// Stream B1 (fibers) B1.4a — a truly-SUSPENDING fiber-task async layer
// (`go` / `wait` / `cancel`) over the M:1 scheduler, in pure sx. In contrast
// with 1805's `context.io.async` (which runs each worker INLINE to completion
// before returning a `.ready` future — no interleaving), here `s.go(work)` runs
// `work` as a REAL fiber and `t.wait()` SUSPENDS the caller until that fiber
// finishes, so a task that yields mid-body lets a sibling task run before the
// first completes — genuine cooperative interleaving.
//
// `work` is a NULLARY thunk: any inputs are captured in the lambda at the call
// site (no `..args` pack crosses the fiber boundary — that would hit issue 0156
// Part 2). Outputs flow OUT through pointers captured in the thunk (the shared
// `Log` struct), since closure capture-by-value does not write back.
//
// What this proves:
//   - REAL suspend + interleave: task A records 1, YIELDS; task B then records 2
//     and completes; A resumes, records 3, completes → interleave order 1 2 3.
//   - awaited VALUES: A returns 42, B returns 100 (recorded after both waits).
//     → sequence: 1 2 3 42 100.
//   - cancel rides the `!` channel (model (a), like 1806): a canceled task's
//     `wait()` raises `.Canceled`, taken by the `or` default → -99.
//
// `wait` must run inside a fiber (it parks `self.current`), so the "main task"
// is itself a `s.spawn(...)` fiber that drives the two `go` tasks.
//
// aarch64-macOS-pinned (the scheduler's asm + guard-page mmap constants are
// per-arch / Apple-specific): runs end-to-end on a matching host, ir-only on a
// mismatch.
#import "modules/std.sx";
sched :: #import "modules/std/sched.sx";

Log :: struct { seq: [16]i64; n: i64; }
rec :: (l: *Log, v: i64) { l.seq[l.n] = v; l.n = l.n + 1; }

main :: () -> i64 {
    lg : Log = .{ n = 0 };   // seq[] zero-filled

    s := sched.Scheduler.init();
    ps := @s;
    pl := @lg;

    // The "main task" fiber: drives two real tasks, waits both, then exercises
    // cancel. It runs as a fiber so `wait` has a `self.current` to park.
    s.spawn(() => {
        // Task A yields mid-body so B interleaves before A completes.
        a := ps.go(() -> i64 => {
            rec(pl, 1);
            ps.yield_now();   // suspend A; B (already spawned) runs to completion
            rec(pl, 3);
            42
        });
        // Task B runs straight through (no yield).
        b := ps.go(() -> i64 => {
            rec(pl, 2);
            100
        });

        // Wait both — suspends the main-task fiber until each completes.
        va := a.wait() or { -1 };
        vb := b.wait() or { -1 };
        rec(pl, va);
        rec(pl, vb);

        // Cancel case: cancel before the worker runs; `wait` raises .Canceled,
        // the `or` default (-99) is taken.
        c := ps.go(() -> i64 => 7);
        c.cancel();
        rec(pl, c.wait() or { -99 });
    });

    s.run();

    // Interleaving + value contract: 1 2 3 42 100, then the cancel default -99.
    print("sequence:");
    i := 0;
    while i < lg.n {
        print(" {}", lg.seq[i]);
        i = i + 1;
    }
    print("\n");
    print("spawned: {}\n", s.n_spawned);
    return 0;
}