//! `hive-github-notify` binary — long-running per-agent **github.com**
//! notification poller. Same delivery path as its Forgejo sibling: unread
//! list, per-thread summary, todo upsert on the harness's in-agent socket,
//! mark read on the source.
//!
//! Takes no arguments. `HYPERHIVE_STATE_DIR` holds the PAT
//! (`github-token`, fetched from the swarm secret store by
//! `nix/agent-modules/github-token.nix` — see `docs/integrations/github.md`)
//! and `HIVE_AGENT_SOCKET` is the harness's todo socket.
//! Having a PAT *is* the opt-in: with no token the poller logs why and
//! exits 0, so deploying this unit to an agent that never gets one costs a
//! settled process rather than a restart loop. Once polling, it re-reads
//! `github-token` on every tick, so a rotated PAT takes effect on the next
//! poll without a restart.
//!
//! ⚠️ Reading the notification stream needs the **`notifications` scope**
//! on the PAT — a token minted for `gh` + `git push` usually carries `repo`
//! only, which is enough to push and open PRs but not to read (or mark
//! read) notifications. A PAT without it is not fatal: the poller logs the
//! refusal and stays quiet, so the symptom is silence rather than an error.

mod source;

use std::collections::HashMap;
use std::time::Duration;

use hive_forge_notify::notify::{
    POLL_INTERVAL_SECS, TOKEN_RETRY_MAX, TOKEN_RETRY_SECS, poll_once, resolve_own_login,
};
use hive_forge_notify::{HTTP_TIMEOUT_SECS, agent_socket, init_tracing};
use source::GithubSource;
use tracing::{debug, info, warn};

#[tokio::main]
async fn main() {
    init_tracing();

    let socket = agent_socket();
    info!(socket = %socket.display(), "hive-github-notify starting");

    // Returns only when no PAT ever arrives; otherwise loops forever.
    github_loop(hive_forge_notify::state_dir(), socket).await;
}

/// Waits for the PAT to appear: the agent's store fetch writes the token
/// out of band and it takes effect without a rebuild, so an agent that gains
/// a PAT mid-session starts getting notifications on the next tick rather
/// than after a restart. Gives up — returning, so the process exits 0
/// rather than restart-looping — when no PAT ever arrives, which is the
/// common case for an agent that has the unit but no account.
async fn github_loop(state_dir: String, socket: std::path::PathBuf) {
    let token_path = format!("{state_dir}/github-token");
    let mut attempts = 0u32;
    let token = loop {
        match tokio::fs::read_to_string(&token_path).await {
            Ok(t) if !t.trim().is_empty() => break t.trim().to_owned(),
            _ => debug!("forge_notify: no github token at {token_path} yet"),
        }
        attempts += 1;
        if attempts >= TOKEN_RETRY_MAX {
            debug!(
                "forge_notify: no github token after {TOKEN_RETRY_MAX} retries — github disabled"
            );
            return;
        }
        tokio::time::sleep(Duration::from_secs(TOKEN_RETRY_SECS)).await;
    };

    let client = match reqwest::Client::builder()
        .timeout(Duration::from_secs(HTTP_TIMEOUT_SECS))
        .build()
    {
        Ok(c) => c,
        Err(e) => {
            warn!("forge_notify: failed to build github HTTP client: {e}");
            return;
        }
    };

    let mut pat = Pat::new(source::API_BASE, token_path, token);
    let mut own_login = resolve_own_login(&client, &pat.source).await;
    let mut delivered: HashMap<String, String> = HashMap::new();

    // GitHub tells callers how often it is willing to be polled
    // (`X-Poll-Interval`, 60s in practice) and rate-limits those who
    // ignore it. Start at our own cadence and re-arm to whatever the
    // server asks for — never faster than it wants, never slower than we
    // need.
    let mut cadence = POLL_INTERVAL_SECS;
    let mut interval = tokio::time::interval(Duration::from_secs(cadence));
    interval.set_missed_tick_behavior(tokio::time::MissedTickBehavior::Delay);
    interval.tick().await;

    info!("forge_notify: github polling started");

    loop {
        interval.tick().await;
        let hint = poll_tick(&mut pat, &mut own_login, &client, &socket, &mut delivered).await;
        if let Some(secs) = hint.filter(|s| *s > cadence) {
            debug!(
                secs,
                "forge_notify: github asked for a slower poll — re-arming"
            );
            cadence = secs;
            interval = tokio::time::interval(Duration::from_secs(cadence));
            interval.set_missed_tick_behavior(tokio::time::MissedTickBehavior::Delay);
            interval.tick().await;
        }
    }
}

/// One poll: pick up a rotated PAT, resolve the own login if it is not
/// known for the PAT in use, then poll. Returns the server's poll-interval
/// hint.
async fn poll_tick(
    pat: &mut Pat,
    own_login: &mut String,
    client: &reqwest::Client,
    socket: &std::path::Path,
    delivered: &mut HashMap<String, String>,
) -> Option<u64> {
    if pat.reread() {
        info!("forge_notify: github token changed on disk; using the new one");
        own_login.clear();
    }
    if own_login.is_empty() {
        *own_login = resolve_own_login(client, &pat.source).await;
    }
    poll_once(&pat.source, client, socket, delivered, own_login).await
}

/// The PAT in use and the source built from it. The agent's store fetch
/// replaces `github-token` by atomic rename when the PAT rotates and never
/// deletes it, so a missing or empty file means "not readable right now"
/// and keeps the current token.
struct Pat {
    api_base: String,
    path: std::path::PathBuf,
    token: String,
    source: GithubSource,
}

impl Pat {
    fn new(api_base: &str, path: impl Into<std::path::PathBuf>, token: String) -> Self {
        let source = GithubSource::new(api_base, &token);
        Self {
            api_base: api_base.to_owned(),
            path: path.into(),
            token,
            source,
        }
    }

    /// Re-read the file and swap to its token if it differs. `true` when
    /// the token changed.
    fn reread(&mut self) -> bool {
        match hive_forge_notify::read_first_token(std::slice::from_ref(&self.path)) {
            Some(t) if t != self.token => {
                self.source = GithubSource::new(&self.api_base, &t);
                self.token = t;
                true
            }
            _ => false,
        }
    }
}

#[cfg(test)]
mod tests {
    use std::collections::HashMap;

    use tokio::io::{AsyncReadExt as _, AsyncWriteExt as _};
    use tokio::sync::mpsc;

    use super::{Pat, poll_tick};

    fn scratch(tag: &str) -> std::path::PathBuf {
        let ts = std::time::SystemTime::now()
            .duration_since(std::time::UNIX_EPOCH)
            .map_or(0, |d| d.as_nanos());
        let dir = std::env::temp_dir().join(format!("hive-github-notify-{tag}-{ts}"));
        std::fs::create_dir_all(&dir).expect("create scratch dir");
        dir
    }

    /// A stand-in for api.github.com on loopback. Answers `/user` with a
    /// login and `/notifications` with an empty page, and reports each
    /// request as `(path, Authorization header)`.
    async fn stub() -> (String, mpsc::UnboundedReceiver<(String, String)>) {
        let listener = tokio::net::TcpListener::bind("127.0.0.1:0")
            .await
            .expect("bind");
        let base = format!("http://{}", listener.local_addr().expect("addr"));
        let (tx, rx) = mpsc::unbounded_channel();
        tokio::spawn(async move {
            loop {
                let (mut sock, _) = listener.accept().await.expect("accept");
                let mut buf = Vec::new();
                let mut chunk = [0u8; 1024];
                while !buf.windows(4).any(|w| w == b"\r\n\r\n") {
                    let n = sock.read(&mut chunk).await.expect("read");
                    if n == 0 {
                        break;
                    }
                    buf.extend_from_slice(&chunk[..n]);
                }
                let head = String::from_utf8_lossy(&buf).into_owned();
                let path = head
                    .split_whitespace()
                    .nth(1)
                    .unwrap_or_default()
                    .to_owned();
                let auth = head
                    .lines()
                    .find_map(|l| {
                        let (k, v) = l.split_once(':')?;
                        k.eq_ignore_ascii_case("authorization")
                            .then(|| v.trim().to_owned())
                    })
                    .unwrap_or_default();
                let body = if path.starts_with("/user") {
                    r#"{"login":"me"}"#
                } else {
                    "[]"
                };
                let reply = format!(
                    "HTTP/1.1 200 OK\r\ncontent-type: application/json\r\n\
                     content-length: {}\r\nconnection: close\r\n\r\n{body}",
                    body.len()
                );
                let _ = sock.write_all(reply.as_bytes()).await;
                let _ = tx.send((path, auth));
            }
        });
        (base, rx)
    }

    /// Every request one tick made, in order.
    fn drain(rx: &mut mpsc::UnboundedReceiver<(String, String)>) -> Vec<(String, String)> {
        std::iter::from_fn(|| rx.try_recv().ok()).collect()
    }

    fn poll(path: &str) -> bool {
        path.starts_with("/notifications")
    }

    #[tokio::test]
    async fn a_rotated_token_is_sent_on_the_next_poll() {
        let (base, mut rx) = stub().await;
        let dir = scratch("rotate");
        let path = dir.join("github-token");
        std::fs::write(&path, "old\n").expect("write");
        let mut pat = Pat::new(&base, &path, "old".to_owned());
        let mut own_login = String::new();
        let mut delivered = HashMap::new();
        let client = reqwest::Client::new();
        let socket = dir.join("no-socket");

        poll_tick(&mut pat, &mut own_login, &client, &socket, &mut delivered).await;
        let first = drain(&mut rx);
        assert!(first.iter().any(|(p, a)| poll(p) && a == "Bearer old"));
        assert_eq!(own_login, "me");

        std::fs::write(&path, "new\n").expect("write");
        poll_tick(&mut pat, &mut own_login, &client, &socket, &mut delivered).await;
        let second = drain(&mut rx);
        assert!(second.iter().all(|(_, a)| a == "Bearer new"), "{second:?}");
        assert!(second.iter().any(|(p, _)| poll(p)), "{second:?}");
        // The own login is resolved again, under the new token.
        assert!(second.iter().any(|(p, _)| p == "/user"), "{second:?}");
        let _ = std::fs::remove_dir_all(&dir);
    }

    #[tokio::test]
    async fn an_empty_or_missing_file_keeps_the_token_in_use() {
        let (base, mut rx) = stub().await;
        let dir = scratch("keep");
        let path = dir.join("github-token");
        let mut pat = Pat::new(&base, &path, "old".to_owned());
        let mut own_login = String::new();
        let mut delivered = HashMap::new();
        let client = reqwest::Client::new();
        let socket = dir.join("no-socket");

        std::fs::write(&path, "\n").expect("write");
        poll_tick(&mut pat, &mut own_login, &client, &socket, &mut delivered).await;
        let empty = drain(&mut rx);
        assert!(empty.iter().any(|(p, _)| poll(p)), "{empty:?}");
        assert!(empty.iter().all(|(_, a)| a == "Bearer old"), "{empty:?}");

        std::fs::remove_file(&path).expect("remove");
        poll_tick(&mut pat, &mut own_login, &client, &socket, &mut delivered).await;
        let missing = drain(&mut rx);
        assert!(missing.iter().any(|(p, _)| poll(p)), "{missing:?}");
        assert!(
            missing.iter().all(|(_, a)| a == "Bearer old"),
            "{missing:?}"
        );
        let _ = std::fs::remove_dir_all(&dir);
    }
}