//! `hivectl wg` / `peer-config` — WireGuard mesh helpers: generate this
//! hive's key + the nix snippets to enable the mesh, add a peer, print the
//! block a peer pastes to federate with us, and show the live interface.

use std::path::Path;

use anyhow::{Context as _, Result, bail};

use crate::util::query_hive_urls;

/// Host path of this hive's WireGuard private key (matches the
/// `privateKeyFile` example in the deploy.wireguard nix options).
const WG_KEY_PATH: &str = "/etc/wireguard/hive.key";
/// The mesh interface name hive-c0re's nix module brings up.
const WG_INTERFACE: &str = "wg-hive";

/// Host path of this hive's TLS trust bundle (matches the
/// `services.hyperhive.deploy.hive-controller.tls.stateDir` default in
/// hive-tls.nix). Its existence means the gateway is in self-signed mode,
/// serving a leaf the secret store issued, so a federating peer needs an
/// anchor for it. Absent = ACME / operator cert, trusted by the default CA
/// bundle with nothing to distribute.
const HIVE_TLS_TRUST_BUNDLE_PATH: &str = "/var/lib/hive-tls/trust-bundle.pem";

/// Host path of the secret store's `pki` root (hive-tls.nix's
/// `$svcroot`, folded into the trust bundle). The anchor a whole swarm
/// shares: every hive's gateway leaf and the swarm's service names are
/// issued under it, so a peer host installs it once and every present
/// *and future* hive validates.
const STORE_PKI_ROOT_PATH: &str = "/var/lib/hive-tls/swarm-services-root.pem";

/// Attrset key for a hive in `services.hyperhive.swarm.hives`, derived
/// from its domain's first DNS label.
///
/// A hive occupies `<hiveName>.<swarm.domain>`, so the first label *is*
/// the hive name in any deployment that hasn't overridden `domain` by
/// hand. Where it has, a wrong key fails loudly rather than quietly: on
/// that hive's own host the `hives.<hiveName>` assertion fires, because
/// the directory is supposed to be the same attrset everywhere. The
/// snippets below say so rather than presenting the guess as fact.
fn hive_key(domain: &str) -> &str {
    domain.split('.').next().unwrap_or(domain)
}

/// Best-effort query for this hive's domain from the running daemon
/// (`HostRequest::Urls`, which reads `HYPERHIVE_HIVE_DOMAIN` from c0re's
/// service env). `None` when the daemon is unreachable or the domain is
/// unset — for the callers that treat both as "skip the optional block".
/// Use [`require_hive_domain`] where the distinction matters: it keeps the
/// connect error (and its hint) instead of flattening it away.
async fn query_hive_domain(socket: &Path) -> Option<String> {
    query_hive_urls(socket).await.ok().flatten()?.domain
}

/// Require this hive's domain from the daemon for snippet generation.
/// Errors with a clear hint when it can't be resolved, so `peer-config`
/// never silently emits a wrong key. An unreachable daemon propagates its
/// own (classified) connect error; only a *reachable* daemon with no domain
/// gets the config hint.
pub(crate) async fn require_hive_domain(socket: &Path) -> Result<String> {
    query_hive_urls(socket)
        .await
        .context("could not determine this hive's domain from the daemon")?
        .and_then(|u| u.domain)
        .context("the daemon reported no domain — set `services.hyperhive.domain`")
}

/// `wg init` — generate (if absent) the hive's WireGuard key, print its
/// public key + the nix snippet to enable the mesh, then (best-effort)
/// the `peer-config` block peers paste to federate with this hive, so a
/// fresh setup is one command. The domain comes from the daemon; if it
/// can't be resolved, the peer block is skipped (init still succeeds —
/// its core job is enabling the mesh locally).
pub(crate) async fn wg_init(socket: &Path, address: Option<&str>) -> Result<()> {
    use std::os::unix::fs::PermissionsExt as _;
    let key_path = Path::new(WG_KEY_PATH);
    if key_path.exists() {
        println!(
            "WireGuard private key already present at {WG_KEY_PATH} — reusing (not regenerating)."
        );
    } else {
        if let Some(parent) = key_path.parent() {
            std::fs::create_dir_all(parent)
                .with_context(|| format!("create {}", parent.display()))?;
            std::fs::set_permissions(parent, std::fs::Permissions::from_mode(0o700)).ok();
        }
        let out = std::process::Command::new("wg")
            .arg("genkey")
            .output()
            .context("run `wg genkey` (is wireguard-tools installed?)")?;
        if !out.status.success() {
            bail!(
                "wg genkey failed: {}",
                String::from_utf8_lossy(&out.stderr).trim()
            );
        }
        write_key_0400(key_path, &out.stdout)?;
        println!("Generated WireGuard private key at {WG_KEY_PATH} (0400).");
    }

    let privkey =
        std::fs::read(key_path).with_context(|| format!("read {}", key_path.display()))?;
    let pubkey = wg_pubkey(&privkey)?;
    let addr = address.unwrap_or("<MESH_ADDRESS e.g. 10.42.0.1/32>");
    println!("\nPublic key (share this with peer hives — they pass it to `hivectl wg peer`):");
    println!("  {pubkey}");
    println!("\nAdd to this hive's NixOS config:");
    println!("  services.hyperhive.deploy.wireguard = {{");
    println!("    enable = true;");
    println!("    privateKeyFile = \"{WG_KEY_PATH}\";");
    println!("    address = \"{addr}\";");
    println!("    # listenPort = 51820;  # default");
    println!("  }};");

    // Also print the block a peer pastes to federate with us (CA + this
    // mesh key) — one-stop setup. Domain comes from the daemon;
    // best-effort, so init still succeeds when it can't be resolved.
    if let Some(d) = query_hive_domain(socket).await {
        println!();
        peer_config(&d, address, None);
    }
    Ok(())
}

/// Write `key` to a sibling temp file created `0400` and rename it over
/// `path`, so the key is never readable by anyone else and a crash never
/// leaves half of it at `path`. Errors carry paths, never the key.
fn write_key_0400(path: &Path, key: &[u8]) -> Result<()> {
    use std::io::Write as _;
    use std::os::unix::fs::OpenOptionsExt as _;

    let mut tmp_name = path
        .file_name()
        .with_context(|| format!("{} has no file name", path.display()))?
        .to_owned();
    tmp_name.push(".tmp");
    let tmp = path.with_file_name(tmp_name);
    // A temp file left by a crashed earlier write would fail `create_new`.
    let _ = std::fs::remove_file(&tmp);
    let mut f = std::fs::OpenOptions::new()
        .write(true)
        .create_new(true)
        .mode(0o400)
        .open(&tmp)
        .with_context(|| format!("create {}", tmp.display()))?;
    f.write_all(key)
        .and_then(|()| f.sync_all())
        .with_context(|| format!("write {}", tmp.display()))?;
    std::fs::rename(&tmp, path).with_context(|| format!("rename onto {}", path.display()))
}

/// Derive a WireGuard public key from a private key by piping it through
/// `wg pubkey`.
fn wg_pubkey(privkey: &[u8]) -> Result<String> {
    use std::io::Write as _;
    use std::process::{Command, Stdio};
    let mut child = Command::new("wg")
        .arg("pubkey")
        .stdin(Stdio::piped())
        .stdout(Stdio::piped())
        .stderr(Stdio::piped())
        .spawn()
        .context("run `wg pubkey` (is wireguard-tools installed?)")?;
    child
        .stdin
        .take()
        .context("wg pubkey: stdin unavailable")?
        .write_all(privkey)
        .context("write private key to `wg pubkey`")?;
    let out = child.wait_with_output().context("wait for `wg pubkey`")?;
    if !out.status.success() {
        bail!(
            "wg pubkey failed: {}",
            String::from_utf8_lossy(&out.stderr).trim()
        );
    }
    Ok(String::from_utf8_lossy(&out.stdout).trim().to_owned())
}

/// `wg peer` — print the nix snippet to add a peer hive to the mesh.
/// Pure output (no fallible work), so it returns `()`; the dispatch arm
/// wraps it in `Ok` to match the sibling verbs.
pub(crate) fn wg_peer(domain: &str, pubkey: &str, address: &str, endpoint: Option<&str>) {
    let key = hive_key(domain);
    println!("Add to this hive's NixOS config:");
    println!("  # `hives` describes the whole swarm and is meant to be the same");
    println!("  # attrset on every host — add this entry to all of them.");
    println!("  services.hyperhive.swarm.hives.\"{key}\" = {{");
    println!("    domain = \"{domain}\";");
    println!("    wireguardPublicKey = \"{pubkey}\";");
    println!("    wireguardAddress = \"{address}\";");
    if let Some(ep) = endpoint {
        println!("    wireguardEndpoint = \"{ep}\";");
    }
    println!("  }};");
    println!("  # the key must be that hive's services.hyperhive.hiveName");
}

/// The `peer-config` step carrying the secret store's `pki` root: the
/// certificate itself, or where it will appear when this hive has not
/// fetched it yet.
fn store_root_step(pem: Option<&str>) -> String {
    const HEAD: &str = "# 1. trust the SECRET STORE's pki root on the peer host (once, not per hive);\n\
                        #    every hive's gateway leaf and the swarm's service names are issued under it:\n";
    match pem.map(str::trim_end).filter(|p| !p.is_empty()) {
        Some(p) => format!(
            "{HEAD}{p}\n\
             #    (a self-signed hive in this swarm fetches it itself, into {STORE_PKI_ROOT_PATH})\n"
        ),
        None => format!(
            "{HEAD}#    not on this host yet: swarm-services-cert.service writes it to\n\
             #    {STORE_PKI_ROOT_PATH}; rerun once that unit has succeeded\n"
        ),
    }
}

/// `peer-config` — print the `swarm.hives."<name>"` block a peer
/// operator pastes to federate with THIS hive, plus the store-root step
/// when this hive serves a self-signed chain. Reads
/// local state only (the TLS trust bundle, the store root + the wg key);
/// prints, never mutates.
pub(crate) fn peer_config(domain: &str, wg_address: Option<&str>, wg_endpoint: Option<&str>) {
    let self_signed = Path::new(HIVE_TLS_TRUST_BUNDLE_PATH).exists();
    let key = hive_key(domain);
    // WireGuard public key, when this hive has a mesh key. Best-effort:
    // a missing key or absent `wg` binary just omits the mesh lines.
    let wg_pub = std::fs::read(WG_KEY_PATH)
        .ok()
        .and_then(|k| wg_pubkey(&k).ok());

    if self_signed {
        let store_root = std::fs::read_to_string(STORE_PKI_ROOT_PATH).ok();
        print!("{}", store_root_step(store_root.as_deref()));
        println!();
        println!("# 2. paste into the peer hive's NixOS config:");
    } else {
        println!("# paste into the peer hive's NixOS config:");
    }
    println!("services.hyperhive.swarm.hives.\"{key}\" = {{");
    println!("  domain = \"{domain}\";");
    if let Some(pk) = &wg_pub {
        println!("  wireguardPublicKey = \"{pk}\";");
    }
    if let Some(addr) = wg_address {
        println!("  wireguardAddress = \"{addr}\";");
    }
    if let Some(ep) = wg_endpoint {
        println!("  wireguardEndpoint = \"{ep}\";");
    }
    println!("}};");
    println!("# the key must be this hive's services.hyperhive.hiveName, and the");
    println!("# same entry belongs in every hive's config — `hives` is the swarm.");
    if !self_signed {
        println!(
            "# (this hive's cert chains to a public CA — nothing to install; \
             it's trusted by the default bundle.)"
        );
    }
}

/// `wg status` — show the live mesh interface (`wg show wg-hive`),
/// inheriting stdout so the operator sees it directly.
pub(crate) fn wg_status() -> Result<()> {
    let status = std::process::Command::new("wg")
        .args(["show", WG_INTERFACE])
        .status()
        .context("run `wg show` (is wireguard-tools installed?)")?;
    if !status.success() {
        bail!(
            "`wg show {WG_INTERFACE}` failed — is the mesh enabled + up? \
             (services.hyperhive.deploy.wireguard.enable = true, then deploy)"
        );
    }
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::{STORE_PKI_ROOT_PATH, store_root_step, write_key_0400};

    const PEM: &str = "-----BEGIN CERTIFICATE-----\nMIIB\n-----END CERTIFICATE-----";

    /// The certificate is printed whole, on lines of its own, so a peer
    /// operator can copy it out of the output as a PEM file.
    #[test]
    fn store_root_is_printed_verbatim() {
        let s = store_root_step(Some(&format!("{PEM}\n")));
        assert!(s.contains(&format!("\n{PEM}\n")), "{s}");
    }

    /// A hive that has not fetched the root yet says where it will be,
    /// rather than printing an empty step.
    #[test]
    fn missing_store_root_names_the_path_and_the_unit() {
        for pem in [None, Some(""), Some("\n")] {
            let s = store_root_step(pem);
            assert!(s.contains(STORE_PKI_ROOT_PATH), "{s}");
            assert!(s.contains("swarm-services-cert.service"), "{s}");
            assert!(!s.contains("BEGIN CERTIFICATE"), "{s}");
        }
    }

    /// The key reaches its path only by a rename from a sibling temp: with
    /// the temp path blocked, the write fails and the existing key is left
    /// byte-for-byte as it was. Once unblocked, the key lands at `0400` with
    /// its bytes intact and no temp file beside it.
    #[test]
    fn key_is_written_through_a_temp_and_lands_0400() {
        use std::os::unix::fs::PermissionsExt as _;

        let dir = std::env::temp_dir().join(format!("hivectl-wg-key-{}", std::process::id()));
        std::fs::create_dir_all(&dir).expect("mkdir");
        let path = dir.join("hive.key");
        let tmp = dir.join("hive.key.tmp");
        std::fs::write(&path, "old-key\n").expect("seed");
        std::fs::create_dir(&tmp).expect("block tmp");

        let blocked = write_key_0400(&path, b"key-bytes\n");
        assert!(blocked.is_err(), "a blocked temp must fail the write");
        assert_eq!(std::fs::read(&path).expect("read seed"), b"old-key\n");
        std::fs::remove_dir(&tmp).expect("unblock tmp");

        write_key_0400(&path, b"key-bytes\n").expect("write");
        let mode = std::fs::metadata(&path).expect("stat").permissions().mode() & 0o777;
        let content = std::fs::read(&path).expect("read");
        let entries: Vec<_> = std::fs::read_dir(&dir)
            .expect("readdir")
            .map(|e| e.expect("entry").file_name())
            .collect();
        std::fs::remove_dir_all(&dir).ok();

        assert_eq!(mode, 0o400);
        assert_eq!(content, b"key-bytes\n");
        assert_eq!(entries, [std::ffi::OsString::from("hive.key")]);
    }
}