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

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.openstreetmap.josm.Main;

/**
 * Helper class for specialized extensions preferences.
 * @since 12649 (extracted from gui.preferences package)
 */
public abstract class SourcePrefHelper {

    private final String pref;
    protected final SourceType type;

    /**
     * Constructs a new {@code SourcePrefHelper} for the given preference key.
     * @param pref The preference key
     * @param type The source type
     * @since 12825
     */
    public SourcePrefHelper(String pref, SourceType type) {
        this.pref = pref;
        this.type = type;
    }

    /**
     * Returns the default sources provided by JOSM core.
     * @return the default sources provided by JOSM core
     */
    public abstract Collection<ExtendedSourceEntry> getDefault();

    /**
     * Serializes the given source entry as a map.
     * @param entry source entry to serialize
     * @return map (key=value)
     */
    public abstract Map<String, String> serialize(SourceEntry entry);

    /**
     * Deserializes the given map as a source entry.
     * @param entryStr map (key=value)
     * @return source entry
     */
    public abstract SourceEntry deserialize(Map<String, String> entryStr);

    /**
     * Returns the list of sources.
     * @return The list of sources
     */
    public List<SourceEntry> get() {

        List<Map<String, String>> src = Main.pref.getListOfMaps(pref, null);
        if (src == null)
            return new ArrayList<>(getDefault());

        List<SourceEntry> entries = new ArrayList<>();
        for (Map<String, String> sourcePref : src) {
            SourceEntry e = deserialize(new HashMap<>(sourcePref));
            if (e != null) {
                entries.add(e);
            }
        }
        return entries;
    }

    /**
     * Saves a list of sources to JOSM preferences.
     * @param entries list of sources
     * @return {@code true}, if something has changed (i.e. value is different than before)
     */
    public boolean put(Collection<? extends SourceEntry> entries) {
        List<Map<String, String>> setting = serializeList(entries);
        boolean unset = Main.pref.getListOfMaps(pref, null) == null;
        if (unset) {
            Collection<Map<String, String>> def = serializeList(getDefault());
            if (setting.equals(def))
                return false;
        }
        return Main.pref.putListOfMaps(pref, setting);
    }

    private List<Map<String, String>> serializeList(Collection<? extends SourceEntry> entries) {
        List<Map<String, String>> setting = new ArrayList<>(entries.size());
        for (SourceEntry e : entries) {
            setting.add(serialize(e));
        }
        return setting;
    }

    /**
     * Returns the set of active source URLs.
     * @return The set of active source URLs.
     */
    public final Set<String> getActiveUrls() {
        Set<String> urls = new LinkedHashSet<>(); // retain order
        for (SourceEntry e : get()) {
            if (e.active) {
                urls.add(e.url);
            }
        }
        return urls;
    }
}