// Phase 0 baseline (PLAN-FFI.md step 0.6): sx function passed to C
// as a function pointer; C invokes it; sx-side observable effect.
// Mirrors the `app->onInputEvent` install pattern in
// library/modules/platform/android.sx.
//
// Two arities covered:
//   1. (s32) -> s32                — single-arg callback
//   2. (*void, s32) -> s32         — pointer + value (onInputEvent shape)
//
// Plus a side-effect via a global so we can confirm the callback
// actually fired (return value + state mutation both observable).

#import "modules/std.sx";

#import c {
    #source "ffi-06-callback.c";
};

ffi_apply_callback  :: (cb: (s32) -> s32, value: s32) -> s32 #foreign;
ffi_apply_callback2 :: (cb: (*void, s32) -> s32, ctx: *void, v: s32) -> s32 #foreign;

g_callback_hits : s32 = 0;
g_callback_sum  : s32 = 0;

double_it :: (x: s32) -> s32 {
    g_callback_hits += 1;
    g_callback_sum += x;
    x * 2;
}

add_with_ctx :: (ctx: *void, v: s32) -> s32 {
    g_callback_hits += 1;
    // Pass a sentinel via ctx to prove the pointer arg also survives the
    // round-trip — read it back as an s32 through *s32.
    p : *s32 = xx ctx;
    p.* + v;
}

main :: () -> s32 {
    // ── Single-arg callback ────────────────────────────────────────
    r1 := ffi_apply_callback(double_it, 21);
    print("callback returned        = {}\n", r1);
    print("hits after first call    = {}\n", g_callback_hits);
    print("sum after first call     = {}\n", g_callback_sum);

    // Two more calls confirm the same fn pointer keeps working.
    ffi_apply_callback(double_it, 7);
    ffi_apply_callback(double_it, 11);
    print("hits after three calls   = {}\n", g_callback_hits);
    print("sum after three calls    = {}\n", g_callback_sum);

    // ── Two-arg callback with opaque ctx pointer ───────────────────
    ctx_val : s32 = 100;
    r2 := ffi_apply_callback2(add_with_ctx, xx @ctx_val, 42);
    print("ctx + value              = {}\n", r2);
    print("hits after ctx callback  = {}\n", g_callback_hits);

    0;
}