/* This file is part of Clementine.
   Copyright 2010, David Sansome <me@davidsansome.com>

   Clementine is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   Clementine is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with Clementine.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "albumcoverfetcher.h"
#include "albumcoverfetchersearch.h"
#include "coverprovider.h"
#include "coverproviders.h"
#include "core/logging.h"
#include "core/network.h"

#include <QMutexLocker>
#include <QNetworkReply>
#include <QTimer>
#include <QtDebug>

#include <cmath>

const int AlbumCoverFetcherSearch::kSearchTimeoutMs = 10000;
const int AlbumCoverFetcherSearch::kImageLoadTimeoutMs = 2500;
const int AlbumCoverFetcherSearch::kTargetSize = 500;
const float AlbumCoverFetcherSearch::kGoodScore = 1.85;

AlbumCoverFetcherSearch::AlbumCoverFetcherSearch(const CoverSearchRequest& request,
                                                 QNetworkAccessManager* network,
                                                 QObject* parent)
  : QObject(parent),
    request_(request),
    image_load_timeout_(new NetworkTimeouts(kImageLoadTimeoutMs, this)),
    network_(network)
{
  // we will terminate the search after kSearchTimeoutMs miliseconds if we are not
  // able to find all of the results before that point in time
  QTimer::singleShot(kSearchTimeoutMs, this, SLOT(TerminateSearch()));
}

void AlbumCoverFetcherSearch::TerminateSearch() {
  foreach (int id, pending_requests_.keys()) {
    pending_requests_.take(id)->CancelSearch(id);
  }

  AllProvidersFinished();
}

void AlbumCoverFetcherSearch::Start() {
  CoverProviders* providers = &CoverProviders::instance();

  foreach(CoverProvider* provider, providers->List()) {
    connect(provider, SIGNAL(SearchFinished(int,QList<CoverSearchResult>)),
            SLOT(ProviderSearchFinished(int,QList<CoverSearchResult>)));
    const int id = providers->NextId();
    const bool success = provider->StartSearch(
          request_.artist, request_.album, id);

    if (success) {
      pending_requests_[id] = provider;
    }
  }

  // end this search before it even began if there are no providers...
  if(pending_requests_.isEmpty()) {
    TerminateSearch();
  }
}

static bool CompareCategories(const CoverSearchResult& a,
                              const CoverSearchResult& b) {
  return a.category < b.category;
}

void AlbumCoverFetcherSearch::ProviderSearchFinished(
    int id, const QList<CoverSearchResult>& results) {
  if (!pending_requests_.contains(id))
    return;

  CoverProvider* provider = pending_requests_.take(id);

  CoverSearchResults results_copy(results);
  // Add categories to the results if the provider didn't specify them
  for (int i=0 ; i<results_copy.count() ; ++i) {
    if (results_copy[i].category.isEmpty()) {
      results_copy[i].category = provider->name();
    }
  }

  // Add results from the current provider to our pool
  results_.append(results_copy);

  // do we have more providers left?
  if(!pending_requests_.isEmpty()) {
    return;
  }

  AllProvidersFinished();
}

void AlbumCoverFetcherSearch::AllProvidersFinished() {
  // if we only wanted to do the search then we're done
  if (request_.search) {
    emit SearchFinished(request_.id, results_);
    return;
  }

  // no results?
  if (results_.isEmpty()) {
    emit AlbumCoverFetched(request_.id, QImage());
    return;
  }

  // Now we have to load some images and figure out which one is the best.
  // We'll sort the list of results by category, then load the first few images
  // from each category and use some heuristics to score them.  If no images
  // are good enough we'll keep loading more images until we find one that is
  // or we run out of results.
  qStableSort(results_.begin(), results_.end(), CompareCategories);
  FetchMoreImages();
}

void AlbumCoverFetcherSearch::FetchMoreImages() {
  // Try the first one in each category.
  QString last_category;
  for (int i=0 ; i<results_.count() ; ++i) {
    if (results_[i].category == last_category) {
      continue;
    }

    CoverSearchResult result = results_.takeAt(i--);
    last_category = result.category;

    qLog(Debug) << "Loading" << result.image_url << "from" << result.category;

    QNetworkReply* image_reply = network_->get(QNetworkRequest(result.image_url));
    connect(image_reply, SIGNAL(finished()), SLOT(ProviderCoverFetchFinished()));
    pending_image_loads_ << image_reply;
    image_load_timeout_->AddReply(image_reply);
  }

  if (pending_image_loads_.isEmpty()) {
    // There were no more results?  Time to give up.
    SendBestImage();
  }
}

void AlbumCoverFetcherSearch::ProviderCoverFetchFinished() {
  QNetworkReply* reply = qobject_cast<QNetworkReply*>(sender());
  reply->deleteLater();
  pending_image_loads_.removeAll(reply);

  if (reply->error() != QNetworkReply::NoError) {
    qLog(Info) << "Error requesting" << reply->url() << reply->errorString();
  } else {
    QImage image;
    if (!image.loadFromData(reply->readAll())) {
      qLog(Info) << "Error decoding image data from" << reply->url();
    } else {
      const float score = ScoreImage(image);
      candidate_images_.insertMulti(score, image);

      qLog(Debug) << reply->url() << "scored" << score;
    }
  }

  if (pending_image_loads_.isEmpty()) {
    // We've fetched everything we wanted to fetch for now, check if we have an
    // image that's good enough.
    float best_score = 0.0;

    if (!candidate_images_.isEmpty()) {
      best_score = candidate_images_.keys().last();
    }

    qLog(Debug) << "Best image so far has a score of" << best_score;
    if (best_score >= kGoodScore) {
      SendBestImage();
    } else {
      FetchMoreImages();
    }
  }
}

float AlbumCoverFetcherSearch::ScoreImage(const QImage& image) const {
  // Invalid images score nothing
  if (image.isNull()) {
    return 0.0;
  }

  // A 500x500px image scores 1.0, bigger scores higher
  const float size_score = std::sqrt(float(image.width() * image.height())) / kTargetSize;

  // A 1:1 image scores 1.0, anything else scores less
  const float aspect_score = 1.0 - float(image.height() - image.width()) /
                                   std::max(image.height(), image.width());

  return size_score + aspect_score;
}

void AlbumCoverFetcherSearch::SendBestImage() {
  QImage image;

  if (!candidate_images_.isEmpty()) {
    image = candidate_images_.values().back();
  }

  emit AlbumCoverFetched(request_.id, image);
}