"""Implement Mach5 menus."""

import os
import errno
import yaml
from collections import OrderedDict
import subprocess


def get_data_from(menu_file):
    """Get menu data from a yaml menu definition file."""
    menu_file = os.path.expanduser(menu_file)
    if not os.path.exists(menu_file):
        raise FileNotFoundError(errno.ENOENT,
                                os.strerror(errno.ENOENT), menu_file)
    with open(menu_file, 'r') as yaml_file:
        menu_data = yaml.safe_load(yaml_file)

        #######################################################################
        #                               WARNING                               #
        # yaml.safe_load does NOT return and OrderedDict                      #
        # so far, dict in Python are ordered, but IT CAN CHANGE               #
        #######################################################################

    if 'entries' not in menu_data:
        raise ValueError(f"Malformed file {menu_file}.\
        First entry is not a menu")
    return menu_data


class Command:
    """A Mach5 command."""

    def __init__(self, cmd_data):
        """Construct a Mach5 command object."""
        if len(cmd_data['sc']) != 1:
            raise ValueError(f"Shortcut must be only one character.\
            {cmd_data['sc']} is invalid.")
        self._name = cmd_data['name']
        self._cmd = cmd_data['cmd']
        self._sc = cmd_data['sc']

    def show(self):
        """Return string for Command."""
        return f"{self._sc} - {self._name}"

    def __repr__(self):
        """Return representation string for Command object."""
        return f"{self._sc!r} - {self._name!r} - {self._cmd!r}"

    def __str__(self):
        """Return string conversion for command."""
        return f"{self._sc} - {self._name}"

    def execute(self):
        """Execute command."""
        print(f"Execute command {self._name}")
        subprocess.Popen(os.path.expanduser(self._cmd))


class Menu:
    """A Mach5 menu class."""

    def __init__(self, menu_data):
        """Init a menu object instance from a menu data dict."""
        self._name = menu_data['name']
        self._entries = OrderedDict()
        self._sc = menu_data['sc']
        for e in menu_data['entries']:
            if e['sc'] in self._entries:
                raise ValueError(f"Repeated shortcut {e['sc']}")
            if 'entries' in e:
                self._entries[e['sc']] = Menu(e)
            else:
                self._entries[e['sc']] = Command(e)

    def __len__(self):
        """Return number of items in menu."""
        return len(self._entries)

    def __iter__(self):
        return MenuIter(self)

    def from_file(path):
        """Return a Menu instance from menu definition file."""
        return Menu(get_data_from(path))

    def __repr__(self):
        """Return repr string for menu object."""
        return f"{self._sc!r} - {self._name!r}"

    def __str__(self):
        """Return string conversion for menu."""
        if self._sc:
            return f"{self._sc} - {self._name}"
        else:
            return f"{self._name}"

    def get_entries(self):
        """Return entries for menu instance."""
        return self._entries

class MenuIter:
    """A helper class to make iterables Menu objects"""

    def __init__(self, menu):
        """Return an iterable menu"""
        self._entries = menu.get_entries()
        self._current = 0

    def __iter__(self):
        return self

    def __next__(self):
        if self._current < len(self._entries):
            item = self._entries[self._current]
            self._current += 1
            return item
        raise StopIteration