// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "components/offline_pages/core/snapshot_controller.h"

#include "base/check_op.h"
#include "base/functional/bind.h"
#include "base/location.h"
#include "base/task/single_thread_task_runner.h"
#include "base/time/time.h"
#include "components/offline_pages/core/offline_page_feature.h"

namespace {
// Default delay, in milliseconds, between the main document parsed event and
// snapshot. Note: this snapshot might not occur if the OnLoad event and
// OnLoad delay elapses first to trigger a final snapshot.
const int64_t kDefaultDelayAfterDocumentAvailableMs = 7000;

// Default delay, in milliseconds, between the main document OnLoad event and
// snapshot.
const int64_t kDelayAfterDocumentOnLoadCompletedMsForeground = 1000;

// Delay for testing to keep polling times reasonable.
const int64_t kDelayForTests = 0;

}  // namespace

namespace offline_pages {

SnapshotController::SnapshotController(
    const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
    SnapshotController::Client* client)
    : task_runner_(task_runner),
      client_(client),
      state_(State::READY),
      delay_after_document_available_ms_(kDefaultDelayAfterDocumentAvailableMs),
      delay_after_document_on_load_completed_ms_(
          kDelayAfterDocumentOnLoadCompletedMsForeground) {
  if (offline_pages::ShouldUseTestingSnapshotDelay()) {
    delay_after_document_available_ms_ = kDelayForTests;
    delay_after_document_on_load_completed_ms_ = kDelayForTests;
  }
}

SnapshotController::~SnapshotController() = default;

void SnapshotController::Reset() {
  // Cancel potentially delayed tasks that relate to the previous 'session'.
  weak_ptr_factory_.InvalidateWeakPtrs();
  state_ = State::READY;
  current_page_quality_ = PageQuality::POOR;
}

void SnapshotController::Stop() {
  state_ = State::STOPPED;
}

void SnapshotController::PendingSnapshotCompleted() {
  // Unless the controller is "stopped", enable the subsequent snapshots.
  // Stopped state prevents any further snapshots form being started.
  if (state_ == State::STOPPED)
    return;
  state_ = State::READY;
}

void SnapshotController::PrimaryMainDocumentElementAvailable() {
  if (state_ == State::STOPPED) {
    // We don't need to schedule a delayed task if the controller is stopped
    // because the controller can restart only when Reset() is called which also
    // resets queued delayed tasks.
    return;
  }
  DCHECK_EQ(PageQuality::POOR, current_page_quality_);
  // Post a delayed task to snapshot.
  task_runner_->PostDelayedTask(
      FROM_HERE,
      base::BindOnce(&SnapshotController::MaybeStartSnapshot,
                     weak_ptr_factory_.GetWeakPtr(),
                     PageQuality::FAIR_AND_IMPROVING),
      base::Milliseconds(delay_after_document_available_ms_));
}

void SnapshotController::DocumentOnLoadCompletedInPrimaryMainFrame() {
  if (state_ == State::STOPPED) {
    // We don't need to schedule a delayed task if the controller is stopped
    // because the controller can restart only when Reset() is called which also
    // resets queued delayed tasks.
    return;
  }
  // Post a delayed task to snapshot and then stop this controller.
  task_runner_->PostDelayedTask(
      FROM_HERE,
      base::BindOnce(&SnapshotController::MaybeStartSnapshotThenStop,
                     weak_ptr_factory_.GetWeakPtr()),
      base::Milliseconds(delay_after_document_on_load_completed_ms_));
}

void SnapshotController::MaybeStartSnapshot(PageQuality updated_page_quality) {
  if (state_ != State::READY)
    return;
  DCHECK_LT(current_page_quality_, updated_page_quality);
  current_page_quality_ = updated_page_quality;
  state_ = State::SNAPSHOT_PENDING;
  client_->StartSnapshot();
}

void SnapshotController::MaybeStartSnapshotThenStop() {
  MaybeStartSnapshot(PageQuality::HIGH);
  Stop();
}

int64_t SnapshotController::GetDelayAfterDocumentAvailableForTest() {
  return delay_after_document_available_ms_;
}

int64_t SnapshotController::GetDelayAfterDocumentOnLoadCompletedForTest() {
  return delay_after_document_on_load_completed_ms_;
}

}  // namespace offline_pages