//! `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 swarm.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.tls.stateDir` default in hive-tls.nix). Its
/// existence means the gateway serves a self-signed, hive-CA-signed
/// leaf, so a federating peer needs an anchor for it — which is now the
/// swarm root, not a per-hive CA. Absent = ACME / operator cert, trusted
/// by the default CA bundle with nothing to distribute.
///
/// The bundle rather than `ca.pem`: the hive CA is an intermediate under
/// the swarm root, so `ca.pem` alone is not a chain a peer can validate
/// against (openssl will not stop at a trusted non-self-signed cert).
/// The bundle is whatever this hive is currently rooted at — the CA
/// alone on a hive that predates the swarm root — so this stays a single
/// path with no mode to branch on.
const HIVE_TLS_TRUST_BUNDLE_PATH: &str = "/var/lib/hive-tls/trust-bundle.pem";

/// Host path of the swarm root CA cert (matches the
/// `services.hyperhive.swarm.ca.stateDir` default in swarm-ca.nix). The
/// anchor a whole swarm shares: install it once per host and every
/// present *and future* hive under it validates, which is what replaced
/// the per-hive CA pinning.
const SWARM_CA_ROOT_PATH: &str = "/var/lib/swarm-ca/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()
            );
        }
        std::fs::write(key_path, &out.stdout)
            .with_context(|| format!("write {}", key_path.display()))?;
        std::fs::set_permissions(key_path, std::fs::Permissions::from_mode(0o400))
            .with_context(|| format!("chmod 400 {}", key_path.display()))?;
        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.swarm.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(())
}

/// 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");
}

/// `peer-config` — print the `swarm.hives."<name>"` block a peer
/// operator pastes to federate with THIS hive, plus the swarm-root
/// install step when this hive serves a self-signed chain. Reads local
/// state only (the TLS trust bundle's presence + 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 {
        // One anchor for the whole swarm, installed once per host — not
        // a file per peer. That is the point of the hierarchy: a hive
        // joining later needs no edit on the hives already running.
        println!("# 1. install the SWARM ROOT on the peer host (once, not per hive):");
        println!("scp {SWARM_CA_ROOT_PATH} <peer-host>:{SWARM_CA_ROOT_PATH}");
        println!("#    (skip if that host already has the swarm root)");
        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.swarm.wireguard.enable = true, then deploy)"
        );
    }
    Ok(())
}