//! Client for `swarm-authelia-bridge` — this daemon's only access to the
//! swarm's authelia users database, in either direction (see that crate's
//! README for why the file cannot be touched from here).
//!
//! Authenticated with THIS daemon's own queue OIDC identity
//! (`SWARM_CONTROLLER_OIDC_*`, the same one `swarm-queue-client` mints for
//! the queue connection) — "one identity per principal" means a second
//! op that needs to prove who this process is reuses the identity it
//! already has rather than provisioning a new one. A fresh token is
//! minted per call for the same reason the queue client mints one per
//! connection attempt: no window in which this process holds a token
//! that outlives its intended use.
//!
//! `None` when this deployment did not wire a bridge up — the bridge only
//! exists on hosts that also run `swarm-authelia`, so a controller split
//! from it can neither create an identity nor read the roster.
//!
//! Each caller answers that absence in its own terms rather than this
//! module inventing a shared one: `SwarmNodeKind::CreateIdentity` fails
//! the job explicitly, and the roster endpoint refuses. Neither substitutes
//! an empty answer, which is the failure mode a default here would create.

use anyhow::{Context, Result};
use swarm_authelia_bridge_sock::{BridgeRequest, BridgeResponse};

/// A configured connection to `swarm-authelia-bridge`.
#[derive(Clone)]
pub struct AuthBridge {
    http: reqwest::Client,
    base_url: String,
    queue_cfg: swarm_queue_client::QueueConfig,
}

impl AuthBridge {
    /// Read `SWARM_CONTROLLER_AUTH_BRIDGE_URL`; `Ok(None)` when unset.
    ///
    /// The queue identity (`SWARM_CONTROLLER_OIDC_*`) is not optional once
    /// the bridge URL is set: the nix module sets `queueEnv` unconditionally
    /// for every controller (the queue is required, not just co-located
    /// service), so a bridge URL with no queue identity to authenticate
    /// with is a deployment bug, not an absent-feature case — hence the
    /// hard error rather than a second `None`.
    pub fn from_env() -> Result<Option<Self>> {
        let Ok(base_url) = std::env::var("SWARM_CONTROLLER_AUTH_BRIDGE_URL") else {
            return Ok(None);
        };
        let queue_cfg = swarm_queue_client::QueueConfig::from_env("SWARM_CONTROLLER")
            .context("reading the queue OIDC identity the auth bridge authenticates with")?
            .ok_or_else(|| {
                anyhow::anyhow!(
                    "SWARM_CONTROLLER_AUTH_BRIDGE_URL is set but SWARM_CONTROLLER_OIDC_* is \
                     not — the bridge is authenticated with this daemon's queue identity, so \
                     that identity must exist first"
                )
            })?;
        Ok(Some(Self {
            http: reqwest::Client::new(),
            base_url,
            queue_cfg,
        }))
    }

    /// Idempotently ensure `name` exists as an authelia subject.
    pub async fn ensure_agent_identity(&self, name: &str) -> Result<BridgeResponse> {
        self.request(&BridgeRequest::EnsureAgentIdentity {
            name: name.to_owned(),
        })
        .await
    }

    /// The swarm's agent roster, straight from the identity store.
    ///
    /// Returns the names rather than the whole [`BridgeResponse`]: every
    /// other variant is a protocol error for this request, and a caller that
    /// had to match them would be free to treat one as an empty roster. An
    /// empty roster and a bridge that answered something else are different
    /// facts, and only one of them is a valid render.
    pub async fn list_agent_identities(&self) -> Result<Vec<String>> {
        match self.request(&BridgeRequest::ListAgentIdentities).await? {
            BridgeResponse::Agents { agents } => Ok(agents
                .into_iter()
                .map(|entry| entry.name.into_string())
                .collect()),
            other => {
                anyhow::bail!("swarm-authelia-bridge answered a roster request with {other:?}")
            }
        }
    }

    /// One authenticated round-trip to the bridge.
    ///
    /// A fresh token per call, deliberately — see the module doc. Shared by
    /// every operation so the auth and the error handling cannot drift
    /// between them; a second copy is how one path ends up treating a 500 as
    /// an answer.
    async fn request(&self, req: &BridgeRequest) -> Result<BridgeResponse> {
        // `mint_token_for` builds its own HTTP client (trusting the queue's
        // configured CA, if any) — deliberately not `self.http`, which is
        // the bridge's own client and has nothing to do with authelia's
        // token endpoint's trust anchors.
        let token = swarm_queue_client::mint_token_for(&self.queue_cfg)
            .await
            .context("minting a bearer token for swarm-authelia-bridge")?;

        let response = self
            .http
            .post(format!("{}/requests", self.base_url))
            .bearer_auth(token)
            .json(req)
            .send()
            .await
            .context("calling swarm-authelia-bridge")?;

        let status = response.status();
        let body = response.text().await.unwrap_or_default();
        if !status.is_success() {
            anyhow::bail!("swarm-authelia-bridge refused the request ({status}): {body}");
        }

        serde_json::from_str(&body).context("parsing swarm-authelia-bridge's response")
    }
}

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

    /// The common case: no bridge wired up for this deployment.
    #[test]
    fn absent_url_is_not_an_error() {
        assert!(std::env::var("SWARM_CONTROLLER_AUTH_BRIDGE_URL").is_err());
        assert!(
            AuthBridge::from_env()
                .expect("absent is not an error")
                .is_none()
        );
    }
}