// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <lib/fidl-async/cpp/bind.h>
#include <lib/fidl-async/cpp/channel_transaction.h>
#include <lib/fidl/llcpp/transaction.h>
#include <lib/fidl/trace.h>
#include <lib/fidl/txn_header.h>
#include <lib/zx/channel.h>
#include <zircon/syscalls.h>

#include <type_traits>

namespace fidl {

namespace internal {

SimpleBinding::SimpleBinding(async_dispatcher_t* dispatcher, zx::channel channel, void* impl,
                             TypeErasedDispatchFn dispatch_fn,
                             TypeErasedOnChannelClosedFn on_channel_closed_fn)
    : async_wait_t({
          .state = ASYNC_STATE_INIT,
          .handler = &MessageHandler,
          .object = channel.release(),
          .trigger = ZX_CHANNEL_READABLE | ZX_CHANNEL_PEER_CLOSED,
          .options = 0,
      }),
      dispatcher_(dispatcher),
      interface_(impl),
      dispatch_fn_(dispatch_fn),
      on_channel_closed_fn_(std::move(on_channel_closed_fn)) {}

SimpleBinding::~SimpleBinding() {
  zx_handle_close(async_wait_t::object);
  if (on_channel_closed_fn_) {
    on_channel_closed_fn_(interface_);
  }
}

void SimpleBinding::MessageHandler(async_dispatcher_t* dispatcher, async_wait_t* wait,
                                   zx_status_t status, const zx_packet_signal_t* signal) {
  std::unique_ptr<SimpleBinding> binding(static_cast<SimpleBinding*>(wait));
  if (status != ZX_OK) {
    return;
  }

  if (signal->observed & ZX_CHANNEL_READABLE) {
    char bytes[ZX_CHANNEL_MAX_MSG_BYTES];
    zx_handle_t handles[ZX_CHANNEL_MAX_MSG_HANDLES];
    for (uint64_t i = 0; i < signal->count; i++) {
      fidl_incoming_msg_t msg = {
          .bytes = bytes,
          .handles = handles,
          .num_bytes = 0u,
          .num_handles = 0u,
      };
      fidl_trace(WillLLCPPAsyncChannelRead);
      status = zx_channel_read(wait->object, 0, bytes, handles, ZX_CHANNEL_MAX_MSG_BYTES,
                               ZX_CHANNEL_MAX_MSG_HANDLES, &msg.num_bytes, &msg.num_handles);
      if (status != ZX_OK)
        return;

      // Do basic validation on the message.
      status = msg.num_bytes < sizeof(fidl_message_header_t)
                   ? ZX_ERR_INVALID_ARGS
                   : fidl_validate_txn_header(reinterpret_cast<fidl_message_header_t*>(msg.bytes));
      if (status != ZX_OK) {
        zx_handle_close_many(msg.handles, msg.num_handles);
        return;
      }
      fidl_trace(DidLLCPPAsyncChannelRead, nullptr /* type */, bytes, msg.num_bytes,
                 msg.num_handles);

      auto hdr = reinterpret_cast<fidl_message_header_t*>(msg.bytes);
      ChannelTransaction txn(hdr->txid, std::move(binding));
      txn.Dispatch(msg);
      binding = txn.TakeBinding();
      if (!binding) {
        return;
      }
    }

    // Will only get here if every single message was handled synchronously and successfully.
    BeginWait(&binding);
  } else {
    ZX_DEBUG_ASSERT(signal->observed & ZX_CHANNEL_PEER_CLOSED);
  }
}

zx_status_t BeginWait(std::unique_ptr<SimpleBinding>* unique_binding) {
  SimpleBinding* binding = unique_binding->release();
  zx_status_t status;
  if ((status = async_begin_wait(binding->dispatcher_, binding)) != ZX_OK) {
    // Failed to transfer binding ownership to async dispatcher.
    unique_binding->reset(binding);
  }
  return status;
}

zx_status_t TypeErasedBind(async_dispatcher_t* dispatcher, zx::channel channel, void* impl,
                           TypeErasedDispatchFn dispatch_fn,
                           TypeErasedOnChannelClosedFn on_channel_closed_fn) {
  auto binding = std::make_unique<SimpleBinding>(dispatcher, std::move(channel), impl, dispatch_fn,
                                                 std::move(on_channel_closed_fn));
  auto status = BeginWait(&binding);
  return status;
}

}  // namespace internal

}  // namespace fidl