ksdssdownloader.h

/*
    SPDX-FileCopyrightText: 2016 Akarsh Simha <akarsh.simha@kdemail.net>
 
    SPDX-License-Identifier: GPL-2.0-or-later
*/
 
#pragma once
 
#include "ksdssimage.h"
 
#include <QObject>
#include <QString>
#include <QStringList>
#include <QTemporaryFile>
#include <QUrl>
 
#include <functional>
 
class FileDownloader;
class SkyPoint;
class dms;
 
/**
 * @class KSDssDownloader
 * @short Helps download a DSS image
 * @author Akarsh Simha <akarsh.simha@kdemail.net>
 *
 * @note This object is designed to commit suicide (calls
 * QObject::deleteLater() )! Never allocate this using anything but
 * new -- do not allocate it on the stack! This is ideal for its
 * operation, as it deletes itself after downloading.
 */
 
class KSDssDownloader : public QObject
{
    Q_OBJECT
 
  public:
    /** @short Constructor */
    explicit KSDssDownloader(QObject *parent = nullptr);
 
    /**
     * @short Constructor that initiates a "standard" DSS download job, calls the downloadReady slot, and finally self destructs
     * @note Very important that if you create with this constructor,
     * the object will self-destruct. Avoid keeping pointers to it, or
     * things may segfault!
     */
    KSDssDownloader(const SkyPoint *const p, const QString &destFileName,
                    const std::function<void(bool)> &slotDownloadReady, QObject *parent = nullptr);
 
    /**
     * @short Stateful single-download of a supplied URL. Use when the flexibility is required
     * @note Does not self-delete this object. Construct with default constructor, and delete as usual.
     * @param srcUrl source DSS URL to download
     * @param destFileName destination image file (will be of PNG format)
     * @param md DSS image metadata to write into image file
     * @note emits downloadComplete with success state when done
     */
    void startSingleDownload(const QUrl srcUrl, const QString &destFileName, KSDssImage::Metadata &md);
 
    /**
     * @short High-level method to create a URL to obtain a DSS image for a given SkyPoint
     * @note If SkyPoint is a DeepSkyObject, this method automatically
     * decides the image size required to fit the object.
     * @note Moved from namespace KSUtils (--asimha, Jan 5 2016)
     */
    static QString getDSSURL(const SkyPoint *const p, const QString &version = "all",
                             struct KSDssImage::Metadata *md = nullptr);
 
    /**
     * @short High-level method to create a URL to obtain a DSS image for a given SkyPoint
     * @note This method includes an option to set the height, but uses default values for many parameters
     */
    static QString getDSSURL(const SkyPoint *const p, float width, float height = 0, const QString &version = "all",
                             struct KSDssImage::Metadata *md = nullptr);
 
    /**
     * @short Create a URL to obtain a DSS image for a given RA, Dec
     * @param ra The J2000.0 Right Ascension of the point
     * @param dec The J2000.0 Declination of the point
     * @param width The width of the image in arcminutes
     * @param height The height of the image in arcminutes
     * @param type_ The image type, either gif or fits.
     * @param version_ string describing which version to get
     * @param md If a valid pointer is provided, fill with metadata
     * @note This method resets height and width to fall within the range accepted by DSS
     * @note Moved from namespace KSUtils (--asimha, Jan 5 2016)
     *
     * @note Valid versions are: dss1, poss2ukstu_red, poss2ukstu_ir,
     * poss2ukstu_blue, poss1_blue, poss1_red, all, quickv,
     * phase2_gsc2, phase2_gsc1. Of these, dss1 uses POSS1 Red in the
     * north and POSS2/UKSTU Blue in the south. all uses the best of a
     * combined list of all plates.
     *
     */
    static QString getDSSURL(const dms &ra, const dms &dec, float width = 0, float height = 0,
                             const QString &type_ = "gif", const QString &version_ = "all",
                             struct KSDssImage::Metadata *md = nullptr);
 
    /** @short Write image metadata into file */
    static bool writeImageWithMetadata(const QString &srcFile, const QString &destFile, const KSDssImage::Metadata &md);
 
  signals:
    void downloadComplete(bool success);
    void downloadCanceled();
 
  private slots:
    void downloadAttemptFinished();
    void singleDownloadFinished();
    void downloadError(const QString &errorString);
 
  private:
    void startDownload(const SkyPoint *const p, const QString &destFileName);
    void initiateSingleDownloadAttempt(QUrl srcUrl);
    bool writeImageFile();
 
    QStringList m_VersionPreference;
    int m_attempt { 0 };
    struct KSDssImage::Metadata m_AttemptData;
    QString m_FileName;
    QTemporaryFile m_TempFile;
    FileDownloader *downloadJob { nullptr };
};