// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Copyright 2022 The Lynx Authors. All rights reserved.
// Licensed under the Apache License Version 2.0 that can be found in the
// LICENSE file in the root directory of this source tree.

#define FML_USED_ON_EMBEDDER

#include "base/include/fml/shared_thread_merger.h"

#include <algorithm>
#include <set>

#include "base/include/fml/macros.h"

namespace lynx {
namespace fml {

SharedThreadMerger::SharedThreadMerger(fml::TaskQueueId owner,
                                       fml::TaskQueueId subsumed)
    : owner_(owner),
      subsumed_(subsumed),
      task_queues_(fml::MessageLoopTaskQueues::GetInstance()),
      enabled_(true) {}

bool SharedThreadMerger::MergeWithLease(RasterThreadMergerId caller,
                                        size_t lease_term) {
  // TODO(zhengsenyao): Uncomment DCHECK code when DCHECK available.
  // DCHECK(lease_term > 0) << "lease_term should be positive.";
  std::scoped_lock lock(mutex_);
  if (IsMergedUnSafe()) {
    return true;
  }
  bool success = task_queues_->Merge(owner_, subsumed_);
  // TODO(zhengsenyao): Replace LYNX_BASE_CHECK with CHECK when CHECK available.
  LYNX_BASE_CHECK(success);
  // << "Unable to merge the raster and platform threads.";
  // Save the lease term
  lease_term_by_caller_[caller] = lease_term;
  return success;
}

bool SharedThreadMerger::UnMergeNowUnSafe() {
  // TODO(zhengsenyao): Replace LYNX_BASE_CHECK with CHECK when CHECK available.
  LYNX_BASE_CHECK(IsAllLeaseTermsZeroUnSafe());
  // << "all lease term records must be zero before calling "
  //  "UnMergeNowUnSafe()";
  bool success = task_queues_->Unmerge(owner_, subsumed_);
  LYNX_BASE_CHECK(success);
  // << "Unable to un-merge the raster and platform threads.";
  return success;
}

bool SharedThreadMerger::UnMergeNowIfLastOne(RasterThreadMergerId caller) {
  std::scoped_lock lock(mutex_);
  lease_term_by_caller_.erase(caller);
  if (!lease_term_by_caller_.empty()) {
    return true;
  }
  return UnMergeNowUnSafe();
}

bool SharedThreadMerger::DecrementLease(RasterThreadMergerId caller) {
  std::scoped_lock lock(mutex_);
  auto entry = lease_term_by_caller_.find(caller);
  bool exist = entry != lease_term_by_caller_.end();
  if (exist) {
    std::atomic_size_t& lease_term_ref = entry->second;
    // TODO(zhengsenyao): Replace LYNX_BASE_CHECK with CHECK when CHECK
    // available.
    LYNX_BASE_CHECK(lease_term_ref > 0);
    // << "lease_term should always be positive when merged, lease_term="
    // << lease_term_ref;
    lease_term_ref--;
  } else {
    // TODO(zhengsenyao): Uncomment LOGW code when LOGW available.
    // LOGW(
    //     "The caller does not exist when calling "
    //     "DecrementLease(), ignored. This may happens after "
    //     "caller is erased in UnMergeNowIfLastOne(). caller="
    //     << caller);
  }
  if (IsAllLeaseTermsZeroUnSafe()) {
    // Unmerge now because lease_term_ decreased to zero.
    UnMergeNowUnSafe();
    return true;
  }
  return false;
}

void SharedThreadMerger::ExtendLeaseTo(RasterThreadMergerId caller,
                                       size_t lease_term) {
  // TODO(zhengsenyao): Uncomment DCHECK code when DCHECK available.
  // DCHECK(lease_term > 0) << "lease_term should be positive.";
  std::scoped_lock lock(mutex_);
  // DCHECK(IsMergedUnSafe()) << "should be merged state when calling this
  // method";
  lease_term_by_caller_[caller] = lease_term;
}

bool SharedThreadMerger::IsMergedUnSafe() const {
  return !IsAllLeaseTermsZeroUnSafe();
}

bool SharedThreadMerger::IsEnabledUnSafe() const { return enabled_; }

void SharedThreadMerger::SetEnabledUnSafe(bool enabled) { enabled_ = enabled; }

bool SharedThreadMerger::IsAllLeaseTermsZeroUnSafe() const {
  return std::all_of(lease_term_by_caller_.begin(), lease_term_by_caller_.end(),
                     [&](const auto& item) { return item.second == 0; });
}

}  // namespace fml
}  // namespace lynx