//! Is the mission gateway configured, and is anything listening?
//!
//! The third sibling of [`crate::runtime_preflight`] and
//! [`crate::validator_preflight`], for the same class of failure: the
//! configuration is absent or wrong, and nothing says so until a mission pays
//! for it.
//!
//! `ZEROCLAW_GATEWAY_URL` and `ZEROCLAW_TOKEN` have no defaults and are read at
//! FIRST USE, inside `ZeroClawDriveExecutor::from_env`. So a deployment missing
//! them boots clean, serves every page, lists every mission — and fails the
//! first time someone presses run, with an error that surfaces on a phase
//! rather than at startup. The information exists the whole time; nobody is
//! told until it is expensive.
//!
//! A report, not a gate, matching its siblings. A server with no gateway should
//! still boot: the frontend, the catalogue and every read path work without it,
//! and refusing to start would turn a degraded deployment into a dead one.

use std::time::Duration;

const PROBE_TIMEOUT: Duration = Duration::from_secs(5);

/// What the preflight found.
#[derive(Debug, PartialEq, Eq)]
pub enum Verdict {
    /// No gateway configured. Missions on the container tier cannot run.
    NotConfigured { missing: Vec<String> },
    /// Configured but nothing answered at that address.
    Unreachable { url: String, error: String },
    /// Configured and something answered.
    Reachable { url: String },
}

impl Verdict {
    /// The line to print at boot.
    ///
    /// Each names the CONSEQUENCE, not just the state. "ZEROCLAW_TOKEN not set"
    /// tells an operator what is missing; it does not tell them that every
    /// container-tier mission they launch will fail on its first phase.
    pub fn message(&self) -> String {
        match self {
            Verdict::NotConfigured { missing } => format!(
                "gateway_preflight: NOT CONFIGURED ({}) — container-tier missions \
                 cannot run. They will launch, provision a runtime, and fail on \
                 the first turn; the server is otherwise healthy",
                missing.join(", ")
            ),
            Verdict::Unreachable { url, error } => format!(
                "gateway_preflight: {url} is configured but did not answer ({error}) \
                 — container-tier missions will fail on their first turn. The \
                 config is right and the machine is not"
            ),
            Verdict::Reachable { url } => {
                format!("gateway_preflight: {url} answered")
            }
        }
    }
}

/// Which required variables are absent.
///
/// Split from the network probe so the rule is testable without a gateway:
/// this is the half that is pure, and it is the half that is wrong most often.
pub fn missing_config(url: Option<&str>, token: Option<&str>, pairing: Option<&str>) -> Vec<String> {
    let mut missing = Vec::new();
    if url.map(str::trim).unwrap_or("").is_empty() {
        missing.push("ZEROCLAW_GATEWAY_URL".to_string());
    }
    // Either credential works: a durable token, or a one-time pairing code the
    // executor exchanges on first use.
    let has_token = !token.map(str::trim).unwrap_or("").is_empty();
    let has_pairing = !pairing.map(str::trim).unwrap_or("").is_empty();
    if !has_token && !has_pairing {
        missing.push("ZEROCLAW_TOKEN or ZEROCLAW_PAIRING_CODE".to_string());
    }
    missing
}

fn env_opt(key: &str) -> Option<String> {
    std::env::var(key).ok().filter(|v| !v.trim().is_empty())
}

/// Probe the configured gateway.
pub async fn check() -> Verdict {
    let url = env_opt("ZEROCLAW_GATEWAY_URL");
    let missing = missing_config(
        url.as_deref(),
        env_opt("ZEROCLAW_TOKEN").as_deref(),
        env_opt("ZEROCLAW_PAIRING_CODE").as_deref(),
    );
    if !missing.is_empty() {
        return Verdict::NotConfigured { missing };
    }
    let url = url.expect("checked above");

    // Any HTTP answer proves something is listening and routable, which is the
    // question this preflight exists to answer. Authenticating here would need
    // a pairing exchange that BURNS a one-time code — a preflight that costs
    // the deployment its credential is worse than no preflight.
    let client = match reqwest::Client::builder().timeout(PROBE_TIMEOUT).build() {
        Ok(c) => c,
        Err(e) => {
            return Verdict::Unreachable {
                url,
                error: e.to_string(),
            }
        }
    };
    match client.get(&url).send().await {
        Ok(_) => Verdict::Reachable { url },
        Err(e) => Verdict::Unreachable {
            url,
            error: e.to_string(),
        },
    }
}

/// Run the probe and print the verdict. Never panics, never blocks boot.
pub fn report_at_boot() {
    tokio::spawn(async {
        eprintln!("{}", check().await.message());
    });
}

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

    #[test]
    fn a_fully_configured_deployment_is_missing_nothing() {
        assert!(missing_config(Some("http://gw:42617"), Some("tok"), None).is_empty());
        // A pairing code alone is enough — the executor exchanges it on first use.
        assert!(missing_config(Some("http://gw:42617"), None, Some("123456")).is_empty());
    }

    #[test]
    fn an_empty_string_counts_as_absent() {
        // The failure this whole module exists for: `unwrap_or_default` and an
        // empty env var turn "unconfigured" into "configured with nothing",
        // which fails later as a 401 rather than now as a missing setting.
        let missing = missing_config(Some("  "), Some(""), Some("   "));
        assert_eq!(missing.len(), 2, "both must be reported: {missing:?}");
        assert!(missing[0].contains("GATEWAY_URL"));
        assert!(missing[1].contains("ZEROCLAW_TOKEN"));
    }

    #[test]
    fn the_message_names_the_consequence_not_just_the_state() {
        let v = Verdict::NotConfigured {
            missing: vec!["ZEROCLAW_GATEWAY_URL".into()],
        };
        let m = v.message();
        assert!(m.contains("ZEROCLAW_GATEWAY_URL"));
        assert!(
            m.contains("cannot run"),
            "an operator needs to know what stops working, not only what is \
             unset: {m}"
        );
    }
}