#!/usr/bin/env python2
# -*- coding: utf-8 -*-
"""Combined config file and argument parser."""

from ConfigParser import SafeConfigParser, NoOptionError
from argparse import ArgumentParser
import sys


class _Dummy(object):
    """Placeholder for config sections."""
    pass


class ComboParser(object):
    """Parse configuration from INI file and command-line arguments.

    Command-line arguments override INI file values.
    """

    def __init__(self, ini):
        self.items = []
        self.cparser = SafeConfigParser()
        self.aparser = ArgumentParser()
        self.ini = ini
        self.loaded = False
        self.args = None

    def add_item(self, section, name, type, default, desc, required):
        """Add a configuration item."""
        def str2bool(val):
            return val.lower() in ('true', '1', 'yes')

        self.items.append({
            'section': section,
            'name': name,
            'type': type,
            'default': default,
            'required': required,
        })
        self.aparser.add_argument(
            '--%s.%s' % (section, name),
            help='%s (default: %s)' % (desc, default),
            type=type if type is not bool else str2bool,
            default=None,
            required=False
        )

    def load(self):
        """Load configuration from file and command-line."""
        if self.loaded:
            return
        self.loaded = True

        try:
            self.cparser.read(self.ini)
        except Exception:
            pass  # Config file missing or unreadable, use defaults

        self.args = self.aparser.parse_args()

        for item in self.items:
            section = item['section']
            name = item['name']

            # Ensure section object exists
            if not hasattr(self, section):
                setattr(self, section, _Dummy())
            obj = getattr(self, section)

            # Start with default value
            value = item['default']
            found = False

            # Try to read from config file
            try:
                if item['type'] is bool:
                    value = self.cparser.getboolean(section, name)
                elif item['type'] is float:
                    value = self.cparser.getfloat(section, name)
                elif item['type'] is int:
                    value = self.cparser.getint(section, name)
                elif item['type'] is str:
                    value = self.cparser.get(section, name)
                found = True
            except NoOptionError:
                pass

            # Command-line overrides config file
            arg_name = '%s.%s' % (section, name)
            arg_value = getattr(self.args, arg_name, None)
            if arg_value is not None:
                value = arg_value
                found = True

            # Handle missing required items
            if not found:
                if item['required']:
                    sys.stderr.write(
                        'error: required config item "%s" not found in section "%s" of "%s"\n'
                        % (name, section, self.ini)
                    )
                    sys.exit(1)
                else:
                    sys.stderr.write(
                        'warning: assigned default value of "%s" to "%s.%s"\n'
                        % (item['default'], section, name)
                    )

            setattr(obj, name, value)