# -*- coding: utf-8 -*-
"""
Detect new translatable fields in all models and sync database structure.

You will need to execute this command in two cases:

    1. When you add new languages to settings.LANGUAGES.
    2. When you add new translatable fields to your models.

Credits: Heavily inspired by django-transmeta's sync_transmeta_db command.
"""
from django.conf import settings
from django.core.management.base import BaseCommand
from django.core.management.color import no_style
from django.db import connection, transaction
from django.db.models import get_models

from modeltranslation.translator import translator, NotRegistered
from modeltranslation.utils import build_localized_fieldname


def ask_for_confirmation(sql_sentences, model_full_name):
    print '\nSQL to synchronize "%s" schema:' % model_full_name
    for sentence in sql_sentences:
        print '   %s' % sentence
    while True:
        prompt = ('\nAre you sure that you want to execute the previous SQL: '
                  '(y/n) [n]: ')
        answer = raw_input(prompt).strip()
        if answer == '':
            return False
        elif answer not in ('y', 'n', 'yes', 'no'):
            print 'Please answer yes or no'
        elif answer == 'y' or answer == 'yes':
            return True
        else:
            return False


def print_missing_langs(missing_langs, field_name, model_name):
    print 'Missing languages in "%s" field from "%s" model: %s' % (
        field_name, model_name, ", ".join(missing_langs))


class Command(BaseCommand):
    help = ('Detect new translatable fields or new available languages and '
            'sync database structure')

    def handle(self, *args, **options):
        """
        Command execution.
        """
        self.cursor = connection.cursor()
        self.introspection = connection.introspection

        all_models = get_models()
        found_missing_fields = False
        for model in all_models:
            try:
                options = translator.get_options_for_model(model)
                # Options returns full-wide spectrum of localized fields but
                # we only want to synchronize the local fields attached to the
                # model.
                local_field_names = [field.name for field
                                     in model._meta.local_fields]
                translatable_fields = [field for field
                                       in options.localized_fieldnames
                                       if field in local_field_names]
                model_full_name = '%s.%s' % (model._meta.app_label,
                                             model._meta.module_name)
                db_table = model._meta.db_table
                for field_name in translatable_fields:
                    missing_langs = list(
                        self.get_missing_languages(field_name, db_table))
                    if missing_langs:
                        found_missing_fields = True
                        print_missing_langs(
                            missing_langs, field_name, model_full_name)
                        sql_sentences = self.get_sync_sql(
                            field_name, missing_langs, model)
                        execute_sql = ask_for_confirmation(
                            sql_sentences, model_full_name)
                        if execute_sql:
                            print 'Executing SQL...',
                            for sentence in sql_sentences:
                                self.cursor.execute(sentence)
                            print 'Done'
                        else:
                            print 'SQL not executed'
            except NotRegistered:
                pass

        transaction.commit_unless_managed()

        if not found_missing_fields:
            print 'No new translatable fields detected'

    def get_table_fields(self, db_table):
        """
        Gets table fields from schema.
        """
        db_table_desc = self.introspection.get_table_description(
            self.cursor, db_table)
        return [t[0] for t in db_table_desc]

    def get_missing_languages(self, field_name, db_table):
        """
        Gets only missings fields.
        """
        db_table_fields = self.get_table_fields(db_table)
        for lang_code, lang_name in settings.LANGUAGES:
            if build_localized_fieldname(
                    field_name, lang_code) not in db_table_fields:
                yield lang_code

    def get_sync_sql(self, field_name, missing_langs, model):
        """
        Returns SQL needed for sync schema for a new translatable field.
        """
        qn = connection.ops.quote_name
        style = no_style()
        sql_output = []
        db_table = model._meta.db_table
        for lang in missing_langs:
            new_field = build_localized_fieldname(field_name, lang)
            f = model._meta.get_field(new_field)
            col_type = f.db_type(connection=connection)
            field_sql = [style.SQL_FIELD(qn(f.column)),
                         style.SQL_COLTYPE(col_type)]
            # column creation
            sql_output.append(
                "ALTER TABLE %s ADD COLUMN %s;" % (
                    qn(db_table), ' '.join(field_sql)))
            if not f.null and lang == settings.LANGUAGE_CODE:
                sql_output.append(
                    ("ALTER TABLE %s MODIFY COLUMN %s %s %s;" % (
                        qn(db_table), qn(f.column), col_type,
                        style.SQL_KEYWORD('NOT NULL'))))
        return sql_output