path: root/e-util/e-plugin.c

/*
 * This program 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 of the License, or (at your option) version 3.
 *
 * 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with the program; if not, see <http://www.gnu.org/licenses/>  
 *
 *
 * Copyright (C) 1999-2008 Novell, Inc. (www.novell.com)
 */

#include <config.h>

#include <sys/types.h>
#include <string.h>

#include <glib/gi18n.h>

#include <gconf/gconf-client.h>

#include <libedataserver/e-msgport.h>
#include <libedataserver/e-data-server-util.h>
#include <libedataserver/e-xml-utils.h>

#include "e-plugin.h"
#include "e-util-private.h"

/* plugin debug */
#define pd(x)
/* plugin hook debug */
#define phd(x)

/*
<camel-plugin
  class="org.gnome.camel.plugin.provider:1.0"
  id="org.gnome.camel.provider.imap:1.0"
  type="shlib"
  location="/opt/gnome2/lib/camel/1.0/libcamelimap.so"
  factory="camel_imap_provider_new">
 <name>imap</name>
 <description>IMAP4 and IMAP4v1 mail store</description>
 <class-data class="org.gnome.camel.plugin.provider:1.0"
   protocol="imap"
   domain="mail"
   flags="remote,source,storage,ssl"/>
</camel-plugin>

<camel-plugin
  class="org.gnome.camel.plugin.sasl:1.0"
  id="org.gnome.camel.sasl.plain:1.0"
  type="shlib"
  location="/opt/gnome2/lib/camel/1.0/libcamelsasl.so"
  factory="camel_sasl_plain_new">
 <name>PLAIN</name>
 <description>SASL PLAIN authentication mechanism</description>
</camel-plugin>
*/

/* EPlugin stuff */
static gpointer ep_parent_class;

/* global table of plugin types by pluginclass.type */
static GHashTable *ep_types;
/* plugin load path */
static GSList *ep_path;
/* global table of plugins by plugin.id */
static GHashTable *ep_plugins;
/* a table of GSLists of plugins by hook class for hooks not loadable yet */
static GHashTable *ep_plugins_pending_hooks;
/* list of all cached xml docs:struct _plugin_doc's */
static EDList ep_plugin_docs = E_DLIST_INITIALISER(ep_plugin_docs);
/* gconf client */
static GConfClient *ep_gconf;
/* the list of disabled plugins from gconf */
static GSList *ep_disabled;

/* All classes which implement EPluginHooks, by class.id */
static GHashTable *eph_types;

struct _plugin_doc {
    struct _plugin_doc *next;
    struct _plugin_doc *prev;

    char *filename;
    xmlDocPtr doc;

    GSList *plugin_hooks;   /* EPlugin objects with pending hooks */
    GSList *plugins;    /* xmlNodePtr's of plugins with unknown type (mono,etc) */
};

enum {
    EP_PROP_0,
    EP_PROP_ENABLED
};

static gboolean
ep_check_enabled (const char *id)
{
    /* Return TRUE if 'id' is NOT in the disabled list. */
    return !g_slist_find_custom (ep_disabled, id, (GCompareFunc) strcmp);
}

static void
ep_set_enabled (const char *id, int state)
{
    /* Bail out if no change to state, when expressed as a boolean: */
    if ((state == 0) == (ep_check_enabled(id) == 0))
        return;

    if (state) {
        GSList *link;

        link = g_slist_find_custom (
            ep_disabled, id, (GCompareFunc) strcmp);
        if (link != NULL) {
            g_free (link->data);
            ep_disabled = g_slist_remove_link (ep_disabled, link);
        }
    } else
        ep_disabled = g_slist_prepend (ep_disabled, g_strdup (id));

    gconf_client_set_list(
        ep_gconf, "/apps/evolution/eplugin/disabled",
        GCONF_VALUE_STRING, ep_disabled, NULL);
}

static int
ep_construct (EPlugin *ep, xmlNodePtr root)
{
    xmlNodePtr node;
    int res = -1;
    char *localedir;

    ep->domain = e_plugin_xml_prop(root, "domain");
    if (ep->domain
        && (localedir = e_plugin_xml_prop(root, "localedir"))) {
#ifdef G_OS_WIN32
        char *mapped_localedir =
            e_util_replace_prefix (EVOLUTION_PREFIX,
                           e_util_get_prefix (),
                           localedir);
        g_free (localedir);
        localedir = mapped_localedir;
#endif
        bindtextdomain(ep->domain, localedir);
        g_free(localedir);
    }

    ep->name = e_plugin_xml_prop_domain(root, "name", ep->domain);

    pd(printf("creating plugin '%s' '%s'\n", ep->name?ep->name:"un-named", ep->id));

    node = root->children;
    while (node) {
        if (strcmp((char *)node->name, "hook") == 0) {
            struct _EPluginHook *hook;
            EPluginHookClass *type;
            char *class = e_plugin_xml_prop(node, "class");

            if (class == NULL) {
                g_warning("Plugin '%s' load failed in '%s', missing class property for hook", ep->id, ep->path);
                goto fail;
            }

            if (ep->enabled
                && eph_types != NULL
                && (type = g_hash_table_lookup(eph_types, class)) != NULL) {
                g_free(class);
                hook = g_object_new(G_OBJECT_CLASS_TYPE(type), NULL);
                res = type->construct(hook, ep, node);
                if (res == -1) {
                    g_warning("Plugin '%s' failed to load hook", ep->name);
                    g_object_unref(hook);
                    goto fail;
                } else {
                    ep->hooks = g_slist_append(ep->hooks, hook);
                }
            } else {
                gpointer l, oldclass;

                if (ep_plugins_pending_hooks == NULL)
                    ep_plugins_pending_hooks = g_hash_table_new(g_str_hash, g_str_equal);
                if (!g_hash_table_lookup_extended (ep_plugins_pending_hooks, class, &oldclass, &l)) {
                    oldclass = class;
                    l = NULL;
                }
                else {
                    g_free(class);
                }
                l = g_slist_prepend (l, ep);
                g_hash_table_insert (ep_plugins_pending_hooks, oldclass, l);
                ep->hooks_pending = g_slist_prepend (ep->hooks_pending, node);
            }
        } else if (strcmp((char *)node->name, "description") == 0) {
            ep->description = e_plugin_xml_content_domain(node, ep->domain);
        } else if (strcmp((char *)node->name, "author") == 0) {
            char *name = e_plugin_xml_prop(node, "name");
            char *email = e_plugin_xml_prop(node, "email");

            if (name || email) {
                EPluginAuthor *epa = g_malloc0(sizeof(*epa));

                epa->name = name;
                epa->email = email;
                ep->authors = g_slist_append(ep->authors, epa);
            }
        }
        node = node->next;
    }
    res = 0;
fail:
    return res;
}

static void
ep_enable (EPlugin *ep, int state)
{
    GSList *iter;

    ep->enabled = state;
    for (iter = ep->hooks; iter != NULL; iter = iter->next) {
        EPluginHook *hook = iter->data;
        e_plugin_hook_enable (hook, state);
    }

    ep_set_enabled(ep->id, state);
}

static void
ep_set_property (GObject *object,
                 guint property_id,
                 const GValue *value,
                 GParamSpec *pspec)
{
    switch (property_id) {
        case EP_PROP_ENABLED:
            e_plugin_enable (
                E_PLUGIN (object),
                g_value_get_boolean (value));
            return;
    }

    G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
}

static void
ep_get_property (GObject *object,
                 guint property_id,
                 GValue *value,
                 GParamSpec *pspec)
{
    EPlugin *ep = E_PLUGIN (object);

    switch (property_id) {
        case EP_PROP_ENABLED:
            g_value_set_boolean (value, ep->enabled);
            return;
    }

    G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
}

static void
ep_finalize (GObject *object)
{
    EPlugin *ep = E_PLUGIN (object);

    g_free (ep->id);
    g_free (ep->description);
    g_free (ep->name);
    g_free (ep->domain);
    g_slist_free (ep->hooks_pending);

    g_slist_foreach (ep->hooks, (GFunc) g_object_unref, NULL);
    g_slist_free (ep->hooks);

    /* Chain up to parent's finalize() method. */
    G_OBJECT_CLASS (ep_parent_class)->finalize (object);
}

static void
ep_class_init (EPluginClass *class)
{
    GObjectClass *object_class;

    ep_parent_class = g_type_class_peek_parent (class);

    object_class = G_OBJECT_CLASS (class);
    object_class->set_property = ep_set_property;
    object_class->get_property = ep_get_property;
    object_class->finalize = ep_finalize;

    class->construct = ep_construct;
    class->enable = ep_enable;

    g_object_class_install_property (
        object_class,
        EP_PROP_ENABLED,
        g_param_spec_boolean (
            "enabled",
            _("Enabled"),
            _("Whether the plugin is enabled"),
            TRUE,
            G_PARAM_READWRITE));
}

static void
ep_init (EPlugin *ep)
{
    ep->enabled = TRUE;
}

/**
 * e_plugin_get_type:
 *
 * Standard GObject type function.  This is only an abstract class, so
 * you can only use this to subclass EPlugin.
 *
 * Return value: The type.
 **/
GType
e_plugin_get_type (void)
{
    static GType type = 0;

    if (G_UNLIKELY (type == 0)) {
        char *path, *col, *p;

        static const GTypeInfo type_info = {
            sizeof (EPluginClass),
            (GBaseInitFunc) NULL,
            (GBaseFinalizeFunc) NULL,
            (GClassInitFunc) ep_class_init,
            (GClassFinalizeFunc) NULL,
            NULL,  /* class_data */
            sizeof (EPlugin),
            0,     /* n_preallocs */
            (GInstanceInitFunc) ep_init,
            NULL   /* value_table */
        };

        type = g_type_register_static (
            G_TYPE_OBJECT, "EPlugin", &type_info, 0);

        /* Add paths in the environment variable or default global
         * and user specific paths */
        path = g_strdup(g_getenv("EVOLUTION_PLUGIN_PATH"));
        if (path == NULL) {
            /* Add the global path */
            e_plugin_add_load_path(EVOLUTION_PLUGINDIR);

            path = g_build_filename(g_get_home_dir(), ".eplugins", NULL);
        }

        p = path;
        while ((col = strchr(p, G_SEARCHPATH_SEPARATOR))) {
            *col++ = 0;
            e_plugin_add_load_path(p);
            p = col;
        }
        e_plugin_add_load_path(p);
        g_free(path);
    }

    return type;
}

static EPlugin *
ep_load_plugin(xmlNodePtr root, struct _plugin_doc *pdoc)
{
    char *prop, *id;
    EPluginClass *class;
    EPlugin *ep;

    id = e_plugin_xml_prop(root, "id");
    if (id == NULL) {
        g_warning("Invalid e-plugin entry in '%s': no id", pdoc->filename);
        return NULL;
    }

    if (g_hash_table_lookup(ep_plugins, id)) {
        g_warning("Plugin '%s' already defined", id);
        g_free(id);
        return NULL;
    }

    prop = (char *)xmlGetProp(root, (const unsigned char *)"type");
    if (prop == NULL) {
        g_free(id);
        g_warning("Invalid e-plugin entry in '%s': no type", pdoc->filename);
        return NULL;
    }

    /* If we can't find a plugin, add it to a pending list which is checked when a new type is registered */
    class = g_hash_table_lookup(ep_types, prop);
    if (class == NULL) {
        pd(printf("Delaying loading of plugin '%s' unknown type '%s'\n", id, prop));
        g_free(id);
        xmlFree(prop);
        pdoc->plugins = g_slist_prepend(pdoc->plugins, root);
        return NULL;
    }
    xmlFree(prop);

    ep = g_object_new(G_TYPE_FROM_CLASS(class), NULL);
    ep->id = id;
    ep->path = g_strdup(pdoc->filename);
    ep->enabled = ep_check_enabled(id);
    if (e_plugin_construct(ep, root) == -1)
        e_plugin_enable(ep, FALSE);
    g_hash_table_insert(ep_plugins, ep->id, ep);

    return ep;
}

static int
ep_load(const char *filename, int load_level)
{
    xmlDocPtr doc;
    xmlNodePtr root;
    int res = -1;
    EPlugin *ep = NULL;
    int cache = FALSE;
    struct _plugin_doc *pdoc;

    doc = e_xml_parse_file (filename);
    if (doc == NULL)
        return -1;

    root = xmlDocGetRootElement(doc);
    if (strcmp((char *)root->name, "e-plugin-list") != 0) {
        g_warning("No <e-plugin-list> root element: %s", filename);
        xmlFreeDoc(doc);
        return -1;
    }

    pdoc = g_malloc0(sizeof(*pdoc));
    pdoc->doc = doc;
    pdoc->filename = g_strdup(filename);

    for (root = root->children; root ; root = root->next) {
        if (strcmp((char *)root->name, "e-plugin") == 0) {
            char *plugin_load_level, *is_system_plugin;

            plugin_load_level = NULL;
            plugin_load_level = e_plugin_xml_prop (root, "load_level");
            if (plugin_load_level) {
                if ((atoi (plugin_load_level) == load_level) ) {
                    ep = ep_load_plugin(root, pdoc);

                    if (ep) {
                        if (load_level == 1)
                            e_plugin_invoke (ep, "load_plugin_type_register_function", NULL);
                    }
                } 
            } else if (load_level == 2) {
                ep = ep_load_plugin(root, pdoc);
            }

            if (ep) {
                pd(printf ("\nloading plugin [%s] at load_level [%d]\n", ep->name, load_level));

                /* README: May be we can use load_levels to achieve the same thing.
                   But it may be confusing for a plugin writer */
                is_system_plugin = e_plugin_xml_prop (root, "system_plugin");
                if (is_system_plugin && !strcmp (is_system_plugin, "true")) {
                    e_plugin_enable (ep, TRUE);
                    ep->flags |= E_PLUGIN_FLAGS_SYSTEM_PLUGIN;
                } else
                    ep->flags &= ~E_PLUGIN_FLAGS_SYSTEM_PLUGIN;
                g_free (is_system_plugin);

                pdoc->plugin_hooks = g_slist_prepend(pdoc->plugin_hooks, ep);
                cache |= (ep->hooks_pending != NULL);
                ep = NULL;
            }
            cache |= pdoc->plugins != NULL;
        }
    }

    res = 0;

    if (cache) {
        pd(printf("Caching plugin description '%s' for unknown future hooks\n", filename));
        e_dlist_addtail(&ep_plugin_docs, (EDListNode *)pdoc);
    } else {
        pd(printf("freeing plugin description '%s', nothing uses it\n", filename));
        xmlFreeDoc(pdoc->doc);
        g_free(pdoc->filename);
        g_free(pdoc);
    }

    return res;
}

/* This loads a hook that was pending on a given plugin but the type wasn't registered yet */
/* This works in conjunction with ep_construct and e_plugin_hook_register_type to make sure
   everything works nicely together.  Apparently. */
static int
ep_load_pending(EPlugin *ep, EPluginHookClass *type)
{
    int res = 0;
    GSList *l, *p;

    phd(printf("New hook type registered '%s', loading pending hooks on plugin '%s'\n", type->id, ep->id));

    l = ep->hooks_pending;
    p = NULL;
    while (l) {
        GSList *n = l->next;
        xmlNodePtr node = l->data;
        char *class = (char *)xmlGetProp(node, (const unsigned char *)"class");
        EPluginHook *hook;

        phd(printf(" checking pending hook '%s'\n", class?class:"<unknown>"));

        if (class) {
            if (strcmp(class, type->id) == 0) {
                hook = g_object_new(G_OBJECT_CLASS_TYPE(type), NULL);

                /* Don't bother loading hooks for plugins that are not anyway enabled */
                if (ep->enabled) {
                    res = type->construct(hook, ep, node);
                    if (res == -1) {
                        g_warning("Plugin '%s' failed to load hook '%s'", ep->name, type->id);
                        g_object_unref(hook);
                    } else {
                        ep->hooks = g_slist_append(ep->hooks, hook);
                    }
                }

                if (p)
                    p->next = n;
                else
                    ep->hooks_pending = n;
                g_slist_free_1(l);
                l = p;
            }

            xmlFree(class);
        }

        p = l;
        l = n;
    }

    return res;
}

/**
 * e_plugin_add_load_path:
 * @path: The path to add to search for plugins.
 *
 * Add a path to be searched when e_plugin_load_plugins() is called.
 * By default the system plugin directory and ~/.eplugins is used as
 * the search path unless overriden by the environmental variable
 * %EVOLUTION_PLUGIN_PATH.
 *
 * %EVOLUTION_PLUGIN_PATH is a : separated list of paths to search for
 * plugin definitions in order.
 *
 * Plugin definitions are XML files ending in the extension ".eplug".
 **/
void
e_plugin_add_load_path(const char *path)
{
    ep_path = g_slist_append(ep_path, g_strdup(path));
}

/**
 * e_plugin_load_plugins:
 *
 * Scan the search path, looking for plugin definitions, and load them
 * into memory.
 *
 * Return value: Returns -1 if an error occurred.
 **/
int
e_plugin_load_plugins(void)
{
    GSList *l;
    int i;

    if (ep_types == NULL) {
        g_warning("no plugin types defined");
        return 0;
    }

    for (i=0; i < 3; i++) {
        for (l = ep_path;l;l = g_slist_next(l)) {
            GDir *dir;
            const char *d;
            char *path = l->data;

            pd(printf("scanning plugin dir '%s'\n", path));

            dir = g_dir_open(path, 0, NULL);
            if (dir == NULL) {
                /*g_warning("Could not find plugin path: %s", path);*/
                continue;
            }

            while ( (d = g_dir_read_name(dir)) ) {
                if (g_str_has_suffix  (d, ".eplug")) {
                    char * name = g_build_filename(path, d, NULL);

                    ep_load(name, i);
                    g_free(name);
                }
            }

            g_dir_close(dir);
        }
    }

    return 0;
}

/**
 * e_plugin_register_type:
 * @type: The GObject type of the plugin loader.
 *
 * Register a new plugin type with the plugin system.  Each type must
 * subclass EPlugin and must override the type member of the
 * EPluginClass with a unique name.
 **/
void
e_plugin_register_type(GType type)
{
    EPluginClass *class;
    struct _plugin_doc *pdoc, *ndoc;

    if (ep_types == NULL) {
        ep_types = g_hash_table_new(g_str_hash, g_str_equal);
        ep_plugins = g_hash_table_new(g_str_hash, g_str_equal);
        /* TODO: notify listening */
        ep_gconf = gconf_client_get_default();
        ep_disabled = gconf_client_get_list(ep_gconf, "/apps/evolution/eplugin/disabled", GCONF_VALUE_STRING, NULL);
    }

    class = g_type_class_ref(type);

    pd(printf("register plugin type '%s'\n", class->type));

    g_hash_table_insert(ep_types, (void *)class->type, class);

    /* check for pending plugins */
    pdoc = (struct _plugin_doc *)ep_plugin_docs.head;
    ndoc = pdoc->next;
    while (ndoc) {
        if (pdoc->plugins) {
            GSList *l, *add = NULL;

            for (l=pdoc->plugins;l;l=g_slist_next(l)) {
                xmlNodePtr root = l->data;
                char *prop_type;

                prop_type = (char *)xmlGetProp(root, (const unsigned char *)"type");
                if (!strcmp(prop_type, class->type))
                    add = g_slist_append(add, l->data);
                xmlFree(prop_type);
            }

            for (l=add;l;l=g_slist_next(l)) {
                xmlNodePtr root = l->data;
                EPlugin *ep;

                pdoc->plugins = g_slist_remove(pdoc->plugins, root);
                ep = ep_load_plugin(root, pdoc);
                if (ep)
                    pdoc->plugin_hooks = g_slist_prepend(pdoc->plugin_hooks, ep);
                /* TODO: garbage collect plugin doc? */
            }

            g_slist_free(add);
        }

        pdoc = ndoc;
        ndoc = ndoc->next;
    }
}

static void
ep_list_plugin(void *key, void *val, void *dat)
{
    GSList **l = (GSList **)dat;

    *l = g_slist_prepend(*l, g_object_ref(val));
}

/**
 * e_plugin_list_plugins: List all plugins.
 *
 * Static class method to retrieve a list of all current plugins.  They
 * are listed in no particular order.
 *
 * Return value: A GSList of all plugins, they must be
 * g_object_unref'd and the list freed.
 **/
GSList *
e_plugin_list_plugins(void)
{
    GSList *l = NULL;

    if (ep_plugins)
        g_hash_table_foreach(ep_plugins, ep_list_plugin, &l);

    return l;
}

/**
 * e_plugin_construct:
 * @ep: An EPlugin derived object.
 * @root: The XML root node of the sub-tree containing the plugin
 * definition.
 *
 * Helper to invoke the construct virtual method.
 *
 * Return value: The return from the construct virtual method.
 **/
int
e_plugin_construct(EPlugin *ep, xmlNodePtr root)
{
    EPluginClass *class;

    g_return_val_if_fail (E_IS_PLUGIN (ep), -1);

    class = E_PLUGIN_GET_CLASS (ep);
    g_return_val_if_fail (class->construct != NULL, -1);

    return class->construct (ep, root);
}

/**
 * e_plugin_invoke:
 * @ep:
 * @name: The name of the function to invoke. The format of this name
 * will depend on the EPlugin type and its language conventions.
 * @data: The argument to the function. Its actual type depends on
 * the hook on which the function resides. It is up to the called
 * function to get this right.
 *
 * Helper to invoke the invoke virtual method.
 *
 * Return value: The return of the plugin invocation.
 **/
void *
e_plugin_invoke(EPlugin *ep, const char *name, void *data)
{
    EPluginClass *class;

    g_return_val_if_fail (E_IS_PLUGIN (ep), NULL);
    g_return_val_if_fail (name != NULL, NULL);

    /* Prevent invocation on a disabled plugin. */
    g_return_val_if_fail (ep->enabled, NULL);

    class = E_PLUGIN_GET_CLASS (ep);
    g_return_val_if_fail (class->invoke != NULL, NULL);

    return class->invoke (ep, name, data);
}

/**
 * e_plugin_get_symbol:
 * @ep: an #EPlugin
 * @name: The name of the symbol to fetch. The format of this name
 * will depend on the EPlugin type and its language conventions.
 *
 * Helper to fetch a symbol name from a plugin.
 *
 * Return value: the symbol value, or %NULL if not found
 **/
void *
e_plugin_get_symbol(EPlugin *ep, const char *name)
{
    EPluginClass *class;

    g_return_val_if_fail (E_IS_PLUGIN (ep), NULL);

    class = E_PLUGIN_GET_CLASS (ep);
    g_return_val_if_fail (class->get_symbol != NULL, NULL);

    return class->get_symbol (ep, name);
}

/**
 * e_plugin_enable:
 * @ep:
 * @state:
 *
 * Set the enable state of a plugin.
 *
 * THIS IS NOT FULLY IMPLEMENTED YET
 **/
void
e_plugin_enable(EPlugin *ep, int state)
{
    EPluginClass *class;

    g_return_if_fail (E_IS_PLUGIN (ep));

    if ((ep->enabled == 0) == (state == 0))
        return;

    class = E_PLUGIN_GET_CLASS (ep);
    g_return_if_fail (class->enable != NULL);

    class->enable (ep, state);
    g_object_notify (G_OBJECT (ep), "enabled");
}

/**
 * e_plugin_get_configure_widget
 * @ep: an #EPlugin
 *
 * Plugin itself should have implemented "e_plugin_lib_get_configure_widget"
 * function * of prototype EPluginLibGetConfigureWidgetFunc.
 *
 * Returns: Configure widget or %NULL
 **/
GtkWidget *
e_plugin_get_configure_widget (EPlugin *ep)
{
    EPluginClass *class;

    g_return_val_if_fail (E_IS_PLUGIN (ep), NULL);

    class = E_PLUGIN_GET_CLASS (ep);
    if (class->get_configure_widget == NULL)
        return NULL;

    return class->get_configure_widget (ep);
}

/**
 * e_plugin_xml_prop:
 * @node: An XML node.
 * @id: The name of the property to retrieve.
 *
 * A static helper function to look up a property on an XML node, and
 * ensure it is allocated in GLib system memory.  If GLib isn't using
 * the system malloc then it must copy the property value.
 *
 * Return value: The property, allocated in GLib memory, or NULL if no
 * such property exists.
 **/
char *
e_plugin_xml_prop(xmlNodePtr node, const char *id)
{
    char *p = (char *)xmlGetProp(node, (const unsigned char *)id);

    if (g_mem_is_system_malloc()) {
        return p;
    } else {
        char * out = g_strdup(p);

        if (p)
            xmlFree(p);
        return out;
    }
}

/**
 * e_plugin_xml_prop_domain:
 * @node: An XML node.
 * @id: The name of the property to retrieve.
 * @domain: The translation domain for this string.
 *
 * A static helper function to look up a property on an XML node, and
 * translate it based on @domain.
 *
 * Return value: The property, allocated in GLib memory, or NULL if no
 * such property exists.
 **/
char *
e_plugin_xml_prop_domain(xmlNodePtr node, const char *id, const char *domain)
{
    char *p, *out;

    p = (char *)xmlGetProp(node, (const unsigned char *)id);
    if (p == NULL)
        return NULL;

    out = g_strdup(dgettext(domain, p));
    xmlFree(p);

    return out;
}

/**
 * e_plugin_xml_int:
 * @node: An XML node.
 * @id: The name of the property to retrieve.
 * @def: A default value if the property doesn't exist.  Can be used
 * to determine if the property isn't set.
 *
 * A static helper function to look up a property on an XML node as an
 * integer.  If the property doesn't exist, then @def is returned as a
 * default value instead.
 *
 * Return value: The value if set, or @def if not.
 **/
int
e_plugin_xml_int(xmlNodePtr node, const char *id, int def)
{
    char *p = (char *)xmlGetProp(node, (const unsigned char *)id);

    if (p)
        return atoi(p);
    else
        return def;
}

/**
 * e_plugin_xml_content:
 * @node:
 *
 * A static helper function to retrieve the entire textual content of
 * an XML node, and ensure it is allocated in GLib system memory.  If
 * GLib isn't using the system malloc them it must copy the content.
 *
 * Return value: The node content, allocated in GLib memory.
 **/
char *
e_plugin_xml_content(xmlNodePtr node)
{
    char *p = (char *)xmlNodeGetContent(node);

    if (g_mem_is_system_malloc()) {
        return p;
    } else {
        char * out = g_strdup(p);

        if (p)
            xmlFree(p);
        return out;
    }
}

/**
 * e_plugin_xml_content_domain:
 * @node:
 * @domain:
 *
 * A static helper function to retrieve the entire textual content of
 * an XML node, and ensure it is allocated in GLib system memory.  If
 * GLib isn't using the system malloc them it must copy the content.
 *
 * Return value: The node content, allocated in GLib memory.
 **/
char *
e_plugin_xml_content_domain(xmlNodePtr node, const char *domain)
{
    char *p, *out;

    p = (char *)xmlNodeGetContent(node);
    if (p == NULL)
        return NULL;

    out = g_strdup(dgettext(domain, p));
    xmlFree(p);

    return out;
}

/* ********************************************************************** */

static gpointer epl_parent_class;

/* TODO:
   We need some way to manage lifecycle.
   We need some way to manage state.

   Maybe just the g module init method will do, or we could add
   another which returns context.

   There is also the question of per-instance context, e.g. for config
   pages.
*/

static GList *missing_symbols = NULL;

static int
epl_loadmodule(EPlugin *ep, gboolean fatal)
{
    EPluginLib *epl = E_PLUGIN_LIB (ep);
    EPluginLibEnableFunc enable;

    if (epl->module != NULL)
        return 0;

    if ((epl->module = g_module_open(epl->location, 0)) == NULL) {
        if (fatal)
            g_warning("can't load plugin '%s': %s", epl->location, g_module_error());
        else
            missing_symbols = g_list_prepend (missing_symbols, g_object_ref (ep));
        return -1;
    }

    if (g_module_symbol(epl->module, "e_plugin_lib_enable", (void *)&enable)) {
        if (enable(epl, TRUE) != 0) {
            ep->enabled = FALSE;
            g_module_close(epl->module);
            epl->module = NULL;
            return -1;
        }
    }

    return 0;
}

void
e_plugin_load_plugins_with_missing_symbols (void)
{
    GList *list = missing_symbols;

    while (list) {
        EPlugin *ep = list->data;
        epl_loadmodule (ep, TRUE);
        g_object_unref (ep);
        list = g_list_next (list);
    }

    g_list_free (missing_symbols);
    missing_symbols = NULL;
}

static void *
epl_invoke(EPlugin *ep, const char *name, void *data)
{
    EPluginLib *epl = E_PLUGIN_LIB (ep);
    EPluginLibFunc cb;

    if (!ep->enabled) {
        g_warning("trying to invoke '%s' on disabled plugin '%s'", name, ep->id);
        return NULL;
    }

    if (epl_loadmodule(ep, FALSE) != 0)
        return NULL;

    if (!g_module_symbol(epl->module, name, (void *)&cb)) {
        g_warning("Cannot resolve symbol '%s' in plugin '%s' (not exported?)", name, epl->location);
        return NULL;
    }

    return cb(epl, data);
}

static void *
epl_get_symbol(EPlugin *ep, const gchar *name)
{
    EPluginLib *epl = E_PLUGIN_LIB (ep);
    gpointer symbol;

    if (epl_loadmodule (ep, FALSE) != 0)
        return NULL;

    if (!g_module_symbol (epl->module, name, &symbol))
        return NULL;

    return symbol;
}

static int
epl_construct(EPlugin *ep, xmlNodePtr root)
{
    EPluginLib *epl = E_PLUGIN_LIB (ep);

    if (E_PLUGIN_CLASS (epl_parent_class)->construct (ep, root) == -1)
        return -1;

    epl->location = e_plugin_xml_prop(root, "location");

    if (epl->location == NULL) {
        g_warning("Library plugin '%s' has no location", ep->id);
        return -1;
    }
#ifdef G_OS_WIN32
    {
        char *mapped_location =
            e_util_replace_prefix (EVOLUTION_PREFIX,
                           e_util_get_prefix (),
                           epl->location);
        g_free (epl->location);
        epl->location = mapped_location;
    }
#endif
    /* If we're enabled, check for the load-on-startup property */
    if (ep->enabled) {
        xmlChar *tmp;

        tmp = xmlGetProp(root, (const unsigned char *)"load-on-startup");
        if (tmp) {
            if (strcmp ((const char *)tmp, "after-ui") == 0) {
                missing_symbols = g_list_prepend (missing_symbols, g_object_ref (ep));
            } else {
                if (epl_loadmodule(ep, FALSE) != 0) {
                    xmlFree(tmp);
                    return -1;
                }
            }
            xmlFree(tmp);
        }
    }

    return 0;
}

static GtkWidget *
epl_get_configure_widget (EPlugin *ep)
{
    EPluginLib *epl = E_PLUGIN_LIB (ep);
    EPluginLibGetConfigureWidgetFunc get_configure_widget;

    pd (printf ("\n epl_get_configure_widget \n"));

    if (epl_loadmodule (ep, FALSE) != 0) {
        pd (printf ("\n epl_loadmodule  \n"));
        return NULL;
    }

    if (g_module_symbol (epl->module, "e_plugin_lib_get_configure_widget", (void *)&get_configure_widget)) {
        pd (printf ("\n g_module_symbol is loaded\n"));
        return (GtkWidget*) get_configure_widget (epl);
    }
    return NULL;
}

static void
epl_enable(EPlugin *ep, int state)
{
    EPluginLib *epl = E_PLUGIN_LIB (ep);
    EPluginLibEnableFunc enable;

    E_PLUGIN_CLASS (epl_parent_class)->enable (ep, state);

    /* if we're disabling and it isn't loaded, nothing to do */
    if (!state && epl->module == NULL)
        return;

    /* this will noop if we're disabling since we tested it above */
    if (epl_loadmodule(ep, FALSE) != 0)
        return;

    if (g_module_symbol(epl->module, "e_plugin_lib_enable", (void *)&enable)) {
        if (enable(epl, state) != 0)
            return;
    }
#if 0
    if (!state) {
        g_module_close(epl->module);
        epl->module = NULL;
    }
#endif
}

static void
epl_finalize (GObject *object)
{
    EPluginLib *epl = E_PLUGIN_LIB (object);

    g_free (epl->location);

    if (epl->module)
        g_module_close (epl->module);

    /* Chain up to parent's finalize() method. */
    G_OBJECT_CLASS (epl_parent_class)->finalize (object);
}

static void
epl_class_init (EPluginClass *class)
{
    GObjectClass *object_class;

    epl_parent_class = g_type_class_peek_parent (class);

    object_class = G_OBJECT_CLASS (class);
    object_class->finalize = epl_finalize;

    class->construct = epl_construct;
    class->invoke = epl_invoke;
    class->get_symbol = epl_get_symbol;
    class->enable = epl_enable;
    class->get_configure_widget = epl_get_configure_widget;
    class->type = "shlib";
}

/**
 * e_plugin_lib_get_type:
 *
 * Standard GObject function to retrieve the EPluginLib type.  Use to
 * register the type with the plugin system if you want to use shared
 * library plugins.
 *
 * Return value: The EPluginLib type.
 **/
GType
e_plugin_lib_get_type (void)
{
    static GType type = 0;

    if (G_UNLIKELY (type == 0)) {
        static const GTypeInfo type_info = {
            sizeof (EPluginLibClass),
            (GBaseInitFunc) NULL,
            (GBaseFinalizeFunc) NULL,
            (GClassInitFunc) epl_class_init,
            (GClassFinalizeFunc) NULL,
            NULL,  /* class_data */
            sizeof (EPluginLib),
            0,     /* n_preallocs */
            (GInstanceInitFunc) NULL,
            NULL   /* value_table */
        };

        type = g_type_register_static (
            e_plugin_get_type (), "EPluginLib", &type_info, 0);
    }

    return type;
}

/* ********************************************************************** */

static gpointer eph_parent_class;

static int
eph_construct(EPluginHook *eph, EPlugin *ep, xmlNodePtr root)
{
    eph->plugin = ep;

    return 0;
}

static void
eph_enable(EPluginHook *eph, int state)
{
    /* NOOP */
}

static void
eph_class_init(EPluginHookClass *class)
{
    eph_parent_class = g_type_class_peek_parent (class);

    class->construct = eph_construct;
    class->enable = eph_enable;
}

/**
 * e_plugin_hook_get_type:
 *
 * Standard GObject function to retrieve the EPluginHook type.  Since
 * EPluginHook is an abstract class, this is only used to subclass it.
 *
 * Return value: The EPluginHook type.
 **/
GType
e_plugin_hook_get_type(void)
{
    static GType type = 0;

    if (G_UNLIKELY (type == 0)) {
        static const GTypeInfo type_info = {
            sizeof (EPluginHookClass),
            (GBaseInitFunc) NULL,
            (GBaseFinalizeFunc) NULL,
            (GClassInitFunc) eph_class_init,
            (GClassFinalizeFunc) NULL,
            NULL,  /* class_data */
            sizeof (EPluginHook),
            0,     /* n_preallocs */
            (GInstanceInitFunc) NULL,
            NULL   /* value_table */
        };

        type = g_type_register_static (
            G_TYPE_OBJECT, "EPluginHook", &type_info, 0);
    }

    return type;
}

/**
 * e_plugin_hook_enable: Set hook enabled state.
 * @eph:
 * @state:
 *
 * Set the enabled state of the plugin hook.  This is called by the
 * plugin code.
 *
 * THIS IS NOT FULY IMEPLEMENTED YET
 **/
void
e_plugin_hook_enable (EPluginHook *eph, int state)
{
    EPluginHookClass *class;

    g_return_if_fail (E_IS_PLUGIN_HOOK (eph));

    class = E_PLUGIN_HOOK_GET_CLASS (eph);
    g_return_if_fail (class->enable != NULL);

    class->enable (eph, state);
}

/**
 * e_plugin_hook_register_type:
 * @type:
 *
 * Register a new plugin hook type with the plugin system.  Each type
 * must subclass EPluginHook and must override the id member of the
 * EPluginHookClass with a unique identification string.
 **/
void
e_plugin_hook_register_type(GType type)
{
    EPluginHookClass *klass, *oldklass;
    GSList *l;

    gpointer plugins; /* GSList */
    gpointer class;

    if (eph_types == NULL)
        eph_types = g_hash_table_new(g_str_hash, g_str_equal);

    klass = g_type_class_ref(type);

    oldklass = g_hash_table_lookup(eph_types, (void *)klass->id);
    if (oldklass == klass) {
        g_type_class_unref(klass);
        return;
    } else if (oldklass != NULL) {
        g_warning("Trying to re-register hook type '%s'", klass->id);
        return;
    }

    phd(printf("register plugin hook type '%s'\n", klass->id));
    g_hash_table_insert(eph_types, (void *)klass->id, klass);

    /* if we've already loaded a plugin that needed this hook but it didn't exist, re-load it now */

    if (ep_plugins_pending_hooks
        && g_hash_table_lookup_extended (ep_plugins_pending_hooks, klass->id, &class, &plugins)) {
        struct _plugin_doc *pdoc, *ndoc;

        g_hash_table_remove (ep_plugins_pending_hooks, class);
        g_free (class);
        for (l = plugins; l; l = g_slist_next(l)) {
            EPlugin *ep = l->data;

            ep_load_pending (ep, klass);
        }
        g_slist_free (plugins);

        /* See if we can now garbage collect the xml definition since its been fully loaded */

        /* This is all because libxml doesn't refcount! */

        pdoc = (struct _plugin_doc *)ep_plugin_docs.head;
        ndoc = pdoc->next;
        while (ndoc) {
            if (pdoc->doc) {
                int cache = pdoc->plugins != NULL;

                for (l=pdoc->plugin_hooks;!cache && l;l=g_slist_next(l))
                    cache |= (((EPlugin *)l->data)->hooks_pending != NULL);

                if (!cache) {
                    pd(printf("Gargabe collecting plugin description '%s'\n", pdoc->filename));
                    e_dlist_remove((EDListNode *)pdoc);
                    xmlFreeDoc(pdoc->doc);
                    g_free(pdoc->filename);
                    g_free(pdoc);
                }
            }

            pdoc = ndoc;
            ndoc = ndoc->next;
        }
    }
}

/**
 * e_plugin_hook_mask:
 * @root: An XML node.
 * @map: A zero-fill terminated array of EPluginHookTargeKeys used to
 * map a string with a bit value.
 * @prop: The property name.
 *
 * This is a static helper function which looks up a property @prop on
 * the XML node @root, and then uses the @map table to convert it into
 * a bitmask.  The property value is a comma separated list of
 * enumeration strings which are indexed into the @map table.
 *
 * Return value: A bitmask representing the inclusive-or of all of the
 * integer values of the corresponding string id's stored in the @map.
 **/
guint32
e_plugin_hook_mask(xmlNodePtr root, const struct _EPluginHookTargetKey *map, const char *prop)
{
    char *val, *p, *start, c;
    guint32 mask = 0;

    val = (char *)xmlGetProp(root, (const unsigned char *)prop);
    if (val == NULL)
        return 0;

    p = val;
    do {
        start = p;
        while (*p && *p != ',')
            p++;
        c = *p;
        *p = 0;
        if (start != p) {
            int i;

            for (i=0;map[i].key;i++) {
                if (!strcmp(map[i].key, start)) {
                    mask |= map[i].value;
                    break;
                }
            }
        }
        *p++ = c;
    } while (c);

    xmlFree(val);

    return mask;
}

/**
 * e_plugin_hook_id:
 * @root:
 * @map:
 * @prop:
 *
 * This is a static helper function which looks up a property @prop on
 * the XML node @root, and then uses the @map table to convert it into
 * an integer.
 *
 * This is used as a helper wherever you need to represent an
 * enumerated value in the XML.
 *
 * Return value: If the @prop value is in @map, then the corresponding
 * integer value, if not, then ~0.
 **/
guint32
e_plugin_hook_id(xmlNodePtr root, const struct _EPluginHookTargetKey *map, const char *prop)
{
    char *val;
    int i;

    val = (char *)xmlGetProp(root, (const unsigned char *)prop);
    if (val == NULL)
        return ~0;

    for (i=0;map[i].key;i++) {
        if (!strcmp(map[i].key, val)) {
            xmlFree(val);
            return map[i].value;
        }
    }

    xmlFree(val);

    return ~0;
}

/* ********************************************************************** */
/* Plugin plugin */

static gpointer epth_parent_class;

static int
epth_load_plugin(void *d)
{
    EPluginHook *eph = d;
    EPluginTypeHook *epth = d;
    GType type;

    epth->idle = 0;

    type = GPOINTER_TO_UINT(e_plugin_invoke(eph->plugin, epth->get_type, eph->plugin));
    if (type != 0)
        e_plugin_register_type(type);

    return FALSE;
}

static int
epth_construct(EPluginHook *eph, EPlugin *ep, xmlNodePtr root)
{
    EPluginTypeHook *epth = E_PLUGIN_TYPE_HOOK (eph);
    xmlNodePtr node;

    phd(printf("loading plugin hook\n"));

    if (((EPluginHookClass *)epth_parent_class)->construct(eph, ep, root) == -1)
        return -1;

    node = root->children;
    while (node) {
        if (strcmp((char *)node->name, "plugin-type") == 0) {
            epth->get_type = e_plugin_xml_prop(node, "get-type");
            /* We need to run this in an idle handler,
             * since at this point the parent EPlugin wont
             * be fully initialised ... darn */
            if (epth->get_type)
                epth->idle = g_idle_add(epth_load_plugin, epth);
            else
                g_warning("Plugin type plugin missing get-type callback");
        }
        node = node->next;
    }

    eph->plugin = ep;

    return 0;
}

static void
epth_finalize (GObject *object)
{
    EPluginTypeHook *epth = E_PLUGIN_TYPE_HOOK (object);

    if (epth->idle != 0)
        g_source_remove (epth->idle);

    g_free (epth->get_type);

    /* Chain up to parent's finalize() method. */
    G_OBJECT_CLASS (epth_parent_class)->finalize (object);
}

static void
epth_class_init (EPluginTypeHookClass *class)
{
    GObjectClass *object_class;
    EPluginHookClass *hook_class;

    epth_parent_class = g_type_class_peek_parent (class);

    object_class = G_OBJECT_CLASS (class);
    object_class->finalize = epth_finalize;

    hook_class = E_PLUGIN_HOOK_CLASS (class);
    hook_class->construct = epth_construct;
    hook_class->id = "org.gnome.evolution.plugin.type:1.0";
}

/**
 * e_plugin_type_hook_get_type:
 *
 * Get the type for the plugin plugin hook.
 *
 * Return value: The type of the plugin type hook.
 **/
GType
e_plugin_type_hook_get_type(void)
{
    static GType type = 0;

    if (G_UNLIKELY (type == 0)) {
        static const GTypeInfo type_info = {
            sizeof (EPluginTypeHookClass),
            (GBaseInitFunc) NULL,
            (GBaseFinalizeFunc) NULL,
            (GClassInitFunc) epth_class_init,
            (GClassFinalizeFunc) NULL,
            NULL,  /* class_data */
            sizeof (EPluginTypeHook),
            0,     /* n_preallocs */
            (GInstanceInitFunc) NULL,
            NULL   /* value_table */
        };

        type = g_type_register_static (
            E_TYPE_PLUGIN_HOOK, "EPluginTypeHook", &type_info, 0);
    }

    return type;
}