7 files changed, 287 insertions, 115 deletions

diff --git a/camel/ChangeLog b/camel/ChangeLog
index 28bc79c521..8a9babf597 100644
--- a/camel/ChangeLog
+++ b/camel/ChangeLog
@@ -1,3 +1,22 @@
+2000-04-06  Dan Winship  <danw@helixcode.com>
+
+	* camel-store.[ch]: Reorganize the folder-fetching methods and
+	implement a folder cache so that multiple requests for the same
+	folder will yield the same CamelFolder object (as long as it
+	remains active). Includes some code to remove no-longer-active
+	folders from the cache, but it doesn't get used since nothing is
+	ever unref'ed in Camel right now...
+	
+	* providers/mbox/camel-mbox-store.c:
+	* providers/pop3/camel-pop3-store.c: update for CamelStore
+	changes.
+
+	* camel-folder.[ch]: Remove the (unused) CamelException argument
+	from camel_folder_get_name and camel_folder_get_full_name.
+	(camel_folder_set_name): make this go away since changing a
+	folder's name after it has been created could result in it
+	conflicting with a separately-issued folder.
+	
 2000-04-05  Dan Winship  <danw@helixcode.com>
 
 	* g_url_new really wanted to take a CamelException. So, rename
diff --git a/camel/camel-folder.c b/camel/camel-folder.c
index e6ab27b876..dffbb7d011 100644
--- a/camel/camel-folder.c
+++ b/camel/camel-folder.c
@@ -70,9 +70,8 @@ static void _close_async (CamelFolder *folder,
 static void _set_name (CamelFolder *folder, 
 		       const gchar *name, 
 		       CamelException *ex);
-static const gchar *_get_name (CamelFolder *folder, 
-			       CamelException *ex);
-static const gchar *_get_full_name (CamelFolder *folder, CamelException *ex);
+static const gchar *_get_name (CamelFolder *folder);
+static const gchar *_get_full_name (CamelFolder *folder);
 
 
 static gboolean _can_hold_folders  (CamelFolder *folder);
@@ -270,7 +269,7 @@ _init (CamelFolder *folder, CamelStore *parent_store,
 	folder->open_mode = FOLDER_OPEN_UNKNOWN;
 	folder->open_state = FOLDER_CLOSE;
 	folder->separator = separator;
-	camel_folder_set_name (folder, name, ex);
+	CF_CLASS (folder)->set_name (folder, name, ex);
 }
 
 
@@ -462,8 +461,7 @@ _set_name (CamelFolder *folder,
 
 	if (folder->parent_folder) {
 		parent_full_name =
-			camel_folder_get_full_name (folder->parent_folder, ex);
-		if (camel_exception_get_id (ex)) return;
+			camel_folder_get_full_name (folder->parent_folder);
 		
 		full_name = g_strdup_printf ("%s%c%s", parent_full_name,
 					     folder->separator, name);
@@ -479,24 +477,9 @@ _set_name (CamelFolder *folder,
 }
 
 
-/**
- * camel_folder_set_name:set the (short) name of the folder
- * @folder: folder
- * @name: new name of the folder
- * @ex: exception object
- **/
-void
-camel_folder_set_name (CamelFolder *folder, const gchar *name,
-		       CamelException *ex)
-{
-	g_assert (folder != NULL);
-	CF_CLASS (folder)->set_name (folder, name, ex);
-}
-
-
 
 static const gchar *
-_get_name (CamelFolder *folder, CamelException *ex)
+_get_name (CamelFolder *folder)
 {
 	return folder->name;
 }
@@ -512,16 +495,16 @@ _get_name (CamelFolder *folder, CamelException *ex)
  * Return value: name of the folder
  **/
 const gchar *
-camel_folder_get_name (CamelFolder *folder, CamelException *ex)
+camel_folder_get_name (CamelFolder *folder)
 {
 	g_assert (folder != NULL);
-	return CF_CLASS (folder)->get_name (folder, ex);
+	return CF_CLASS (folder)->get_name (folder);
 }
 
 
 
 static const gchar *
-_get_full_name (CamelFolder *folder, CamelException *ex)
+_get_full_name (CamelFolder *folder)
 {
 	return folder->full_name;
 }
@@ -535,10 +518,10 @@ _get_full_name (CamelFolder *folder, CamelException *ex)
  * Return value: full name of the folder
  **/
 const gchar *
-camel_folder_get_full_name (CamelFolder *folder, CamelException *ex)
+camel_folder_get_full_name (CamelFolder *folder)
 {
 	g_assert (folder != NULL);
-	return CF_CLASS (folder)->get_full_name (folder, ex);
+	return CF_CLASS (folder)->get_full_name (folder);
 }
 
 
@@ -648,9 +631,7 @@ _get_subfolder (CamelFolder *folder,
 	
 	g_assert (folder->parent_store != NULL);
 	
-	current_folder_full_name = camel_folder_get_full_name (folder, ex);
-	if (camel_exception_get_id (ex)) return NULL;
-
+	current_folder_full_name = camel_folder_get_full_name (folder);
 
 	full_name = g_strdup_printf ("%s%c%s", current_folder_full_name,
 				     folder->separator, folder_name);
diff --git a/camel/camel-folder.h b/camel/camel-folder.h
index c6a36cd3a7..9a717e3db6 100644
--- a/camel/camel-folder.h
+++ b/camel/camel-folder.h
@@ -115,11 +115,9 @@ typedef struct {
 			     const gchar *name, 
 			     CamelException *ex);
 
-	const gchar *  (*get_name)  (CamelFolder *folder, 
-				     CamelException *ex);
+	const gchar *  (*get_name)  (CamelFolder *folder);
 
-	const gchar *  (*get_full_name)  (CamelFolder *folder, 
-					  CamelException *ex);
+	const gchar *  (*get_full_name)  (CamelFolder *folder);
 
 	gboolean   (*can_hold_folders)   (CamelFolder *folder);
 
@@ -253,14 +251,9 @@ GList *            camel_folder_expunge                (CamelFolder *folder,
 							CamelException *ex);
 
 
-/* folder name manipulation operations */
-void               camel_folder_set_name               (CamelFolder *folder, 
-							const gchar *name, 
-							CamelException *ex);
-const gchar *      camel_folder_get_name               (CamelFolder *folder, 
-							CamelException *ex);
-const gchar *      camel_folder_get_full_name          (CamelFolder *folder, 
-							CamelException *ex);
+/* folder name operations */
+const gchar *      camel_folder_get_name               (CamelFolder *folder);
+const gchar *      camel_folder_get_full_name          (CamelFolder *folder);
 
 
 /* various properties accessors */
diff --git a/camel/camel-store.c b/camel/camel-store.c
index a8a72c4d25..58079bdab6 100644
--- a/camel/camel-store.c
+++ b/camel/camel-store.c
@@ -1,10 +1,11 @@
 /* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
-/* camelStore.c : Abstract class for an email store */
+/* camel-store.c : Abstract class for an email store */
 
 /* 
  *
- * Author : 
+ * Authors:
  *  Bertrand Guiheneuf <bertrand@helixcode.com>
+ *  Dan Winship <danw@helixcode.com>
  *
  * Copyright 1999, 2000 Helix Code, Inc. (http://www.helixcode.com)
  *
@@ -25,6 +26,7 @@
  */
 #include <config.h>
 #include "camel-store.h"
+#include "camel-folder.h"
 #include "camel-exception.h"
 #include "camel-log.h"
 
@@ -33,35 +35,50 @@ static CamelServiceClass *parent_class = NULL;
 /* Returns the class for a CamelStore */
 #define CS_CLASS(so) CAMEL_STORE_CLASS (GTK_OBJECT(so)->klass)
 
-static CamelFolder *_get_root_folder(CamelStore *store, CamelException *ex);
-static CamelFolder *_get_default_folder(CamelStore *store, CamelException *ex);
-static CamelFolder *_get_folder (CamelStore *store, const gchar *folder_name, CamelException *ex);
+static CamelFolder *get_folder (CamelStore *store, const char *folder_name,
+				CamelException *ex);
+
+static char *get_folder_name (CamelStore *store, const char *folder_name,
+			      CamelException *ex);
+static char *get_root_folder_name (CamelStore *store, CamelException *ex);
+static char *get_default_folder_name (CamelStore *store, CamelException *ex);
+
+static CamelFolder *lookup_folder (CamelStore *store, const char *folder_name);
+static void cache_folder (CamelStore *store, const char *folder_name,
+			  CamelFolder *folder);
+static void uncache_folder (CamelStore *store, CamelFolder *folder);
+
+static void finalize (GtkObject *object);
 
 static void
 camel_store_class_init (CamelStoreClass *camel_store_class)
 {
+	GtkObjectClass *gtk_object_class =
+		GTK_OBJECT_CLASS (camel_store_class);
 
 	parent_class = gtk_type_class (camel_service_get_type ());
-	
-	/* virtual method definition */
-	camel_store_class->get_folder = _get_folder;
-	camel_store_class->get_root_folder = _get_root_folder;
-	camel_store_class->get_default_folder = _get_default_folder;
-}
-
-
-
 
+	/* virtual method definition */
+	camel_store_class->get_folder = get_folder;
+	camel_store_class->get_folder_name = get_folder_name;
+	camel_store_class->get_root_folder_name = get_root_folder_name;
+	camel_store_class->get_default_folder_name = get_default_folder_name;
+	camel_store_class->lookup_folder = lookup_folder;
+	camel_store_class->cache_folder = cache_folder;
+	camel_store_class->uncache_folder = uncache_folder;
 
+	/* virtual method override */
+	gtk_object_class->finalize = finalize;
+}
 
 
 GtkType
 camel_store_get_type (void)
 {
 	static GtkType camel_store_type = 0;
-	
-	if (!camel_store_type)	{
-		GtkTypeInfo camel_store_info =	
+
+	if (!camel_store_type) {
+		GtkTypeInfo camel_store_info =
 		{
 			"CamelStore",
 			sizeof (CamelStore),
@@ -72,73 +89,187 @@ camel_store_get_type (void)
 				/* reserved_2 */ NULL,
 			(GtkClassInitFunc) NULL,
 		};
-		
+
 		camel_store_type = gtk_type_unique (CAMEL_SERVICE_TYPE, &camel_store_info);
 	}
-	
+
 	return camel_store_type;
 }
 
 
+static void
+finalize (GtkObject *object)
+{
+	CamelStore *store = CAMEL_STORE (object);
 
+	if (store->folders) {
+		if (g_hash_table_size (store->folders) != 0) {
+			g_warning ("Folder cache for store %p contains "
+				   "%d folders at destruction.", store,
+				   g_hash_table_size (store->folders));
+		}
+		g_hash_table_destroy (store->folders);
+	}
+}
+
+
+static CamelFolder *
+get_folder (CamelStore *store, const char *folder_name, CamelException *ex)
+{
+	g_warning ("CamelStore::get_folder not implemented for `%s'",
+		   gtk_type_name (GTK_OBJECT_TYPE (store)));
+	return NULL;
+}
+
+static char *
+get_folder_name (CamelStore *store, const char *folder_name,
+		 CamelException *ex)
+{
+	g_warning ("CamelStore::get_folder_name not implemented for `%s'",
+		   gtk_type_name (GTK_OBJECT_TYPE (store)));
+	return NULL;
+}
+
+static char *
+get_root_folder_name (CamelStore *store, CamelException *ex)
+{
+	return g_strdup ("/");
+}
+
+static char *
+get_default_folder_name (CamelStore *store, CamelException *ex)
+{
+	return CS_CLASS (store)->get_root_folder_name (store, ex);
+}
 
 static CamelFolder *
-_get_folder (CamelStore *store, const gchar *folder_name, CamelException *ex)
+lookup_folder (CamelStore *store, const char *folder_name)
 {
+	if (store->folders)
+		return g_hash_table_lookup (store->folders, folder_name);
 	return NULL;
 }
 
+static void
+cache_folder (CamelStore *store, const char *folder_name, CamelFolder *folder)
+{
+	if (!store->folders)
+		return;
+
+	if (g_hash_table_lookup (store->folders, folder_name)) {
+		g_warning ("Caching folder %s that already exists.",
+			   folder_name);
+	}
+	g_hash_table_insert (store->folders, (gpointer)folder_name, folder);
+	gtk_signal_connect_object (GTK_OBJECT (folder), "destroy",
+				   GTK_SIGNAL_FUNC (CS_CLASS (store)->uncache_folder),
+				   GTK_OBJECT (store));
+}
+
+static void
+uncache_folder (CamelStore *store, CamelFolder *folder)
+{
+	g_hash_table_remove (store->folders,
+			     camel_folder_get_full_name (folder));
+}
+
+
+static CamelFolder *
+get_folder_internal (CamelStore *store, const char *folder_name,
+		     CamelException *ex)
+{
+	CamelFolder *folder = NULL;
+
+	/* Try cache first. */
+	folder = CS_CLASS (store)->lookup_folder (store, folder_name);
+
+	if (!folder) {
+		folder = CS_CLASS (store)->get_folder (store, folder_name, ex);
+		if (!folder)
+			return NULL;
+
+		CS_CLASS (store)->cache_folder (store, folder_name, folder);
+	}
+
+	gtk_object_ref (GTK_OBJECT (folder));
+	return folder;
+}
+
+
 
 /** 
- * camel_store_get_folder: return the folder corresponding to a path.
- * @store: store
+ * camel_store_get_folder: Return the folder corresponding to a path.
+ * @store: a CamelStore
  * @folder_name: name of the folder to get
+ * @ex: a CamelException
  * 
- * Returns the folder corresponding to the path "name". 
- * If the path begins with the separator caracter, it 
- * is relative to the root folder. Otherwise, it is
- * relative to the default folder.
- * The folder does not necessarily exist on the store.
- * To make sure it already exists, use its "exists" method.
- * If it does not exist, you can create it with its 
- * "create" method.
- *
+ * Returns the folder corresponding to the path "name". If the path
+ * begins with the separator character, it is relative to the root
+ * folder. Otherwise, it is relative to the default folder. The folder
+ * does not necessarily already exist on the store. To test if it
+ * already exists, use its "exists" method. If it does not exist, you
+ * can create it with its "create" method.
  *
  * Return value: the folder
  **/
 CamelFolder *
-camel_store_get_folder (CamelStore *store, const gchar *folder_name, CamelException *ex)
+camel_store_get_folder (CamelStore *store, const char *folder_name,
+			CamelException *ex)
 {
-	return CS_CLASS(store)->get_folder (store, folder_name, ex);
+	char *name;
+	CamelFolder *folder = NULL;
+
+	name = CS_CLASS (store)->get_folder_name (store, folder_name, ex);
+	if (name) {
+		folder = get_folder_internal (store, name, ex);
+		g_free (name);
+	}
+	return folder;
 }
 
 
 /**
- * camel_store_get_root_folder : return the toplevel folder
+ * camel_store_get_root_folder: return the top-level folder
  * 
- * Returns the folder which is at the top of the folder
- * hierarchy. This folder is generally different from
- * the default folder. 
+ * Returns the folder which is at the top of the folder hierarchy.
+ * This folder may or may not be the same as the default folder.
  * 
- * @Return value: the toplevel folder.
+ * Return value: the top-level folder.
  **/
-static CamelFolder *
-_get_root_folder (CamelStore *store, CamelException *ex)
+CamelFolder *
+camel_store_get_root_folder (CamelStore *store, CamelException *ex)
 {
-    return NULL;
+	char *name;
+	CamelFolder *folder = NULL;
+
+	name = CS_CLASS (store)->get_root_folder_name (store, ex);
+	if (name) {
+		folder = get_folder_internal (store, name, ex);
+		g_free (name);
+	}
+	return folder;
 }
 
 /** 
- * camel_store_get_default_folder : return the store default folder
+ * camel_store_get_default_folder: return the store default folder
  *
- * The default folder is the folder which is presented 
- * to the user in the default configuration. The default
- * is often the root folder.
+ * The default folder is the folder which is presented to the user in
+ * the default configuration. This defaults to the root folder if
+ * the store doesn't override it.
  *
- *  @Return value: the default folder.
+ * Return value: the default folder.
  **/
-static CamelFolder *
-_get_default_folder (CamelStore *store, CamelException *ex)
+CamelFolder *
+camel_store_get_default_folder (CamelStore *store, CamelException *ex)
 {
-    return NULL;
+	char *name;
+	CamelFolder *folder = NULL;
+
+	name = CS_CLASS (store)->get_default_folder_name (store, ex);
+	if (name) {
+		folder = get_folder_internal (store, name, ex);
+		g_free (name);
+	}
+	return folder;
 }
+
diff --git a/camel/camel-store.h b/camel/camel-store.h
index af5aa959a6..d66e6344b5 100644
--- a/camel/camel-store.h
+++ b/camel/camel-store.h
@@ -46,32 +46,51 @@ extern "C" {
 
 struct _CamelStore
 {
-	CamelService parent_object;	
-	
+	CamelService parent_object;
+
+	GHashTable *folders;
+
 };
 
 
 
 typedef struct {
 	CamelServiceClass parent_class;
-	
-	CamelFolder *       (*get_folder)           (CamelStore *store, 
-						     const gchar *folder_name, 
+
+	CamelFolder *   (*get_folder)               (CamelStore *store,
+						     const char *folder_name,
+						     CamelException *ex);
+
+	char *          (*get_folder_name)          (CamelStore *store,
+						     const char *folder_name,
 						     CamelException *ex);
-	CamelFolder *       (*get_root_folder)      (CamelStore *store, 
+	char *          (*get_root_folder_name)     (CamelStore *store,
 						     CamelException *ex);
-	CamelFolder *       (*get_default_folder)   (CamelStore *store, 
+	char *          (*get_default_folder_name)  (CamelStore *store,
 						     CamelException *ex);
 
-} CamelStoreClass;
+        CamelFolder *   (*lookup_folder)            (CamelStore *store,
+						     const char *folder_name);
+	void            (*cache_folder)             (CamelStore *store,
+						     const char *folder_name,
+						     CamelFolder *folder);
+        void            (*uncache_folder)           (CamelStore *store,
+						     CamelFolder *folder);
 
+} CamelStoreClass;
 
-/* public methods */
 
 /* Standard Gtk function */
 GtkType camel_store_get_type (void);
 
-CamelFolder *    camel_store_get_folder       (CamelStore *store, const gchar *folder_name, CamelException *ex);
+/* public methods */
+CamelFolder *    camel_store_get_folder         (CamelStore *store,
+					         const char *folder_name,
+					         CamelException *ex);
+CamelFolder *    camel_store_get_root_folder    (CamelStore *store,
+					         CamelException *ex);
+CamelFolder *    camel_store_get_default_folder (CamelStore *store,
+						 CamelException *ex);
 
 #ifdef __cplusplus
 }
diff --git a/camel/providers/mbox/camel-mbox-store.c b/camel/providers/mbox/camel-mbox-store.c
index 32d25becf1..0081aedb0e 100644
--- a/camel/providers/mbox/camel-mbox-store.c
+++ b/camel/providers/mbox/camel-mbox-store.c
@@ -35,8 +35,10 @@
 #define CF_CLASS(so) CAMEL_FOLDER_CLASS (GTK_OBJECT(so)->klass)
 #define CMBOXF_CLASS(so) CAMEL_MBOX_FOLDER_CLASS (GTK_OBJECT(so)->klass)
 
-static CamelFolder *_get_folder (CamelStore *store, const gchar *folder_name, CamelException *ex);
-
+static CamelFolder *get_folder (CamelStore *store, const char *folder_name,
+				CamelException *ex);
+static char *get_folder_name (CamelStore *store, const char *folder_name,
+			      CamelException *ex);
 
 static void
 camel_mbox_store_class_init (CamelMboxStoreClass *camel_mbox_store_class)
@@ -44,7 +46,8 @@ camel_mbox_store_class_init (CamelMboxStoreClass *camel_mbox_store_class)
 	CamelStoreClass *camel_store_class = CAMEL_STORE_CLASS (camel_mbox_store_class);
 	
 	/* virtual method overload */
-	camel_store_class->get_folder = _get_folder;
+	camel_store_class->get_folder = get_folder;
+	camel_store_class->get_folder_name = get_folder_name;
 }
 
 
@@ -53,8 +56,12 @@ static void
 camel_mbox_store_init (gpointer object, gpointer klass)
 {
 	CamelService *service = CAMEL_SERVICE (object);
+	CamelStore *store = CAMEL_STORE (object);
 
 	service->url_flags = CAMEL_SERVICE_URL_NEED_PATH;
+
+	/* mbox names are filenames, so they are case-sensitive. */
+	store->folders = g_hash_table_new (g_str_hash, g_str_equal);
 }
 
 
@@ -97,15 +104,11 @@ camel_mbox_store_get_toplevel_dir (CamelMboxStore *store)
 
 
 static CamelFolder *
-_get_folder (CamelStore *store, const gchar *folder_name, CamelException *ex)
+get_folder (CamelStore *store, const char *folder_name, CamelException *ex)
 {
 	CamelMboxFolder *new_mbox_folder;
 	CamelFolder *new_folder;
 
-	/* check if folder has already been created */
-	/* call the standard routine for that when  */
-	/* it is done ... */
-
 	CAMEL_LOG_FULL_DEBUG ("Entering CamelMboxStore::get_folder\n");
 	new_mbox_folder =  gtk_type_new (CAMEL_MBOX_FOLDER_TYPE);
 	new_folder = CAMEL_FOLDER (new_mbox_folder);
@@ -121,3 +124,10 @@ _get_folder (CamelStore *store, const gchar *folder_name, CamelException *ex)
 
 	return new_folder;
 }
+
+static char *
+get_folder_name (CamelStore *store, const char *folder_name,
+		 CamelException *ex)
+{
+	return g_strdup (folder_name);
+}
diff --git a/camel/providers/pop3/camel-pop3-store.c b/camel/providers/pop3/camel-pop3-store.c
index f14ed1dc55..b63cd30342 100644
--- a/camel/providers/pop3/camel-pop3-store.c
+++ b/camel/providers/pop3/camel-pop3-store.c
@@ -55,8 +55,11 @@ static gboolean pop3_disconnect (CamelService *service, CamelException *ex);
 static GList *query_auth_types (CamelService *service);
 static void free_auth_types (CamelService *service, GList *authtypes);
 
-static CamelFolder *get_folder (CamelStore *store, const gchar *folder_name, 
+static CamelFolder *get_folder (CamelStore *store, const char *folder_name, 
 				CamelException *ex);
+static char *get_folder_name (CamelStore *store, const char *folder_name, 
+			      CamelException *ex);
+static char *get_root_folder_name (CamelStore *store, CamelException *ex);
 
 
 static void
@@ -79,9 +82,9 @@ camel_pop3_store_class_init (CamelPop3StoreClass *camel_pop3_store_class)
 	camel_service_class->query_auth_types = query_auth_types;
 	camel_service_class->free_auth_types = free_auth_types;
 
-	camel_store_class->get_root_folder = camel_pop3_folder_new;
-	camel_store_class->get_default_folder = camel_pop3_folder_new;
 	camel_store_class->get_folder = get_folder;
+	camel_store_class->get_folder_name = get_folder_name;
+	camel_store_class->get_root_folder_name = get_root_folder_name;
 }
 
 
@@ -90,9 +93,11 @@ static void
 camel_pop3_store_init (gpointer object, gpointer klass)
 {
 	CamelService *service = CAMEL_SERVICE (object);
+	CamelStore *store = CAMEL_STORE (object);
 
 	service->url_flags = ( CAMEL_SERVICE_URL_NEED_USER |
 			       CAMEL_SERVICE_URL_NEED_HOST );
+	store->folders = g_hash_table_new (g_str_hash, g_str_equal);
 }
 
 
@@ -324,11 +329,18 @@ pop3_disconnect (CamelService *service, CamelException *ex)
 	return TRUE;
 }
 
-static CamelFolder *get_folder (CamelStore *store, const gchar *folder_name, 
-				CamelException *ex)
+static CamelFolder *
+get_folder (CamelStore *store, const char *folder_name, CamelException *ex)
+{
+	return camel_pop3_folder_new (store, ex);
+}
+
+static char *
+get_folder_name (CamelStore *store, const char *folder_name,
+		 CamelException *ex)
 {
 	if (!strcasecmp (folder_name, "inbox"))
-		return camel_pop3_folder_new (store, ex);
+		return g_strdup ("inbox");
 	else {
 		camel_exception_setv (ex, CAMEL_EXCEPTION_FOLDER_INVALID,
 				      "No such folder `%s'.", folder_name);
@@ -336,6 +348,13 @@ static CamelFolder *get_folder (CamelStore *store, const gchar *folder_name,
 	}
 }
 
+static char *
+get_root_folder_name (CamelStore *store, CamelException *ex)
+{
+	return g_strdup ("inbox");
+}
+
+
 /**
  * camel_pop3_command: Send a command to a POP3 server.
  * @store: the POP3 store