/*

 * modules.c   -- modules handling

 *

 * Copyright (C) 2010 Myhailo Danylenko <isbear@ukrpost.net>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 2 of the License, or (at

 * your option) any later version.

 *

 * This program is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307

 * USA

 */

#include <glib.h>

#include <gmodule.h>

#include <string.h>

#include "settings.h"

#include "config.h"

#include "modules.h"

#include "logprint.h"

#include "utils.h"

static gint module_list_comparator(gconstpointer arg1, gconstpointer arg2)

{

  const loaded_module_t *module = arg1;

  const char *name = arg2;

  return g_strcmp0(module->name, name);

}

//  module_load(modulename, manual, force)

// Tries to load specified module and any modules, that this module

// depends on. Returns NULL on success or constant error string in a

// case of error. Error message not necessarily indicates error.

const gchar *module_load(const gchar *arg, gboolean manual, gboolean force)

{

  GModule       *mod;

  module_info_t *info;

  if (!arg || !*arg)

    return "Missing module name";

  { // Check if module is already loaded

    GSList *lmod = g_slist_find_custom(loaded_modules, arg,

                                       module_list_comparator);

    if (lmod) {

      loaded_module_t *module = lmod->data;

      if (manual) {

        if (!module->locked) {

          module->locked = TRUE;

          module->refcount += 1;

          return force ? NULL : "Module is already automatically loaded, "

                                "marked as manually loaded";

        } else

          return force ? NULL : "Module is already loaded";

      } else {

        module->refcount += 1;

        return NULL;

      }

    }

  }

  { // Load module

    gchar *mdir = expand_filename(settings_opt_get("modules_dir"));

    gchar *path = g_module_build_path(mdir ? mdir : PKGLIB_DIR, arg);

    g_free(mdir);

    mod = g_module_open(path, G_MODULE_BIND_LAZY);

    g_free(path);

    if (!mod)

      return g_module_error();

  }

    gchar *varname = g_strdup_printf("info_%s", arg);

    gpointer var = NULL;

    // convert to a valid symbol name

    g_strcanon(varname, "abcdefghijklmnopqrstuvwxyz0123456789", '_');

    if (!g_module_symbol(mod, varname, &var)) {

      if (!force) {

        g_free(varname);

        return "Module provides no information structure";

      }

      scr_LogPrint(LPRINT_LOGNORM, "Forced to ignore error: "

                                 "Module provides no information structure.");

    }

    g_free(varname);

    info = var;

  }

    }

  }

  // Load dependencies

  if (info && info->requires) {

    const gchar **dep;

    for (dep = info->requires; *dep; ++dep) {

      const gchar *err = module_load(*dep, FALSE, FALSE);

      if (err) {

        GSList *mel;

        scr_LogPrint(LPRINT_LOGNORM, "Error loading dependency module %s: %s.",

                     *dep, err);

        // Unload already loaded dependencies

        for (mel = deps; mel; mel = mel->next) {

          gchar *ldmname = mel->data;

          err = module_unload(ldmname, FALSE, FALSE);

          scr_LogPrint(LPRINT_LOGNORM,

                       "Error unloading dependency module %s: %s.",

                       ldmname, err);

          g_free(ldmname);

        }

        g_slist_free(deps);

        // Unload module

        if (!g_module_close(mod))

          scr_LogPrint(LPRINT_LOGNORM, "Error unloading module %s: %s.",

                       arg, g_module_error());

        return "Dependency problems";

      }

    }

  }

  { // Register module

    loaded_module_t *module = g_new(loaded_module_t, 1);

    module->refcount     = 1;

    module->locked       = manual;

    module->name         = g_strdup(arg);

    module->module       = mod;

    module->info         = info;

    loaded_modules = g_slist_prepend(loaded_modules, module);

  }

  // Run initialization routine

  if (info && info->init)

    info->init();

  // XXX Run hk_loaded_module hook (and move this line there)

  scr_LogPrint(LPRINT_LOGNORM, "Loaded module %s.", arg);

  return NULL;

}

//  module_unload(modulename, manual, force)

// Unload specified module and any automatically loaded modules

// that are no more required.

const gchar *module_unload(const gchar *arg, gboolean manual, gboolean force)

{

  GSList          *lmod;

  loaded_module_t *module;

  module_info_t   *info;

  if (!arg || !*arg)

    return "Missing module name";

  lmod = g_slist_find_custom(loaded_modules, arg, module_list_comparator);

  if (!lmod)

    return "Module not found";

  module = lmod->data;

  // Check if user can unload this module

  if (manual) {

    if (!module->locked) {

      if (force)

        scr_LogPrint(LPRINT_LOGNORM, "Forced to ignore error: "

                     "Manually unloading automatically loaded module.");

      else

        return "Module is not loaded manually";

    }

    module->locked = FALSE;

  }

  // Check refcount

  module->refcount -= 1;

  if (module->refcount > 0) {

    if (force)

      scr_LogPrint(LPRINT_LOGNORM, "Forced to ignore error: "

                   "Refcount is not zero (%u).", module->refcount);

    else

      return manual ? "Module is required by some other modules" : NULL;

  }

  info = module->info;

  // Run uninitialization routine

  if (info && info->uninit)

    info->uninit();

  module->info = NULL;

  // Unload module

  if (!g_module_close(module->module))

    return g_module_error(); // XXX destroy structure?

  // Destroy structure

  loaded_modules = g_slist_delete_link(loaded_modules, lmod);

  g_free(module->name);

  g_free(module);

  scr_LogPrint(LPRINT_LOGNORM, "Unloaded module %s.", arg);

  return NULL;

}

//  module_list_print(void)

// Prints into status buffer and log list of the currently loaded

// modules.

void module_list_print(void)

{

  GSList *mel;

  gsize maxlen = 0;

  gchar *format;

  GString *message;

  if (!loaded_modules) {

    scr_LogPrint(LPRINT_LOGNORM, "No modules loaded.");

    return;

  }

  for (mel = loaded_modules; mel; mel = mel -> next) {

    loaded_module_t *module = mel->data;

    gsize len = strlen(module->name);

    if (len > maxlen)

      maxlen = len;

  }

  // Create format string

  format = g_strdup_printf("%%-%us  %%2u (%%c)", maxlen);

  // Fill the message to be printed

  message = g_string_new("Loaded modules:\n");

  for (mel = loaded_modules; mel; mel = mel -> next) {

    loaded_module_t *module = mel->data;

    g_string_append_printf(message, format, module->name, module->refcount,

                           module->locked ? 'M' : 'A');

      }

    }

    g_string_append_c(message, '\n');

  }

  // Chop extra "\n"

  g_string_truncate(message, message->len - 1);

  scr_LogPrint(LPRINT_LOGNORM, "%s", message->str);

  g_string_free(message, TRUE);

  g_free(format);

}

//  modules_init()

// Initializes module system.

void modules_init(void)

{

}

//  modules_deinit()

// Unloads all the modules.

void modules_deinit(void)

{

  GSList *mel;

  // We need only manually loaded modules

  for (mel = loaded_modules; mel; mel = mel->next) {

    loaded_module_t *module = mel->data;

    if (module->locked)

      break;

  }

  while (mel) {