// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "chromecast/base/device_capabilities_impl.h"

#include <stddef.h>

#include <utility>

#include "base/containers/contains.h"
#include "base/functional/bind.h"
#include "base/functional/callback_helpers.h"
#include "base/json/json_writer.h"
#include "base/logging.h"
#include "base/memory/ptr_util.h"
#include "base/strings/string_util.h"
#include "base/task/single_thread_task_runner.h"
#include "base/values.h"

namespace chromecast {

namespace {

const char kPathSeparator = '.';

// Determines if a key passed to Register() is valid. No path separators can
// be present in the key and it must not be empty.
bool IsValidRegisterKey(const std::string& key) {
  return !key.empty() && !base::Contains(key, kPathSeparator);
}

// Determines if a path is valid. This is true if there are no empty keys
// anywhere in the path (ex: .foo, foo., foo..bar are all invalid).
bool IsValidPath(const std::string& path) {
  return !path.empty() && *path.begin() != kPathSeparator &&
         *path.rbegin() != kPathSeparator &&
         path.find("..") == std::string::npos;
}

// Given a path, gets the first key present in the path (ex: for path "foo.bar"
// return "foo").
std::string GetFirstKey(const std::string& path) {
  std::size_t length_to_first_separator = path.find(kPathSeparator);
  return (length_to_first_separator == std::string::npos)
             ? path
             : path.substr(0, length_to_first_separator);
}

}  // namespace

// static Default Capability Keys
const char DeviceCapabilities::kKeyAssistantSupported[] = "assistant_supported";
const char DeviceCapabilities::kKeyBluetoothSupported[] = "bluetooth_supported";
const char DeviceCapabilities::kKeyDisplaySupported[] = "display_supported";
const char DeviceCapabilities::kKeyHiResAudioSupported[] =
    "hi_res_audio_supported";

// static
std::unique_ptr<DeviceCapabilities> DeviceCapabilities::Create() {
  return base::WrapUnique(new DeviceCapabilitiesImpl);
}

// static
std::unique_ptr<DeviceCapabilities> DeviceCapabilities::CreateForTesting() {
  DeviceCapabilities* capabilities = new DeviceCapabilitiesImpl;
  capabilities->SetCapability(kKeyBluetoothSupported, base::Value(false));
  capabilities->SetCapability(kKeyDisplaySupported, base::Value(true));
  capabilities->SetCapability(kKeyHiResAudioSupported, base::Value(false));
  capabilities->SetCapability(kKeyAssistantSupported, base::Value(true));
  return base::WrapUnique(capabilities);
}

scoped_refptr<DeviceCapabilities::Data> DeviceCapabilities::CreateData() {
  return base::WrapRefCounted(new Data);
}

scoped_refptr<DeviceCapabilities::Data> DeviceCapabilities::CreateData(
    base::Value::Dict dictionary) {
  return base::WrapRefCounted(new Data(std::move(dictionary)));
}

DeviceCapabilities::Validator::Validator(DeviceCapabilities* capabilities)
    : capabilities_(capabilities) {
  DCHECK(capabilities);
}

void DeviceCapabilities::Validator::SetPublicValidatedValue(
    const std::string& path,
    base::Value new_value) const {
  capabilities_->SetPublicValidatedValue(path, std::move(new_value));
}

void DeviceCapabilities::Validator::SetPrivateValidatedValue(
    const std::string& path,
    base::Value new_value) const {
  capabilities_->SetPrivateValidatedValue(path, std::move(new_value));
}

DeviceCapabilities::Data::Data() : Data(base::Value::Dict()) {}

DeviceCapabilities::Data::Data(base::Value::Dict dictionary)
    : dictionary_(std::move(dictionary)),
      json_string_(base::WriteJson(dictionary_).value_or("")) {}

DeviceCapabilitiesImpl::Data::~Data() = default;

DeviceCapabilitiesImpl::ValidatorInfo::ValidatorInfo(Validator* validator)
    : validator_(validator),
      task_runner_(base::SingleThreadTaskRunner::GetCurrentDefault()) {
  DCHECK(validator_);
  DCHECK(task_runner_.get());
}

DeviceCapabilitiesImpl::ValidatorInfo::~ValidatorInfo() {
  // Check that ValidatorInfo is being destroyed on the same thread that it was
  // constructed on.
  DCHECK(task_runner_->BelongsToCurrentThread());
}

void DeviceCapabilitiesImpl::ValidatorInfo::Validate(
    const std::string& path,
    base::Value proposed_value) const {
  // Check that we are running Validate on the same thread that ValidatorInfo
  // was constructed on.
  DCHECK(task_runner_->BelongsToCurrentThread());
  validator_->Validate(path, std::move(proposed_value));
}

DeviceCapabilitiesImpl::DeviceCapabilitiesImpl()
    : all_data_(CreateData()),
      public_data_(CreateData()),
      task_runner_for_writes_(
          base::SingleThreadTaskRunner::GetCurrentDefault()),
      observer_list_(new base::ObserverListThreadSafe<Observer>) {
  DCHECK(task_runner_for_writes_.get());
}

DeviceCapabilitiesImpl::~DeviceCapabilitiesImpl() {
  // Make sure that any registered Validators have unregistered at this point
  DCHECK(validator_map_.empty())
      << "Some validators weren't properly unregistered: " << [this] {
           std::vector<std::string> keys;
           for (const auto& pair : validator_map_) {
             keys.push_back(pair.first);
           }
           return base::JoinString(keys, ", ");
         }();
  // Make sure that all observers have been removed at this point
  observer_list_->AssertEmpty();
}

void DeviceCapabilitiesImpl::Register(const std::string& key,
                                      Validator* validator) {
  DCHECK(IsValidRegisterKey(key));
  DCHECK(validator);

  base::AutoLock auto_lock(validation_lock_);
  // Check that a validator has not already been registered for this key
  DCHECK_EQ(0u, validator_map_.count(key));
  validator_map_[key] = std::make_unique<ValidatorInfo>(validator);
}

void DeviceCapabilitiesImpl::Unregister(const std::string& key,
                                        const Validator* validator) {
  base::AutoLock auto_lock(validation_lock_);
  auto validator_it = validator_map_.find(key);
  CHECK(validator_it != validator_map_.end());
  // Check that validator being unregistered matches the original for |key|.
  // This prevents managers from accidentally unregistering incorrect
  // validators.
  DCHECK_EQ(validator, validator_it->second->validator());
  // Check that validator is unregistering on same thread that it was
  // registered on
  DCHECK(validator_it->second->task_runner()->BelongsToCurrentThread());
  validator_map_.erase(validator_it);
}

DeviceCapabilities::Validator* DeviceCapabilitiesImpl::GetValidator(
    const std::string& key) const {
  base::AutoLock auto_lock(validation_lock_);
  auto validator_it = validator_map_.find(key);
  return validator_it == validator_map_.end()
             ? nullptr
             : validator_it->second->validator();
}

bool DeviceCapabilitiesImpl::BluetoothSupported() const {
  scoped_refptr<Data> data_ref = GetAllData();
  auto bluetooth_supported =
      data_ref->dictionary().FindBool(kKeyBluetoothSupported);
  DCHECK(bluetooth_supported);
  return *bluetooth_supported;
}

bool DeviceCapabilitiesImpl::DisplaySupported() const {
  scoped_refptr<Data> data_ref = GetAllData();
  auto display_supported =
      data_ref->dictionary().FindBool(kKeyDisplaySupported);
  DCHECK(display_supported);
  return *display_supported;
}

bool DeviceCapabilitiesImpl::HiResAudioSupported() const {
  scoped_refptr<Data> data_ref = GetAllData();
  auto hi_res_audio_supported =
      data_ref->dictionary().FindBool(kKeyHiResAudioSupported);
  DCHECK(hi_res_audio_supported);
  return *hi_res_audio_supported;
}

bool DeviceCapabilitiesImpl::AssistantSupported() const {
  scoped_refptr<Data> data_ref = GetAllData();
  auto assistant_supported =
      data_ref->dictionary().FindBool(kKeyAssistantSupported);
  DCHECK(assistant_supported);
  return *assistant_supported;
}

base::Value DeviceCapabilitiesImpl::GetCapability(
    const std::string& path) const {
  scoped_refptr<Data> data_ref = GetAllData();
  const base::Value* value = data_ref->dictionary().FindByDottedPath(path);
  return value ? value->Clone() : base::Value();
}

scoped_refptr<DeviceCapabilities::Data> DeviceCapabilitiesImpl::GetAllData()
    const {
  // Need to acquire lock here when copy constructing all_data_ otherwise we
  // could concurrently be writing to scoped_refptr in SetPublicValidatedValue()
  // or SetPrivateValidatedValue(), which could cause a bad scoped_refptr read.
  base::AutoLock auto_lock(data_lock_);
  return all_data_;
}

scoped_refptr<DeviceCapabilities::Data> DeviceCapabilitiesImpl::GetPublicData()
    const {
  // Need to acquire lock here when copy constructing public_data_ otherwise we
  // could concurrently be writing to scoped_refptr in SetPublicValidatedValue()
  // or SetPrivateValidatedValue(), which could cause a bad scoped_refptr read.
  base::AutoLock auto_lock(data_lock_);
  return public_data_;
}

void DeviceCapabilitiesImpl::SetCapability(const std::string& path,
                                           base::Value proposed_value) {
  if (!IsValidPath(path)) {
    LOG(DFATAL) << "Invalid capability path encountered for SetCapability()";
    return;
  }

  {
    base::AutoLock auto_lock(validation_lock_);
    // Check for Validator registered under first key per the Register()
    // interface.
    auto validator_it = validator_map_.find(GetFirstKey(path));
    if (validator_it != validator_map_.end()) {
      // We do not want to post a task directly for the Validator's Validate()
      // method here because if another thread is in the middle of unregistering
      // that Validator, there will be an outstanding call to Validate() that
      // occurs after it has unregistered. Since ValidatorInfo gets destroyed
      // in Unregister() on same thread that validation should run on, we can
      // post a task to the Validator's thread with weak_ptr. This way, if the
      // Validator gets unregistered, the call to Validate will get skipped.
      validator_it->second->task_runner()->PostTask(
          FROM_HERE, base::BindOnce(&ValidatorInfo::Validate,
                                    validator_it->second->AsWeakPtr(), path,
                                    std::move(proposed_value)));
      return;
    }
  }
  // Since we are done checking for a registered Validator at this point, we
  // can release the lock. All further member access will be for capabilities.
  // By default, a capability without a validator will be public.
  SetPublicValidatedValue(path, std::move(proposed_value));
}

void DeviceCapabilitiesImpl::MergeDictionary(const base::Value::Dict& dict) {
  for (const auto [key, value] : dict) {
    SetCapability(key, value.Clone());
  }
}

void DeviceCapabilitiesImpl::AddCapabilitiesObserver(Observer* observer) {
  DCHECK(observer);
  observer_list_->AddObserver(observer);
}

void DeviceCapabilitiesImpl::RemoveCapabilitiesObserver(Observer* observer) {
  DCHECK(observer);
  observer_list_->RemoveObserver(observer);
}

void DeviceCapabilitiesImpl::SetPublicValidatedValue(const std::string& path,
                                                     base::Value new_value) {
  // All internal writes/modifications of capabilities must occur on same
  // thread to avoid race conditions.
  if (!task_runner_for_writes_->BelongsToCurrentThread()) {
    task_runner_for_writes_->PostTask(
        FROM_HERE,
        base::BindOnce(&DeviceCapabilitiesImpl::SetPublicValidatedValue,
                       base::Unretained(this), path, std::move(new_value)));
    return;
  }

  DCHECK(IsValidPath(path));

  // If the capability exists, it must be public (present in all_data_ and
  // public_data_). We cannot change the privacy of an already existing
  // capability.
  bool is_private = all_data_->dictionary().Find(path) &&
                    !public_data_->dictionary().Find(path);
  if (is_private) {
    NOTREACHED() << "Cannot make a private capability '" << path << "' public.";
  }

  // We don't need to acquire lock here when reading public_data_ because we
  // know that all writes to public_data_ must occur serially on thread that
  // we're on.
  const base::Value* cur_value =
      public_data_->dictionary().FindByDottedPath(path);
  bool capability_unchanged = cur_value && *cur_value == new_value;
  if (capability_unchanged) {
    DVLOG(1) << "Ignoring unchanged public capability: " << path;
    return;
  }

  // In this sequence, we create deep copies for both dictionaries, modify the
  // copies, and then do a pointer swap. We do this to have minimal time spent
  // in the data_lock_. If we were to lock and modify the capabilities
  // dictionary directly, there may be expensive writes that block other
  // threads.
  scoped_refptr<Data> new_public_data = GenerateDataWithNewValue(
      public_data_->dictionary(), path, new_value.Clone());
  scoped_refptr<Data> new_data = GenerateDataWithNewValue(
      all_data_->dictionary(), path, std::move(new_value));

  {
    base::AutoLock auto_lock(data_lock_);
    // Using swap instead of assignment operator here because it's a little
    // faster. Avoids an extra call to AddRef()/Release().
    public_data_.swap(new_public_data);
    all_data_.swap(new_data);
  }

  // Even though ObserverListThreadSafe notifications are always asynchronous
  // (posts task even if to same thread), no locks should be held at this point
  // in the code. This is just to be safe that no deadlocks occur if Observers
  // call DeviceCapabilities methods in OnCapabilitiesChanged().
  observer_list_->Notify(FROM_HERE, &Observer::OnCapabilitiesChanged, path);
}

void DeviceCapabilitiesImpl::SetPrivateValidatedValue(const std::string& path,
                                                      base::Value new_value) {
  // All internal writes/modifications of capabilities must occur on same
  // thread to avoid race conditions.
  if (!task_runner_for_writes_->BelongsToCurrentThread()) {
    task_runner_for_writes_->PostTask(
        FROM_HERE,
        base::BindOnce(&DeviceCapabilitiesImpl::SetPrivateValidatedValue,
                       base::Unretained(this), path, std::move(new_value)));
    return;
  }

  DCHECK(IsValidPath(path));

  // If the capability exists, it must be private (present in all_data_ only).
  // We cannot change the privacy of an already existing capability.
  const auto* is_public = public_data_->dictionary().Find(path);
  if (is_public) {
    NOTREACHED() << "Cannot make a public capability '" << path << "' private.";
  }

  // We don't need to acquire lock here when reading all_data_ because we know
  // that all writes to all_data_ must occur serially on thread that we're on.
  const base::Value* cur_value = all_data_->dictionary().FindByDottedPath(path);
  bool capability_unchanged = cur_value && *cur_value == new_value;
  if (capability_unchanged) {
    DVLOG(1) << "Ignoring unchanged capability: " << path;
    return;
  }

  // In this sequence, we create a deep copy, modify the deep copy, and then
  // do a pointer swap. We do this to have minimal time spent in the
  // data_lock_. If we were to lock and modify the capabilities
  // dictionary directly, there may be expensive writes that block other
  // threads.
  scoped_refptr<Data> new_data = GenerateDataWithNewValue(
      all_data_->dictionary(), path, std::move(new_value));

  {
    base::AutoLock auto_lock(data_lock_);
    // Using swap instead of assignment operator here because it's a little
    // faster. Avoids an extra call to AddRef()/Release().
    all_data_.swap(new_data);
  }

  // Even though ObserverListThreadSafe notifications are always asynchronous
  // (posts task even if to same thread), no locks should be held at this point
  // in the code. This is just to be safe that no deadlocks occur if Observers
  // call DeviceCapabilities methods in OnCapabilitiesChanged().
  observer_list_->Notify(FROM_HERE, &Observer::OnCapabilitiesChanged, path);
}

scoped_refptr<DeviceCapabilities::Data>
DeviceCapabilitiesImpl::GenerateDataWithNewValue(const base::Value::Dict& dict,
                                                 const std::string& path,
                                                 base::Value new_value) {
  base::Value::Dict dict_deep_copy(dict.Clone());
  dict_deep_copy.SetByDottedPath(path, std::move(new_value));
  return CreateData(std::move(dict_deep_copy));
}

}  // namespace chromecast