class ConfigChanges:
    """Manage a user's proposed configuration option changes.

    Names used across multiple methods:
        page -- one of the 4 top-level dicts representing a
                .idlerc/config-x.cfg file.
        config_type -- name of a page.
        section -- a section within a page/file.
        item -- name of a value within a section.
        value -- value for the item.

    Methods
        add_item: 
        save_all: Save all the changes to the config file.

        reset: Clear all changes by clearing each page.
        set_user_value: Set value *in idleConf* for page, section, item.
    """
    def __init__(self):
        "Create a page for each configuration file"
        self.pages = {}
        for config_type in ('main', 'highlight', 'keys', 'extensions'):
            self[config_type] = {}
            self.pages.add(self[config_type])

   def add_item(self, config_type, section, item, value):
        "Add item/value pair for config_type and section."
        page = self[config_type]
        value = str(value)  # Make sure we use a string.
        if section not in page:
            page[section] = {}
        page[section][item] = value

    def save_all(self):
        "Save configuration changes to the user config file."

        idleConf.userCfg['main'].Save()
        for config_type in changes:
            cfg_type_changed = False
            for section in changes[config_type]:
                if section == 'HelpFiles':
                    # This section gets completely replaced.
                    idleConf.userCfg['main'].remove_section('HelpFiles')
                    cfg_type_changed = True
                for item in changes[config_type][section]:
                    value = self.changed_items[config_type][section][item]
                    if self.set_user_value(config_type, section, item, value):
                        cfg_type_changed = True
            if cfg_type_changed:
                idleConf.userCfg[config_type].Save()
        for config_type in ['keys', 'highlight']:
            # Save these even if unchanged!
            idleConf.userCfg[config_type].Save()
        self.clear()  # Clear the changed items dict.
        self.save_all_changed_extensions()  # Uses a different mechanism.

    def delete_section(self, config_type, section):
        """Delete a section from this page.

        Used to delete custom themes and keysets.
        """
        if section in self[config_type]:
            del self[config_type][section]
        
    def clear(self):  # was
        """Clear all 4 pages.

        Called in save_all(_changed_configs) after saving to idleConf.
        XXX Mark window *title* when there are changes; unmark here.
        """
        for page in self.config_types:
            page.clear()