = registry_path()?;
    let mut registry = Registry::load(&registry_path)?;
    if !registry.remove(name) {
        println!("no such host: {name}");
        return Ok(());
    }
    registry.save(&registry_path)?;

    // Drop the SSH alias too, if the client has one. A missing ~/.ssh/config
    // means there's nothing to drop — don't create the file just to remove
    // from it.
    let ssh_config_path = client_ssh_config_path()?;
    if let Ok(existing) = std::fs::read_to_string(&ssh_config_path) {
        let updated = remove_ssh_config_block(&existing, name);
        std::fs::write(&ssh_config_path, updated)
            .with_context(|| format!("writing {}", ssh_config_path.display()))?;
    }

    println!("removed {name}");
    Ok(())
}

// ---------------------------------------------------------------------
// host discover
// ---------------------------------------------------------------------

/// The `a.b.c` prefix of `ip`'s /24, for the empty-result message.
fn base_prefix(ip: std::net::Ipv4Addr) -> String {
    let o = ip.octets();
    format!("{}.{}.{}", o[0], o[1], o[2])
}

/// Scan the local `/24` for hosts answering on `port`, printing each reachable
/// `ip:port` — labeled `(known: <name>)` when the IP already appears in a
/// registered host's `ssh_target`. Finding nothing is success (exit 0), not
/// an error; a probe is a bare TCP connect, no auth, no data.
pub fn host_discover(port: u16, timeout_ms: u64, subnet: Option<std::net::Ipv4Addr>) -> Result<()> {
    let base = match subnet {
        Some(b) => b,
        None => crate::subnet::local_ipv4()
            .context("could not determine the local IPv4 address; pass --subnet a.b.c.0")?,
    };
    let ips = crate::subnet::hosts_in_slash24(base);
    let found =
        crate::scan::scan_port(&ips, port, std::time::Duration::from_millis(timeout_ms), 64);

    // Cross-reference the registry so already-added hosts are labeled.
    let reg = Registry::load(&registry_path()?).unwrap_or_default();
    if found.is_empty() {
        println!(
            "no hosts responding on port {port} in {}.0/24",
            base_prefix(base)
        );
        return Ok(());
    }
    for ip in found {
        let s = ip.to_string();
        match reg.list().iter().find(|h| h.ssh_target.contains(&s)) {
            Some(h) => println!("{s}:{port}  (known: {})", h.name),
            None => println!("{s}:{port}"),
        }
    }
    Ok(())
}

// ---------------------------------------------------------------------
// status — fleet health/liveness/drift
// ---------------------------------------------------------------------

/// One host's status, as `probe_status` diagnoses it. `Reachable` carries
/// exactly what the host's own `selfcheck` reported; `Broken` is a real ssh
/// connection that came back unhealthy (selfcheck errored); `Unreachable` is
/// no connection at all — the graduated diagnosis `status` needs to tell
/// "the box is off" from "the box is up but git-ark is broken on it".
#[derive(Debug, Clone, PartialEq)]
pub enum HostStatus {
    Reachable {
        version: String,
        disk_free: u64,
        disk_low: bool,
        config_valid: bool,
    },
    Broken(String),
    Unreachable,
}

/// Probe `host` over the control channel: run its own `selfcheck` and parse
/// the result. Never errors — a dead or misconfigured host is a `HostStatus`
/// variant, not a `Result::Err`, so `status()` can report the whole fleet
/// even when part of it is down.
pub fn probe_status(host: &Host) -> HostStatus {
    let (user, hostname) = match parse_target(&host.ssh_target) {
        Ok(v) => v,
        Err(e) => return HostStatus::Broken(e.to_string()),
    };
    let spec = SshSpec {
        user,
        host: hostname,
        port: Some(host.port),
        identity: host.identity.clone(),
    };

    match ssh_run(&spec, &selfcheck_command(&host.install_dir)) {
        Ok(out) => {
            let kv = parse_kv(&out);
            let version = kv.get("git_ark_version").cloned().unwrap_or_default();
            let disk_free = kv
                .get("disk_free_bytes")
                .and_then(|s| s.parse::<u64>().ok())
                .unwrap_or(0);
            let disk_low = kv.get("disk_low").map(String::as_str) == Some("true");
            let config_valid = kv.get("config_valid").map(String::as_str) == Some("true");
            HostStatus::Reachable {
                version,
                disk_free,
                disk_low,
                config_valid,
            }
        }
        // The selfcheck itself failed (bad config, missing binary, …) —
        // distinguish that from no connection at all with a cheap `true`.
        Err(_) => match ssh_run(&spec, "true") {
            Ok(_) => HostStatus::Broken("selfcheck failed".to_string()),
            Err(_) => HostStatus::Unreachable,
        },
    }
}

/// Render one `status` row. PURE — `probe_status` does the SSH; this only
/// formats what it found. `mirror` (from the registry entry, not carried on
/// `HostStatus`) appends a `★ mirror` marker.
pub fn format_status_row(name: &str, mirror: bool, s: &HostStatus) -> String {
    let mirror_marker = if mirror { "  ★ mirror" } else { "" };
    match s {
        HostStatus::Reachable {
            version,
            disk_free,
            disk_low,
            config_valid,
        } => {
            let mark = if *disk_low { "⚠" } else { "✓" };
            let mut line = format!(
                "{mark} {name}  v{version}  {} free",
                crate::backup::human_bytes(*disk_free)
            );
            if *disk_low {
                line.push_str("  disk low");
            }
            if !config_valid {
                line.push_str("  config invalid");
            }
            line.push_str(mirror_marker);
            line
        }
        HostStatus::Broken(reason) => format!("✗ {name}  broken: {reason}{mirror_marker}"),
        HostStatus::Unreachable => format!("✗ {name}  unreachable{mirror_marker}"),
    }
}

/// Print a fleet health/liveness/drift dashboard: one row per registered
/// host, probed over the control channel. Never fails the process on a
/// dead/broken host — that's the point of the dashboard — only on a genuine
/// local error (e.g. an unreadable registry).
pub fn status() -> Result<()> {
    let registry = Registry::load(&registry_path()?)?;
    let mut hosts: Vec<&Host> = registry.list().iter().collect();
    if hosts.is_empty() {
        println!("no hosts — run `git-ark host add`");
        return Ok(());
    }
    hosts.sort_by(|a, b| a.name.cmp(&b.name));
    for h in hosts {
        let s = probe_status(h);
        println!("{}", format_status_row(&h.name, h.mirror, &s));
    }
    Ok(())
}

// ---------------------------------------------------------------------
// upgrade — push a new binary to a host (or all) from the client
// ---------------------------------------------------------------------

/// Resolve which hosts `upgrade` targets. `all` wins outright — every
/// registered host, bailing on an empty registry (nothing to upgrade) —
/// without even looking at `names`, so a stray unknown name alongside
/// `--all` never turns a fleet-wide upgrade into an error. Absent `all`,
/// explicit `names` must each resolve to a registered host (bailing on the
/// first that doesn't); naming neither is an error, not a silent no-op.
fn resolve_upgrade_targets(registry: &Registry, names: &[String], all: bool) -> Result<Vec<Host>> {
    if all {
        if registry.list().is_empty() {
            bail!("no hosts registered — nothing to upgrade");
        }
        return Ok(registry.list().to_vec());
    }
    if names.is_empty() {
        bail!("name a host or pass --all");
    }
    names
        .iter()
        .map(|name| {
            registry
                .list()
                .iter()
                .find(|h| &h.name == name)
                .cloned()
                .ok_or_else(|| {
                    anyhow::anyhow!(
                        "no such host: {name} (run `git-ark host list` to see registered hosts)"
                    )
                })
        })
        .collect()
}

/// Stream `bytes` to `host`'s binary path and re-verify with its own
/// `selfcheck`, printing the version it now reports. Split out of `upgrade`
/// so a per-host failure can be caught there with `?` and reported without
/// aborting the rest of the fleet.
fn upgrade_one(host: &Host, bytes: &[u8]) -> Result<()> {
    let (user, hostname) = parse_target(&host.ssh_target)?;
    let spec = SshSpec {
        user,
        host: hostname,
        port: Some(host.port),
        identity: host.identity.clone(),
    };
    ssh_pipe_file(
        &spec,
        &format!("{}/bin/git-ark", host.install_dir),
        bytes,
        0o755,
    )?;
    let out = ssh_run(&spec, &selfcheck_command(&host.install_dir))?;
    let kv = parse_kv(&out);
    let version = kv.get("git_ark_version").cloned().unwrap_or_default();
    println!("✓ {} upgraded → {version}", host.name);
    Ok(())
}

/// Push `binary` to `names` (or every registered host, with `all`) over the
/// control channel and re-verify each with `selfcheck`. The binary is read
/// once and streamed unchanged to every target. A per-host failure is
/// printed and does not abort the rest — the fleet-wide `--all` case must
/// finish attempting every host before this returns a non-zero error, so a
/// script driving it can detect a partial upgrade without losing the hosts
/// that did succeed.
pub fn upgrade(names: &[String], all: bool, binary: Option<&Path>) -> Result<()> {
    let registry = Registry::load(&registry_path()?)?;
    let targets = resolve_upgrade_targets(&registry, names, all)?;

    // With --binary, read it once — it applies to every target. Without it,
    // auto-fetch the matching release asset per host triple, caching by triple
    // so hosts of the same arch share a single download.
    let explicit = match binary {
        Some(path) => Some(
            std::fs::read(path).with_context(|| format!("reading --binary {}", path.display()))?,
        ),
        None => None,
    };
    let mut fetched: HashMap<String, Vec<u8>> = HashMap::new();

    let mut any_failed = false;
    for host in &targets {
        let bytes: &[u8] = if let Some(explicit) = &explicit {
            if let Some(path) = binary {
                if !path.to_string_lossy().contains(&host.triple) {
                    eprintln!(
                        "⚠ --binary {} doesn't look like it's built for {}'s triple ({}) — continuing anyway",
                        path.display(),
                        host.name,
                        host.triple
                    );
                }
            }
            explicit
        } else {
            if !fetched.contains_key(&host.triple) {
                println!(
                    "• fetching git-ark v{} for {} ({})…",
                    release::version(),
                    host.name,
                    host.triple
                );
                match release::fetch_host_binary(&host.triple) {
                    Ok(b) => {
                        fetched.insert(host.triple.clone(), b);
                    }
                    Err(e) => {
                        println!("✗ {}: {e}", host.name);
                        any_failed = true;
                        continue;
                    }
                }
            }
            &fetched[&host.triple]
        };

        if let Err(e) = upgrade_one(host, bytes) {
            println!("✗ {}: {e}", host.name);
            any_failed = true;
        }
    }

    if any_failed {
        bail!("one or more hosts failed to upgrade — see above");
    }
    Ok(())
}

// ---------------------------------------------------------------------
// mirror designation
// ---------------------------------------------------------------------

/// Pure singleton-selection: given the current registry and a target host
/// `name`, decide which host (if any) must be demoted and which is promoted.
/// `target` is always promoted; `demote` is `Some(other)` when some *other*
/// host currently holds `mirror==true` — `None` when there's no current
/// mirror, or the target already is it (both are no-op demotes).
fn mirror_transition(registry: &Registry, target: &str) -> (Option<String>, String) {
    let demote = registry
        .mirror_host()
        .filter(|h| h.name != target)
        .map(|h| h.name.clone());
    (demote, target.to_string())
}

/// Re-render and re-push `config.toml`/`secrets.toml` to `host` over SSH —
/// the same shape `host_add` writes on first wiring, minus the probe/binary/
/// authorized_keys steps (the host is already fully wired; only its config
/// changes). `config.toml` gets the host's stored S3 values + its per-host
/// prefix + `mirror`; `secrets.toml` gets the host's write-only S3
/// credential (from `GIT_ARK_HOST_S3_KEY_ID`/`GIT_ARK_HOST_S3_SECRET` — so
/// reassigning the mirror needs these set too, same as `host add`) plus
/// `github_token`.
fn apply_host_config(host: &Host, mirror: bool, github_token: Option<&str>) -> Result<()> {
    let key_id = std::env::var("GIT_ARK_HOST_S3_KEY_ID")
        .ok()
        .filter(|s| !s.is_empty());
    let secret = std::env::var("GIT_ARK_HOST_S3_SECRET")
        .ok()
        .filter(|s| !s.is_empty());
    let (key_id, secret) = match (key_id, secret) {
        (Some(k), Some(s)) => (k, s),
        _ => bail!(
            "GIT_ARK_HOST_S3_KEY_ID and GIT_ARK_HOST_S3_SECRET must both be set to re-apply \
             {}'s config (changing the mirror re-renders secrets.toml, which needs the host's \
             write-only S3 credential, not just the GitHub token)",
            host.name
        ),
    };

    let (user, hostname) = parse_target(&host.ssh_target)?;
    let spec = SshSpec {
        user,
        host: hostname,
        port: Some(host.port),
        identity: host.identity.clone(),
    };

    let s3 = S3Config {
        bucket: host.bucket.clone(),
        region: host.region.clone(),
        prefix: per_host_prefix(&host.prefix, &host.name),
        endpoint: host.endpoint.clone(),
    };
    let config_text = render_config(&host.install_dir, &host.recipient, &s3, mirror);
    ssh_pipe_file(
        &spec,
        &format!("{}/config.toml", host.install_dir),
        config_text.as_bytes(),
        0o644,
    )?;
    let secrets_text = render_secrets(&key_id, &secret, github_token);
    ssh_pipe_file(
        &spec,
        &format!("{}/secrets.toml", host.install_dir),
        secrets_text.as_bytes(),
        0o600,
    )?;
    Ok(())
}

/// Enforce the client-enforced single-mirror invariant: reassign the GitHub
/// mirror designation to `name`, demoting whichever other host currently
/// holds it — config `mirror=false`, secrets stripped of `[github]` (a
/// client-side revocation) — before promoting the target — config
/// `mirror=true`, secrets carrying `github_token`. Bails, before touching any
/// host, if `name` isn't registered.
fn designate_mirror(registry: &mut Registry, name: &str, github_token: &str) -> Result<()> {
    if !registry.list().iter().any(|h| h.name == name) {
        bail!("no such host: {name} (run `git-ark host list` to see registered hosts)");
    }
    let (demote, promote) = mirror_transition(registry, name);

    if let Some(old_name) = &demote {
        let old = registry
            .list()
            .iter()
            .find(|h| &h.name == old_name)
            .expect("mirror_transition only names a host present in the registry")
            .clone();
        apply_host_config(&old, false, None)?;
        registry
            .hosts
            .iter_mut()
            .find(|h| h.name == old.name)
            .expect("just found above")
            .mirror = false;
        // Persist the demotion NOW: if the promote below fails, the on-disk
        // registry must not still claim this demoted, token-stripped host is the
        // mirror. Worst case is a transient no-mirror that a re-run repairs.
        registry.save(&registry_path()?)?;
    }

    let target = registry
        .list()
        .iter()
        .find(|h| h.name == promote)
        .expect("checked at the top of this fn")
        .clone();
    apply_host_config(&target, true, Some(github_token)).with_context(|| {
        format!(
            "demoted the previous mirror but could not promote {promote} — the fleet has no \
             mirror right now; re-run `git-ark mirror set {promote}` once it is reachable"
        )
    })?;
    registry
        .hosts
        .iter_mut()
        .find(|h| h.name == promote)
        .expect("just found above")
        .mirror = true;

    registry.save(&registry_path()?)?;
    Ok(())
}

/// Reassign the GitHub mirror to `name`: load the registry, require the host
/// exists, read the token from `GIT_ARK_GITHUB_TOKEN` (never argv), and
/// enforce the singleton via `designate_mirror`.
pub fn mirror_set(name: &str) -> Result<()> {
    let mut registry = Registry::load(&registry_path()?)?;
    if !registry.list().iter().any(|h| h.name == name) {
        bail!("no such host: {name} (run `git-ark host list` to see registered hosts)");
    }
    let token = match std::env::var("GIT_ARK_GITHUB_TOKEN")
        .ok()
        .filter(|s| !s.is_empty())
    {
        Some(t) => t,
        None => bail!("GIT_ARK_GITHUB_TOKEN must be set to designate a GitHub mirror"),
    };
    designate_mirror(&mut registry, name, &token)?;
    println!("✓ {name} is now the GitHub mirror");
    Ok(())
}

/// Print the current mirror host's name, or `none`.
pub fn mirror_show() -> Result<()> {
    let registry = Registry::load(&registry_path()?)?;
    match registry.mirror_host() {
        Some(h) => println!("{}", h.name),
        None => println!("none"),
    }
    Ok(())
}

// ---------------------------------------------------------------------
// routing — multi-host push fan-out
// ---------------------------------------------------------------------

/// The `<alias>:<repo>` push URL for each host in `host_names`, in order. The
/// alias is the one the registry records for that host (`Host::push_alias()`) —
/// `git-ark-<name>` for a conventional host, its real alias for a hand-wired or
/// adopted one. A name not in the registry falls back to the convention (route
/// rejects unknown names before this, so that path is only exercised in tests).
fn push_urls(registry: &Registry, host_names: &[String], repo: &str) -> Vec<String> {
    host_names
        .iter()
        .map(|name| {
            let alias = registry
                .list()
                .iter()
                .find(|h| &h.name == name)
                .map(|h| h.push_alias())
                .unwrap_or_else(|| format!("git-ark-{name}"));
            format!("{alias}:{repo}")
        })
        .collect()
}

/// Run a `git remote` subcommand against `repo_path`, bailing with its
/// stderr on failure.
fn git_remote(repo_path: &Path, args: &[&str]) -> Result<()> {
    let out = Command::new("git")
        .arg("-C")
        .arg(repo_path)
        .arg("remote")
        .args(args)
        .output()
        .with_context(|| format!("spawning git remote {}", args.join(" ")))?;
    if !out.status.success() {
        bail!(
            "git remote {} failed: {}",
            args.join(" "),
            String::from_utf8_lossy(&out.stderr).trim()
        );
    }
    Ok(())
}

/// Fan a repo's `git push git-ark` out across `host_names`: verify every
/// name is registered, then (re)materialize the `git-ark` remote in
/// `repo_path` with one push URL per host, so a single `git push git-ark`
/// reaches all of them. Idempotent — re-running (even with a different
/// `host_names`) removes and rebuilds the remote rather than accumulating
/// stale push URLs alongside new ones.
pub fn route(repo_path: &Path, host_names: &[String]) -> Result<()> {
    if host_names.is_empty() {
        bail!("--to <names> is required (comma-separated host names)");
    }

    let registry = Registry::load(&registry_path()?)?;
    let unknown: Vec<&String> = host_names
        .iter()
        .filter(|n| !registry.list().iter().any(|h| &h.name == *n))
        .collect();
    if !unknown.is_empty() {
        let names: Vec<&str> = unknown.iter().map(|s| s.as_str()).collect();
        bail!(
            "unknown host(s): {} (run `git-ark host list` to see registered hosts)",
            names.join(", ")
        );
    }

    // Canonicalize first so a relative path like "." resolves to a real
    // directory name — `Path::new(".").file_name()` is `None`.
    let abs = repo_path
        .canonicalize()
        .with_context(|| format!("resolving {}", repo_path.display()))?;
    let repo = abs
        .file_name()
        .and_then(|n| n.to_str())
        .ok_or_else(|| anyhow::anyhow!("{} has no usable directory name", repo_path.display()))?
        .to_string();
    let urls = push_urls(&registry, host_names, &repo);

    // Remove any prior git-ark remote first — ignore failure (there may be
    // none yet) — so re-routing never leaves a stale push URL alongside the
    // fresh set.
    let _ = Command::new("git")
        .arg("-C")
        .arg(repo_path)
        .args(["remote", "remove", "git-ark"])
        .output();

    git_remote(repo_path, &["add", "git-ark", &urls[0]])?;
    for url in &urls {
        git_remote(repo_path, &["set-url", "--add", "--push", "git-ark", url])?;
    }

    println!(
        "✓ {repo} → git push git-ark fans to: {}",
        host_names.join(",")
    );
    Ok(())
}

// ---------------------------------------------------------------------
// mirror check — preflight the GitHub token against a repo's mirror config
// ---------------------------------------------------------------------

/// Whether `repo_path/.github/workflows` exists and has at least one entry —
/// the signal that mirroring this repo needs the token's `workflow` scope
/// (classic PAT) or Workflows:write (fine-grained).
fn needs_workflow(repo_path: &Path) -> bool {
    std::fs::read_dir(repo_path.join(".github").join("workflows"))
        .map(|mut entries| entries.next().is_some())
        .unwrap_or(false)
}

/// Format a `TokenCheck` as the report `mirror_check` prints: one line per
/// check, `✗`-prefixed lines are hard failures.
fn format_check(c: &github::TokenCheck, owner: &str, repo: &str) -> String {
    let mut lines = Vec::new();

    lines.push(if c.valid {
        format!(
            "✓ authenticates (login: {})",
            c.login.as_deref().unwrap_or("?")
        )
    } else {
        "✗ token does not authenticate".to_string()
    });

    lines.push(match &c.repo {
        github::RepoAccess::Exists { admin: true, .. } => {
            format!("✓ can administer {owner}/{repo}")
        }
        github::RepoAccess::Exists {
            push: true,
            admin: false,
        } => format!("✓ can push {owner}/{repo} (no admin — ok if it already exists)"),
        github::RepoAccess::Exists { push: false, .. } => {
            format!("✗ no push access to {owner}/{repo}")
        }
        github::RepoAccess::Absent => format!(
            "⚠ {owner}/{repo}: 404 — absent (created on first mirror) OR the token can't see it \
             (missing org access / unauthorized SSO PAT). GitHub returns 404 either way — verify \
             before relying on it"
        ),
        github::RepoAccess::Error(e) => format!("✗ {owner}/{repo}: {e}"),
    });

    if c.needs_workflow {
        lines.push(match c.has_workflow_scope() {
            Some(true) => "✓ workflow scope".to_string(),
            Some(false) => {
                "✗ missing 'workflow' scope (needed to push .github/workflows/)".to_string()
            }
            None => "⚠ repo ships workflows; a fine-grained PAT needs Workflows:write (can't verify here)".to_string(),
        });
    }

    lines.join("\n")
}

/// Preflight the GitHub token against a repo's mirror config: read the
/// committed `.git-ark.yml` github block, check the token's auth/scopes and
/// its access to the target repo, and print a report — catching a token
/// lacking org access or the `workflow` scope before a real push does.
pub fn mirror_check(repo_path: &Path) -> Result<()> {
    let policy = read_repo_policy(repo_path)?;
    let g = policy
        .as_ref()
        .and_then(|p| p.github.as_ref())
        .filter(|g| g.enabled)
        .ok_or_else(|| {
            anyhow::anyhow!(
                "{} has no enabled `github:` block in .git-ark.yml — nothing to check",
                repo_path.display()
            )
        })?;
    let repo_name = g.repo.clone().unwrap_or_else(|| {
        repo_path
            .canonicalize()
            .ok()
            .and_then(|p| p.file_name().map(|n| n.to_string_lossy().into_owned()))
            .unwrap_or_default()
    });

    let token = std::env::var("GIT_ARK_GITHUB_TOKEN")
        .ok()
        .filter(|s| !s.is_empty())
        .ok_or_else(|| anyhow::anyhow!("GIT_ARK_GITHUB_TOKEN must be set to run `mirror check`"))?;

    let workflow = needs_workflow(repo_path);
    let check = github::check_token(&token, &g.owner, &repo_name, workflow);
    let report = format_check(&check, &g.owner, &repo_name);
    println!("{report}");

    if report.lines().any(|l| l.starts_with('✗')) {
        bail!("mirror check found hard failures — see above");
    }
    Ok(())
}

// ---------------------------------------------------------------------
// host setup-key — generate + copy a client SSH key to a host
// ---------------------------------------------------------------------

/// What `pick_or_plan_keygen` decided for the client's control key: reuse
/// an existing one, or generate a fresh one. Both carry the PRIVATE key
/// path — its public half is always `<path>.pub`, the standard ssh-keygen
/// naming.
#[derive(Debug, Clone, PartialEq)]
pub enum KeyPlan {
    Reuse(PathBuf),
    Generate(PathBuf),
}

/// Candidate private-key basenames in `~/.ssh`, most-preferred first — the
/// same three `ssh` itself tries by default.
const KEY_CANDIDATES: [&str; 3] = ["id_ed25519", "id_ecdsa", "id_rsa"];

/// Decide which client key `host setup-key` should use. PURE: `existing` is
/// the set of candidate basenames the caller found actually present in
/// `ssh_dir` — this only picks among them. Reuses the first preferred name
/// present (ed25519 > ecdsa > rsa); plans to generate `id_ed25519` when none
/// exist. Never plans to overwrite an existing key.
pub fn pick_or_plan_keygen(ssh_dir: &Path, existing: &[String]) -> KeyPlan {
    for candidate in KEY_CANDIDATES {
        if existing.iter().any(|e| e == candidate) {
            return KeyPlan::Reuse(ssh_dir.join(candidate));
        }
    }
    KeyPlan::Generate(ssh_dir.join("id_ed25519"))
}

/// Print the public key at `pub_path` plus the manual fallback instructions
/// for `target` — used both when `ssh-copy-id` fails/is missing and when the
/// post-copy verify still can't authenticate.
fn print_manual_fallback(target: &str, pub_path: &Path) -> Result<()> {
    let pubkey = std::fs::read_to_string(pub_path)
        .with_context(|| format!("reading {}", pub_path.display()))?;
    println!("{}", pubkey.trim());
    println!(
        "add this line to {target}:~/.ssh/authorized_keys (e.g. via console access), \
         then re-run git-ark host add"
    );
    Ok(())
}

/// Generate a client SSH key (if none exists) and copy it to `target` via
/// `ssh-copy-id`, so a box without key auth set up can get to "sshable"
/// without leaving git-ark. This is the operator's own CONTROL key, never
/// the forced-command key `host add` goes on to install — `setup-key` never
/// touches an existing key, only creates one when none exists.
///
/// Wraps the standard tools (`ssh-keygen`, `ssh-copy-id`, `ssh`) rather than
/// reimplementing them; all three inherit this process's stdio (the
/// `Command` default), so a password prompt reaches the user's own terminal
/// — git-ark itself never sees or prints the password.
pub fn host_setup_key(target: &str, port: Option<u16>) -> Result<()> {
    let ssh_dir = home_dir()?.join(".ssh");
    // std::fs, not a unix-only DirBuilder mode — the client is
    // cross-platform. `ssh`/`ssh-keygen` are the ones that actually care
    // about `~/.ssh`'s permissions, and they run on the host's own platform
    // defaults regardless of what we set here.
    std::fs::create_dir_all(&ssh_dir).with_context(|| format!("creating {}", ssh_dir.display()))?;

    let existing: Vec<String> = KEY_CANDIDATES
        .iter()
        .filter(|name| ssh_dir.join(name).exists())
        .map(|s| s.to_string())
        .collect();

    let priv_path = match pick_or_plan_keygen(&ssh_dir, &existing) {
        KeyPlan::Reuse(p) => {
            println!("using existing key {}", p.display());
            p
        }
        KeyPlan::Generate(p) => {
            println!(
                "no SSH key found in {} — generating {}",
                ssh_dir.display(),
                p.display()
            );
            let status = Command::new("ssh-keygen")
                .args(["-t", "ed25519", "-f"])
                .arg(&p)
                .args(["-N", ""])
                .status()
                .context("spawning ssh-keygen")?;
            if !status.success() {
                bail!("ssh-keygen failed generating {}", p.display());
            }
            p
        }
    };
    let pub_path = PathBuf::from(format!("{}.pub", priv_path.display()));

    let mut copy_args: Vec<String> = vec!["-i".to_string(), pub_path.display().to_string()];
    if let Some(port) = port {
        copy_args.push("-p".to_string());
        copy_args.push(port.to_string());
    }
    copy_args.push(target.to_string());
    let copy_ok = Command::new("ssh-copy-id")
        .args(&copy_args)
        .status()
        .map(|s| s.success())
        .unwrap_or(false);
    if !copy_ok {
        print_manual_fallback(target, &pub_path)?;
        bail!("ssh-copy-id to {target} did not succeed");
    }

    // Verify with only the new key and no interactive fallback — proves key
    // auth actually works rather than trusting ssh-copy-id's exit code alone.
    let mut verify_args: Vec<String> = vec![
        "-o".to_string(),
        "BatchMode=yes".to_string(),
        "-o".to_string(),
        "ConnectTimeout=5".to_string(),
    ];
    if let Some(port) = port {
        verify_args.push("-p".to_string());
        verify_args.push(port.to_string());
    }
    verify_args.push("-i".to_string());
    verify_args.push(priv_path.display().to_string());
    verify_args.push(target.to_string());
    verify_args.push("true".to_string());
    let verified = Command::new("ssh")
        .args(&verify_args)
        .status()
        .map(|s| s.success())
        .unwrap_or(false);

    if !verified {
        print_manual_fallback(target, &pub_path)?;
        bail!("key auth to {target} still doesn't work after setup-key");
    }

    match port {
        Some(p) => println!(
            "✓ key auth to {target} works — now run: git-ark host add <name> {target} \
             --identity {} --port {p} --bucket … --recipient … --binary …",
            priv_path.display()
        ),
        None => println!(
            "✓ key auth to {target} works — now run: git-ark host add <name> {target} \
             --identity {} --bucket … --recipient … --binary …",
            priv_path.display()
        ),
    }
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn parse_target_splits_user_and_host() {
        let (user, host) = parse_target("ark@example.com").unwrap();
        assert_eq!(user, "ark");
        assert_eq!(host, "example.com");
    }

    #[test]
    fn parse_target_rejects_bare_host() {
        assert!(parse_target("example.com").is_err());
    }

    #[test]
    fn parse_target_rejects_empty_user_or_host() {
        assert!(parse_target("@example.com").is_err());
        assert!(parse_target("ark@").is_err());
    }

    #[test]
    fn find_alias_discovers_the_nas_style_manual_block() {
        // The exact shape of git-ark's own hand-wired NAS.
        let cfg = "Host git-ark\n  HostName store.lan\n  User pfugate\n  \
                   IdentityFile ~/.ssh/git-ark\n  IdentitiesOnly yes\n";
        assert_eq!(
            find_alias_for_target(cfg, "store.lan", Some("pfugate"), "nas"),
            Some("git-ark".to_string())
        );
    }

    #[test]
    fn find_alias_prefers_exact_name_then_git_ark_then_first() {
        // Two stanzas reach the same target; exact git-ark-<name> wins.
        let cfg = "Host git-ark\n  HostName store.lan\n  User pfugate\n\n\
                   Host git-ark-nas\n  HostName store.lan\n  User pfugate\n";
        assert_eq!(
            find_alias_for_target(cfg, "store.lan", Some("pfugate"), "nas"),
            Some("git-ark-nas".to_string())
        );
        // With no exact match, the first git-ark* alias wins over a plain one.
        let cfg2 = "Host box\n  HostName store.lan\n  User pfugate\n\n\
                    Host git-ark\n  HostName store.lan\n  User pfugate\n";
        assert_eq!(
            find_alias_for_target(cfg2, "store.lan", Some("pfugate"), "nas"),
            Some("git-ark".to_string())
        );
    }

    #[test]
    fn find_alias_filters_by_user_but_tolerates_a_userless_stanza() {
        let cfg = "Host wrong\n  HostName store.lan\n  User someoneelse\n\n\
                   Host right\n  HostName store.lan\n";
        // The wrong-user stanza is rejected; the User-less one matches.
        assert_eq!(
            find_alias_for_target(cfg, "store.lan", Some("pfugate"), "nas"),
            Some("right".to_string())
        );
    }

    #[test]
    fn find_alias_none_when_no_stanza_reaches_the_target() {
        let cfg = "Host other\n  HostName elsewhere.example\n  User pfugate\n";
        assert_eq!(
            find_alias_for_target(cfg, "store.lan", Some("pfugate"), "nas"),
            None
        );
    }

    #[test]
    fn find_alias_handles_multiple_aliases_on_one_host_line() {
        // `Host a b` declares two aliases for one stanza; a git-ark* one wins.
        let cfg = "Host shorty git-ark-nas\n  HostName store.lan\n  User pfugate\n";
        assert_eq!(
            find_alias_for_target(cfg, "store.lan", Some("pfugate"), "nas"),
            Some("git-ark-nas".to_string())
        );
    }

    #[test]
    fn adopt_parses_config_path_from_forced_command() {
        let ak = "ssh-rsa AAAA someone@key\n\
            command=\"/home/op/git-ark/bin/git-ark shell --config /home/op/git-ark/config.toml\",no-pty,no-port-forwarding ssh-ed25519 AAAA git-ark\n";
        assert_eq!(
            parse_forced_command_config(ak).as_deref(),
            Some("/home/op/git-ark/config.toml")
        );
    }

    #[test]
    fn adopt_config_path_none_without_a_git_ark_line() {
        assert_eq!(
            parse_forced_command_config("ssh-ed25519 AAAA me@host\n"),
            None
        );
    }

    #[test]
    fn adopt_maps_uname_to_triple() {
        assert_eq!(
            triple_from_uname("Linux\nx86_64").unwrap(),
            "x86_64-unknown-linux-musl"
        );
        assert_eq!(
            triple_from_uname("Linux\naarch64").unwrap(),
            "aarch64-unknown-linux-musl"
        );
        assert!(triple_from_uname("Darwin\narm64").is_err());
    }

    #[test]
    fn ssh_args_includes_port_and_identity_when_set() {
        let spec = SshSpec {
            user: "ark".to_string(),
            host: "example.com".to_string(),
            port: Some(2222),
            identity: Some(PathBuf::from("/home/op/.ssh/id_ed25519")),
        };
        let args = ssh_args(&spec);
        assert_eq!(
            args,
            vec![
                "-p".to_string(),
                "2222".to_string(),
                "-i".to_string(),
                "/home/op/.ssh/id_ed25519".to_string(),
                "-o".to_string(),
                "StrictHostKeyChecking=accept-new".to_string(),
                "ark@example.com".to_string(),
            ]
        );
    }

    #[test]
    fn ssh_args_omits_port_and_identity_when_unset() {
        let spec = SshSpec {
            user: "ark".to_string(),
            host: "example.com".to_string(),
            port: None,
            identity: None,
        };
        let args = ssh_args(&spec);
        assert_eq!(
            args,
            vec![
                "-o".to_string(),
                "StrictHostKeyChecking=accept-new".to_string(),
                "ark@example.com".to_string(),
            ]
        );
    }

    #[test]
    fn pipe_file_command_stages_then_atomically_moves() {
        let cmd = pipe_file_command("/home/ark/git-ark/bin/git-ark", 0o755);
        assert!(cmd.starts_with("umask 077; cat > "));
        assert!(cmd.contains("chmod 755"));
        assert!(cmd.contains("mv "));
        assert!(cmd.contains("/home/ark/git-ark/bin/git-ark.uploading"));
        assert!(cmd.ends_with("/home/ark/git-ark/bin/git-ark"));
    }

    #[test]
    fn append_unique_script_filters_marker_before_appending() {
        let script = append_unique_script("~/.ssh/authorized_keys", "/home/ark/git-ark");
        assert!(script.starts_with("f=~/.ssh/authorized_keys;"));
        // Replace semantics (grep -v), not skip-if-present (grep -q) — see
        // append_unique_script_replaces_stale_line_on_key_rotation below for
        // the behavior this enables.
        assert!(script.contains("grep -vF"));
        assert!(!script.contains("grep -qF"));
        assert!(script.contains("/home/ark/git-ark"));
        assert!(script.contains(".bak"));
    }

    /// Proves the S2 fix end to end at the shell level (not just the string
    /// shape): a rotated key must evict the stale forced-command line, not
    /// sit alongside it or leave it in place. Runs the generated script for
    /// real against a temp file via `sh` — Unix-only (`sh` isn't reliably on
    /// PATH on Windows; this doesn't run in CI there either, see ci.yml).
    #[test]
    #[cfg(unix)]
    fn append_unique_script_replaces_stale_line_on_key_rotation() {
        let dir = tempfile::tempdir().unwrap();
        let f = dir.path().join("authorized_keys");
        std::fs::write(&f, "ssh-rsa UNRELATED someone-else@laptop\n").unwrap();

        let run = |line: &str| {
            let script = append_unique_script(&f.display().to_string(), "/home/ark/git-ark");
            let mut child = Command::new("sh")
                .arg("-c")
                .arg(&script)
                .stdin(Stdio::piped())
                .spawn()
                .unwrap();
            child
                .stdin
                .take()
                .unwrap()
                .write_all(line.as_bytes())
                .unwrap();
            assert!(child.wait().unwrap().success());
        };

        let old_line = "command=\"/home/ark/git-ark/bin/git-ark shell --config /home/ark/git-ark/config.toml\",no-pty ssh-ed25519 OLDKEY git-ark-testbox";
        let new_line = "command=\"/home/ark/git-ark/bin/git-ark shell --config /home/ark/git-ark/config.toml\",no-pty ssh-ed25519 NEWKEY git-ark-testbox";

        run(old_line);
        let after_first = std::fs::read_to_string(&f).unwrap();
        assert!(after_first.contains("OLDKEY"));
        assert!(after_first.contains("UNRELATED"));

        // Simulate rotation: same marker (install_dir), regenerated pubkey.
        run(new_line);
        let after_rotation = std::fs::read_to_string(&f).unwrap();
        assert!(
            after_rotation.contains("NEWKEY"),
            "rotated key must be authorized"
        );
        assert!(
            !after_rotation.contains("OLDKEY"),
            "stale key must be evicted, not left authorized"
        );
        assert!(
            after_rotation.contains("UNRELATED"),
            "unrelated authorized_keys lines must be preserved"
        );
        assert_eq!(
            after_rotation.matches("git-ark-testbox").count(),
            1,
            "must not duplicate the forced-command line"
        );
    }

    #[test]
    fn selfcheck_command_quotes_install_dir() {
        let cmd = selfcheck_command("/home/ark/git ark");
        assert!(cmd.contains("'/home/ark/git ark/bin/git-ark'"));
        assert!(cmd.contains("--config"));
        assert!(cmd.contains("'/home/ark/git ark/config.toml'"));
    }

    #[test]
    fn selfcheck_command_has_expected_shape_without_special_chars() {
        let cmd = selfcheck_command("/home/ark/git-ark");
        assert_eq!(
            cmd,
            "/home/ark/git-ark/bin/git-ark selfcheck --config /home/ark/git-ark/config.toml"
        );
    }

    #[test]
    fn parse_kv_reads_selfcheck_shaped_output() {
        let out = "git_ark_version=0.1.0\nrepos_root=/home/ark/git-ark/repos\nconfig_valid=true\n";
        let kv = parse_kv(out);
        assert_eq!(kv.get("git_ark_version").map(String::as_str), Some("0.1.0"));
        assert_eq!(kv.get("config_valid").map(String::as_str), Some("true"));
    }

    #[test]
    fn client_dir_is_under_config() {
        assert_eq!(
            client_dir(Path::new("/home/op")),
            PathBuf::from("/home/op/.config/git-ark")
        );
    }

    #[test]
    fn registry_path_honors_git_ark_hosts_override() {
        std::env::set_var("GIT_ARK_HOSTS", "/tmp/git-ark-test-hosts.toml");
        let p = registry_path().unwrap();
        std::env::remove_var("GIT_ARK_HOSTS");
        assert_eq!(p, PathBuf::from("/tmp/git-ark-test-hosts.toml"));
    }

    #[test]
    fn upsert_ssh_config_block_appends_when_absent() {
        let existing = "Host other\n  HostName elsewhere.example.com\n";
        let block = "Host git-ark-testbox\n  HostName example.com\n  Port 2222\n  User ark\n  IdentityFile /k\n  IdentitiesOnly yes\n";
        let out = upsert_ssh_config_block(existing, "testbox", block);
        assert!(out.contains("Host other"));
        assert!(out.contains("Host git-ark-testbox"));
        assert!(out.contains("HostName example.com"));
    }

    #[test]
    fn upsert_ssh_config_block_replaces_in_place_and_preserves_siblings() {
        let existing = "Host before\n  HostName a\n\nHost git-ark-testbox\n  HostName old.example.com\n  Port 22\n\nHost after\n  HostName b\n";
        let block = "Host git-ark-testbox\n  HostName new.example.com\n  Port 2222\n  User ark\n  IdentityFile /k\n  IdentitiesOnly yes\n";
        let out = upsert_ssh_config_block(existing, "testbox", block);

        assert!(out.contains("Host before"));
        assert!(out.contains("Host after"));
        assert!(out.contains("HostName new.example.com"));
        assert!(!out.contains("old.example.com"));
        // Only one git-ark-testbox block remains.
        assert_eq!(out.matches("Host git-ark-testbox").count(), 1);
    }

    #[test]
    fn upsert_ssh_config_block_is_idempotent() {
        let block = "Host git-ark-testbox\n  HostName example.com\n  Port 2222\n  User ark\n  IdentityFile /k\n  IdentitiesOnly yes\n";
        let once = upsert_ssh_config_block("", "testbox", block);
        let twice = upsert_ssh_config_block(&once, "testbox", block);
        assert_eq!(once, twice);
        assert_eq!(once.matches("Host git-ark-testbox").count(), 1);
    }

    #[test]
    fn remove_ssh_config_block_drops_only_the_named_block() {
        let existing = "Host before\n  HostName a\n\nHost git-ark-testbox\n  HostName old.example.com\n  Port 22\n\nHost after\n  HostName b\n";
        let out = remove_ssh_config_block(existing, "testbox");
        assert!(out.contains("Host before"));
        assert!(out.contains("Host after"));
        assert!(!out.contains("git-ark-testbox"));
        assert!(!out.contains("old.example.com"));
    }

    #[test]
    fn remove_ssh_config_block_absent_is_a_no_op() {
        let existing = "Host other\n  HostName elsewhere.example.com\n";
        let out = remove_ssh_config_block(existing, "testbox");
        assert_eq!(out, "Host other\n  HostName elsewhere.example.com\n");
    }

    #[test]
    fn remove_ssh_config_block_of_only_block_leaves_empty_file() {
        let existing = "Host git-ark-testbox\n  HostName example.com\n  Port 2222\n";
        let out = remove_ssh_config_block(existing, "testbox");
        assert_eq!(out, "");
    }

    /// S1: an ssh_config stanza is terminated by `Host ` *or* `Match `. A
    /// terminator that only recognized `Host ` would swallow a trailing
    /// `Match` block into the dropped git-ark body and silently delete it.
    #[test]
    fn remove_ssh_config_block_preserves_trailing_match_block() {
        let existing = "Host git-ark-box\n  HostName example.com\n  Port 22\n  User ark\n  IdentityFile /k\n  IdentitiesOnly yes\n\nMatch host *.corp\n  User alice\n";
        let out = remove_ssh_config_block(existing, "box");
        assert!(!out.contains("git-ark-box"));
        assert!(out.contains("Match host *.corp"));
        assert!(out.contains("User alice"));
    }

    #[test]
    fn validate_host_name_accepts_ordinary_names() {
        assert!(validate_host_name("testbox").is_ok());
        assert!(validate_host_name("box-1.prod_east").is_ok());
    }

    #[test]
    fn validate_host_name_rejects_path_traversal() {
        assert!(validate_host_name("../../etc/passwd").is_err());
        assert!(validate_host_name("..").is_err());
        assert!(validate_host_name(".").is_err());
    }

    #[test]
    fn validate_host_name_rejects_empty_and_unsafe_chars() {
        assert!(validate_host_name("").is_err());
        assert!(validate_host_name("box/name").is_err());
        assert!(validate_host_name("box name").is_err());
        assert!(validate_host_name("box$(rm)").is_err());
    }

    #[test]
    fn home_dir_falls_back_to_userprofile_when_home_unset() {
        let saved_home = std::env::var("HOME").ok();
        std::env::remove_var("HOME");
        std::env::set_var("USERPROFILE", "/Users/win");

        let result = home_dir();

        std::env::remove_var("USERPROFILE");
        if let Some(home) = saved_home {
            std::env::set_var("HOME", home);
        }

        assert_eq!(result.unwrap(), PathBuf::from("/Users/win"));
    }

    fn test_host(name: &str, mirror: bool) -> Host {
        Host {
            name: name.to_string(),
            ssh_target: format!("ark@{name}.example.com"),
            port: 22,
            identity: None,
            triple: "x86_64-unknown-linux-musl".to_string(),
            install_dir: "/home/ark/git-ark".to_string(),
            recipient: "age1abc".to_string(),
            bucket: "b".to_string(),
            region: "us-east-1".to_string(),
            prefix: "git-ark".to_string(),
            endpoint: None,
            mirror,
            push_alias: None,
        }
    }

    #[test]
    fn mirror_transition_promotes_target_when_no_current_mirror() {
        let mut registry = Registry::default();
        registry.upsert(test_host("nas", false));
        registry.upsert(test_host("ec2", false));

        let (demote, promote) = mirror_transition(&registry, "ec2");
        assert_eq!(demote, None);
        assert_eq!(promote, "ec2");
    }

    #[test]
    fn mirror_transition_demotes_a_different_current_mirror() {
        let mut registry = Registry::default();
        registry.upsert(test_host("nas", true));
        registry.upsert(test_host("ec2", false));

        let (demote, promote) = mirror_transition(&registry, "ec2");
        assert_eq!(demote, Some("nas".to_string()));
        assert_eq!(promote, "ec2");
    }

    #[test]
    fn mirror_transition_is_a_no_op_demote_when_target_already_mirror() {
        let mut registry = Registry::default();
        registry.upsert(test_host("nas", false));
        registry.upsert(test_host("ec2", true));

        let (demote, promote) = mirror_transition(&registry, "ec2");
        assert_eq!(demote, None);
        assert_eq!(promote, "ec2");
    }

    // -----------------------------------------------------------------
    // status
    // -----------------------------------------------------------------

    #[test]
    fn format_status_row_reachable_healthy() {
        let s = HostStatus::Reachable {
            version: "0.1.0".to_string(),
            disk_free: 60_000_000_000_000,
            disk_low: false,
            config_valid: true,
        };
        let row = format_status_row("nas", false, &s);
        assert!(row.contains("nas"));
        assert!(row.contains('✓'));
        assert!(row.contains("0.1.0"));
        assert!(
            row.contains("54.6 TB"),
            "expected a human free size, got: {row}"
        );
        assert!(!row.contains('★'));
    }

    #[test]
    fn format_status_row_reachable_marks_mirror() {
        let s = HostStatus::Reachable {
            version: "0.1.0".to_string(),
            disk_free: 60_000_000_000_000,
            disk_low: false,
            config_valid: true,
        };
        let row = format_status_row("nas", true, &s);
        assert!(row.contains('★'));
        assert!(row.to_lowercase().contains("mirror"));
    }

    #[test]
    fn format_status_row_reachable_disk_low_warns() {
        let s = HostStatus::Reachable {
            version: "0.1.0".to_string(),
            disk_free: 1_000_000_000,
            disk_low: true,
            config_valid: true,
        };
        let row = format_status_row("nas", false, &s);
        assert!(row.contains('⚠'));
    }

    #[test]
    fn format_status_row_broken_shows_reason() {
        let s = HostStatus::Broken("selfcheck: config invalid".to_string());
        let row = format_status_row("nas", false, &s);
        assert!(row.starts_with('✗'));
        assert!(row.to_lowercase().contains("broken"));
        assert!(row.contains("selfcheck: config invalid"));
    }

    #[test]
    fn format_status_row_unreachable() {
        let s = HostStatus::Unreachable;
        let row = format_status_row("nas", false, &s);
        assert!(row.starts_with('✗'));
        assert!(row.to_lowercase().contains("unreachable"));
    }

    #[test]
    fn push_urls_uses_the_registrys_recorded_alias() {
        let mut registry = Registry::default();
        // Conventional host: no recorded alias → git-ark-<name>.
        registry.upsert(test_host("ec2", false));
        // Hand-wired/adopted host: records a non-standard alias.
        let mut nas = test_host("nas", false);
        nas.push_alias = Some("git-ark".to_string());
        registry.upsert(nas);

        // Includes an unregistered name to exercise the convention fallback.
        let names = vec!["nas".to_string(), "ec2".to_string(), "ghost".to_string()];
        assert_eq!(
            push_urls(&registry, &names, "myrepo"),
            vec![
                "git-ark:myrepo".to_string(),       // recorded alias wins
                "git-ark-ec2:myrepo".to_string(),   // conventional
                "git-ark-ghost:myrepo".to_string(), // unregistered → fallback
            ]
        );
    }

    #[test]
    fn host_rows_resolve_alias_and_sort_by_name() {
        let mut registry = Registry::default();
        registry.upsert(test_host("zeta", false));
        let mut nas = test_host("nas", true);
        nas.push_alias = Some("git-ark".to_string());
        registry.upsert(nas);

        let rows = host_rows(&registry);
        assert_eq!(rows[0].name, "nas"); // sorted
        assert_eq!(rows[0].alias, "git-ark"); // resolved recorded alias
        assert!(rows[0].mirror);
        assert_eq!(rows[1].name, "zeta");
        assert_eq!(rows[1].alias, "git-ark-zeta"); // conventional

        // Serializes as an array of objects carrying the resolved alias.
        let json = serde_json::to_string(&rows).unwrap();
        assert!(json.contains("\"alias\":\"git-ark\""));
        assert!(json.contains("\"name\":\"nas\""));
    }

    // -----------------------------------------------------------------
    // mirror check
    // -----------------------------------------------------------------

    #[test]
    fn needs_workflow_true_when_workflows_dir_has_entries() {
        let dir = tempfile::tempdir().unwrap();
        let workflows = dir.path().join(".github").join("workflows");
        std::fs::create_dir_all(&workflows).unwrap();
        std::fs::write(workflows.join("ci.yml"), "name: ci\n").unwrap();
        assert!(needs_workflow(dir.path()));
    }

    #[test]
    fn needs_workflow_false_when_workflows_dir_empty() {
        let dir = tempfile::tempdir().unwrap();
        std::fs::create_dir_all(dir.path().join(".github").join("workflows")).unwrap();
        assert!(!needs_workflow(dir.path()));
    }

    #[test]
    fn needs_workflow_false_when_no_github_dir() {
        let dir = tempfile::tempdir().unwrap();
        assert!(!needs_workflow(dir.path()));
    }

    fn token_check(
        valid: bool,
        repo: github::RepoAccess,
        scopes: Option<Vec<&str>>,
        needs_workflow: bool,
    ) -> github::TokenCheck {
        github::TokenCheck {
            valid,
            login: if valid { Some("me".to_string()) } else { None },
            scopes: scopes.map(|s| s.into_iter().map(str::to_string).collect()),
            repo,
            needs_workflow,
        }
    }

    #[test]
    fn format_check_reports_failed_auth() {
        let c = token_check(false, github::RepoAccess::Absent, None, false);
        let out = format_check(&c, "acme", "app");
        assert!(out.contains("✗ token does not authenticate"));
    }

    #[test]
    fn format_check_reports_successful_auth_with_login() {
        let c = token_check(
            true,
            github::RepoAccess::Exists {
                push: true,
                admin: true,
            },
            None,
            false,
        );
        let out = format_check(&c, "acme", "app");
        assert!(out.contains("✓ authenticates (login: me)"));
    }

    #[test]
    fn format_check_repo_admin() {
        let c = token_check(
            true,
            github::RepoAccess::Exists {
                push: true,
                admin: true,
            },
            None,
            false,
        );
        let out = format_check(&c, "acme", "app");
        assert!(out.contains("✓ can administer acme/app"));
    }

    #[test]
    fn format_check_repo_push_without_admin() {
        let c = token_check(
            true,
            github::RepoAccess::Exists {
                push: true,
                admin: false,
            },
            None,
            false,
        );
        let out = format_check(&c, "acme", "app");
        assert!(out.contains("✓ can push acme/app"));
        assert!(out.contains("no admin"));
    }

    #[test]
    fn format_check_repo_no_push() {
        let c = token_check(
            true,
            github::RepoAccess::Exists {
                push: false,
                admin: false,
            },
            None,
            false,
        );
        let out = format_check(&c, "acme", "app");
        assert!(out.contains("✗ no push access to acme/app"));
    }

    #[test]
    fn format_check_repo_absent() {
        let c = token_check(true, github::RepoAccess::Absent, None, false);
        let out = format_check(&c, "acme", "app");
        // A 404 is a soft warning (not a hard ✗) but must name the org-access /
        // SSO ambiguity, not assert the repo will be created.
        assert!(out.contains("⚠ acme/app"));
        assert!(out.contains("404") && out.contains("org access"));
    }

    #[test]
    fn format_check_repo_error() {
        let c = token_check(
            true,
            github::RepoAccess::Error("HTTP 403".to_string()),
            None,
            false,
        );
        let out = format_check(&c, "acme", "app");
        assert!(out.contains("✗ acme/app: HTTP 403"));
    }

    #[test]
    fn format_check_omits_workflow_line_when_not_needed() {
        let c = token_check(
            true,
            github::RepoAccess::Exists {
                push: true,
                admin: true,
            },
            Some(vec!["repo"]),
            false,
        );
        let out = format_check(&c, "acme", "app");
        assert!(!out.contains("workflow"));
    }

    #[test]
    fn format_check_workflow_scope_present() {
        let c = token_check(
            true,
            github::RepoAccess::Exists {
                push: true,
                admin: true,
            },
            Some(vec!["repo", "workflow"]),
            true,
        );
        let out = format_check(&c, "acme", "app");
        assert!(out.contains("✓ workflow scope"));
    }

    #[test]
    fn format_check_workflow_scope_missing() {
        let c = token_check(
            true,
            github::RepoAccess::Exists {
                push: true,
                admin: true,
            },
            Some(vec!["repo"]),
            true,
        );
        let out = format_check(&c, "acme", "app");
        assert!(out.contains("✗ missing 'workflow' scope"));
    }

    #[test]
    fn format_check_workflow_scope_uninspectable() {
        let c = token_check(
            true,
            github::RepoAccess::Exists {
                push: true,
                admin: true,
            },
            None,
            true,
        );
        let out = format_check(&c, "acme", "app");
        assert!(out.contains("⚠ repo ships workflows"));
    }

    // -----------------------------------------------------------------
    // upgrade
    // -----------------------------------------------------------------

    #[test]
    fn resolve_upgrade_targets_all_returns_every_host() {
        let mut registry = Registry::default();
        registry.upsert(test_host("nas", false));
        registry.upsert(test_host("ec2", true));

        let targets = resolve_upgrade_targets(&registry, &[], true).unwrap();
        let mut names: Vec<&str> = targets.iter().map(|h| h.name.as_str()).collect();
        names.sort();
        assert_eq!(names, vec!["ec2", "nas"]);
    }

    #[test]
    fn resolve_upgrade_targets_all_bails_on_empty_registry() {
        let registry = Registry::default();
        assert!(resolve_upgrade_targets(&registry, &[], true).is_err());
    }

    #[test]
    fn resolve_upgrade_targets_named_returns_those_hosts() {
        let mut registry = Registry::default();
        registry.upsert(test_host("nas", false));
        registry.upsert(test_host("ec2", true));

        let names = vec!["ec2".to_string()];
        let targets = resolve_upgrade_targets(&registry, &names, false).unwrap();
        assert_eq!(targets.len(), 1);
        assert_eq!(targets[0].name, "ec2");
    }

    #[test]
    fn resolve_upgrade_targets_bails_on_unknown_name() {
        let mut registry = Registry::default();
        registry.upsert(test_host("nas", false));

        let names = vec!["nope".to_string()];
        let err = resolve_upgrade_targets(&registry, &names, false).unwrap_err();
        assert!(err.to_string().contains("nope"));
    }

    #[test]
    fn resolve_upgrade_targets_bails_when_neither_all_nor_names() {
        let mut registry = Registry::default();
        registry.upsert(test_host("nas", false));

        let err = resolve_upgrade_targets(&registry, &[], false).unwrap_err();
        assert!(err.to_string().contains("--all"));
    }

    #[test]
    fn resolve_upgrade_targets_all_wins_over_names() {
        let mut registry = Registry::default();
        registry.upsert(test_host("nas", false));
        registry.upsert(test_host("ec2", true));

        // An unknown name would normally bail — proves `all` short-circuits
        // past name resolution entirely rather than validating both.
        let names = vec!["nope".to_string()];
        let targets = resolve_upgrade_targets(&registry, &names, true).unwrap();
        assert_eq!(targets.len(), 2);
    }

    // -----------------------------------------------------------------
    // host setup-key
    // -----------------------------------------------------------------

    #[test]
    fn pick_or_plan_keygen_reuses_existing_ed25519() {
        let dir = PathBuf::from("/home/op/.ssh");
        let existing = vec!["id_ed25519".to_string()];
        assert_eq!(
            pick_or_plan_keygen(&dir, &existing),
            KeyPlan::Reuse(dir.join("id_ed25519"))
        );
    }

    #[test]
    fn pick_or_plan_keygen_reuses_rsa_when_thats_all_there_is() {
        let dir = PathBuf::from("/home/op/.ssh");
        let existing = vec!["id_rsa".to_string()];
        assert_eq!(
            pick_or_plan_keygen(&dir, &existing),
            KeyPlan::Reuse(dir.join("id_rsa"))
        );
    }

    #[test]
    fn pick_or_plan_keygen_prefers_ecdsa_over_rsa() {
        let dir = PathBuf::from("/home/op/.ssh");
        let existing = vec!["id_rsa".to_string(), "id_ecdsa".to_string()];
        assert_eq!(
            pick_or_plan_keygen(&dir, &existing),
            KeyPlan::Reuse(dir.join("id_ecdsa"))
        );
    }

    #[test]
    fn pick_or_plan_keygen_generates_ed25519_when_none_exist() {
        let dir = PathBuf::from("/home/op/.ssh");
        assert_eq!(
            pick_or_plan_keygen(&dir, &[]),
            KeyPlan::Generate(dir.join("id_ed25519"))
        );
    }
}