//! The CI metrics poller agreement: where its forge token and its OIDC client
//! secret live in the store, and what each object holds.
//!
//! swarm-controller mints the forge token; the poller reads it, and its client
//! secret, under its own certificate. Its read stanza in `swarm-bao.nix` names
//! exactly these two paths.

use serde::{Deserialize, Serialize};

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

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

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

/// The path holding the secret of the poller's OIDC client `client_id`, where
/// `swarm-secret-publisher.nix` puts every swarm service's.
///
/// # Errors
/// [`Error::PathSegment`] when `client_id` is not a single path segment.
pub fn client_secret_path(client_id: &str) -> Result<String, Error> {
    let prefix = principal_prefix(Kind::Service, client_id)?;
    Ok(format!("{prefix}/oidc/client"))
}

/// What [`client_secret_path`] holds.
///
/// No `Debug`: `value` authenticates the poller at the collector.
#[derive(Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct ClientSecret {
    /// The secret, under the field name the publisher writes.
    pub value: String,
}

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

    #[test]
    fn the_paths_are_the_ones_the_store_grants() {
        // Spelled out: `swarm-bao.nix` grants each literal.
        assert_eq!(
            forge_token_path().expect("a constant segment is legal"),
            "swarm/services/ci-metrics/forge/token"
        );
        assert_eq!(
            client_secret_path("swarm-ci-metrics").expect("a plain id is legal"),
            "swarm/services/swarm-ci-metrics/oidc/client"
        );
    }
}