//! Pre-launch checks for the client-side state FIFA depends on.
//!
//! # Why
//!
//! On 2026-08-11 the game machine rebooted. Everything `client_arm.sh` sets —
//! `ptrace_scope=0`, the DNAT of EA's hardcoded redirector IP, the
//! `easw.easports.com` mapping — is volatile and was silently gone. The launcher
//! started, the local services started, the game started, and forty minutes later
//! the only symptom was FIFA's own dialog: *"the servers for this title have been
//! shut down"*. Nothing in the stack said anything, because nothing was looking.
//!
//! Every one of those conditions is observable **without privilege**. This module
//! looks, and reports before the user clicks Launch.
//!
//! # Deliberately not checked here
//!
//! Certificate parity across the FIFA-facing TLS services — the fault that cost
//! three redirector gates — is the single most valuable check available, but the
//! launcher has no TLS dependency (`account_sync` speaks plaintext HTTP by hand)
//! and adding one is a decision, not a detail. `scripts/check-tls-parity.sh` on
//! the server covers it in the meantime.
//!
//! # Advisory, not a gate
//!
//! Results colour the UI; they never disable Launch. A preflight that is itself
//! wrong must not be able to lock the user out of their own game.

use std::net::{IpAddr, SocketAddr, TcpStream, ToSocketAddrs};
use std::time::Duration;

use crate::config::LauncherConfig;

const PROBE_TIMEOUT: Duration = Duration::from_secs(2);
const PTRACE_SCOPE: &str = "/proc/sys/kernel/yama/ptrace_scope";

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum State {
    Pass,
    /// Genuinely wrong, but something else in the stack covers it, so the game
    /// can still work. Kept distinct from [`State::Fail`] because a checker that
    /// cries "this will fail" and is then contradicted by a working game teaches
    /// the user to ignore it — which is worse than not checking at all.
    Warn,
    Fail,
    /// Not configured, so there is nothing to assert. Never reported as a pass:
    /// "we did not look" and "we looked and it was fine" must not look alike.
    Skipped,
}

#[derive(Debug, Clone)]
pub struct Check {
    pub name: String,
    pub state: State,
    pub detail: String,
}

impl Check {
    fn pass(name: &str, detail: impl Into<String>) -> Self {
        Self {
            name: name.into(),
            state: State::Pass,
            detail: detail.into(),
        }
    }
    fn fail(name: &str, detail: impl Into<String>) -> Self {
        Self {
            name: name.into(),
            state: State::Fail,
            detail: detail.into(),
        }
    }
    fn warn(name: &str, detail: impl Into<String>) -> Self {
        Self {
            name: name.into(),
            state: State::Warn,
            detail: detail.into(),
        }
    }
    fn skip(name: &str, detail: impl Into<String>) -> Self {
        Self {
            name: name.into(),
            state: State::Skipped,
            detail: detail.into(),
        }
    }
}

/// Run every applicable check. Order is the order the game exercises them.
pub fn run(cfg: &LauncherConfig) -> Vec<Check> {
    vec![
        ptrace_scope(cfg),
        ea_redirect(cfg),
        hostname_mapping(cfg),
        backend_reachable(cfg),
    ]
}

/// Checks that will stop the game working.
pub fn failures(checks: &[Check]) -> usize {
    checks.iter().filter(|c| c.state == State::Fail).count()
}

/// Checks that are wrong but survivable.
pub fn warnings(checks: &[Check]) -> usize {
    checks.iter().filter(|c| c.state == State::Warn).count()
}

/// autopatch writes to FIFA's process memory; Yama blocks that unless
/// `ptrace_scope` is 0. At 1 the patch silently does nothing and the game fails
/// its TLS handshake much later, with no message naming the cause.
fn ptrace_scope(cfg: &LauncherConfig) -> Check {
    const NAME: &str = "ptrace_scope (autopatch)";
    // `fifa17_tools_dir` carries a conventional default, so a non-empty value
    // does not mean the tools are installed. Key off the directory actually
    // existing: that is what decides whether autopatch will run at all, and it
    // keeps this from failing on a machine that never uses local services.
    let tools = cfg.fifa17_tools_dir.trim();
    if tools.is_empty() || !std::path::Path::new(tools).is_dir() {
        return Check::skip(NAME, "no local services installed");
    }
    match std::fs::read_to_string(PTRACE_SCOPE) {
        Ok(v) => ptrace_verdict(&v),
        // Not every kernel has Yama. Absent means unenforced, which is what we want.
        Err(_) => Check::skip(NAME, "Yama not present on this kernel"),
    }
}

/// The decision, split from the file read so it can be tested.
///
/// Reading `/proc` in a test would assert facts about the machine running the
/// suite rather than about this code — and left inline, "any value is fine"
/// was a mutation no test could catch.
fn ptrace_verdict(raw: &str) -> Check {
    const NAME: &str = "ptrace_scope (autopatch)";
    let v = raw.trim();
    if v == "0" {
        Check::pass(NAME, "0 — autopatch can attach")
    } else {
        Check::fail(
            NAME,
            format!("{v} — autopatch cannot patch FIFA. Click 'Arm client'."),
        )
    }
}

/// FIFA dials EA's redirector by hardcoded IP. Armed, that address is DNAT'd to
/// the OpenFUT server and connects instantly; unarmed it leaves the LAN and
/// times out — which is exactly the "servers have been shut down" dialog.
///
/// This tests the *effect* rather than reading firewall rules, so it needs no
/// privilege and stays honest about what the game will actually experience.
fn ea_redirect(cfg: &LauncherConfig) -> Check {
    const NAME: &str = "EA redirector IP is redirected";
    let ip = cfg.ea_redirect_probe_ip.trim();
    if ip.is_empty() {
        return Check::skip(NAME, "no probe IP configured");
    }
    let Ok(addr) = ip.parse::<IpAddr>() else {
        return Check::fail(NAME, format!("ea_redirect_probe_ip is not an IP: {ip:?}"));
    };
    let port = cfg.openfut_blaze_redirector_port;
    match TcpStream::connect_timeout(&SocketAddr::new(addr, port), PROBE_TIMEOUT) {
        Ok(_) => Check::pass(NAME, format!("{ip}:{port} answered — redirect is in place")),
        Err(e) => Check::fail(
            NAME,
            format!("{ip}:{port} did not answer ({e}). Click 'Arm client'."),
        ),
    }
}

/// The dead EA hostnames should resolve to the OpenFUT server.
///
/// Resolution is done with `getaddrinfo`, the same call the game makes, so a
/// duplicate `/etc/hosts` line that shadows the OpenFUT one is caught by its
/// effect. Parsing `/etc/hosts` would miss it: the file can contain the right
/// line and still resolve to the wrong address, because the first match wins.
///
/// # Why a warning and not a failure
///
/// Measured, not assumed. On 2026-08-11 this reported `easw.easports.com ->
/// ::1,127.0.0.1` and the game reached the FUT hub regardless. The reason is in
/// `client_arm.sh`'s own header: the responders run with `OPENFUT_ADVERTISE`
/// set, so after the first redirected contact the game is handed the server's
/// *address* for every later hop and stops using the hostname. The name is only
/// CardsDLL's built-in fallback.
///
/// So this is a real misconfiguration worth fixing and not a reason to expect
/// failure. Reporting it as fatal, and then being contradicted by a working
/// game, is how a checklist trains its user to ignore it.
fn hostname_mapping(cfg: &LauncherConfig) -> Check {
    const NAME: &str = "EA hostnames point at OpenFUT";
    if cfg.ea_hostnames.is_empty() {
        return Check::skip(NAME, "no EA hostnames configured");
    }
    let server = cfg.openfut_server_host.trim();
    if server.is_empty() {
        return Check::skip(NAME, "no OpenFUT server configured");
    }
    let want = match resolve(server) {
        Ok(ips) if !ips.is_empty() => ips,
        _ => {
            return Check::fail(
                NAME,
                format!("cannot resolve the OpenFUT server {server:?}"),
            )
        }
    };

    let mut wrong = Vec::new();
    for host in &cfg.ea_hostnames {
        match resolve(host) {
            Ok(got) if got.iter().any(|ip| want.contains(ip)) => {}
            Ok(got) => wrong.push(format!(
                "{host} -> {} (expected {})",
                join(&got),
                join(&want)
            )),
            Err(e) => wrong.push(format!("{host} -> unresolvable ({e})")),
        }
    }

    if wrong.is_empty() {
        Check::pass(
            NAME,
            format!("{} host(s) resolve to {server}", cfg.ea_hostnames.len()),
        )
    } else {
        Check::warn(
            NAME,
            format!(
                "{}. Look for an earlier /etc/hosts line shadowing it. \
                 Usually survivable: the server advertises its address, so the \
                 game stops using this name after the first hop.",
                wrong.join("; ")
            ),
        )
    }
}

/// The server side of the same question: are the ports the game will use open?
fn backend_reachable(cfg: &LauncherConfig) -> Check {
    const NAME: &str = "OpenFUT server reachable";
    let host = cfg.openfut_server_host.trim();
    if host.is_empty() {
        return Check::skip(NAME, "no OpenFUT server configured");
    }
    let ports = [
        ("blaze redirector", cfg.openfut_blaze_redirector_port),
        ("account sync", cfg.openfut_account_sync_port),
    ];
    let mut dead = Vec::new();
    for (label, port) in ports {
        if !connects(host, port) {
            dead.push(format!("{label} :{port}"));
        }
    }
    if dead.is_empty() {
        Check::pass(NAME, format!("{host}: all {} ports answering", ports.len()))
    } else {
        Check::fail(NAME, format!("{host}: no answer on {}", dead.join(", ")))
    }
}

fn connects(host: &str, port: u16) -> bool {
    match (host, port).to_socket_addrs() {
        Ok(mut addrs) => addrs.any(|a| TcpStream::connect_timeout(&a, PROBE_TIMEOUT).is_ok()),
        Err(_) => false,
    }
}

fn resolve(host: &str) -> std::io::Result<Vec<IpAddr>> {
    Ok((host, 0u16).to_socket_addrs()?.map(|a| a.ip()).collect())
}

fn join(ips: &[IpAddr]) -> String {
    ips.iter()
        .map(|i| i.to_string())
        .collect::<Vec<_>>()
        .join(",")
}

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

    fn cfg() -> LauncherConfig {
        LauncherConfig::default()
    }

    #[test]
    fn an_unconfigured_launcher_skips_rather_than_passes() {
        // The distinction that matters: a fresh config must not display four
        // green ticks. "Not checked" is not "checked and fine".
        let mut c = cfg();
        // `default()` points this at a conventional path whose existence varies
        // by machine. Pin it so the assertion is about the code, not this box.
        c.fifa17_tools_dir = "/nonexistent/openfut-tools".into();
        let checks = run(&c);
        assert!(
            checks.iter().all(|k| k.state == State::Skipped),
            "{checks:#?}"
        );
        assert_eq!(failures(&checks), 0, "nothing configured is not a failure");
    }

    #[test]
    fn only_ptrace_scope_zero_lets_autopatch_work() {
        assert_eq!(ptrace_verdict("0\n").state, State::Pass);
        // 1 is the default on most distributions and is exactly the state that
        // let autopatch fail silently for forty minutes on 2026-08-11.
        assert_eq!(ptrace_verdict("1\n").state, State::Fail);
        assert_eq!(ptrace_verdict("2").state, State::Fail);
        assert_eq!(ptrace_verdict("3").state, State::Fail);
        assert!(ptrace_verdict("1").detail.contains("Arm client"));
    }

    #[test]
    fn ptrace_is_skipped_when_the_tools_dir_does_not_exist() {
        // Regression: the gate used to be "is the field non-empty", and the
        // field has a default — so this check ran (and failed) on machines that
        // never use autopatch at all.
        let mut c = cfg();
        c.fifa17_tools_dir = "/nonexistent/openfut-tools".into();
        assert_eq!(ptrace_scope(&c).state, State::Skipped);
    }

    #[test]
    fn a_malformed_probe_ip_fails_loudly_instead_of_being_skipped() {
        let mut c = cfg();
        c.ea_redirect_probe_ip = "not-an-ip".into();
        let check = ea_redirect(&c);
        assert_eq!(check.state, State::Fail);
        assert!(check.detail.contains("not an IP"), "{}", check.detail);
    }

    #[test]
    fn hostname_check_is_skipped_without_a_server_but_not_passed() {
        let mut c = cfg();
        c.ea_hostnames = vec!["easw.easports.com".into()];
        assert_eq!(hostname_mapping(&c).state, State::Skipped);
    }

    #[test]
    fn hostname_check_detects_a_host_pointing_somewhere_else() {
        // localhost and 127.0.0.1 resolve without a network; this is the
        // shadowed-/etc/hosts shape without depending on the real one.
        let mut c = cfg();
        c.openfut_server_host = "127.0.0.2".into();
        c.ea_hostnames = vec!["localhost".into()];
        let check = hostname_mapping(&c);
        // Warn, not Fail: observed on 2026-08-11 to be survivable, because the
        // server advertises its address after the first hop.
        assert_eq!(check.state, State::Warn, "{}", check.detail);
        assert!(check.detail.contains("localhost -> "), "{}", check.detail);
    }

    /// A shadowed hostname must not be counted as a reason to expect failure.
    /// This is the exact case the first version got wrong.
    #[test]
    fn a_shadowed_hostname_is_a_warning_not_a_failure() {
        let mut c = cfg();
        c.openfut_server_host = "127.0.0.2".into();
        c.ea_hostnames = vec!["localhost".into()];
        c.fifa17_tools_dir = "/nonexistent/openfut-tools".into();
        let checks = run(&c);
        assert_eq!(failures(&checks), 0, "must not be reported as fatal");
        assert_eq!(warnings(&checks), 1);
    }

    #[test]
    fn hostname_check_passes_when_it_points_at_the_server() {
        let mut c = cfg();
        c.openfut_server_host = "127.0.0.1".into();
        c.ea_hostnames = vec!["localhost".into()];
        // `localhost` may resolve to ::1 as well; the check requires only that
        // one resolved address matches, which mirrors what connecting does.
        assert_eq!(hostname_mapping(&c).state, State::Pass);
    }

    #[test]
    fn ptrace_check_is_skipped_when_local_services_are_not_configured() {
        let mut c = cfg();
        c.fifa17_tools_dir.clear();
        assert_eq!(ptrace_scope(&c).state, State::Skipped);
    }

    #[test]
    fn a_dead_backend_port_is_reported_as_a_failure() {
        let mut c = cfg();
        c.openfut_server_host = "127.0.0.1".into();
        // Port 1 requires root to bind, so nothing is listening on it.
        c.openfut_blaze_redirector_port = 1;
        c.openfut_account_sync_port = 1;
        let check = backend_reachable(&c);
        assert_eq!(check.state, State::Fail, "{}", check.detail);
        assert!(check.detail.contains("no answer on"), "{}", check.detail);
    }
}