//! The state file: a first start, surviving a restart, its limits, and refusing a damaged file
//! instead of guessing (M4a spec, section 9). Do not edit.

#[path = "support/tmp.rs"]
mod tmp;

use std::os::unix::fs::PermissionsExt;

use gatewayd::state::{InFlight, RECENT_KEPT, State, StateError, THREADS_KEPT};
use tmp::TempDir;

const CHAN: &str = "c0000000000000000000000000";
const DM: &str = "d0000000000000000000000000";

fn id(n: usize) -> String {
    format!("p{n:025}")
}

fn turn(n: usize) -> InFlight {
    InFlight {
        session: format!("mm-{}", id(n)),
        channel: DM.to_string(),
        root: id(n),
    }
}

#[test]
fn a_first_start_then_a_restart() {
    let dir = TempDir::new("state-restart");
    let path = dir.path().join("gateway/state.json");
    let mut s = State::load(&path).unwrap();
    assert!(!path.exists(), "loading writes nothing");
    assert_eq!(
        (s.since(CHAN), s.channels().len(), s.seen(&id(1))),
        (None, 0, false)
    );
    s.handled(&id(1), CHAN, 2000).unwrap();
    s.handled(&id(2), CHAN, 1500).unwrap();
    s.mark(DM, 3000).unwrap();
    s.mark(DM, 9000).unwrap();
    s.join_thread(&id(1)).unwrap();
    s.start_turn(turn(1)).unwrap();
    s.start_turn(turn(2)).unwrap();
    s.end_turn(&format!("mm-{}", id(2))).unwrap();

    let mode = std::fs::metadata(&path).unwrap().permissions().mode() & 0o777;
    let dir_mode = std::fs::metadata(path.parent().unwrap())
        .unwrap()
        .permissions()
        .mode()
        & 0o777;
    assert_eq!((mode, dir_mode), (0o600, 0o700));
    assert!(!dir.path().join("gateway/state.json.tmp").exists());

    let mut again = State::load(&path).unwrap();
    assert_eq!(again.since(CHAN), Some(2000), "the mark never moves back");
    assert_eq!(
        again.since(DM),
        Some(3000),
        "mark only sets a channel without one"
    );
    assert_eq!(again.channels(), [CHAN, DM]);
    assert!(again.seen(&id(1)) && again.seen(&id(2)));
    assert!(again.knows_thread(&id(1)) && !again.knows_thread(&id(2)));
    assert_eq!(again.take_in_flight().unwrap(), [turn(1)]);
    assert!(
        State::load(&path)
            .unwrap()
            .take_in_flight()
            .unwrap()
            .is_empty(),
        "taking is saved"
    );
}

#[test]
fn only_the_newest_posts_and_threads_are_kept() {
    let dir = TempDir::new("state-limits");
    // A full file to start from: posts 0.. and threads 0.., at their limits.
    let recent: Vec<String> = (0..RECENT_KEPT).map(id).collect();
    let threads: Vec<String> = (0..THREADS_KEPT).map(id).collect();
    let full =
        serde_json::json!({"channels": {}, "recent": recent, "threads": threads, "in_flight": []});
    let path = dir.write("state.json", &full.to_string());
    let mut s = State::load(&path).unwrap();
    s.handled(&id(RECENT_KEPT), CHAN, 1).unwrap();
    s.handled(&id(RECENT_KEPT + 1), CHAN, 1).unwrap();
    s.handled(&id(RECENT_KEPT + 1), CHAN, 1).unwrap();
    s.join_thread(&id(THREADS_KEPT)).unwrap();
    s.join_thread(&id(3)).unwrap();
    let s = State::load(&path).unwrap();
    assert!(!s.seen(&id(0)) && !s.seen(&id(1)) && s.seen(&id(2)) && s.seen(&id(RECENT_KEPT + 1)));
    assert!(!s.knows_thread(&id(0)) && s.knows_thread(&id(1)) && s.knows_thread(&id(THREADS_KEPT)));
    let text = std::fs::read_to_string(&path).unwrap();
    let v: serde_json::Value = serde_json::from_str(&text).unwrap();
    assert_eq!(
        v["recent"].as_array().unwrap().len(),
        RECENT_KEPT,
        "a repeat is not stored twice"
    );
    assert_eq!(v["threads"].as_array().unwrap().len(), THREADS_KEPT);
}

#[test]
fn a_damaged_file_stops_with_its_pointer() {
    let dir = TempDir::new("state-damaged");
    let good_turn = r#"{"session":"mm-p0000000000000000000000001","channel":"d0000000000000000000000000","root":"p0000000000000000000000001"}"#;
    let cases = [
        "".to_string(),
        "{".to_string(),
        "[]".to_string(),
        r#"{"channels":{},"recent":[],"threads":[]}"#.to_string(),
        r#"{"channels":{},"recent":[],"threads":[],"in_flight":[],"extra":1}"#.to_string(),
        r#"{"channels":{"../x":1},"recent":[],"threads":[],"in_flight":[]}"#.to_string(),
        r#"{"channels":{},"recent":["short"],"threads":[],"in_flight":[]}"#.to_string(),
        r#"{"channels":{},"recent":[],"threads":["P0000000000000000000000000"],"in_flight":[]}"#
            .to_string(),
        format!(
            r#"{{"channels":{{}},"recent":[],"threads":[],"in_flight":[{}]}}"#,
            good_turn.replace("mm-", "xx-")
        ),
        format!(
            r#"{{"channels":{{}},"recent":[],"threads":[],"in_flight":[{}]}}"#,
            good_turn.replace("\"d0", "\"D0")
        ),
    ];
    for (n, text) in cases.iter().enumerate() {
        let path = dir.write(&format!("s{n}.json"), text);
        match State::load(&path) {
            Err(e @ StateError::Read(..)) => {
                let message = e.to_string();
                assert!(
                    message.starts_with(&path.display().to_string()),
                    "{message}"
                );
                assert!(
                    message.ends_with("\nsee docs/runbook.md#gateway-state-damaged"),
                    "{message}"
                );
            }
            Err(e) => panic!("{text}: {e}"),
            Ok(_) => panic!("accepted: {text}"),
        }
    }
    let ok = dir.write(
        "ok.json",
        &format!(
            r#"{{"channels":{{"{CHAN}":5}},"recent":[],"threads":[],"in_flight":[{good_turn}]}}"#
        ),
    );
    assert_eq!(State::load(&ok).unwrap().since(CHAN), Some(5));
    std::fs::create_dir(dir.path().join("adir")).unwrap();
    assert!(matches!(
        State::load(&dir.path().join("adir")),
        Err(StateError::Read(..))
    ));
}

#[test]
fn a_failed_write_is_an_error_and_keeps_the_old_file() {
    let dir = TempDir::new("state-readonly");
    let sub = dir.path().join("gateway");
    let path = sub.join("state.json");
    let mut s = State::load(&path).unwrap();
    s.handled(&id(1), CHAN, 5).unwrap();
    let before = std::fs::read(&path).unwrap();
    std::fs::set_permissions(&sub, std::fs::Permissions::from_mode(0o500)).unwrap();
    let got = s.handled(&id(2), CHAN, 6);
    std::fs::set_permissions(&sub, std::fs::Permissions::from_mode(0o700)).unwrap();
    let e = got.unwrap_err();
    assert!(matches!(e, StateError::Write(..)), "{e}");
    assert!(
        e.to_string()
            .ends_with("see docs/runbook.md#gateway-state-damaged"),
        "{e}"
    );
    assert_eq!(std::fs::read(&path).unwrap(), before);
}