nim-ffi/examples/timer/cpp_bindings/main.cpp

#include "my_timer.hpp"
#include <atomic>
#include <chrono>
#include <future>
#include <iostream>
#include <thread>

// The generated bindings never throw: every call returns a Result<T>. We
// branch on isErr() and read value()/error() instead of using try/catch.
int main() {
    auto ctxRes = MyTimerCtx::create(TimerConfig{"cpp-demo"});
    if (ctxRes.isErr()) {
        std::cerr << "Error: " << ctxRes.error() << "\n";
        return 1;
    }
    auto ctx = std::move(ctxRes.value());
    std::cout << "[1] Context created\n";

    auto versionFuture = ctx->versionAsync();
    auto echo1Future = ctx->echoAsync(EchoRequest{"hello from C++", 200});
    auto echo2Future = ctx->echoAsync(EchoRequest{"second C++ request", 50});

    auto version = versionFuture.get();
    if (version.isErr()) {
        std::cerr << "Error: " << version.error() << "\n";
        return 1;
    }
    std::cout << "[2] Version: " << version.value() << "\n";

    auto echo = echo1Future.get();
    if (echo.isErr()) {
        std::cerr << "Error: " << echo.error() << "\n";
        return 1;
    }
    std::cout << "[3] Echo 1: echoed=" << echo->echoed
              << ", timerName=" << echo->timerName << "\n";

    auto echo2 = echo2Future.get();
    if (echo2.isErr()) {
        std::cerr << "Error: " << echo2.error() << "\n";
        return 1;
    }
    std::cout << "[4] Echo 2: echoed=" << echo2->echoed
              << ", timerName=" << echo2->timerName << "\n";

    auto complexReq = ComplexRequest{
        std::vector<EchoRequest>{EchoRequest{"one", 10}, EchoRequest{"two", 20}},
        std::vector<std::string>{"fast", "async"},
        std::optional<std::string>("extra note"),
        std::optional<int64_t>(3)
    };

    auto complex = ctx->complexAsync(complexReq).get();
    if (complex.isErr()) {
        std::cerr << "Error: " << complex.error() << "\n";
        return 1;
    }
    std::cout << "[5] Complex: summary=" << complex->summary
              << ", itemCount=" << complex->itemCount
              << ", hasNote=" << complex->hasNote << "\n";

    // ── 6. Call with three complex parameters ─────────────────────
    // Each parameter is its own generated C++ struct. The nim-ffi
    // macro packs all three into one CBOR envelope on the wire — at
    // the call site, this is just a typed method invocation.
    auto job = JobSpec{
        /*name*/ "nightly-rollup",
        /*payload*/ std::vector<std::string>{"rollup", "v2"},
        /*priority*/ 10,
    };
    auto retry = RetryPolicy{
        /*maxAttempts*/ 3,
        /*backoffMs*/ 500,
        /*retryOn*/ std::vector<std::string>{"timeout", "5xx"},
    };
    auto schedule = ScheduleConfig{
        /*startAtMs*/ 1000,
        /*intervalMs*/ 15000,
        /*jitter*/ std::optional<int64_t>(250),
    };

    auto scheduleRes = ctx->scheduleAsync(job, retry, schedule).get();
    if (scheduleRes.isErr()) {
        std::cerr << "Error: " << scheduleRes.error() << "\n";
        return 1;
    }
    std::cout << "[6] Schedule (3 complex params): jobId=" << scheduleRes->jobId
              << ", willRunCount=" << scheduleRes->willRunCount
              << ", firstRunAtMs=" << scheduleRes->firstRunAtMs
              << ", effectiveBackoffMs=" << scheduleRes->effectiveBackoffMs
              << "\n";

    // Each `{.ffiEvent.}` declared on the Nim side gets a typed
    // registration method — `addOnEchoFiredListener(handler)` here.
    // A second `addEventListener` overload registers a catch-all
    // wildcard listener that receives every event as raw envelope
    // bytes plus the FFI return code. Both fire from the lib's
    // dispatch thread, so synchronise via std::promise / atomics.
    std::promise<EchoEvent> echoEvtPromise;
    auto echoEvtFuture = echoEvtPromise.get_future();
    const auto typedHandle = ctx->addOnEchoFiredListener(
        [&](const EchoEvent& evt) { echoEvtPromise.set_value(evt); });

    std::atomic<int> wildcardHits{0};
    // Wildcard listener receives every event with the wire `eventId`
    // pre-extracted plus a span view over the raw CBOR envelope
    // bytes (zero-copy; valid only for the duration of this call).
    // Dispatch on `eventId` and use `decodeEventPayload<T>` to lift
    // the payload into a typed value without hand-parsing CBOR.
    const auto wildcardHandle = ctx->addEventListener(
        [&](int retCode, const std::string& eventId,
            std::span<const std::uint8_t> envelope) {
            wildcardHits.fetch_add(1);
            std::cout << "[7] wildcard event: retCode=" << retCode
                      << ", eventId=" << eventId
                      << ", envelope bytes=" << envelope.size() << "\n";
            if (retCode != 0) return;
            if (eventId == "on_echo_fired") {
                EchoEvent decoded{};
                if (decodeEventPayload(envelope, decoded)) {
                    std::cout << "    decoded EchoEvent: message="
                              << decoded.message
                              << ", echoCount=" << decoded.echoCount << "\n";
                }
            }
        });

    ctx->echo(EchoRequest{"event-demo", 1});
    const auto evt = echoEvtFuture.get();
    std::cout << "[7] typed event onEchoFired: message=" << evt.message
              << ", echoCount=" << evt.echoCount
              << ", wildcardHits=" << wildcardHits.load() << "\n";

    // Drop the typed listener — only the wildcard fires for the
    // follow-up echo. Sleep briefly to give the lib thread time to
    // deliver before we tear the ctx down.
    ctx->removeEventListener(typedHandle);
    ctx->echo(EchoRequest{"event-demo-after-remove", 1});
    std::this_thread::sleep_for(std::chrono::milliseconds(50));
    std::cout << "[7] after removeEventListener: wildcardHits="
              << wildcardHits.load() << "\n";
    ctx->removeEventListener(wildcardHandle);

    std::cout << "\nDone.\n";
    return 0;
}