/*
 * Copyright (C) 2008 Nokia Corporation.
 * Copyright (C) 2008 Zeeshan Ali (Khattak) <zeeshanak@gnome.org>.
 * Copyright (C) 2012 Intel Corporation.
 *
 * Author: Zeeshan Ali (Khattak) <zeeshanak@gnome.org>
 *         Jens Georg <jensg@openismus.com>
 *
 * This file is part of Rygel.
 *
 * Rygel is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * Rygel 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

using GUPnP;
using Gee;

/**
 * This class is responsible for plugin loading.
 *
 * It probes for shared library files in a specific directory, tries to 
 * find a module_init() function with this signature:
 * ``void module_init (RygelPluginLoader* loader);``
 *
 * It then calls that function, passing a pointer to itself. The loaded
 * module can then add plugins to Rygel by calling the
 * rygel_plugin_loader_add_plugin() function.
 */
public class Rygel.PluginLoader : RecursiveModuleLoader {
    private delegate void ModuleInitFunc (PluginLoader loader);

    private HashMap<string,Plugin>            plugin_hash;
    private HashMap<string,PluginInformation> available_plugins;
    private HashSet<string>                   loaded_modules;
    private Configuration                     config;

    // Signals
    public signal void plugin_available (Plugin plugin);

    public PluginLoader () {
        Object (base_path: get_config_path ());
    }

    public override void constructed () {
        base.constructed ();

        if (this.base_path == null) {
            this.base_path = get_config_path ();
        }
        this.plugin_hash = new HashMap<string,Plugin> ();
        this.loaded_modules = new HashSet<string> ();
        this.config = MetaConfig.get_default ();
        this.config.section_changed.connect (this.on_section_changed);
        this.available_plugins = new HashMap<string, PluginInformation> ();
    }

    /**
     * Checks if a plugin is disabled by the user
     *
     * @param name the name of plugin to check for.
     *
     * @return true if plugin is disabled, false if not.
     */
    public bool plugin_disabled (string name) {
        var enabled = true;
        try {
            enabled = this.config.get_enabled (name);
        } catch (GLib.Error err) {
            debug ("Could not find plugin '%s' in configuration: %s",
                   name,
                   err.message);
        }

        return !enabled;
    }

    public void add_plugin (Plugin plugin) {
        message (_("New plugin “%s” available"), plugin.name);
        this.plugin_hash.set (plugin.name, plugin);
        this.plugin_available (plugin);
    }

    public Plugin? get_plugin_by_name (string name) {
        return this.plugin_hash.get (name);
    }

    public Collection<Plugin> list_plugins () {
        return this.plugin_hash.values;
    }

    protected override bool load_module_from_file (File module_file) {
        if (module_file.get_basename () in this.loaded_modules) {
            warning (_("A module named %s is already loaded"),
                     module_file.get_basename ());

            return true;
        }

        Module module = Module.open (module_file.get_path (),
                                     ModuleFlags.BIND_LOCAL);
        if (module == null) {
            warning (_("Failed to load module from path “%s”: %s"),
                     module_file.get_path (),
                     Module.error ());

            return true;
        }

        void* function;

        if (!module.symbol("module_init", out function)) {
            warning (_("Failed to find entry point function “%s” in “%s”: %s"),
                     "module_init",
                     module_file.get_path (),
                     Module.error ());

            return true;
        }

        unowned ModuleInitFunc module_init = (ModuleInitFunc) function;
        assert (module_init != null);
        this.loaded_modules.add (module_file.get_basename ());

        // We don't want our modules to ever unload
        module.make_resident ();

        module_init (this);

        debug ("Loaded module source: '%s'", module.name());

        return true;
    }

    protected override bool load_module_from_info (PluginInformation info) {
        this.available_plugins.set (info.name, info);
        if (this.plugin_disabled (info.name)) {
            debug ("Module '%s' disabled by user. Ignoring…",
                   info.name);

            return true;
        }

        var module_file = File.new_for_path (info.module_path);

        return this.load_module_from_file (module_file);
    }

    private void on_section_changed (string section, SectionEntry entry) {
        if (entry == SectionEntry.ENABLED) {
            try {
                var enabled = this.config.get_enabled (section);
                if (!enabled) {
                    if (section in plugin_hash) {
                        plugin_hash[section].active = enabled;
                    }
                } else {
                    if (section in plugin_hash) {
                        plugin_hash[section].active = enabled;
                    } else {
                        if (section in available_plugins) {
                            this.load_module_from_info
                                (available_plugins[section]);
                        }
                    }
                }
            } catch (Error error) {
                debug ("Failed to get enabled state for %s: %s",
                       section,
                       error.message);
            }
        }
    }

    private static string get_config_path () {
        var path = BuildConfig.PLUGIN_DIR;
        try {
            path = MetaConfig.get_default ().get_plugin_path ();
        } catch (Error error) {
            debug ("Could not get plugin path from config: %s, using %s",
                   error.message,
                   path);
        }

        return path;
    }
}
