// Copyright 2016 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 "peridot/bin/ledger/storage/fake/fake_page_storage.h"

#include <string>
#include <utility>
#include <vector>

#include <lib/async/cpp/task.h>
#include <lib/async/default.h>
#include <lib/fit/function.h>
#include <lib/fsl/socket/strings.h>
#include <lib/fsl/vmo/strings.h>
#include <lib/fxl/logging.h>
#include <lib/fxl/strings/concatenate.h>
#include <lib/zx/time.h>

#include "peridot/bin/ledger/encryption/primitives/hash.h"
#include "peridot/bin/ledger/storage/fake/fake_commit.h"
#include "peridot/bin/ledger/storage/fake/fake_journal.h"
#include "peridot/bin/ledger/storage/fake/fake_object.h"
#include "peridot/bin/ledger/storage/public/constants.h"

namespace storage {
namespace fake {

namespace {

Status ToBuffer(convert::ExtendedStringView value, int64_t offset,
                int64_t max_size, fsl::SizedVmo* buffer) {
  size_t start = value.size();
  // Valid indices are between -N and N-1.
  if (offset >= -static_cast<int64_t>(value.size()) &&
      offset < static_cast<int64_t>(value.size())) {
    start = offset < 0 ? value.size() + offset : offset;
  }
  size_t length = max_size < 0 ? value.size() : max_size;
  bool result = fsl::VmoFromString(value.substr(start, length), buffer);
  return result ? Status::OK : Status::INTERNAL_IO_ERROR;
}

}  // namespace

FakePageStorage::FakePageStorage(ledger::Environment* environment,
                                 PageId page_id)
    : page_id_(std::move(page_id)),
      environment_(environment),
      encryption_service_(environment_->dispatcher()) {}

FakePageStorage::~FakePageStorage() {}

PageId FakePageStorage::GetId() { return page_id_; }

void FakePageStorage::GetHeadCommitIds(
    fit::function<void(Status, std::vector<CommitId>)> callback) {
  std::vector<CommitId> commit_ids(heads_.begin(), heads_.end());
  if (commit_ids.empty()) {
    commit_ids.emplace_back();
  }
  callback(Status::OK, std::move(commit_ids));
}

void FakePageStorage::GetCommit(
    CommitIdView commit_id,
    fit::function<void(Status, std::unique_ptr<const Commit>)> callback) {
  auto it = journals_.find(commit_id.ToString());
  if (it == journals_.end()) {
    callback(Status::NOT_FOUND, nullptr);
    return;
  }

  async::PostDelayedTask(
      environment_->dispatcher(),
      [this, commit_id = commit_id.ToString(), callback = std::move(callback)] {
        callback(Status::OK,
                 std::make_unique<FakeCommit>(journals_[commit_id].get()));
      },
      kFakePageStorageDelay);
}

void FakePageStorage::StartCommit(
    const CommitId& commit_id, JournalType /*journal_type*/,
    fit::function<void(Status, std::unique_ptr<Journal>)> callback) {
  uint64_t next_generation = 0;
  FakeJournalDelegate::Data data;
  if (journals_.find(commit_id) != journals_.end()) {
    next_generation = journals_[commit_id].get()->GetGeneration() + 1;
    data = journals_[commit_id].get()->GetData();
  }
  auto delegate = std::make_unique<FakeJournalDelegate>(
      environment_->random(), std::move(data), commit_id, autocommit_,
      next_generation);
  auto journal = std::make_unique<FakeJournal>(delegate.get());
  journals_[delegate->GetId()] = std::move(delegate);
  callback(Status::OK, std::move(journal));
}

void FakePageStorage::StartMergeCommit(
    const CommitId& left, const CommitId& right,
    fit::function<void(Status, std::unique_ptr<Journal>)> callback) {
  auto delegate = std::make_unique<FakeJournalDelegate>(
      environment_->random(), journals_[left].get()->GetData(), left, right,
      autocommit_,
      1 + std::max(journals_[left].get()->GetGeneration(),
                   journals_[right].get()->GetGeneration()));
  auto journal = std::make_unique<FakeJournal>(delegate.get());
  journals_[delegate->GetId()] = std::move(delegate);
  callback(Status::OK, std::move(journal));
}

void FakePageStorage::CommitJournal(
    std::unique_ptr<Journal> journal,
    fit::function<void(Status, std::unique_ptr<const storage::Commit>)>
        callback) {
  static_cast<FakeJournal*>(journal.get())
      ->Commit([this, callback = std::move(callback)](
                   Status status,
                   std::unique_ptr<const storage::Commit> commit) {
        for (const storage::CommitIdView& parent_id : commit->GetParentIds()) {
          auto it = heads_.find(parent_id.ToString());
          if (it != heads_.end()) {
            heads_.erase(it);
          }
        }
        heads_.emplace(commit->GetId());
        if (!drop_commit_notifications_) {
          for (CommitWatcher* watcher : watchers_) {
            async::PostTask(
                environment_->dispatcher(),
                [watcher, commit = commit->Clone()]() mutable {
                  std::vector<std::unique_ptr<const Commit>> commits;
                  commits.push_back(std::move(commit));
                  watcher->OnNewCommits(commits, ChangeSource::LOCAL);
                });
          }
        }
        callback(status, std::move(commit));
      });
}

void FakePageStorage::RollbackJournal(std::unique_ptr<Journal> journal,
                                      fit::function<void(Status)> callback) {
  callback(static_cast<FakeJournal*>(journal.get())->Rollback());
}

Status FakePageStorage::AddCommitWatcher(CommitWatcher* watcher) {
  watchers_.emplace(watcher);
  return Status::OK;
}

Status FakePageStorage::RemoveCommitWatcher(CommitWatcher* watcher) {
  auto it = watchers_.find(watcher);
  if (it != watchers_.end()) {
    watchers_.erase(it);
  }
  return Status::OK;
}

void FakePageStorage::IsSynced(fit::function<void(Status, bool)> callback) {
  callback(Status::OK, is_synced_);
}

void FakePageStorage::AddObjectFromLocal(
    ObjectType /*object_type*/, std::unique_ptr<DataSource> data_source,
    fit::function<void(Status, ObjectIdentifier)> callback) {
  auto value = std::make_unique<std::string>();
  auto data_source_ptr = data_source.get();
  data_source_ptr->Get([this, data_source = std::move(data_source),
                        value = std::move(value),
                        callback = std::move(callback)](
                           std::unique_ptr<DataSource::DataChunk> chunk,
                           DataSource::Status status) mutable {
    if (status == DataSource::Status::ERROR) {
      callback(Status::IO_ERROR, {});
      return;
    }
    auto view = chunk->Get();
    value->append(view.data(), view.size());
    if (status == DataSource::Status::DONE) {
      ObjectIdentifier object_identifier =
          encryption_service_.MakeObjectIdentifier(FakeDigest(*value));
      objects_[object_identifier] = std::move(*value);
      callback(Status::OK, std::move(object_identifier));
    }
  });
}

void FakePageStorage::GetObject(
    ObjectIdentifier object_identifier, Location /*location*/,
    fit::function<void(Status, std::unique_ptr<const Object>)> callback) {
  GetPiece(object_identifier, std::move(callback));
}

void FakePageStorage::GetObjectPart(
    ObjectIdentifier object_identifier, int64_t offset, int64_t max_size,
    Location location, fit::function<void(Status, fsl::SizedVmo)> callback) {
  GetPiece(object_identifier,
           [offset, max_size, callback = std::move(callback)](
               Status status, std::unique_ptr<const Object> piece) {
             if (status != Status::OK) {
               callback(status, nullptr);
               return;
             }
             fxl::StringView data;
             Status data_status = piece->GetData(&data);
             if (data_status != Status::OK) {
               callback(data_status, nullptr);
               return;
             }
             fsl::SizedVmo buffer;
             Status buffer_status = ToBuffer(data, offset, max_size, &buffer);
             if (buffer_status != Status::OK) {
               callback(buffer_status, nullptr);
               return;
             }
             callback(Status::OK, std::move(buffer));
           });
}

void FakePageStorage::GetPiece(
    ObjectIdentifier object_identifier,
    fit::function<void(Status, std::unique_ptr<const Object>)> callback) {
  object_requests_.emplace_back(
      [this, object_identifier = std::move(object_identifier),
       callback = std::move(callback)] {
        auto it = objects_.find(object_identifier);
        if (it == objects_.end()) {
          callback(Status::NOT_FOUND, nullptr);
          return;
        }

        callback(Status::OK,
                 std::make_unique<FakeObject>(object_identifier, it->second));
      });
  async::PostDelayedTask(
      environment_->dispatcher(), [this] { SendNextObject(); },
      kFakePageStorageDelay);
}

void FakePageStorage::GetCommitContents(const Commit& commit,
                                        std::string min_key,
                                        fit::function<bool(Entry)> on_next,
                                        fit::function<void(Status)> on_done) {
  FakeJournalDelegate* journal = journals_[commit.GetId()].get();
  if (!journal) {
    on_done(Status::NOT_FOUND);
    return;
  }

  for (auto it = journal->GetData().lower_bound(min_key);
       it != journal->GetData().end(); ++it) {
    if (!on_next(it->second)) {
      break;
    }
  }
  on_done(Status::OK);
}

void FakePageStorage::GetEntryFromCommit(
    const Commit& commit, std::string key,
    fit::function<void(Status, Entry)> callback) {
  FakeJournalDelegate* journal = journals_[commit.GetId()].get();
  if (!journal) {
    callback(Status::NOT_FOUND, Entry());
    return;
  }
  const fake::FakeJournalDelegate::Data& data = journal->GetData();
  auto it = data.find(key);
  if (it == data.end()) {
    callback(Status::NOT_FOUND, Entry());
    return;
  }
  callback(Status::OK, it->second);
}

const std::map<std::string, std::unique_ptr<FakeJournalDelegate>>&
FakePageStorage::GetJournals() const {
  return journals_;
}

const std::map<ObjectIdentifier, std::string>& FakePageStorage::GetObjects()
    const {
  return objects_;
}

ObjectDigest FakePageStorage::FakeDigest(fxl::StringView value) const {
  // Builds a fake ObjectDigest by computing the hash of |value|, and prefixes
  // it with 0xFACEFEED to intentionally make it longer than real object
  // digests, start with a 1 bit, and easy to spot in logs. This is incompatible
  // with real object digests, but is enough for a fake because all clients of
  // the fake should treat object digests as opaque blobs.
  return ObjectDigest(fxl::Concatenate(
      {"\xFA\xCE\xFE\xED", encryption::SHA256WithLengthHash(value)}));
}

void FakePageStorage::SendNextObject() {
  auto rng = environment_->random()->NewBitGenerator<uint64_t>();
  std::uniform_int_distribution<size_t> distribution(
      0u, object_requests_.size() - 1);
  auto it = object_requests_.begin() + distribution(rng);
  auto closure = std::move(*it);
  object_requests_.erase(it);
  closure();
}

void FakePageStorage::DeleteObjectFromLocal(
    const ObjectIdentifier& object_identifier) {
  objects_.erase(object_identifier);
}

void FakePageStorage::SetDropCommitNotifications(bool drop) {
  drop_commit_notifications_ = drop;
}

}  // namespace fake
}  // namespace storage