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/*
 * e-shell-migrate.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)
 *
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include "e-shell-migrate.h"

#include <libedataserver/libedataserver.h>

#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <glib/gi18n.h>
#include <glib/gstdio.h>

#include "es-event.h"
#include "evo-version.h"

/******************** Begin XDG Base Directory Migration ********************/
/* These are the known EShellBackend names as of Evolution 3.0 */
static const gchar *shell_backend_names[] =
    { "addressbook", "calendar", "mail", "memos", "tasks", NULL };

static gboolean
shell_xdg_migrate_rename (const gchar *old_filename,
                          const gchar *new_filename)
{
    gboolean old_filename_is_dir;
    gboolean old_filename_exists;
    gboolean new_filename_exists;
    gboolean success = TRUE;

    old_filename_is_dir = g_file_test (old_filename, G_FILE_TEST_IS_DIR);
    old_filename_exists = g_file_test (old_filename, G_FILE_TEST_EXISTS);
    new_filename_exists = g_file_test (new_filename, G_FILE_TEST_EXISTS);

    if (!old_filename_exists)
        return TRUE;

    g_print ("  mv %s %s\n", old_filename, new_filename);

    /* It's safe to go ahead and move directories because rename ()
     * will fail if the new directory already exists with content.
     * With regular files we have to be careful not to overwrite
     * new files with old files. */
    if (old_filename_is_dir || !new_filename_exists) {
        if (g_rename (old_filename, new_filename) < 0) {
            g_printerr ("  FAILED: %s\n", g_strerror (errno));
            success = FALSE;
        }
    } else {
        g_printerr ("  FAILED: Destination file already exists\n");
        success = FALSE;
    }

    return success;
}

static gboolean
shell_xdg_migrate_rmdir (const gchar *dirname)
{
    GDir *dir = NULL;
    gboolean success = TRUE;

    if (g_file_test (dirname, G_FILE_TEST_IS_DIR)) {
        g_print ("  rmdir %s\n", dirname);
        if (g_rmdir (dirname) < 0) {
            g_printerr ("  FAILED: %s", g_strerror (errno));
            if (errno == ENOTEMPTY) {
                dir = g_dir_open (dirname, 0, NULL);
                g_printerr (" (contents follows)");
            }
            g_printerr ("\n");
            success = FALSE;
        }
    }

    /* List the directory's contents to aid debugging. */
    if (dir != NULL) {
        const gchar *basename;

        /* Align the filenames beneath the error message. */
        while ((basename = g_dir_read_name (dir)) != NULL)
            g_print ("          %s\n", basename);

        g_dir_close (dir);
    }

    return success;
}

static void
shell_xdg_migrate_process_corrections (GHashTable *corrections)
{
    GHashTableIter iter;
    gpointer old_filename;
    gpointer new_filename;

    g_hash_table_iter_init (&iter, corrections);

    while (g_hash_table_iter_next (&iter, &old_filename, &new_filename)) {
        gboolean is_directory;

        is_directory = g_file_test (old_filename, G_FILE_TEST_IS_DIR);

        /* If the old filename is a directory and the new filename
         * is NULL, treat it as a request to remove the directory. */
        if (is_directory && new_filename == NULL)
            shell_xdg_migrate_rmdir (old_filename);
        else
            shell_xdg_migrate_rename (old_filename, new_filename);

        g_hash_table_iter_remove (&iter);
    }
}

static gboolean
shell_xdg_migrate_rename_files (const gchar *src_directory,
                                const gchar *dst_directory)
{
    GDir *dir;
    GHashTable *corrections;
    const gchar *basename;
    const gchar *home_dir;
    gchar *old_base_dir;
    gchar *new_base_dir;

    dir = g_dir_open (src_directory, 0, NULL);
    if (dir == NULL)
        return FALSE;

    /* This is to avoid renaming files which we're iterating over the
     * directory.  POSIX says the outcome of that is unspecified. */
    corrections = g_hash_table_new_full (
        g_str_hash, g_str_equal,
        (GDestroyNotify) g_free,
        (GDestroyNotify) g_free);

    g_mkdir_with_parents (dst_directory, 0700);

    home_dir = g_get_home_dir ();
    old_base_dir = g_build_filename (home_dir, ".evolution", NULL);
    e_filename_make_safe (old_base_dir);
    new_base_dir = g_strdup (e_get_user_data_dir ());
    e_filename_make_safe (new_base_dir);

    while ((basename = g_dir_read_name (dir)) != NULL) {
        GString *buffer;
        gchar *old_filename;
        gchar *new_filename;
        gchar *cp;

        buffer = g_string_new (basename);

        if ((cp = strstr (basename, old_base_dir)) != NULL) {
            g_string_erase (
                buffer, cp - basename,
                strlen (old_base_dir));
            g_string_insert (
                buffer, cp - basename, new_base_dir);
        }

        old_filename = g_build_filename (
            src_directory, basename, NULL);
        new_filename = g_build_filename (
            dst_directory, buffer->str, NULL);

        g_string_free (buffer, TRUE);

        g_hash_table_insert (corrections, old_filename, new_filename);
    }

    g_free (old_base_dir);
    g_free (new_base_dir);

    g_dir_close (dir);

    shell_xdg_migrate_process_corrections (corrections);
    g_hash_table_destroy (corrections);

    /* It's tempting to want to remove the source directory here.
     * Don't.  We might be iterating over the source directory's
     * parent directory, and removing the source directory would
     * screw up the iteration. */

    return TRUE;
}

static gboolean
shell_xdg_migrate_move_contents (const gchar *src_directory,
                                 const gchar *dst_directory)
{
    GDir *dir;
    GHashTable *corrections;
    const gchar *basename;

    dir = g_dir_open (src_directory, 0, NULL);
    if (dir == NULL)
        return FALSE;

    /* This is to avoid renaming files which we're iterating over the
     * directory.  POSIX says the outcome of that is unspecified. */
    corrections = g_hash_table_new_full (
        g_str_hash, g_str_equal,
        (GDestroyNotify) g_free,
        (GDestroyNotify) g_free);

    g_mkdir_with_parents (dst_directory, 0700);

    while ((basename = g_dir_read_name (dir)) != NULL) {
        gchar *old_filename;
        gchar *new_filename;

        old_filename = g_build_filename (src_directory, basename, NULL);
        new_filename = g_build_filename (dst_directory, basename, NULL);

        g_hash_table_insert (corrections, old_filename, new_filename);
    }

    g_dir_close (dir);

    shell_xdg_migrate_process_corrections (corrections);
    g_hash_table_destroy (corrections);

    /* It's tempting to want to remove the source directory here.
     * Don't.  We might be iterating over the source directory's
     * parent directory, and removing the source directory would
     * screw up the iteration. */

    return TRUE;
}

static void
shell_xdg_migrate_cache_dir (EShell *shell,
                             const gchar *old_base_dir)
{
    const gchar *new_cache_dir;
    gchar *old_cache_dir;
    gchar *old_filename;
    gchar *new_filename;

    old_cache_dir = g_build_filename (old_base_dir, "cache", NULL);
    new_cache_dir = e_get_user_cache_dir ();

    g_print ("Migrating cached data\n");

    g_mkdir_with_parents (new_cache_dir, 0700);

    old_filename = g_build_filename (old_cache_dir, "http", NULL);
    new_filename = g_build_filename (new_cache_dir, "http", NULL);
    shell_xdg_migrate_rename (old_filename, new_filename);
    g_free (old_filename);
    g_free (new_filename);

    old_filename = g_build_filename (old_cache_dir, "tmp", NULL);
    new_filename = g_build_filename (new_cache_dir, "tmp", NULL);
    shell_xdg_migrate_rename (old_filename, new_filename);
    g_free (old_filename);
    g_free (new_filename);

    /* Try to remove the old cache directory.  Good chance this will
     * fail on the first try, since E-D-S puts stuff here too. */
    shell_xdg_migrate_rmdir (old_cache_dir);

    g_free (old_cache_dir);
}

static void
shell_xdg_migrate_config_dir_common (EShell *shell,
                                     const gchar *old_base_dir,
                                     const gchar *backend_name)
{
    GDir *dir;
    const gchar *user_config_dir;
    gchar *old_config_dir;
    gchar *new_config_dir;
    gchar *old_filename;
    gchar *new_filename;
    gchar *dirname;

    user_config_dir = e_get_user_config_dir ();

    old_config_dir = g_build_filename (old_base_dir, backend_name, NULL);
    new_config_dir = g_build_filename (user_config_dir, backend_name, NULL);

    g_mkdir_with_parents (new_config_dir, 0700);

    old_filename = g_build_filename (old_config_dir, "views", NULL);
    new_filename = g_build_filename (new_config_dir, "views", NULL);
    shell_xdg_migrate_rename_files (old_filename, new_filename);
    g_free (old_filename);
    g_free (new_filename);

    old_filename = g_build_filename (old_config_dir, "searches.xml", NULL);
    new_filename = g_build_filename (new_config_dir, "searches.xml", NULL);
    shell_xdg_migrate_rename (old_filename, new_filename);
    g_free (old_filename);
    g_free (new_filename);

    /* This one only occurs in calendar and memos.
     * For other backends this will just be a no-op. */
    old_filename = g_build_filename (
        old_config_dir, "config", "MemoPad", NULL);
    new_filename = g_build_filename (new_config_dir, "MemoPad", NULL);
    shell_xdg_migrate_rename (old_filename, new_filename);
    g_free (old_filename);
    g_free (new_filename);

    /* This one only occurs in calendar and tasks.
     * For other backends this will just be a no-op. */
    old_filename = g_build_filename (
        old_config_dir, "config", "TaskPad", NULL);
    new_filename = g_build_filename (new_config_dir, "TaskPad", NULL);
    shell_xdg_migrate_rename (old_filename, new_filename);
    g_free (old_filename);
    g_free (new_filename);

    /* Subtle name change: config/state --> state.ini */
    old_filename = g_build_filename (old_config_dir, "config", "state", NULL);
    new_filename = g_build_filename (new_config_dir, "state.ini", NULL);
    shell_xdg_migrate_rename (old_filename, new_filename);
    g_free (old_filename);
    g_free (new_filename);

    /* GIO had a bug for awhile where it would leave behind an empty
     * temp file with the pattern .goutputstream-XXXXXX if an output
     * stream operation was cancelled.  We've had several reports of
     * these files in config directories, so remove any we find. */
    dirname = g_build_filename (old_config_dir, "config", NULL);
    dir = g_dir_open (dirname, 0, NULL);
    if (dir != NULL) {
        const gchar *basename;

        while ((basename = g_dir_read_name (dir)) != NULL) {
            gchar *filename;
            struct stat st;

            if (!g_str_has_prefix (basename, ".goutputstream"))
                continue;

            filename = g_build_filename (dirname, basename, NULL);

            /* Verify the file is indeed empty. */
            if (g_stat (filename, &st) == 0 && st.st_size == 0)
                g_unlink (filename);

            g_free (filename);
        }

        g_dir_close (dir);
    }
    g_free (dirname);

    g_free (old_config_dir);
    g_free (new_config_dir);
}

static void
shell_xdg_migrate_config_dir_mail (EShell *shell,
                                   const gchar *old_base_dir)
{
    const gchar *user_config_dir;
    gchar *old_config_dir;
    gchar *new_config_dir;
    gchar *old_filename;
    gchar *new_filename;

    user_config_dir = e_get_user_config_dir ();

    old_config_dir = g_build_filename (old_base_dir, "mail", NULL);
    new_config_dir = g_build_filename (user_config_dir, "mail", NULL);

    old_filename = g_build_filename (old_config_dir, "filters.xml", NULL);
    new_filename = g_build_filename (new_config_dir, "filters.xml", NULL);
    shell_xdg_migrate_rename (old_filename, new_filename);
    g_free (old_filename);
    g_free (new_filename);

    old_filename = g_build_filename (old_config_dir, "vfolders.xml", NULL);
    new_filename = g_build_filename (new_config_dir, "vfolders.xml", NULL);
    shell_xdg_migrate_rename (old_filename, new_filename);
    g_free (old_filename);
    g_free (new_filename);

    /* I hate this file.  GtkHtml uses style properties for fonts. */
    old_filename = g_build_filename (
        old_config_dir, "config", "gtkrc-mail-fonts", NULL);
    new_filename = g_build_filename (
        new_config_dir, "gtkrc-mail-fonts", NULL);
    shell_xdg_migrate_rename (old_filename, new_filename);
    g_free (old_filename);
    g_free (new_filename);

    /* This file is no longer used.  Try removing it. */
    old_filename = g_build_filename (
        old_config_dir, "config",
        "folder-tree-expand-state.xml", NULL);
    g_unlink (old_filename);
    g_free (old_filename);

    /* Everything else in the "config" directory just should be
     * per-folder ETree files recording the expanded state of mail
     * threads.  Rename this directory to "folders". */
    old_filename = g_build_filename (old_config_dir, "config", NULL);
    new_filename = g_build_filename (new_config_dir, "folders", NULL);
    shell_xdg_migrate_rename_files (old_filename, new_filename);
    g_free (old_filename);
    g_free (new_filename);

    g_free (old_config_dir);
    g_free (new_config_dir);
}

static void
shell_xdg_migrate_dir_cleanup (EShell *shell,
                                      const gchar *old_base_dir,
                                      const gchar *backend_name,
                                      const gchar *dir_name)
{
    gchar *dirname;

    dirname = g_build_filename (
        old_base_dir, backend_name, dir_name, NULL);

    shell_xdg_migrate_rmdir (dirname);

    g_free (dirname);
}

static void
shell_xdg_migrate_config_dir (EShell *shell,
                              const gchar *old_base_dir)
{
    const gchar *old_config_dir;
    const gchar *new_config_dir;
    gchar *old_filename;
    gchar *new_filename;
    gint ii;

    g_print ("Migrating config data\n");

    /* Some files are common to all shell backends. */
    for (ii = 0; shell_backend_names[ii] != NULL; ii++)
        shell_xdg_migrate_config_dir_common (
            shell, old_base_dir, shell_backend_names[ii]);

    /* Handle backend-specific files. */
    shell_xdg_migrate_config_dir_mail (shell, old_base_dir);

    /* Remove leftover config directories. */
    for (ii = 0; shell_backend_names[ii] != NULL; ii++) {
        shell_xdg_migrate_dir_cleanup (
            shell, old_base_dir, shell_backend_names[ii], "config");
        shell_xdg_migrate_dir_cleanup (
            shell, old_base_dir, shell_backend_names[ii], "views");
    }

    /*** Miscellaneous configuration files. ***/

    old_config_dir = old_base_dir;
    new_config_dir = e_get_user_config_dir ();

    /* Subtle name change: datetime-formats --> datetime-formats.ini */
    old_filename = g_build_filename (old_config_dir, "datetime-formats", NULL);
    new_filename = g_build_filename (new_config_dir, "datetime-formats.ini", NULL);
    shell_xdg_migrate_rename (old_filename, new_filename);
    g_free (old_filename);
    g_free (new_filename);

    /* Subtle name change: printing --> printing.ini */
    old_filename = g_build_filename (old_config_dir, "printing", NULL);
    new_filename = g_build_filename (new_config_dir, "printing.ini", NULL);
    shell_xdg_migrate_rename (old_filename, new_filename);
    g_free (old_filename);
    g_free (new_filename);
}

static void
shell_xdg_migrate_data_dir (EShell *shell,
                            const gchar *old_base_dir)
{
    GDir *dir;
    GHashTable *corrections;
    const gchar *basename;
    const gchar *old_data_dir;
    const gchar *new_data_dir;
    gchar *src_directory;
    gchar *dst_directory;

    g_print ("Migrating local user data\n");

    old_data_dir = old_base_dir;
    new_data_dir = e_get_user_data_dir ();

    /* The mail hierarchy is complex and Camel doesn't distinguish
     * between user data files and disposable cache files, so just
     * move everything to the data directory for now.  We'll sort
     * it out sometime down the road. */

    src_directory = g_build_filename (old_data_dir, "mail", NULL);
    dst_directory = g_build_filename (new_data_dir, "mail", NULL);

    dir = g_dir_open (src_directory, 0, NULL);
    if (dir == NULL)
        goto skip_mail;

    /* This is to avoid removing directories while we're iterating
     * over the parent directory.  POSIX says the outcome of that
     * is unspecified. */
    corrections = g_hash_table_new_full (
        g_str_hash, g_str_equal,
        (GDestroyNotify) g_free,
        (GDestroyNotify) g_free);

    /* Iterate over the base CamelProvider directories. */
    while ((basename = g_dir_read_name (dir)) != NULL) {
        gchar *provider_src_directory;
        gchar *provider_dst_directory;

        provider_src_directory =
            g_build_filename (src_directory, basename, NULL);
        provider_dst_directory =
            g_build_filename (dst_directory, basename, NULL);

        if (!g_file_test (provider_src_directory, G_FILE_TEST_IS_DIR)) {
            g_free (provider_src_directory);
            g_free (provider_dst_directory);
            continue;
        }

        shell_xdg_migrate_move_contents (
            provider_src_directory, provider_dst_directory);

        g_hash_table_insert (corrections, provider_src_directory, NULL);
        g_free (provider_dst_directory);
    }

    g_dir_close (dir);

    /* Remove the old base CamelProvider directories. */
    shell_xdg_migrate_process_corrections (corrections);
    g_hash_table_destroy (corrections);

skip_mail:

    g_free (src_directory);
    g_free (dst_directory);

    /* We don't want to move the source directory directly because the
     * destination directory may already exist with content.  Instead
     * we want to merge the content of the source directory into the
     * destination directory.
     *
     * For example, given:
     *
     *    $(src_directory)/A   and   $(dst_directory)/B
     *    $(src_directory)/C
     *
     * we want to end up with:
     *
     *    $(dst_directory)/A
     *    $(dst_directory)/B
     *    $(dst_directory)/C
     *
     * Any name collisions will be left in the source directory.
     */

    src_directory = g_build_filename (old_data_dir, "signatures", NULL);
    dst_directory = g_build_filename (new_data_dir, "signatures", NULL);

    shell_xdg_migrate_move_contents (src_directory, dst_directory);
    shell_xdg_migrate_rmdir (src_directory);

    g_free (src_directory);
    g_free (dst_directory);

    /* Move all remaining regular files to the new data directory. */

    dir = g_dir_open (old_data_dir, 0, NULL);
    if (dir == NULL)
        return;

    /* This is to avoid renaming files while we're iterating over the
     * directory.  POSIX says the outcome of that is unspecified. */
    corrections = g_hash_table_new_full (
        g_str_hash, g_str_equal,
        (GDestroyNotify) g_free,
        (GDestroyNotify) g_free);

    while ((basename = g_dir_read_name (dir)) != NULL) {
        gchar *old_filename;
        gchar *new_filename;

        old_filename = g_build_filename (old_data_dir, basename, NULL);
        new_filename = g_build_filename (new_data_dir, basename, NULL);

        /* If we encounter a directory, try removing it.  This
         * will only work if the directory is empty, so there's
         * no risk of data loss. */
        if (g_file_test (old_filename, G_FILE_TEST_IS_DIR)) {
            shell_xdg_migrate_rmdir (old_filename);
            g_free (old_filename);
            g_free (new_filename);
            continue;
        }

        g_hash_table_insert (corrections, old_filename, new_filename);
    }

    g_dir_close (dir);

    shell_xdg_migrate_process_corrections (corrections);
    g_hash_table_destroy (corrections);
}

static void
shell_migrate_to_xdg_base_dirs (EShell *shell)
{
    const gchar *home_dir;
    gchar *old_base_dir;

    g_return_if_fail (E_IS_SHELL (shell));

    /* XXX This blocks, but it's all just local file
     *     renames so it should be nearly instantaneous. */

    home_dir = g_get_home_dir ();
    old_base_dir = g_build_filename (home_dir, ".evolution", NULL);

    /* Is there even anything to migrate? */
    if (!g_file_test (old_base_dir, G_FILE_TEST_IS_DIR))
        goto exit;

    shell_xdg_migrate_cache_dir (shell, old_base_dir);
    shell_xdg_migrate_config_dir (shell, old_base_dir);
    shell_xdg_migrate_data_dir (shell, old_base_dir);

    /* Try to remove the old base directory.  Good chance this will
     * fail on the first try, since Evolution puts stuff here too. */
    g_rmdir (old_base_dir);

exit:
    g_free (old_base_dir);
}

/********************* End XDG Base Directory Migration *********************/

static gboolean
shell_migrate_attempt (EShell *shell,
                       gint major,
                       gint minor,
                       gint micro)
{
    GtkWindow *parent;
    GList *backends;
    gboolean success = TRUE;

    parent = e_shell_get_active_window (shell);
    backends = e_shell_get_shell_backends (shell);

    /* New user accounts have nothing to migrate. */
    if (major == 0 && minor == 0 && micro == 0)
        return TRUE;

    /* We only support migrating from version 2 now. */
    if (major < 2) {
        gchar *version;
        gint response;

        version = g_strdup_printf ("%d.%d", major, minor);
        response = e_alert_run_dialog_for_args (
            parent, "shell:upgrade-version-too-old",
            version, NULL);
        g_free (version);

        return (response == GTK_RESPONSE_OK);
    }

    /* Ask each of the shell backends to migrate their own data.
     * XXX If something fails the user may end up with only partially
     *     migrated data.  Need transaction semantics here, but how? */
    while (success && backends != NULL) {
        EShellBackend *shell_backend = backends->data;
        GError *error = NULL;

        success = e_shell_backend_migrate (
            shell_backend, major, minor, micro, &error);

        if (error != NULL) {
            gint response;

            response = e_alert_run_dialog_for_args (
                parent, "shell:upgrade-failed",
                error->message, NULL);

            success = (response == GTK_RESPONSE_OK);

            g_error_free (error);
        }

        backends = g_list_next (backends);
    }

    return success;
}

static void
shell_migrate_get_version (EShell *shell,
                           gint *major,
                           gint *minor,
                           gint *micro)
{
    GSettings *settings;
    gchar *string;

    *major = 0;
    *minor = 0;
    *micro = 0;

    settings = g_settings_new ("org.gnome.evolution");
    string = g_settings_get_string (settings, "version");

    if (string != NULL) {
        /* Since 1.4.0 we've kept the version key in GSettings. */
        sscanf (string, "%d.%d.%d", major, minor, micro);
        g_free (string);
    }

    g_object_unref (settings);
}

static gboolean
shell_migrate_downgraded (gint previous_major,
                          gint previous_minor,
                          gint previous_micro)
{
    gboolean downgraded;

    /* This could just be a single boolean expression,
     * but I find this form easier to understand. */

    if (previous_major == EVO_MAJOR_VERSION) {
        if (previous_minor == EVO_MINOR_VERSION) {
            downgraded = (previous_micro > EVO_MICRO_VERSION);
        } else {
            downgraded = (previous_minor > EVO_MINOR_VERSION);
        }
    } else {
        downgraded = (previous_major > EVO_MAJOR_VERSION);
    }

    return downgraded;
}

static void
change_dir_modes (const gchar *path)
{
    GDir *dir;
    GError *err = NULL;
    const gchar *file = NULL;

    dir = g_dir_open (path, 0, &err);
    if (err) {
        g_warning ("Error opening directory %s: %s \n", path, err->message);
        g_clear_error (&err);
        return;
    }

    while ((file = g_dir_read_name (dir))) {
        gchar *full_path = g_build_filename (path, file, NULL);

        if (g_file_test (full_path, G_FILE_TEST_IS_DIR))
            change_dir_modes (full_path);

        g_free (full_path);
    }

    g_chmod (path, 0700);
    g_dir_close (dir);
}

static void
fix_folder_permissions (const gchar *data_dir)
{
    struct stat sb;

    if (g_stat (data_dir, &sb) == -1) {
        g_warning ("error stat: %s \n", data_dir);
        return;
    }

    if (((guint32) sb.st_mode & 0777) != 0700)
        change_dir_modes (data_dir);
}

static void
shell_migrate_save_current_version (void)
{
    GSettings *settings;
    gchar *version;

    /* Save the version after the startup wizard has had a chance to
     * run.  If the user chooses to restore data and settings from a
     * backup, Evolution will restart and the restored data may need
     * to be migrated.
     *
     * If we save the version before the restart, then Evolution will
     * think it has already migrated data and settings to the current
     * version and the restored data may not be handled properly.
     *
     * This implies an awareness of module behavior from within the
     * application core, but practical considerations overrule here. */

    settings = g_settings_new ("org.gnome.evolution");

    version = g_strdup_printf (
        "%d.%d.%d",
        EVO_MAJOR_VERSION,
        EVO_MINOR_VERSION,
        EVO_MICRO_VERSION);
    g_settings_set_string (settings, "version", version);
    g_free (version);

    g_object_unref (settings);
}

static void
shell_migrate_ready_to_start_event_cb (EShell *shell)
{
    shell_migrate_save_current_version ();
}

gboolean
e_shell_migrate_attempt (EShell *shell)
{
    ESEvent *ese;
    gint major, minor, micro;

    g_return_val_if_fail (E_IS_SHELL (shell), FALSE);

    shell_migrate_get_version (shell, &major, &minor, &micro);

    /* Abort all migration if the user downgraded. */
    if (shell_migrate_downgraded (major, minor, micro))
        return TRUE;

    /* Migrate to XDG Base Directories first, so shell backends
     * don't have to deal with legacy data and cache directories. */
    shell_migrate_to_xdg_base_dirs (shell);

    /* This sets the folder permissions to S_IRWXU if needed */
    if (major <= 2 && minor <= 30)
        fix_folder_permissions (e_get_user_data_dir ());

    /* Attempt to run migration all the time and let the backend
     * make the choice */
    if (!shell_migrate_attempt (shell, major, minor, micro))
        _exit (EXIT_SUCCESS);

    /* We want our handler to run last, hence g_signal_connect_after(). */
    g_signal_connect_after (
        shell, "event::ready-to-start",
        G_CALLBACK (shell_migrate_ready_to_start_event_cb), NULL);

    /* @Event: Shell attempted upgrade
     * @Id: upgrade.done
     * @Target: ESMenuTargetState
     *
     * This event is emitted whenever the shell successfully attempts
     * an upgrade.
     */
    ese = es_event_peek ();
    e_event_emit (
        (EEvent *) ese, "upgrade.done",
        (EEventTarget *) es_event_target_new_upgrade (
        ese, EVO_MAJOR_VERSION, EVO_MINOR_VERSION, EVO_MICRO_VERSION));

    return TRUE;
}

GQuark
e_shell_migrate_error_quark (void)
{
    static GQuark quark = 0;

    if (G_UNLIKELY (quark == 0))
        quark = g_quark_from_static_string (
            "e-shell-migrate-error-quark");

    return quark;
}