/* 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 "amazoncoverprovider.h"
#include "core/closure.h"
#include "core/logging.h"
#include "core/network.h"
#include "core/utilities.h"

#include <QDateTime>
#include <QNetworkReply>
#include <QStringList>
#include <QXmlStreamReader>

// Amazon has a web crawler that looks for access keys in public source code,
// so we apply some sophisticated encryption to these keys.
const char* AmazonCoverProvider::kAccessKeyB64 = "QUtJQUlRSDI2UlZNNlVaNFdBNlE=";
const char* AmazonCoverProvider::kSecretAccessKeyB64 =
    "ZTQ2UGczM0JRNytDajd4MWR6eFNvODVFd2tpdi9FbGVCcUZjMkVmMQ==";
const char* AmazonCoverProvider::kUrl = "http://ecs.amazonaws.com/onca/xml";
const char* AmazonCoverProvider::kAssociateTag = "clemmusiplay-20";

AmazonCoverProvider::AmazonCoverProvider(QObject* parent)
  : CoverProvider("Amazon", parent),
    network_(new NetworkAccessManager(this))
{
}

bool AmazonCoverProvider::StartSearch(const QString& artist, const QString& album, int id) {
  typedef QPair<QString, QString> Arg;
  typedef QList<Arg> ArgList;

  typedef QPair<QByteArray, QByteArray> EncodedArg;
  typedef QList<EncodedArg> EncodedArgList;

  // Must be sorted by parameter name
  ArgList args = ArgList()
      << Arg("AWSAccessKeyId", QByteArray::fromBase64(kAccessKeyB64))
      << Arg("AssociateTag", kAssociateTag)
      << Arg("Keywords", artist + " " + album)
      << Arg("Operation", "ItemSearch")
      << Arg("ResponseGroup", "Images")
      << Arg("SearchIndex", "All")
      << Arg("Service", "AWSECommerceService")
      << Arg("Timestamp", QDateTime::currentDateTime().toString("yyyy-MM-ddThh:mm:ss.zzzZ"))
      << Arg("Version", "2009-11-01");

  EncodedArgList encoded_args;
  QStringList query_items;

  // Encode the arguments
  foreach (const Arg& arg, args) {
    EncodedArg encoded_arg(QUrl::toPercentEncoding(arg.first),
                           QUrl::toPercentEncoding(arg.second));
    encoded_args << encoded_arg;
    query_items << QString(encoded_arg.first + "=" + encoded_arg.second);
  }

  // Sign the request
  QUrl url(kUrl);

  const QByteArray data_to_sign = QString("GET\n%1\n%2\n%3").arg(
        url.host(), url.path(), query_items.join("&")).toAscii();
  const QByteArray signature(Utilities::HmacSha256(
        QByteArray::fromBase64(kSecretAccessKeyB64), data_to_sign));

  // Add the signature to the request
  encoded_args << EncodedArg("Signature", QUrl::toPercentEncoding(signature.toBase64()));
  url.setEncodedQueryItems(encoded_args);

  QNetworkReply* reply = network_->get(QNetworkRequest(url));
  NewClosure(reply, SIGNAL(finished()),
             this, SLOT(QueryFinished(QNetworkReply*, int)),
             reply, id);

  return true;
}

void AmazonCoverProvider::QueryFinished(QNetworkReply* reply, int id) {
  reply->deleteLater();

  CoverSearchResults results;

  QXmlStreamReader reader(reply);
  while (!reader.atEnd()) {
    reader.readNext();
    if (reader.tokenType() == QXmlStreamReader::StartElement &&
        reader.name() == "Item") {
      ReadItem(&reader, &results);
    }
  }

  emit SearchFinished(id, results);
}

void AmazonCoverProvider::ReadItem(QXmlStreamReader* reader, CoverSearchResults* results) {
  while (!reader->atEnd()) {
    switch (reader->readNext()) {
    case QXmlStreamReader::StartElement:
      if (reader->name() == "LargeImage") {
        ReadLargeImage(reader, results);
      } else {
        reader->skipCurrentElement();
      }
      break;

    case QXmlStreamReader::EndElement:
      return;

    default:
      break;
    }
  }
}

void AmazonCoverProvider::ReadLargeImage(QXmlStreamReader* reader, CoverSearchResults* results) {
  while (!reader->atEnd()) {
    switch (reader->readNext()) {
    case QXmlStreamReader::StartElement:
      if (reader->name() == "URL") {
        CoverSearchResult result;
        result.image_url = QUrl(reader->readElementText());
        results->append(result);
      } else {
        reader->skipCurrentElement();
      }
      break;

    case QXmlStreamReader::EndElement:
      return;

    default:
      break;
    }
  }
}
