// License: GPL. For details, see LICENSE file.
package org.openstreetmap.josm.actions;

import static org.openstreetmap.josm.gui.help.HelpUtil.ht;
import static org.openstreetmap.josm.tools.I18n.tr;

import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.Future;

import org.openstreetmap.josm.gui.MainApplication;
import org.openstreetmap.josm.gui.dialogs.LayerListDialog;
import org.openstreetmap.josm.gui.layer.Layer;
import org.openstreetmap.josm.gui.layer.OsmDataLayer;
import org.openstreetmap.josm.gui.util.GuiHelper;
import org.openstreetmap.josm.tools.ImageProvider;
import org.openstreetmap.josm.tools.Logging;
import org.openstreetmap.josm.tools.Shortcut;
import org.openstreetmap.josm.tools.Utils;

/**
 * Action that merges two or more OSM data layers.
 * @since 1890
 */
public class MergeLayerAction extends AbstractMergeAction {

    /**
     * Constructs a new {@code MergeLayerAction}.
     */
    public MergeLayerAction() {
        super(tr("Merge layer"), "dialogs/mergedown",
            tr("Merge the current layer into another layer"),
            Shortcut.registerShortcut("system:merge", tr("Edit: {0}",
            tr("Merge")), KeyEvent.VK_M, Shortcut.CTRL),
            true, "action/mergelayer", true);
        putValue("help", ht("/Action/MergeLayer"));
    }

    /**
     * Submits merge of layers.
     * @param targetLayers possible target layers
     * @param sourceLayers source layers
     * @return a Future representing pending completion of the merge task, or {@code null}
     * @since 11885 (return type)
     */
    protected Future<?> doMerge(List<Layer> targetLayers, final Collection<Layer> sourceLayers) {
        final Layer targetLayer = askTargetLayer(targetLayers);
        if (targetLayer == null)
            return null;
        final Object actionName = getValue(NAME);
        return MainApplication.worker.submit(() -> {
                final long start = System.currentTimeMillis();
                boolean layerMerged = false;
                for (final Layer sourceLayer: sourceLayers) {
                    if (sourceLayer != null && !sourceLayer.equals(targetLayer)) {
                        if (sourceLayer instanceof OsmDataLayer && targetLayer instanceof OsmDataLayer
                                && ((OsmDataLayer) sourceLayer).isUploadDiscouraged() != ((OsmDataLayer) targetLayer).isUploadDiscouraged()
                                && Boolean.TRUE.equals(GuiHelper.runInEDTAndWaitAndReturn(() ->
                                    warnMergingUploadDiscouragedLayers(sourceLayer, targetLayer)))) {
                            break;
                        }
                        targetLayer.mergeFrom(sourceLayer);
                        GuiHelper.runInEDTAndWait(() -> getLayerManager().removeLayer(sourceLayer));
                        layerMerged = true;
                    }
                }
                if (layerMerged) {
                    getLayerManager().setActiveLayer(targetLayer);
                    Logging.info(tr("{0} completed in {1}", actionName, Utils.getDurationString(System.currentTimeMillis() - start)));
                }
        });
    }

    /**
     * Merges a list of layers together.
     * @param sourceLayers The layers to merge
     * @return a Future representing pending completion of the merge task, or {@code null}
     * @since 11885 (return type)
     */
    public Future<?> merge(List<Layer> sourceLayers) {
        return doMerge(sourceLayers, sourceLayers);
    }

    /**
     * Merges the given source layer with another one, determined at runtime.
     * @param sourceLayer The source layer to merge
     * @return a Future representing pending completion of the merge task, or {@code null}
     * @since 11885 (return type)
     */
    public Future<?> merge(Layer sourceLayer) {
        if (sourceLayer == null)
            return null;
        List<Layer> targetLayers = LayerListDialog.getInstance().getModel().getPossibleMergeTargets(sourceLayer);
        if (targetLayers.isEmpty()) {
            warnNoTargetLayersForSourceLayer(sourceLayer);
            return null;
        }
        return doMerge(targetLayers, Collections.singleton(sourceLayer));
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        merge(getSourceLayer());
    }

    @Override
    protected void updateEnabledState() {
        GuiHelper.runInEDT(() -> {
                final Layer sourceLayer = getSourceLayer();
                if (sourceLayer == null) {
                    setEnabled(false);
                } else {
                    try {
                        setEnabled(!LayerListDialog.getInstance().getModel().getPossibleMergeTargets(sourceLayer).isEmpty());
                    } catch (IllegalStateException e) {
                        // May occur when destroying last layer / exiting JOSM, see #14476
                        setEnabled(false);
                        Logging.error(e);
                    }
                }
        });
    }

    /**
     * Returns the source layer.
     * @return the source layer
     */
    protected Layer getSourceLayer() {
        return getLayerManager().getActiveLayer();
    }

    /**
     * Warns about a discouraged merge operation, ask for confirmation.
     * @param sourceLayer The source layer
     * @param targetLayer The target layer
     * @return {@code true} if the user wants to cancel, {@code false} if they want to continue
     */
    public static final boolean warnMergingUploadDiscouragedLayers(Layer sourceLayer, Layer targetLayer) {
        return GuiHelper.warnUser(tr("Merging layers with different upload policies"),
                "<html>" +
                tr("You are about to merge data between layers ''{0}'' and ''{1}''.<br /><br />"+
                        "These layers have different upload policies and should not been merged as it.<br />"+
                        "Merging them will result to enforce the stricter policy (upload discouraged) to ''{1}''.<br /><br />"+
                        "<b>This is not the recommended way of merging such data</b>.<br />"+
                        "You should instead check and merge each object, one by one, by using ''<i>Merge selection</i>''.<br /><br />"+
                        "Are you sure you want to continue?",
                        Utils.escapeReservedCharactersHTML(sourceLayer.getName()),
                        Utils.escapeReservedCharactersHTML(targetLayer.getName()),
                        Utils.escapeReservedCharactersHTML(targetLayer.getName()))+
                "</html>",
                ImageProvider.get("dialogs", "mergedown"), tr("Ignore this hint and merge anyway"));
    }
}