//! hive-ci Forgejo Actions runner registration, driven from hive-c0re.
//!
//! Moves the runner-registration forge round-trip OFF the container's
//! boot-critical path (it was a host-side `hive-ci-prefetch` oneshot that
//! gated `container@hive-ci` start — see `nix/host-modules/hive-ci.nix`).
//! hive-c0re holds the forge admin token; here it validates the runner's
//! existing credentials and, when they're absent or stale, mints a fresh
//! registration token and hands it to hive-priv, which writes it to the host
//! env-file the container bind-mounts read-only and restarts the in-container
//! runner. The admin token never enters the container — only the registration
//! token does, exactly as the prefetch did.

use anyhow::{Context as _, Result};
use serde_json::Value;
use url::Url;

use super::forge_http_base;

/// Host path to the hive-ci runner's persisted credentials. The container is
/// non-ephemeral, so `.runner` survives restarts; a present file with a sane
/// `id` means the runner is already registered.
const RUNNER_FILE: &str = "/var/lib/nixos-containers/hive-ci/var/lib/gitea-runner/hive/.runner";

/// Whether the operator enabled the CI runner. The nix module sets
/// `HYPERHIVE_FORGE_CI_ENABLED=1` on `hive-c0re.service` when
/// `services.hyperhive.deploy.forgejo.ci.enable` is on; absent means CI is off and
/// there is no hive-ci container to register a runner for.
fn ci_enabled() -> bool {
    std::env::var("HYPERHIVE_FORGE_CI_ENABLED")
        .is_ok_and(|v| v == "1" || v.eq_ignore_ascii_case("true"))
}

/// Ensure the hive-ci runner is registered against the forge. Best-effort:
/// every failure is logged and swallowed so it never aborts the startup
/// sweep ([`super::ensure_all`]). No-op when CI is disabled or the runner
/// already holds valid credentials (so a healthy runner is never restarted).
pub(super) async fn ensure_ci_runner_registered(core_token: &str) {
    if !ci_enabled() {
        return;
    }
    // Existing creds still valid on the forge, AND pointed at the forge
    // address we are configured for → nothing to do.
    if let Some(id) = existing_runner_id()
        && runner_address_current()
        && runner_valid(core_token, id).await
    {
        return;
    }
    // Absent or stale → mint a fresh registration token and hand it to
    // hive-priv (root) to write the env-file + restart the runner.
    match fetch_registration_token(core_token).await {
        Ok(token) => {
            if let Err(e) = crate::priv_client::register_ci_runner(&token).await {
                tracing::warn!(error = ?e, "ci runner: hive-priv register_ci_runner failed");
                crate::warnings::set_boot_warning(
                    "ci_runner_register",
                    "crit",
                    format!("ci runner: hive-priv register_ci_runner failed: {e}"),
                );
            } else {
                tracing::info!("ci runner: registered hive-ci runner with a fresh token");
            }
        }
        Err(e) => {
            tracing::warn!(error = ?e, "ci runner: fetch registration token failed");
            crate::warnings::set_boot_warning(
                "ci_runner_fetch_token",
                "crit",
                format!("ci runner: fetch registration token failed: {e}"),
            );
        }
    }
}

/// Parse the runner id from the persisted `.runner` JSON, if present and sane
/// (a `0` id is the gitea-runner "unregistered" sentinel).
fn existing_runner_id() -> Option<u64> {
    let raw = std::fs::read_to_string(RUNNER_FILE).ok()?;
    let json: Value = serde_json::from_str(&raw).ok()?;
    let id = json.get("id")?.as_u64()?;
    (id != 0).then_some(id)
}

/// Whether the persisted `.runner` still names the forge host we are
/// configured for.
///
/// `act_runner` records the `--instance` URL it was registered with and the
/// daemon reads the address from there and nowhere else — the nix option only
/// reaches `register`, and upstream re-registers on a changed token or labels,
/// never on a changed URL. So a forge rename leaves a runner dialling a name
/// its container's `extraHosts` no longer resolves, with every existing check
/// still green: the runner id is untouched, so `runner_valid` says yes.
///
/// Fail-safe in the same direction as [`runner_valid`]: anything we cannot
/// read or parse returns `true` (keep the existing creds). Only a *positive*
/// disagreement between two parseable hosts is treated as stale, because the
/// cost of a false stale is re-registering on every boot.
fn runner_address_current() -> bool {
    let Ok(raw) = std::fs::read_to_string(RUNNER_FILE) else {
        return true;
    };
    runner_address_matches(&raw, forge_http_base())
}

/// Host-only comparison of `.runner`'s `address` against the configured base.
///
/// Split from [`runner_address_current`] so it is testable without the
/// filesystem. Compares **hosts**, not whole URLs: both strings come from the
/// same nix expression (`http://${swarm.forge.domain}`, reaching the runner as
/// `instances.hive.url` and this daemon as `HIVE_FORGE_URL`), but scheme,
/// port and trailing slash are exactly the kind of cosmetic difference that
/// would otherwise re-register the runner on every boot.
fn runner_address_matches(raw: &str, configured: &str) -> bool {
    let Some(address) = serde_json::from_str::<Value>(raw)
        .ok()
        .and_then(|j| j.get("address")?.as_str().map(str::to_owned))
    else {
        return true;
    };
    match (Url::parse(&address), Url::parse(configured)) {
        (Ok(a), Ok(b)) => match (a.host_str(), b.host_str()) {
            (Some(a), Some(b)) => a.eq_ignore_ascii_case(b),
            _ => true,
        },
        _ => true,
    }
}

/// `GET /admin/runners/{id}` — `true` iff the runner still exists on the forge
/// (HTTP 200). A 404 (deleted from the admin panel) or any other status means
/// re-registration is needed. A transport error (forge unreachable) is treated
/// as "keep the existing creds" so a network blip never wipes a valid runner.
async fn runner_valid(core_token: &str, id: u64) -> bool {
    let url = format!("{}/api/v1/admin/runners/{id}", forge_http_base());
    match reqwest::Client::new()
        .get(&url)
        .header("Authorization", format!("token {core_token}"))
        .send()
        .await
    {
        Ok(resp) => resp.status().is_success(),
        Err(e) => {
            tracing::warn!(error = ?e, "ci runner: validation request failed; keeping existing creds");
            true
        }
    }
}

/// `GET /admin/runners/registration-token` — mint a fresh registration token.
/// forgejo-api (0.11) doesn't wrap this endpoint, so this is a raw request
/// against the local HTTP forge ([`forge_http_base`]), mirroring the prefetch's
/// former curl; Forgejo accepts `Authorization: token <admin>`.
async fn fetch_registration_token(core_token: &str) -> Result<String> {
    let url = format!(
        "{}/api/v1/admin/runners/registration-token",
        forge_http_base()
    );
    let resp = reqwest::Client::new()
        .get(&url)
        .header("Authorization", format!("token {core_token}"))
        .send()
        .await
        .context("GET admin/runners/registration-token")?;
    let status = resp.status();
    let json: Value = resp
        .json()
        .await
        .context("parse registration-token response")?;
    if !status.is_success() {
        anyhow::bail!("registration-token HTTP {status}: {json}");
    }
    json.get("token")
        .and_then(Value::as_str)
        .map(str::to_owned)
        .context("registration-token response missing 'token' field")
}

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

    fn runner(address: &str) -> String {
        format!(r#"{{"id":7,"uuid":"u","name":"hive","token":"t","address":"{address}"}}"#)
    }

    /// The case the bug is about: a forge rename leaves the old host behind.
    #[test]
    fn differing_host_is_stale() {
        assert!(!runner_address_matches(
            &runner("http://forge.pr1ma.darkest.space"),
            "http://forge.constellation.darkest.space",
        ));
    }

    /// Control for the arm above — without it, a helper that always returned
    /// `false` would pass `differing_host_is_stale` and re-register forever.
    #[test]
    fn same_host_is_current() {
        assert!(runner_address_matches(
            &runner("http://forge.example"),
            "http://forge.example",
        ));
    }

    /// Cosmetic differences must NOT count: both sides are rendered from one
    /// nix expression, but a port or trailing slash appearing on one side is
    /// not a rename.
    #[test]
    fn port_scheme_and_trailing_slash_do_not_count() {
        assert!(runner_address_matches(
            &runner("http://forge.example:80/"),
            "https://FORGE.example",
        ));
    }

    /// Fail-safe: anything unreadable keeps the existing credentials, so a
    /// malformed or older `.runner` never costs a working runner.
    #[test]
    fn unparseable_input_keeps_creds() {
        assert!(runner_address_matches("not json", "http://forge.example"));
        assert!(runner_address_matches(
            r#"{"id":7}"#,
            "http://forge.example"
        ));
        assert!(runner_address_matches(
            &runner("://nonsense"),
            "http://forge.example",
        ));
    }
}