import argparse
import datetime
import importlib
import os
import sys

from .config import DJANGO_SETTINGS_MODULE_NAME
from .version import VERSION


class Program(object):  # pylint: disable=too-few-public-methods
    @staticmethod
    def _setup_argparser(parser):
        parser.add_argument('-V', '--version', action='version',
                            version='%(prog)s ' + VERSION)

        parser.add_argument('-a', '--app',
                            action='append', dest='merge_apps', metavar='MODULE',
                            help='Merge settings from the django app MODULE\n'
                                 'Can be used multiple times')

        parser.add_argument('-c', '--create',
                            action='store_true', dest='create',
                            help='Create the django project directory')

        parser.add_argument('project_dir', metavar='PATH',
                            help='The directory, where the django project is or will be installed.')

        return parser

    def _parse_args(self, argv=None):
        if argv is None:
            argv = sys.argv[1:]
        if not argv:
            argv = ()

        return self._argparser.parse_args(argv)

    @staticmethod
    def _install_django_files(project_dir, overwrite=False):
        if os.path.exists(project_dir):
            if not overwrite:
                sys.stderr.write('directory already exists: {}\n'.format(project_dir))
                return os.EX_NOPERM
        else:
            os.makedirs(project_dir)

        settings_module = DJANGO_SETTINGS_MODULE_NAME
        cmd = 'django-admin startproject {name} {path}'.format(name=settings_module,
                                                               path=project_dir)
        sys.stdout.write('Installing django files to {path}\n'.format(path=project_dir))
        exitval = os.system(cmd)
        return exitval

    @staticmethod
    def _add_installed_apps_from_app(project_dir, app):
        settings_dir = os.path.join(project_dir, DJANGO_SETTINGS_MODULE_NAME)

        settings_from_app = importlib.import_module('{}.django_settings'.format(app))
        if hasattr(settings_from_app, 'ADD_INSTALLED_APPS'):
            add_apps = settings_from_app.ADD_INSTALLED_APPS
        else:
            add_apps = []

        if not add_apps:
            sys.stdout.write('{}: do not care about INSTALLED_APPS\n'.format(app))
            return os.EX_OK

        sys.path.insert(0, settings_dir)
        settings = importlib.import_module('settings')
        sys.path.pop(0)

        missing_apps = []
        for app in add_apps:
            if app not in settings.INSTALLED_APPS:
                missing_apps.append(app)

        if missing_apps:
            sys.stdout.write('{app}: adding {apps} to INSTALLED_APPS\n'.format(app=app, apps=missing_apps))
            comment = '### {app}: added apps with django-deploy at {timestamp}'
            code = 'INSTALLED_APPS += [\n'
            for app in missing_apps:
                code += '    \'{}\',\n'.format(app)
            code += ']\n'

            append_text = '\n' + comment + '\n' + code + '\n'
            settings_file = os.path.join(settings_dir, 'settings.py')
            with open(settings_file, 'a') as f:
                now = datetime.datetime.now()
                timestamp = now.strftime('%Y-%m-%d %H:%M:%S')
                f.write(append_text.format(app=app, timestamp=timestamp))
        else:
            sys.stdout.write('{app}: INSTALLED_APPS is fine\n'.format(app=app))

        return os.EX_OK

    def __init__(self):
        self._argparser = argparse.ArgumentParser()
        self._setup_argparser(self._argparser)

    def __call__(self, *args, **kwargs):
        argv = kwargs.get('argv', None)
        cmd_args = self._parse_args(argv)
        exitval = os.EX_OK
        if cmd_args.create:
            exitval = self._install_django_files(cmd_args.project_dir)
            if exitval != os.EX_OK:
                return exitval
        if cmd_args.merge_apps:
            for app in cmd_args.merge_apps:
                exitval = self._add_installed_apps_from_app(cmd_args.project_dir, app)
                if exitval != os.EX_OK:
                    return exitval
        return exitval