//! The CI runner agreement: where the forge's runner registration token lives,
//! and what the object at that path holds.
//!
//! `swarm-controller` fetches the token with the forge's admin API and writes
//! it here; `nix/host-modules/swarm-ci-runner.nix` reads it under the runner's
//! own certificate. That runner's read stanza is the only one in the store that
//! covers this path.

use serde::{Deserialize, Serialize};

use crate::{
    Error,
    path::{Kind, principal_prefix},
};

/// The runner's name segment under [`Kind::Service`].
const SERVICE: &str = "ci-runner";

/// The path holding the forge's runner registration token.
///
/// # Errors
/// Never in practice: the name segment is a constant. The `Result` is
/// [`principal_prefix`]'s.
pub fn registration_token_path() -> Result<String, Error> {
    let prefix = principal_prefix(Kind::Service, SERVICE)?;
    Ok(format!("{prefix}/registration-token"))
}

/// What the registration-token path holds.
///
/// No `Debug` derive: `value` registers a runner that receives jobs from every
/// repo on the forge, and a derived `Debug` is one `{:?}` away from a log line.
#[derive(Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct Credential {
    /// The token itself. `swarm-ci-runner.nix` reads the store with
    /// `bao kv get -field=value`, so this name is load-bearing for a reader
    /// this crate does not control, the same as [`crate::matrix::Credential`]'s.
    pub value: String,
}

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

    #[test]
    fn the_registration_token_is_under_the_runners_service_prefix() {
        // The literal is what `swarm-bao.nix` grants the runner's role, and
        // what the controller's write stanza names.
        assert_eq!(
            registration_token_path().expect("a constant segment is legal"),
            "swarm/services/ci-runner/registration-token"
        );
    }
}