#include <mbgl/storage/default/request.hpp>

#include <mbgl/storage/response.hpp>

#include <mbgl/util/util.hpp>
#include <mbgl/util/uv.hpp>

#include <uv.h>

#include <cassert>
#include <functional>

namespace mbgl {

// Note: This requires that loop is running in the current thread (or not yet running).
Request::Request(const Resource &resource_, uv_loop_t *loop, Callback callback_)
    : callback(callback_), resource(resource_) {
    // When there is no loop supplied (== nullptr), the callback will be fired in an arbitrary
    // thread (the thread notify() is called from) rather than kicking back to the calling thread.
    if (loop) {
        notify_async = new uv_async_t;
        notify_async->data = this;
#if UV_VERSION_MAJOR == 0 && UV_VERSION_MINOR <= 10
        uv_async_init(loop, notify_async, [](uv_async_t *async, int) { notifyCallback(async); });
#else
        uv_async_init(loop, notify_async, notifyCallback);
#endif
    }
}

void Request::notifyCallback(uv_async_t *async) {
    auto request = reinterpret_cast<Request *>(async->data);
    uv::close(async);

    if (!request->destruct_async) {
        // We haven't created a cancel request, so we can safely delete this Request object
        // since it won't be accessed in the future.
        assert(request->response);
        request->callback(*request->response);
        delete request;
    } else {
        // Otherwise, we're waiting for for the destruct notification to be delivered in order
        // to delete the Request object. We're doing this since we can't know whether the
        // DefaultFileSource is still sending a cancel event, which means this object must still
        // exist.
    }
}


Request::~Request() {
    if (notify_async) {
        // Request objects can be destructed in other threads when the user didn't supply a loop.
        MBGL_VERIFY_THREAD(tid)
    }
}

void Request::notify(const std::shared_ptr<const Response> &response_) {
    response = response_;
    if (notify_async) {
        uv_async_send(notify_async);
    } else {
        assert(response);
        callback(*response);
        delete this;
    }
}

void Request::cancel() {
    MBGL_VERIFY_THREAD(tid)
    assert(notify_async);
    assert(!destruct_async);
    destruct_async = new uv_async_t;
    destruct_async->data = this;
#if UV_VERSION_MAJOR == 0 && UV_VERSION_MINOR <= 10
    uv_async_init(notify_async->loop, destruct_async, [](uv_async_t *async, int) { cancelCallback(async); });
#else
    uv_async_init(notify_async->loop, destruct_async, cancelCallback);
#endif
}

void Request::cancelCallback(uv_async_t *async) {
    // The destruct_async will be invoked *after* the notify_async callback has already run.
    auto request = reinterpret_cast<Request *>(async->data);
    uv::close(async);
    delete request;
}

// This gets called from the FileSource thread, and will only ever be invoked after cancel() was called
// in the original requesting thread.
void Request::destruct() {
    if (notify_async) {
        notify(nullptr);
    }

    assert(destruct_async);
    uv_async_send(destruct_async);
}

}