//! An agent's backend environment: an operator hands us the text of a systemd
//! `EnvironmentFile`, and we put it in the swarm's secret store.
//!
//! The agent end is `nix/agent-modules/backend-env.nix`, which reads it under
//! the agent's own certificate into the file its harness and subagent daemon
//! load as `EnvironmentFile=`. This is the operator's path: it replaces
//! whatever the leaf holds, including a value the agent wrote itself while the
//! leaf was empty, and the store's value wins over the agent's
//! `backendEnvironmentFile`.

use axum::Json;
use axum::extract::State;
use axum::http::StatusCode;
use serde::Deserialize;
use swarm_secret_client::backend_env::{self, BackendEnv};
use utoipa::ToSchema;

use super::linked_accounts::AccountStore;
use crate::routes::agents::swarm_hive;
use crate::routes::{AppState, error_problem};

/// The most text one agent's environment may hold.
const MAX_BYTES: usize = 16 * 1024;

/// The text to store for one agent.
///
/// No `Debug` derive: this carries live credentials.
#[derive(Deserialize, ToSchema)]
pub struct PutBackendEnvRequest {
    /// The file text, `NAME=VALUE` per line; blank lines and lines starting
    /// with `#` or `;` are allowed. Never logged, and never returned by this
    /// route.
    env: String,
}

/// Store an agent's backend environment, replacing any stored one.
#[utoipa::path(
    put,
    path = "/api/hives/{hive}/agents/{agent}/backend-env",
    params(
        ("hive" = String, Path, description = "hive the agent runs on"),
        ("agent" = String, Path, description = "agent the environment belongs to"),
    ),
    request_body = PutBackendEnvRequest,
    responses(
        (status = 204, description = "stored"),
        (status = 400, description = "the agent is not an identifier, the text is empty, too large or not `NAME=VALUE` lines, or the hive is not in this swarm (problem+json)", body = String),
        (status = 500, description = "the store could not be written (problem+json)", body = String),
    ),
    tag = "agents"
)]
pub async fn put_backend_env(
    State(state): State<AppState>,
    axum::extract::Path((hive, agent)): axum::extract::Path<(String, String)>,
    Json(req): Json<PutBackendEnvRequest>,
) -> Result<StatusCode, problem_details::ProblemDetails> {
    let hive = swarm_hive(&state, &hive).map_err(|(s, d)| error_problem(s, &d))?;
    let agent = hive_types::Ident::parse(&agent)
        .map_err(|reason| error_problem(StatusCode::BAD_REQUEST, reason))?
        .into_string();
    let path = backend_env::env_path(&agent)
        .map_err(|e| error_problem(StatusCode::BAD_REQUEST, &e.to_string()))?;
    let stored = BackendEnv {
        env: validated(&req.env).map_err(|e| error_problem(StatusCode::BAD_REQUEST, &e))?,
    };

    let store = state.accounts.open().await.map_err(|e| {
        tracing::warn!(error = %e, "connecting to the swarm secret store failed");
        error_problem(StatusCode::INTERNAL_SERVER_ERROR, &e.to_string())
    })?;
    // A plain write, not a create: the operator is authoritative over a value
    // the agent planted in the empty leaf.
    store.write(&path, &stored).await.map_err(|e| {
        // The path names the agent; the value is not in it.
        tracing::warn!(%path, error = %e, "storing the backend env failed");
        error_problem(StatusCode::INTERNAL_SERVER_ERROR, &e.to_string())
    })?;

    tracing::info!(%hive, %agent, "backend env stored");
    Ok(StatusCode::NO_CONTENT)
}

/// The text as it is stored, or why it cannot be.
///
/// systemd skips a line it cannot parse and goes on, so a typo would load as
/// a missing key. A quote that is not closed would swallow the lines after it
/// into one value. The reasons name a line number and never its text.
fn validated(text: &str) -> Result<String, String> {
    let text = text.trim();
    if text.is_empty() {
        return Err("env is required".to_owned());
    }
    if text.len() > MAX_BYTES {
        return Err(format!("env is over {MAX_BYTES} bytes"));
    }
    if text
        .chars()
        .any(|c| c.is_control() && !matches!(c, '\n' | '\r' | '\t'))
    {
        return Err("env holds a control character".to_owned());
    }
    for (n, line) in text.lines().enumerate() {
        if !valid_line(line.trim()) {
            return Err(format!("line {} is not NAME=VALUE", n + 1));
        }
    }
    Ok(format!("{text}\n"))
}

/// A blank line, a comment, or `NAME=VALUE` with a closed quote and no
/// trailing backslash.
fn valid_line(line: &str) -> bool {
    if line.is_empty() || line.starts_with(['#', ';']) {
        return true;
    }
    let Some((name, value)) = line.split_once('=') else {
        return false;
    };
    let mut chars = name.chars();
    let name_ok = chars
        .next()
        .is_some_and(|c| c.is_ascii_alphabetic() || c == '_')
        && chars.all(|c| c.is_ascii_alphanumeric() || c == '_');
    let value = value.trim();
    let closed = match value.chars().next() {
        Some(q @ ('"' | '\'')) => value.len() > 1 && value.ends_with(q),
        _ => true,
    };
    name_ok && closed && !value.ends_with('\\')
}

#[cfg(test)]
mod tests {
    use std::sync::Arc;

    use axum::http::StatusCode;
    use serde_json::json;
    use swarm_secret_client::backend_env::BackendEnv;

    use super::super::linked_accounts::{AccountStore, Accounts, tests::FakeStore};
    use super::{MAX_BYTES, PutBackendEnvRequest, validated};

    const SECRET: &str = "sk-live-0123";

    /// Bare-minimum `AppState`, as `github_account`'s tests build it.
    fn state(store: &Arc<FakeStore>) -> crate::routes::AppState {
        crate::routes::AppState {
            hives: std::sync::Arc::new(vec![crate::routes::hives::HiveEntry {
                name: "pr1ma".to_owned(),
                domain: "pr1ma.example".to_owned(),
                dashboard: "pr1ma.hives.example".to_owned(),
            }]),
            links: std::sync::Arc::new(Vec::new()),
            status: None,
            wanted: None,
            agent_status: None,
            agent_icons: None,
            agents_md: None,
            reported_inference: None,
            agent_login: None,
            jobq: std::sync::Arc::new(std::sync::Mutex::new(hive_jobq::scheduler::Scheduler::new(
                hive_jobq::Graph::new(),
                hive_jobq::resources::ResourceTable::new(),
            ))),
            webhook_secret: None,
            config_prs: std::sync::Arc::default(),
            swarm_name: None,
            auth: None,
            forge: std::sync::Arc::default(),
            create_gate: std::sync::Arc::default(),
            accounts: Accounts::Fake(Arc::clone(store)),
            try_outs: super::super::review_classifier::TryOuts::default(),
            reviews: std::sync::Arc::default(),
            runs: crate::review_classifier::runs::Runs::Live(None),
            builds: crate::builder::runs::Builds::Live(None),
            alerts: None,
        }
    }

    async fn put(
        store: &Arc<FakeStore>,
        agent: &str,
        env: &str,
    ) -> Result<StatusCode, problem_details::ProblemDetails> {
        super::put_backend_env(
            axum::extract::State(state(store)),
            axum::extract::Path(("pr1ma".to_owned(), agent.to_owned())),
            axum::Json(PutBackendEnvRequest {
                env: env.to_owned(),
            }),
        )
        .await
    }

    async fn stored(store: &FakeStore, agent: &str) -> Option<String> {
        store
            .read_optional::<BackendEnv>(&format!("swarm/agents/{agent}/backend-env"))
            .await
            .expect("store answers")
            .map(|b| b.env)
    }

    #[test]
    fn plain_lines_comments_and_quoted_values_are_accepted() {
        let text = "# openrouter\nANTHROPIC_BASE_URL=https://openrouter.ai/api/v1\n\n\
                    ; key\n_K9=\"a b\"\nEMPTY=\nS='x'\n";
        let kept = validated(text).expect("valid");
        assert_eq!(kept, text.trim().to_owned() + "\n");
    }

    #[test]
    fn text_systemd_would_skip_or_misread_is_refused() {
        for bad in [
            "",
            "  \n ",
            "KEY",
            "=value",
            "1KEY=v",
            "KE Y=v",
            "KEY=\"open",
            "KEY='",
            "KEY=trailing\\",
            "A=1\nnot a line\nB=2",
            "A=b\0c",
        ] {
            assert!(validated(bad).is_err(), "{bad:?}");
        }
        assert!(validated(&format!("A={}", "x".repeat(MAX_BYTES))).is_err());
        // The control: the size cap is the only difference.
        assert!(validated(&format!("A={}", "x".repeat(MAX_BYTES - 2))).is_ok());
    }

    #[test]
    fn a_refusal_names_the_line_and_not_its_text() {
        let reason = validated(&format!("A=1\n{SECRET}\n")).expect_err("no `=`");
        assert_eq!(reason, "line 2 is not NAME=VALUE");
        assert!(!reason.contains(SECRET), "{reason}");
    }

    #[tokio::test]
    async fn a_plain_request_is_stored_under_the_agent() {
        let store = Arc::default();
        let status = put(&store, "atlas", &format!("ANTHROPIC_API_KEY={SECRET}"))
            .await
            .expect("stored");
        assert_eq!(status, StatusCode::NO_CONTENT);
        assert_eq!(store.written(), ["swarm/agents/atlas/backend-env"]);
        assert_eq!(
            stored(&store, "atlas").await.as_deref(),
            Some("ANTHROPIC_API_KEY=sk-live-0123\n")
        );
    }

    /// The operator's write replaces a value an agent planted in the leaf.
    #[tokio::test]
    async fn a_value_already_in_the_leaf_is_overwritten() {
        let store = Arc::new(FakeStore::default().with(
            "swarm/agents/atlas/backend-env",
            json!({"env": "PLANTED=1\n"}),
        ));
        put(&store, "atlas", "ANTHROPIC_API_KEY=operator")
            .await
            .expect("overwritten");
        assert_eq!(
            stored(&store, "atlas").await.as_deref(),
            Some("ANTHROPIC_API_KEY=operator\n")
        );
    }

    #[tokio::test]
    async fn a_bad_agent_or_body_is_refused_before_the_store() {
        let store = Arc::default();
        let leaky = format!("{SECRET}-no-equals");
        for (agent, env) in [
            ("Atlas", "A=1"),
            ("../x", "A=1"),
            ("atlas", " "),
            ("atlas", leaky.as_str()),
        ] {
            let problem = put(&store, agent, env).await.expect_err("refused");
            assert_eq!(problem.status, Some(StatusCode::BAD_REQUEST), "{problem:?}");
            assert!(!format!("{problem:?}").contains(SECRET), "{problem:?}");
        }
        assert!(store.written().is_empty());
    }

    #[tokio::test]
    async fn a_store_failure_does_not_echo_the_value() {
        let store = Arc::new(FakeStore::denying());
        let problem = put(&store, "atlas", &format!("ANTHROPIC_API_KEY={SECRET}"))
            .await
            .expect_err("the store refuses");
        assert_eq!(problem.status, Some(StatusCode::INTERNAL_SERVER_ERROR));
        assert!(!format!("{problem:?}").contains(SECRET), "{problem:?}");
    }
}