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"""
Plugin loader for roswtf.
"""

from __future__ import print_function

import os
import sys

import roslib
import rospkg

def load_plugins():
    """
    @return: list of static roswtf plugins, list of online
    roswtf plugins
    @rtype: [fn], [fn]
    """
    rospack = rospkg.RosPack()
    to_check = rospack.get_depends_on('roswtf', implicit=False)
    static_plugins = []
    online_plugins = []
    for pkg in to_check:
        m = rospack.get_manifest(pkg)
        p_module = m.get_export('roswtf', 'plugin')
        if not p_module:
            continue
        elif len(p_module) != 1:
            print("Cannot load plugin [%s]: invalid 'plugin' attribute"%(pkg), file=sys.stderr)
            continue
        p_module = p_module[0]
        try:
            # load that packages namespace
            roslib.load_manifest(pkg)
            
            # import the specified plugin module
            mod = __import__(p_module)
            for sub_mod in p_module.split('.')[1:]:
                mod = getattr(mod, sub_mod)

            # retrieve the roswtf_plugin_static and roswtf_plugin_online functions
            s_attr = o_attr = None
            try:
                s_attr = getattr(mod, 'roswtf_plugin_static')
            except AttributeError: pass
            try:
                o_attr = getattr(mod, 'roswtf_plugin_online')
            except AttributeError: pass
            if s_attr:
                static_plugins.append(s_attr)
            if o_attr:
                online_plugins.append(o_attr)
            if s_attr is None and o_attr is None:
                print("Cannot load plugin [%s]: no 'roswtf_plugin_static' or 'roswtf_plugin_online' attributes [%s]"%(p_module), file=sys.stderr)
            else:
                print("Loaded plugin", p_module)

        except Exception as e:
            print("Unable to load plugin [%s] from package [%s]. Exception thrown: [%s]"%(p_module, pkg, str(e)), file=sys.stderr)
    return static_plugins, online_plugins

