// Copyright 2016 The Chromium 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 "services/catalog/reader.h"

#include "base/bind.h"
#include "base/files/file_enumerator.h"
#include "base/files/file_util.h"
#include "base/json/json_file_value_serializer.h"
#include "base/json/json_reader.h"
#include "base/memory/ptr_util.h"
#include "base/path_service.h"
#include "base/task_runner_util.h"
#include "base/threading/thread_task_runner_handle.h"
#include "services/catalog/constants.h"
#include "services/catalog/entry.h"
#include "services/catalog/manifest_provider.h"
#include "services/catalog/public/interfaces/constants.mojom.h"
#include "services/service_manager/public/interfaces/constants.mojom.h"

namespace catalog {
namespace {

base::FilePath GetManifestPath(const base::FilePath& package_dir,
                               const std::string& name,
                               const std::string& package_name_override) {
  // TODO(beng): think more about how this should be done for exe targets.
  std::string package_name =
      package_name_override.empty() ? name : package_name_override;
  return package_dir.AppendASCII(kPackagesDirName).AppendASCII(
      package_name + "/manifest.json");
}

base::FilePath GetExecutablePath(const base::FilePath& package_dir,
                                 const std::string& name) {
  return package_dir.AppendASCII(name + "/" + name + ".library");
}

std::unique_ptr<Entry> ProcessManifest(
    std::unique_ptr<base::Value> manifest_root,
    const base::FilePath& package_dir) {
  // Manifest was malformed or did not exist.
  if (!manifest_root)
    return nullptr;

  const base::DictionaryValue* dictionary = nullptr;
  if (!manifest_root->GetAsDictionary(&dictionary))
    return nullptr;

  std::unique_ptr<Entry> entry = Entry::Deserialize(*dictionary);
  if (!entry)
    return nullptr;
  entry->set_path(GetExecutablePath(package_dir, entry->name()));
  return entry;
}

std::unique_ptr<Entry> CreateEntryForManifestAt(
    const base::FilePath& manifest_path,
    const base::FilePath& package_dir) {
  JSONFileValueDeserializer deserializer(manifest_path);
  int error = 0;
  std::string message;

  // TODO(beng): probably want to do more detailed error checking. This should
  //             be done when figuring out if to unblock connection completion.
  return ProcessManifest(deserializer.Deserialize(&error, &message),
                         package_dir);
}

void ScanDir(
    const base::FilePath& package_dir,
    const Reader::ReadManifestCallback& read_manifest_callback,
    scoped_refptr<base::SingleThreadTaskRunner> original_thread_task_runner,
    const base::Closure& read_complete_closure) {
  base::FileEnumerator enumerator(package_dir, false,
                                  base::FileEnumerator::DIRECTORIES);
  while (1) {
    base::FilePath path = enumerator.Next();
    if (path.empty())
      break;
    base::FilePath manifest_path = path.AppendASCII("manifest.json");
    std::unique_ptr<Entry> entry =
        CreateEntryForManifestAt(manifest_path, package_dir);
    if (!entry)
      continue;

    // Skip over subdirs that contain only manifests, they're artifacts of the
    // build (e.g. for applications that are packaged into others) and are not
    // valid standalone packages.
    base::FilePath package_path = GetExecutablePath(package_dir, entry->name());
    if (entry->name() != service_manager::mojom::kServiceName &&
        entry->name() != catalog::mojom::kServiceName &&
        !base::PathExists(package_path)) {
      continue;
    }

    original_thread_task_runner->PostTask(
        FROM_HERE,
        base::Bind(read_manifest_callback, base::Passed(&entry)));
  }

  original_thread_task_runner->PostTask(FROM_HERE, read_complete_closure);
}

std::unique_ptr<Entry> ReadManifest(
    const base::FilePath& package_dir,
    const std::string& mojo_name,
    const std::string& package_name_override,
    const base::FilePath& manifest_path_override) {
  base::FilePath manifest_path;
  if (manifest_path_override.empty()) {
    manifest_path =
        GetManifestPath(package_dir, mojo_name, package_name_override);
  } else {
    manifest_path = manifest_path_override;
  }

  std::unique_ptr<Entry> entry = CreateEntryForManifestAt(manifest_path,
                                                          package_dir);
  if (!entry) {
    entry.reset(new Entry(mojo_name));
    entry->set_path(GetExecutablePath(
        package_dir.AppendASCII(kPackagesDirName), mojo_name));
  }
  return entry;
}

void AddEntryToCache(EntryCache* cache, std::unique_ptr<Entry> entry) {
  std::vector<std::unique_ptr<Entry>> children = entry->TakeChildren();
  for (auto& child : children)
    AddEntryToCache(cache, std::move(child));
  (*cache)[entry->name()] = std::move(entry);
}

void DoNothing(service_manager::mojom::ResolveResultPtr) {}

}  // namespace

// A sequenced task runner is used to guarantee requests are serviced in the
// order requested. To do otherwise means we may run callbacks in an
// unpredictable order, leading to flake.
Reader::Reader(base::SequencedWorkerPool* worker_pool,
               ManifestProvider* manifest_provider)
    : Reader(manifest_provider) {
  file_task_runner_ = worker_pool->GetSequencedTaskRunnerWithShutdownBehavior(
      base::SequencedWorkerPool::GetSequenceToken(),
      base::SequencedWorkerPool::SKIP_ON_SHUTDOWN);
}

Reader::Reader(base::SingleThreadTaskRunner* task_runner,
               ManifestProvider* manifest_provider)
    : Reader(manifest_provider) {
  file_task_runner_ = task_runner;
}

Reader::~Reader() {}

void Reader::Read(const base::FilePath& package_dir,
                  EntryCache* cache,
                  const base::Closure& read_complete_closure) {
  file_task_runner_->PostTask(
      FROM_HERE,
      base::Bind(&ScanDir, package_dir,
                 base::Bind(&Reader::OnReadManifest, weak_factory_.GetWeakPtr(),
                            cache, base::Bind(&DoNothing)),
                 base::ThreadTaskRunnerHandle::Get(),
                 read_complete_closure));
}

void Reader::CreateEntryForName(
    const std::string& mojo_name,
    EntryCache* cache,
    const CreateEntryForNameCallback& entry_created_callback) {
  if (manifest_provider_) {
    std::unique_ptr<base::Value> manifest_root =
        manifest_provider_->GetManifest(mojo_name);
    if (manifest_root) {
      base::PostTaskAndReplyWithResult(
          file_task_runner_.get(), FROM_HERE,
          base::Bind(&ProcessManifest, base::Passed(&manifest_root),
                     system_package_dir_),
          base::Bind(&Reader::OnReadManifest, weak_factory_.GetWeakPtr(), cache,
                     entry_created_callback));
      return;
    }
  }

  base::FilePath manifest_path_override;
  {
    auto override_iter = manifest_path_overrides_.find(mojo_name);
    if (override_iter != manifest_path_overrides_.end())
      manifest_path_override = override_iter->second;
  }

  std::string package_name_override;
  {
    auto override_iter = package_name_overrides_.find(mojo_name);
    if (override_iter != package_name_overrides_.end())
      package_name_override = override_iter->second;
  }
  base::PostTaskAndReplyWithResult(
      file_task_runner_.get(), FROM_HERE,
      base::Bind(&ReadManifest, system_package_dir_, mojo_name,
                 package_name_override, manifest_path_override),
      base::Bind(&Reader::OnReadManifest, weak_factory_.GetWeakPtr(), cache,
                  entry_created_callback));
}

void Reader::OverridePackageName(const std::string& service_name,
                                 const std::string& package_name) {
  package_name_overrides_.insert(std::make_pair(service_name, package_name));
}

void Reader::OverrideManifestPath(const std::string& service_name,
                                  const base::FilePath& path) {
  manifest_path_overrides_.insert(std::make_pair(service_name, path));
}

Reader::Reader(ManifestProvider* manifest_provider)
    : manifest_provider_(manifest_provider), weak_factory_(this) {
  PathService::Get(base::DIR_MODULE, &system_package_dir_);
}

void Reader::OnReadManifest(
    EntryCache* cache,
    const CreateEntryForNameCallback& entry_created_callback,
    std::unique_ptr<Entry> entry) {
  if (!entry)
    return;
  service_manager::mojom::ResolveResultPtr result =
      service_manager::mojom::ResolveResult::From(*entry);
  AddEntryToCache(cache, std::move(entry));
  entry_created_callback.Run(std::move(result));
}

}  // namespace catalog