Introduce new Fetcher interfaces

src/main/java/net/sf/jabref/importer/fetcher/IdBasedFetcher.java

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+/*
+ * Copyright (C) 2003-2016 JabRef contributors.
+ * This program 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+package net.sf.jabref.importer.fetcher;
+
+import java.util.Optional;
+
+import net.sf.jabref.model.entry.BibEntry;
+
+/**
+ * Searches web resources for bibliographic information based on an identifier.
+ */
+public interface IdBasedFetcher extends WebFetcher {
+
+    /**
+     * Looks for bibliographic information associated to the given identifier.
+     *
+     * @param identifier a string which uniquely identifies the item
+     * @return a {@link BibEntry} containing the bibliographic information (or an empty optional if no data was found)
+     */
+    Optional<BibEntry> performSearch(String identifier);
+}

src/main/java/net/sf/jabref/importer/fetcher/IdFetcher.java

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+/*
+ * Copyright (C) 2003-2016 JabRef contributors.
+ * This program 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+package net.sf.jabref.importer.fetcher;
+
+import net.sf.jabref.model.entry.BibEntry;
+
+/**
+ * Looks for article identifier based on already present bibliographic information.
+ */
+public interface IdFetcher {
+
+    /**
+     * Looks for an identifier based on the information stored in the given {@link BibEntry} and
+     * then updates the {@link BibEntry} with the found id.
+     *
+     * @param entry the {@link BibEntry} for which an identifier should be found
+     * @return an updated {@link BibEntry} containing the identifier (if an ID was found, otherwise the {@link BibEntry}
+     *         is left unchanged)
+     */
+    BibEntry updateIdentfier(BibEntry entry);
+}

src/main/java/net/sf/jabref/importer/fetcher/SearchBasedFetcher.java

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+/*
+ * Copyright (C) 2003-2016 JabRef contributors.
+ * This program 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+package net.sf.jabref.importer.fetcher;
+
+import java.util.List;
+
+import net.sf.jabref.model.entry.BibEntry;
+
+/**
+ * Searches web resources for bibliographic information based on a free-text query.
+ * May return multiple search hits.
+ */
+public interface SearchBasedFetcher extends WebFetcher {
+
+    /**
+     * Looks for hits which are matched by the given free-text query.
+     * This is the first step in the search procedure and we are mainly interested in the authors, title and the URL.
+     *
+     * @param query search string
+     * @return a list of {@link BibEntry}, which are matched by the query (may be empty)
+     */
+    List<BibEntry> performShallowSearch(String query);
+
+    /**
+     * Enriches the given {@link BibEntry} (which is usually an entry found by
+     * {@link #performShallowSearch(String)}) by additional information.
+     *
+     * @param entry the entry to be completed
+     * @return a {@link BibEntry} containing the enriched bibliographic information
+     */
+    BibEntry performDeepSearch(BibEntry entry);
+}

src/main/java/net/sf/jabref/importer/fetcher/WebFetcher.java

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+/*
+ * Copyright (C) 2003-2016 JabRef contributors.
+ * This program 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+package net.sf.jabref.importer.fetcher;
+
+import net.sf.jabref.gui.help.HelpFile;
+
+/**
+ * Searches web resources for bibliographic information.
+ */
+public interface WebFetcher {
+
+    /**
+     * Returns the localized name of this fetcher.
+     * The title can be used to display the fetcher in the menu and in the side pane.
+     *
+     * @return the localized name
+     */
+    String getName();
+
+    /**
+     * Returns the help page for this fetcher.
+     *
+     * @return the {@link HelpFile} enum constant for the help page
+     */
+    HelpFile getHelpPage();
+}