#! /usr/bin/env python
# coding: utf8
from __future__ import unicode_literals, print_function
import argparse
import codecs
import json
import os
import random
import string
import sys

class Configurator(object):

    def __init__(self, silent=False, **default_overrides):
        self.__values = []
        self.__default_overrides = default_overrides
        if silent:
            self.__input = None
        else:
            try:
                self.__input = raw_input
            except NameError:
                self.__input = input

    def as_dict(self):
        return dict(self.__values)

    def add(self, name, question, default=""):
        default = self.__default_overrides.get(name, default)
        message = question + " (default: \"{}\"): ".format(default)
        value = self.ask(message, default)
        self.set(name, value)

        return self

    def add_boolean(self, name, question, default=True):
        default = self.__default_overrides.get(name, default)
        message = question + " ({}) ".format("Y/n" if default else "y/N")
        value = None
        while value is None:
            answer = self.ask(message, default)
            value = {
                "y": True,
                "n": False,
                default: default,
            }.get(answer)
        self.set(name, value)
        return self

    def ask(self, message, default):
        if self.__input:
            return self.__input(message) or default
        return default

    def get(self, name):
        for key, value in self.__values:
            if key == name:
                return value
        return None

    def set(self, name, value):
        self.__values.append((name, value))


def substitute(src, dst, delimiter='$', **values):
    Template = template_class(delimiter)

    with codecs.open(src, encoding='utf-8') as fi:
        template = Template(fi.read())
    try:
        substituted = template.substitute(**values)
    except KeyError as e:
        sys.stderr.write("ERROR Missing config value '{}' for template {}\n".format(e.args[0], src))
        sys.exit(1)

    with open(dst, 'w') as fo:
        fo.write(substituted)

    print("Generated config file {} (from template {})".format(dst, src))

def template_class(user_delimiter='$'):
    """
    The default delimiter of the python Template class is '$'. Here, we
    generate a Template class with a custom delimiter. This cannot be done
    after the class creation because the Template metaclass uses the delimiter
    value.
    """
    class Template(string.Template):
        delimiter = user_delimiter
    return Template


def main():
    parser = argparse.ArgumentParser("Config file generator for Open edX")
    parser.add_argument('-c', '--config', default="config.json",
                        help="Load default values from this file. Config values will be saved there.")
    parser.add_argument('-s', '--silent', action='store_true',
                        help=(
                            "Be silent and accept all default values. "
                            "This is good for debugging, but probably not what you want"
                        ))
    args = parser.parse_args()

    # Load defaults
    defaults = {}
    if os.path.exists(args.config):
        with open(args.config) as f:
            defaults = json.load(f)

    configurator = Configurator(silent=args.silent, **defaults).add(
        'LMS_HOST', "Your website domain name for students (LMS)", 'www.myopenedx.com'
    ).add(
        'CMS_HOST', "Your website domain name for teachers (CMS)", 'studio.myopenedx.com'
    ).add(
        'SECRET_KEY', "Secret key -- if you don't know what this is, you can safely accept the default",
        "".join([random.choice(string.ascii_letters + string.digits) for _ in range(24)])
    ).add(
        'PLATFORM_NAME', "Platform name/title", "My Open edX"
    ).add(
        'MYSQL_DATABASE', "MySQL database name", 'openedx'
    ).add(
        'MYSQL_USERNAME', "MySQL database username", 'openedx'
    ).add(
        'MYSQL_PASSWORD', "MySQL database password", 'password'
    ).add(
        'MONGODB_DATABASE', "MongoDb database name", 'openedx'
    )

    # Save values
    with open(args.config, 'w') as f:
        json.dump(configurator.as_dict(), f, sort_keys=True, indent=4)
    print("\nConfiguration values were saved to ", args.config)

    # Open edX
    substitute(
        os.path.join('openedx', 'config', 'templates', 'lms.env.json.templ'),
        os.path.join('openedx', 'config', 'lms.env.json'),
        **configurator.as_dict()
    )
    substitute(
        os.path.join('openedx', 'config', 'templates', 'cms.env.json.templ'),
        os.path.join('openedx', 'config', 'cms.env.json'),
        **configurator.as_dict()
    )
    substitute(
        os.path.join('openedx', 'config', 'templates', 'lms.auth.json.templ'),
        os.path.join('openedx', 'config', 'lms.auth.json'),
        **configurator.as_dict()
    )
    substitute(
        os.path.join('openedx', 'config', 'templates', 'cms.auth.json.templ'),
        os.path.join('openedx', 'config', 'cms.auth.json'),
        **configurator.as_dict()
    )

    # MySQL
    substitute(
        os.path.join('mysql', 'config', 'templates', 'username.templ'),
        os.path.join('mysql', 'config', 'username'),
        **configurator.as_dict()
    )
    substitute(
        os.path.join('mysql', 'config', 'templates', 'password.templ'),
        os.path.join('mysql', 'config', 'password'),
        **configurator.as_dict()
    )
    substitute(
        os.path.join('mysql', 'config', 'templates', 'database.templ'),
        os.path.join('mysql', 'config', 'database'),
        **configurator.as_dict()
    )

    # Nginx
    # We need a different delimiter in nginx config files, because the '$' sign
    # is widely used there
    substitute(
        os.path.join('config', 'templates', 'nginx', 'lms.conf.templ'),
        os.path.join('config', 'rendered', 'nginx', 'lms.conf'),
        delimiter='£', **configurator.as_dict()
    )
    substitute(
        os.path.join('config', 'templates', 'nginx', 'cms.conf.templ'),
        os.path.join('config', 'rendered', 'nginx', 'cms.conf'),
        delimiter='£', **configurator.as_dict()
    )

    print("\nConfiguration files were successfuly generated. You may now build the app containers.")


if __name__ == '__main__':
    main()