// Copyright (c) 2013 The Chromium OS 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 "lorgnette/manager.h"

#include <inttypes.h>
#include <setjmp.h>

#include <algorithm>
#include <utility>

#include <base/bits.h>
#include <base/compiler_specific.h>
#include <base/files/file.h>
#include <base/logging.h>
#include <base/strings/string_number_conversions.h>
#include <base/strings/stringprintf.h>
#include <base/strings/string_util.h>
#include <chromeos/dbus/service_constants.h>
#include <libusb.h>
#include <png.h>
#include <re2/re2.h>
#include <uuid/uuid.h>

#include "lorgnette/daemon.h"
#include "lorgnette/enums.h"
#include "lorgnette/epson_probe.h"
#include "lorgnette/firewall_manager.h"
#include "lorgnette/guess_source.h"
#include "lorgnette/ippusb_device.h"

static const char* kDbusDomain = brillo::errors::dbus::kDomain;
using std::string;

namespace lorgnette {

namespace {

constexpr base::TimeDelta kDefaultProgressSignalInterval =
    base::TimeDelta::FromMilliseconds(20);
constexpr size_t kUUIDStringLength = 37;

// The maximum memory size allowed to be allocated for an image.  At the current
// maximum resolution and color depth that the frontend will request, this gives
// 388 sq in, which is more than enough for an 11x17 ledger page or an 8.5x40
// ADF scan.  This limit will need to be reconsidered if we want to enable 1200
// dpi scanning.
constexpr size_t kMaximumImageSize = 400 * 1024 * 1024;

// The default libpng config limits images to 1 million pixels in width and
// height.  Update these constants to match if you add a call to
// png_set_user_limits that changes the defaults.
constexpr size_t kMaximiumImageWidth = 1000000;
constexpr size_t kMaximiumImageHeight = 1000000;

std::string SerializeError(const brillo::ErrorPtr& error_ptr) {
  std::string message;
  const brillo::Error* error = error_ptr.get();
  while (error) {
    // Format error string as "domain/code:message".
    if (!message.empty())
      message += ';';
    message +=
        error->GetDomain() + '/' + error->GetCode() + ':' + error->GetMessage();
    error = error->GetInnerError();
  }
  return message;
}

// Checks that the scan parameters in |params| are supported by our scanning
// and PNG conversion logic.
bool ValidateParams(brillo::ErrorPtr* error, const ScanParameters& params) {
  if (params.depth != 1 && params.depth != 8 && params.depth != 16) {
    brillo::Error::AddToPrintf(error, FROM_HERE, kDbusDomain,
                               kManagerServiceError,
                               "Invalid scan bit depth %d", params.depth);
    return false;
  }

  if (params.depth == 1 && params.format != kGrayscale) {
    brillo::Error::AddTo(error, FROM_HERE, kDbusDomain, kManagerServiceError,
                         "Cannot have bit depth of 1 with non-grayscale scan");
    return false;
  }

  if (params.lines < 0) {
    brillo::Error::AddTo(
        error, FROM_HERE, kDbusDomain, kManagerServiceError,
        "Cannot handle scanning of files with unknown lengths");
    return false;
  }

  if (params.lines == 0) {
    brillo::Error::AddTo(error, FROM_HERE, kDbusDomain, kManagerServiceError,
                         "Cannot scan an image with 0 lines");
    return false;
  }

  // PNG IHDR allows a max height of 2^31, but libpng imposes a default limit of
  // 1 million.  We'll impose the same limit here, since that represents 800+
  // inches at 1200 dpi.
  if (params.lines > kMaximiumImageHeight) {
    brillo::Error::AddToPrintf(
        error, FROM_HERE, kDbusDomain, kManagerServiceError,
        "Cannot scan an image with invalid height (%d)", params.lines);
    return false;
  }

  // PNG IHDR allows a max width of 2^31 and requires a non-zero width.
  // We follow the default libpng limit of 1 million rather than the true max
  // because no real scanner can produce an image that wide.
  if (params.pixels_per_line <= 0 ||
      params.pixels_per_line > kMaximiumImageWidth) {
    brillo::Error::AddToPrintf(
        error, FROM_HERE, kDbusDomain, kManagerServiceError,
        "Cannot scan an image with invalid width (%d)", params.pixels_per_line);
    return false;
  }

  // Make sure bytes_per_line is large enough to be plausible for
  // pixels_per_line.  It is allowed to be bigger in case the device pads up to
  // a multiple of some internal size.
  size_t colors_per_pixel = params.format == kRGB ? 3 : 1;
  uint64_t min_bytes_per_line =
      (params.pixels_per_line * params.depth * colors_per_pixel + 7) / 8;
  if (params.bytes_per_line < min_bytes_per_line) {
    brillo::Error::AddToPrintf(
        error, FROM_HERE, kDbusDomain, kManagerServiceError,
        "bytes_per_line (%d) is too small to hold %d pixels with depth %d",
        params.bytes_per_line, params.pixels_per_line, params.depth);
    return false;
  }

  uint64_t needed = params.lines * params.bytes_per_line;
  if (needed > kMaximumImageSize) {
    brillo::Error::AddToPrintf(
        error, FROM_HERE, kDbusDomain, kManagerServiceError,
        "Needed scan buffer size of %" PRIu64 " is too large", needed);
    return false;
  }

  return true;
}

// Wrapper for libpng functions that handles converting the setjmp based
// exceptions into safe, usable error codes. It is used like so:
//   brillo::ErrorPtr* error = [...];
//   png_struct* png = [...];
//   png_info* info = [...];
//   int result = LibpngErrorWrap(error, png_write_info, png, info);
template <typename Fn, typename... Args>
int LibpngErrorWrap(brillo::ErrorPtr* error,
                    const Fn& libpng_function,
                    png_struct* png,
                    Args... args) {
  jmp_buf* buf = png_set_longjmp_fn(png, longjmp, sizeof(jmp_buf));
  if (!buf) {
    brillo::Error::AddTo(error, FROM_HERE, kDbusDomain, kManagerServiceError,
                         "Failed to initialize jmp_buf");
    return -1;
  }
  int result = setjmp(*buf);
  if (result != 0) {
    // |libpng_function| failed and longjmp'ed here.
    return result;
  }
  libpng_function(png, args...);
  // Disable longjmp so that we don't inadvertently longjmp here from another
  // libpng function.
  png_set_longjmp_fn(png, nullptr, sizeof(jmp_buf));
  return 0;
}

// Initializes libpng, sets up |png_out| and |info_out| to be used for writing
// PNG image data to |out_file|, and writes the PNG header to |out_file|.
// Resolution should be provided with units of pixels per inch.
bool SetupPngHeader(brillo::ErrorPtr* error,
                    const ScanParameters& params,
                    base::Optional<int> resolution,
                    png_struct** png_out,
                    png_info** info_out,
                    const base::ScopedFILE& out_file) {
  if (!png_out || !info_out) {
    return false;
  }

  png_struct* png =
      png_create_write_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);
  if (!png) {
    brillo::Error::AddTo(error, FROM_HERE, kDbusDomain, kManagerServiceError,
                         "Could not initialize PNG write struct");
    return false;
  }

  png_info* info = png_create_info_struct(png);
  if (!info) {
    brillo::Error::AddTo(error, FROM_HERE, kDbusDomain, kManagerServiceError,
                         "Could not initialize PNG info struct");
    png_destroy_write_struct(&png, nullptr);
    return false;
  }

  int width = params.pixels_per_line;
  int height = params.lines;
  int color_type =
      params.format == kGrayscale ? PNG_COLOR_TYPE_GRAY : PNG_COLOR_TYPE_RGB;
  png_set_IHDR(png, info, width, height, params.depth, color_type,
               PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE,
               PNG_FILTER_TYPE_BASE);

  if (resolution.has_value()) {
    constexpr double inches_per_meter = 39.3701;
    uint32_t png_resolution = resolution.value() * inches_per_meter;
    png_set_pHYs(png, info, png_resolution, png_resolution,
                 PNG_RESOLUTION_METER);
  }

  png_init_io(png, out_file.get());
  int ret = LibpngErrorWrap(error, png_write_info, png, info);
  if (ret != 0) {
    brillo::Error::AddToPrintf(error, FROM_HERE, kDbusDomain,
                               kManagerServiceError,
                               "Writing PNG info failed with result %d", ret);
    png_destroy_write_struct(&png, &info);
    return false;
  }

  // Setup output transformations within libpng so that image data from SANE
  // can be converted to the correct endianness or values for PNG data.
  switch (params.depth) {
    case 1:
      // Inverts black and white pixels, since monocolor data from SANE has an
      // inverted representation when compared to PNG.
      png_set_invert_mono(png);
      break;
    case 16:
      // Transpose byte order, since PNG is big-endian and SANE is endian-native
      // i.e. little-endian.
      png_set_swap(png);
      break;
  }

  *png_out = png;
  *info_out = info;
  return true;
}

// Create a ScopedFILE which refers to a copy of |fd|.
base::ScopedFILE SetupOutputFile(brillo::ErrorPtr* error,
                                 const base::ScopedFD& fd) {
  base::ScopedFILE file;
  // Dup fd since fdclose() on file will also close the contained fd.
  base::ScopedFD fd_copy(dup(fd.get()));
  if (fd_copy.get() < 0) {
    brillo::Error::AddTo(error, FROM_HERE, kDbusDomain, kManagerServiceError,
                         "Could not duplicate output FD");
    return file;
  }

  file = base::ScopedFILE(fdopen(fd_copy.get(), "w"));
  if (!file) {
    brillo::Error::AddTo(error, FROM_HERE, kDbusDomain, kManagerServiceError,
                         "Failed to open outfd");
    return file;
  }
  // Release |fd_copy| since it is owned by |file| now.
  (void)fd_copy.release();
  return file;
}

// Uses |firewall_manager| to request port access if |device_name| corresponds
// to a SANE backend that needs the access when connecting to a device. The
// caller should keep the returned object alive as long as port access is
// needed.
base::Optional<PortToken> RequestPortAccessIfNeeded(
    const std::string& device_name, FirewallManager* firewall_manager) {
  if (BackendFromDeviceName(device_name) != kPixma)
    return base::nullopt;

  return firewall_manager->RequestPixmaPortAccess();
}

std::string GenerateUUID() {
  uuid_t uuid_bytes;
  uuid_generate_random(uuid_bytes);
  std::string uuid(kUUIDStringLength, '\0');
  uuid_unparse(uuid_bytes, &uuid[0]);
  // Remove the null terminator from the string.
  uuid.resize(kUUIDStringLength - 1);
  return uuid;
}

}  // namespace

namespace impl {

ColorMode ColorModeFromSaneString(const std::string& mode) {
  if (mode == kScanPropertyModeLineart)
    return MODE_LINEART;
  else if (mode == kScanPropertyModeGray)
    return MODE_GRAYSCALE;
  else if (mode == kScanPropertyModeColor)
    return MODE_COLOR;
  return MODE_UNSPECIFIED;
}

}  // namespace impl

const char Manager::kMetricScanRequested[] = "DocumentScan.ScanRequested";
const char Manager::kMetricScanSucceeded[] = "DocumentScan.ScanSucceeded";
const char Manager::kMetricScanFailed[] = "DocumentScan.ScanFailed";

Manager::Manager(base::Callback<void()> activity_callback,
                 std::unique_ptr<SaneClient> sane_client)
    : org::chromium::lorgnette::ManagerAdaptor(this),
      activity_callback_(activity_callback),
      metrics_library_(new MetricsLibrary),
      sane_client_(std::move(sane_client)),
      progress_signal_interval_(kDefaultProgressSignalInterval) {
  // Set signal sender to be the real D-Bus call by default.
  status_signal_sender_ = base::BindRepeating(
      [](base::WeakPtr<Manager> manager,
         const ScanStatusChangedSignal& signal) {
        if (manager) {
          manager->SendScanStatusChangedSignal(impl::SerializeProto(signal));
        }
      },
      weak_factory_.GetWeakPtr());
}

Manager::~Manager() {}

void Manager::RegisterAsync(
    brillo::dbus_utils::ExportedObjectManager* object_manager,
    brillo::dbus_utils::AsyncEventSequencer* sequencer) {
  CHECK(!dbus_object_) << "Already registered";
  scoped_refptr<dbus::Bus> bus =
      object_manager ? object_manager->GetBus() : nullptr;
  dbus_object_.reset(new brillo::dbus_utils::DBusObject(
      object_manager, bus, dbus::ObjectPath(kManagerServicePath)));
  RegisterWithDBusObject(dbus_object_.get());
  dbus_object_->RegisterAsync(
      sequencer->GetHandler("Manager.RegisterAsync() failed.", true));
  firewall_manager_.reset(new FirewallManager(""));
  firewall_manager_->Init(bus);
}

bool Manager::ListScanners(brillo::ErrorPtr* error,
                           std::vector<uint8_t>* scanner_list_out) {
  LOG(INFO) << "Starting ListScanners()";
  if (!sane_client_) {
    brillo::Error::AddTo(error, FROM_HERE, kDbusDomain, kManagerServiceError,
                         "No connection to SANE");
    return false;
  }

  LOG(INFO) << "Requesting port access";
  PortToken token = firewall_manager_->RequestPixmaPortAccess();

  LOG(INFO) << "Initializing libusb";
  libusb_context* context;
  if (libusb_init(&context) != 0) {
    LOG(ERROR) << "Error initializing libusb";
    return false;
  }
  base::ScopedClosureRunner release_libusb(
      base::BindOnce([](libusb_context* ctxt) { libusb_exit(ctxt); }, context));

  std::vector<ScannerInfo> scanners;
  base::flat_set<std::string> seen_vidpid;
  base::flat_set<std::string> seen_busdev;

  LOG(INFO) << "Finding IPP-USB devices";
  std::vector<ScannerInfo> ippusb_devices = FindIppUsbDevices();
  activity_callback_.Run();
  LOG(INFO) << "Found " << ippusb_devices.size() << " possible IPP-USB devices";
  for (const ScannerInfo& scanner : ippusb_devices) {
    std::unique_ptr<SaneDevice> device =
        sane_client_->ConnectToDevice(nullptr, scanner.name());
    activity_callback_.Run();

    if (!device) {
      LOG(INFO) << "IPP-USB device doesn't support eSCL: " << scanner.name();
      continue;
    }
    scanners.push_back(scanner);
    std::string vid_str, pid_str;
    int vid = 0, pid = 0;
    if (!RE2::FullMatch(
            scanner.name(),
            "ippusb:[^:]+:[^:]+:([0-9a-fA-F]{4})_([0-9a-fA-F]{4})/.*", &vid_str,
            &pid_str)) {
      LOG(ERROR) << "Problem matching ippusb name for " << scanner.name();
      return false;
    }
    if (!(base::HexStringToInt(vid_str, &vid) &&
          base::HexStringToInt(pid_str, &pid))) {
      LOG(ERROR) << "Problems converting" << vid_str + ":" + pid_str
                 << "information into readable format";
      return false;
    }
    seen_vidpid.insert(vid_str + ":" + pid_str);

    // Next open the device to get the bus and dev info.
    // libusb_open_device_with_vid_pid() is the straightforward way to
    // access and open a device given its ScannerInfo
    // It returns the first device matching the vid:pid
    // but doesn't handle multiple devices with same vid:pid but dif bus:dev
    LOG(INFO) << "Opening libusb handle for " << vid_str;
    libusb_device_handle* dev_handle =
        libusb_open_device_with_vid_pid(context, vid, pid);
    if (dev_handle) {
      LOG(INFO) << "Opening libusb device for " << vid_str;
      libusb_device* open_dev = libusb_get_device(dev_handle);
      uint8_t bus = libusb_get_bus_number(open_dev);
      uint8_t dev = libusb_get_device_address(open_dev);
      LOG(INFO) << "Found " << vid_str << " at "
                << base::StringPrintf("%03d:%03d", bus, dev);
      seen_busdev.insert(base::StringPrintf("%03d:%03d", bus, dev));
      libusb_close(dev_handle);
    } else {
      LOG(ERROR) << "Dev handle returned nullptr";
    }
  }

  LOG(INFO) << "Getting list of SANE scanners.";
  base::Optional<std::vector<ScannerInfo>> sane_scanners =
      sane_client_->ListDevices(error);
  if (!sane_scanners.has_value()) {
    return false;
  }
  LOG(INFO) << sane_scanners.value().size() << " scanners returned from SANE";
  // Only add sane scanners that don't have ippusb connection
  RemoveDuplicateScanners(&scanners, seen_vidpid, seen_busdev,
                          sane_scanners.value());
  LOG(INFO) << scanners.size() << " scanners in list after de-duplication";

  activity_callback_.Run();

  LOG(INFO) << "Probing for network scanners";
  std::vector<ScannerInfo> probed_scanners =
      epson_probe::ProbeForScanners(firewall_manager_.get());
  activity_callback_.Run();
  for (const ScannerInfo& scanner : probed_scanners) {
    brillo::ErrorPtr error;
    std::unique_ptr<SaneDevice> device =
        sane_client_->ConnectToDevice(&error, scanner.name());
    activity_callback_.Run();
    if (device) {
      scanners.push_back(scanner);
    } else {
      LOG(INFO) << "Got reponse from Epson scanner " << scanner.name()
                << " that isn't usable for scanning.";
    }
  }
  LOG(INFO) << scanners.size() << " scanners in list after network scan";

  ListScannersResponse response;
  for (ScannerInfo& scanner : scanners) {
    *response.add_scanners() = std::move(scanner);
  }

  std::vector<uint8_t> serialized;
  serialized.resize(response.ByteSizeLong());
  response.SerializeToArray(serialized.data(), serialized.size());

  LOG(INFO) << "Returning scanner list";
  *scanner_list_out = std::move(serialized);
  return true;
}

bool Manager::GetScannerCapabilities(brillo::ErrorPtr* error,
                                     const std::string& device_name,
                                     std::vector<uint8_t>* capabilities_out) {
  LOG(INFO) << "Starting GetScannerCapabilities for device: " << device_name;
  if (!capabilities_out) {
    brillo::Error::AddTo(error, FROM_HERE, kDbusDomain, kManagerServiceError,
                         "'capabilities_out' must be non-null");
    return false;
  }

  if (!sane_client_) {
    brillo::Error::AddTo(error, FROM_HERE, kDbusDomain, kManagerServiceError,
                         "No connection to SANE");
    return false;
  }

  base::Optional<PortToken> token =
      RequestPortAccessIfNeeded(device_name, firewall_manager_.get());
  std::unique_ptr<SaneDevice> device =
      sane_client_->ConnectToDevice(error, device_name);
  if (!device)
    return false;
  LOG(INFO) << "Connected to device";

  base::Optional<ValidOptionValues> options =
      device->GetValidOptionValues(error);
  if (!options.has_value())
    return false;

  const std::vector<uint32_t> supported_resolutions = {75,  100, 150,
                                                       200, 300, 600};

  ScannerCapabilities capabilities;
  for (const uint32_t resolution : options->resolutions) {
    if (base::Contains(supported_resolutions, resolution))
      capabilities.add_resolutions(resolution);
  }

  for (const DocumentSource& source : options->sources) {
    if (source.type() != SOURCE_UNSPECIFIED) {
      *capabilities.add_sources() = source;
    } else {
      LOG(INFO) << "Ignoring source '" << source.name() << "' of unknown type.";
    }
  }

  for (const std::string& mode : options->color_modes) {
    const ColorMode color_mode = impl::ColorModeFromSaneString(mode);
    if (color_mode != MODE_UNSPECIFIED)
      capabilities.add_color_modes(color_mode);
  }

  std::vector<uint8_t> serialized;
  serialized.resize(capabilities.ByteSizeLong());
  capabilities.SerializeToArray(serialized.data(), serialized.size());

  LOG(INFO) << "Returning scanner capabilities";
  *capabilities_out = std::move(serialized);
  return true;
}

std::vector<uint8_t> Manager::StartScan(
    const std::vector<uint8_t>& start_scan_request) {
  LOG(INFO) << "Starting StartScan";
  StartScanResponse response;
  response.set_state(SCAN_STATE_FAILED);

  StartScanRequest request;
  if (!request.ParseFromArray(start_scan_request.data(),
                              start_scan_request.size())) {
    response.set_failure_reason("Failed to parse StartScanRequest");
    return impl::SerializeProto(response);
  }

  brillo::ErrorPtr error;
  std::unique_ptr<SaneDevice> device;
  if (!StartScanInternal(&error, request, &device)) {
    response.set_failure_reason(SerializeError(error));
    return impl::SerializeProto(response);
  }

  base::Optional<std::string> source_name = device->GetDocumentSource(&error);
  if (!source_name.has_value()) {
    response.set_failure_reason("Failed to get DocumentSource: " +
                                SerializeError(error));
    return impl::SerializeProto(response);
  }
  SourceType source_type = GuessSourceType(source_name.value());

  ScanJobState scan_state;
  scan_state.device_name = request.device_name();
  scan_state.device = std::move(device);

  // Set the number of pages based on the source type. If it's ADF, keep
  // scanning until an error is received.
  // Otherwise, stop scanning after one page.
  if (source_type == SOURCE_ADF_SIMPLEX || source_type == SOURCE_ADF_DUPLEX) {
    scan_state.total_pages = base::nullopt;
  } else {
    scan_state.total_pages = 1;
  }

  std::string uuid = GenerateUUID();
  {
    base::AutoLock auto_lock(active_scans_lock_);
    active_scans_.emplace(uuid, std::move(scan_state));
  }

  if (!activity_callback_.is_null())
    activity_callback_.Run();

  response.set_scan_uuid(uuid);
  response.set_state(SCAN_STATE_IN_PROGRESS);
  return impl::SerializeProto(response);
}

void Manager::GetNextImage(
    std::unique_ptr<DBusMethodResponse<std::vector<uint8_t>>> method_response,
    const std::vector<uint8_t>& get_next_image_request,
    const base::ScopedFD& out_fd) {
  GetNextImageResponse response;

  GetNextImageRequest request;
  if (!request.ParseFromArray(get_next_image_request.data(),
                              get_next_image_request.size())) {
    response.set_success(false);
    response.set_failure_reason("Failed to parse GetNextImageRequest");
    method_response->Return(impl::SerializeProto(response));
    return;
  }

  std::string uuid = request.scan_uuid();
  ScanJobState* scan_state;
  {
    base::AutoLock auto_lock(active_scans_lock_);
    if (!base::Contains(active_scans_, uuid)) {
      response.set_success(false);
      response.set_failure_reason("No scan job with UUID " + uuid + " found");
      method_response->Return(impl::SerializeProto(response));
      return;
    }
    scan_state = &active_scans_[uuid];

    if (scan_state->in_use) {
      response.set_success(false);
      response.set_failure_reason("Scan job with UUID " + uuid +
                                  " is currently busy");
      method_response->Return(impl::SerializeProto(response));
      return;
    }
    scan_state->in_use = true;
  }
  base::ScopedClosureRunner release_device(base::BindOnce(
      [](base::WeakPtr<Manager> manager, const std::string& uuid) {
        if (manager) {
          base::AutoLock(manager->active_scans_lock_);
          auto state_entry = manager->active_scans_.find(uuid);
          if (state_entry == manager->active_scans_.end())
            return;

          ScanJobState& state = state_entry->second;
          if (state.cancelled) {
            manager->SendCancelledSignal(uuid);
            manager->active_scans_.erase(uuid);
          } else {
            state.in_use = false;
          }
        }
      },
      weak_factory_.GetWeakPtr(), uuid));

  brillo::ErrorPtr error;
  base::ScopedFILE out_file = SetupOutputFile(&error, out_fd);
  if (!out_file) {
    response.set_success(false);
    response.set_failure_reason("Failed to setup output file: " +
                                SerializeError(error));
    method_response->Return(impl::SerializeProto(response));
    return;
  }

  response.set_success(true);
  method_response->Return(impl::SerializeProto(response));

  GetNextImageInternal(uuid, scan_state, std::move(out_file));
}

std::vector<uint8_t> Manager::CancelScan(
    const std::vector<uint8_t>& cancel_scan_request) {
  CancelScanResponse response;

  CancelScanRequest request;
  if (!request.ParseFromArray(cancel_scan_request.data(),
                              cancel_scan_request.size())) {
    response.set_success(false);
    response.set_failure_reason("Failed to parse CancelScanRequest");
    return impl::SerializeProto(response);
  }
  std::string uuid = request.scan_uuid();
  {
    base::AutoLock auto_lock(active_scans_lock_);
    if (!base::Contains(active_scans_, uuid)) {
      response.set_success(false);
      response.set_failure_reason("No scan job with UUID " + uuid + " found");
      return impl::SerializeProto(response);
    }

    ScanJobState& scan_state = active_scans_[uuid];
    if (scan_state.cancelled) {
      response.set_success(false);
      response.set_failure_reason("Job has already been cancelled");
      return impl::SerializeProto(response);
    }

    if (scan_state.in_use) {
      // We can't just delete the scan job entirely since it's in use.
      // sane_cancel() is required to be async safe, so we can call it even if
      // the device is actively being used.
      brillo::ErrorPtr error;
      if (!scan_state.device->CancelScan(&error)) {
        response.set_success(false);
        response.set_failure_reason("Failed to cancel scan: " +
                                    SerializeError(error));
        return impl::SerializeProto(response);
      }
      // When the job that is actively using the device finishes, it will erase
      // the job, freeing the device for use by other scans.
      scan_state.cancelled = true;
    } else {
      // If we're not actively using the device, just delete the scan job.
      SendCancelledSignal(uuid);
      active_scans_.erase(uuid);
    }
  }

  response.set_success(true);
  return impl::SerializeProto(response);
}

void Manager::SetProgressSignalInterval(base::TimeDelta interval) {
  progress_signal_interval_ = interval;
}

void Manager::SetScanStatusChangedSignalSenderForTest(
    StatusSignalSender sender) {
  status_signal_sender_ = sender;
}

void Manager::RemoveDuplicateScanners(
    std::vector<ScannerInfo>* scanners,
    base::flat_set<std::string> seen_vidpid,
    base::flat_set<std::string> seen_busdev,
    const std::vector<ScannerInfo>& sane_scanners) {
  for (const ScannerInfo& scanner : sane_scanners) {
    std::string scanner_name = scanner.name();
    std::string s_vid, s_pid, s_bus, s_dev;
    // Currently pixma only uses 'pixma' as scanner name
    // while epson has multiple formats (i.e. epsonds and epson2)
    if (RE2::FullMatch(scanner_name,
                       "pixma:([0-9a-fA-F]{4})([0-9a-fA-F]{4})_[0-9a-fA-F]*",
                       &s_vid, &s_pid)) {
      s_vid = base::ToLowerASCII(s_vid);
      s_pid = base::ToLowerASCII(s_pid);
      if (seen_vidpid.contains(s_vid + ":" + s_pid)) {
        continue;
      }
    } else if (RE2::FullMatch(scanner_name,
                              "epson(?:2|ds)?:libusb:([0-9]{3}):([0-9]{3})",
                              &s_bus, &s_dev)) {
      if (seen_busdev.contains(s_bus + ":" + s_dev)) {
        continue;
      }
    }
    scanners->push_back(scanner);
  }
}

bool Manager::StartScanInternal(brillo::ErrorPtr* error,
                                const StartScanRequest& request,
                                std::unique_ptr<SaneDevice>* device_out) {
  LOG(INFO) << "Starting StartScanInternal for device: "
            << request.device_name();
  if (!device_out) {
    brillo::Error::AddTo(error, FROM_HERE, kDbusDomain, kManagerServiceError,
                         "device_out cannot be null");
    return false;
  }

  if (request.device_name() == "") {
    brillo::Error::AddTo(error, FROM_HERE, kDbusDomain, kManagerServiceError,
                         "A device name must be provided");
    return false;
  }

  if (!sane_client_) {
    brillo::Error::AddTo(error, FROM_HERE, kDbusDomain, kManagerServiceError,
                         "No connection to SANE");
    return false;
  }

  LOG(INFO) << "Scanning image from device " << request.device_name();

  base::Optional<PortToken> token =
      RequestPortAccessIfNeeded(request.device_name(), firewall_manager_.get());
  std::unique_ptr<SaneDevice> device =
      sane_client_->ConnectToDevice(error, request.device_name());
  if (!device) {
    return false;
  }
  LOG(INFO) << "Connected to device";

  ReportScanRequested(request.device_name());

  const ScanSettings& settings = request.settings();

  if (settings.resolution() != 0) {
    LOG(INFO) << "User requested resolution: " << settings.resolution();
    if (!device->SetScanResolution(error, settings.resolution())) {
      return false;
    }

    base::Optional<int> resolution = device->GetScanResolution(error);
    if (!resolution.has_value()) {
      return false;
    }
    LOG(INFO) << "Device is using resolution: " << resolution.value();
  }

  if (!settings.source_name().empty()) {
    LOG(INFO) << "User requested document source: '" << settings.source_name()
              << "'";
    if (!device->SetDocumentSource(error, settings.source_name())) {
      return false;
    }
  }

  if (settings.color_mode() != MODE_UNSPECIFIED) {
    LOG(INFO) << "User requested color mode: '"
              << ColorMode_Name(settings.color_mode()) << "'";
    if (!device->SetColorMode(error, settings.color_mode())) {
      return false;
    }
  }

  if (settings.has_scan_region()) {
    const ScanRegion& region = settings.scan_region();
    LOG(INFO) << "User requested scan region: top-left (" << region.top_left_x()
              << ", " << region.top_left_y() << "), bottom-right ("
              << region.bottom_right_x() << ", " << region.bottom_right_y()
              << ")";
    if (!device->SetScanRegion(error, region)) {
      return false;
    }
  }

  LOG(INFO) << "All settings applied.  Starting scan.";
  SANE_Status status = device->StartScan(error);
  if (status != SANE_STATUS_GOOD) {
    brillo::Error::AddToPrintf(error, FROM_HERE, kDbusDomain,
                               kManagerServiceError, "Failed to start scan: %s",
                               sane_strstatus(status));
    ReportScanFailed(request.device_name());
    return false;
  }

  *device_out = std::move(device);
  return true;
}

void Manager::GetNextImageInternal(const std::string& uuid,
                                   ScanJobState* scan_state,
                                   base::ScopedFILE out_file) {
  brillo::ErrorPtr error;
  ScanState result = RunScanLoop(&error, scan_state, std::move(out_file), uuid);
  switch (result) {
    case SCAN_STATE_PAGE_COMPLETED:
      // Do nothing.
      break;
    case SCAN_STATE_CANCELLED:
      SendCancelledSignal(uuid);
      {
        base::AutoLock auto_lock(active_scans_lock_);
        active_scans_.erase(uuid);
      }
      return;
    default:
      LOG(ERROR) << "Unexpected scan state: " << ScanState_Name(result);
      FALLTHROUGH;
    case SCAN_STATE_FAILED:
      ReportScanFailed(scan_state->device_name);
      SendFailureSignal(uuid, SerializeError(error));
      {
        base::AutoLock auto_lock(active_scans_lock_);
        active_scans_.erase(uuid);
      }
      return;
  }

  bool scanned_all_pages =
      scan_state->total_pages.has_value() &&
      scan_state->current_page == scan_state->total_pages.value();

  bool adf_scan = !scan_state->total_pages.has_value();

  SANE_Status status = SANE_STATUS_GOOD;
  if (!scanned_all_pages) {
    // Here, we call StartScan again in order to prepare for scanning the next
    // page of the scan. Additionally, if we're scanning from the ADF, this
    // lets us know if we've run out of pages so that we can signal scan
    // completion.
    status = scan_state->device->StartScan(&error);
  }

  bool scan_complete =
      scanned_all_pages || (status == SANE_STATUS_NO_DOCS && adf_scan);

  SendStatusSignal(uuid, SCAN_STATE_PAGE_COMPLETED, scan_state->current_page,
                   100, !scan_complete);

  if (scan_complete) {
    ReportScanSucceeded(scan_state->device_name);
    SendStatusSignal(uuid, SCAN_STATE_COMPLETED, scan_state->current_page, 100,
                     false);
    LOG(INFO) << __func__ << ": completed image scan and conversion.";

    {
      base::AutoLock auto_lock(active_scans_lock_);
      active_scans_.erase(uuid);
    }

    return;
  }

  if (status == SANE_STATUS_CANCELLED) {
    SendCancelledSignal(uuid);
    {
      base::AutoLock auto_lock(active_scans_lock_);
      active_scans_.erase(uuid);
    }
    return;
  } else if (status != SANE_STATUS_GOOD) {
    // The scan failed.
    brillo::Error::AddToPrintf(&error, FROM_HERE, kDbusDomain,
                               kManagerServiceError, "Failed to start scan: %s",
                               sane_strstatus(status));
    ReportScanFailed(scan_state->device_name);
    SendFailureSignal(uuid, SerializeError(error));
    {
      base::AutoLock auto_lock(active_scans_lock_);
      active_scans_.erase(uuid);
    }
    return;
  }

  scan_state->current_page++;
  if (!activity_callback_.is_null())
    activity_callback_.Run();
}

ScanState Manager::RunScanLoop(brillo::ErrorPtr* error,
                               ScanJobState* scan_state,
                               base::ScopedFILE out_file,
                               const std::string& scan_uuid) {
  SaneDevice* device = scan_state->device.get();
  base::Optional<ScanParameters> params = device->GetScanParameters(error);
  if (!params.has_value()) {
    return SCAN_STATE_FAILED;
  }

  if (!ValidateParams(error, params.value())) {
    return SCAN_STATE_FAILED;
  }

  // Get resolution value in DPI so that we can record it in the PNG.
  brillo::ErrorPtr resolution_error;
  base::Optional<int> resolution = device->GetScanResolution(&resolution_error);
  if (!resolution.has_value()) {
    LOG(WARNING) << "Failed to get scan resolution: "
                 << SerializeError(resolution_error);
  }

  png_struct* png;
  png_info* info;
  if (!SetupPngHeader(error, params.value(), resolution, &png, &info,
                      out_file)) {
    return SCAN_STATE_FAILED;
  }
  base::ScopedClosureRunner cleanup_png(base::BindOnce(
      [](png_struct** png, png_info** info) {
        png_destroy_write_struct(png, info);
      },
      &png, &info));

  // Sanity check to make sure that we're not consuming more data in
  // png_write_row than we have available.
  if (png_get_rowbytes(png, info) > params->bytes_per_line) {
    brillo::Error::AddToPrintf(
        error, FROM_HERE, kDbusDomain, kManagerServiceError,
        "PNG image row requires %zu bytes, but SANE is only providing %d bytes",
        png_get_rowbytes(png, info), params->bytes_per_line);
    return SCAN_STATE_FAILED;
  }

  base::TimeTicks last_progress_sent_time = base::TimeTicks::Now();
  uint32_t last_progress_value = 0;
  size_t rows_written = 0;
  const size_t kMaxBuffer = 1024 * 1024;
  const size_t buffer_length =
      std::max(base::bits::Align(params->bytes_per_line, 4 * 1024), kMaxBuffer);
  std::vector<uint8_t> image_buffer(buffer_length, '\0');
  // The offset within image_buffer to read to. This will be used within the
  // loop for when we've read a partial image line and need to track data that
  // is saved between loop iterations.
  //
  // We maintain the invariant at the start of each loop iteration that indices
  // [0, buffer_offset) hold previously read data.
  size_t buffer_offset = 0;
  while (true) {
    // Get next chunk of scan data from the device.
    size_t read = 0;
    SANE_Status result =
        device->ReadScanData(error, image_buffer.data() + buffer_offset,
                             image_buffer.size() - buffer_offset, &read);

    // Handle non-standard results.
    if (result == SANE_STATUS_GOOD) {
      if (rows_written >= params->lines) {
        brillo::Error::AddTo(
            error, FROM_HERE, kDbusDomain, kManagerServiceError,
            "Whole image has been written, but scanner is still sending data.");
        return SCAN_STATE_FAILED;
      }
    } else if (result == SANE_STATUS_EOF) {
      break;
    } else if (result == SANE_STATUS_CANCELLED) {
      LOG(INFO) << "Scan job has been cancelled.";
      return SCAN_STATE_CANCELLED;
    } else {
      brillo::Error::AddToPrintf(
          error, FROM_HERE, kDbusDomain, kManagerServiceError,
          "Reading scan data failed: %s", sane_strstatus(result));
      return SCAN_STATE_FAILED;
    }

    // Write as many lines of the image as we can with the data we've received.
    // Indices [buffer_offset, buffer_offset + read) hold the data we just read.
    size_t bytes_available = buffer_offset + read;
    size_t bytes_converted = 0;
    while (bytes_available - bytes_converted >= params->bytes_per_line &&
           rows_written < params->lines) {
      int ret = LibpngErrorWrap(error, png_write_row, png,
                                image_buffer.data() + bytes_converted);
      if (ret != 0) {
        brillo::Error::AddToPrintf(
            error, FROM_HERE, kDbusDomain, kManagerServiceError,
            "Writing PNG row failed with result %d", ret);
        return SCAN_STATE_FAILED;
      }
      bytes_converted += params->bytes_per_line;
      rows_written++;
      uint32_t progress = rows_written * 100 / params->lines;
      base::TimeTicks now = base::TimeTicks::Now();
      if (progress != last_progress_value &&
          now - last_progress_sent_time >= progress_signal_interval_) {
        SendStatusSignal(scan_uuid, SCAN_STATE_IN_PROGRESS,
                         scan_state->current_page, progress, false);
        last_progress_value = progress;
        last_progress_sent_time = now;
      }
    }

    // Shift any unconverted data in image_buffer to the start of image_buffer.
    size_t remaining_bytes = bytes_available - bytes_converted;
    memmove(image_buffer.data(), image_buffer.data() + bytes_converted,
            remaining_bytes);
    buffer_offset = remaining_bytes;
  }

  if (rows_written < params->lines || buffer_offset != 0) {
    brillo::Error::AddToPrintf(error, FROM_HERE, kDbusDomain,
                               kManagerServiceError,
                               "Received incomplete scan data, %zu unused "
                               "bytes, %zu of %d rows written",
                               buffer_offset, rows_written, params->lines);
    return SCAN_STATE_FAILED;
  }

  int ret = LibpngErrorWrap(error, png_write_end, png, info);
  if (ret != 0) {
    brillo::Error::AddToPrintf(
        error, FROM_HERE, kDbusDomain, kManagerServiceError,
        "Finalizing PNG write failed with result %d", ret);
    return SCAN_STATE_FAILED;
  }

  return SCAN_STATE_PAGE_COMPLETED;
}

void Manager::ReportScanRequested(const std::string& device_name) {
  DocumentScanSaneBackend backend = BackendFromDeviceName(device_name);
  metrics_library_->SendEnumToUMA(kMetricScanRequested, backend,
                                  DocumentScanSaneBackend::kMaxValue);
}

void Manager::ReportScanSucceeded(const std::string& device_name) {
  DocumentScanSaneBackend backend = BackendFromDeviceName(device_name);
  metrics_library_->SendEnumToUMA(kMetricScanSucceeded, backend,
                                  DocumentScanSaneBackend::kMaxValue);
}

void Manager::ReportScanFailed(const std::string& device_name) {
  DocumentScanSaneBackend backend = BackendFromDeviceName(device_name);
  metrics_library_->SendEnumToUMA(kMetricScanFailed, backend,
                                  DocumentScanSaneBackend::kMaxValue);
}

void Manager::SendStatusSignal(std::string uuid,
                               ScanState state,
                               int page,
                               int progress,
                               bool more_pages) {
  ScanStatusChangedSignal signal;
  signal.set_scan_uuid(uuid);
  signal.set_state(state);
  signal.set_page(page);
  signal.set_progress(progress);
  signal.set_more_pages(more_pages);
  status_signal_sender_.Run(signal);
}

void Manager::SendCancelledSignal(std::string uuid) {
  ScanStatusChangedSignal signal;
  signal.set_scan_uuid(uuid);
  signal.set_state(SCAN_STATE_CANCELLED);
  status_signal_sender_.Run(signal);
}

void Manager::SendFailureSignal(std::string uuid, std::string failure_reason) {
  ScanStatusChangedSignal signal;
  signal.set_scan_uuid(uuid);
  signal.set_state(SCAN_STATE_FAILED);
  signal.set_failure_reason(failure_reason);
  status_signal_sender_.Run(signal);
}

}  // namespace lorgnette