# -*- coding: utf-8 -*-
import os
import re
import hashlib
from typing import Any, Optional
from importlib import import_module
from typing import Text
from six.moves import cStringIO as StringIO

from django.db import connections, DEFAULT_DB_ALIAS
from django.db.utils import OperationalError
from django.apps import apps
from django.core.management import call_command
from django.utils.module_loading import module_has_submodule

FILENAME_SPLITTER = re.compile('[\W\-_]')
TEST_DB_STATUS_DIR = 'var/test_db_status'

def database_exists(database_name, **options):
    # type: (Text, **Any) -> bool
    db = options.get('database', DEFAULT_DB_ALIAS)
    try:
        connection = connections[db]

        with connection.cursor() as cursor:
            cursor.execute("SELECT 1 from pg_database WHERE datname='{}';".format(database_name))
            return_value = bool(cursor.fetchone())
        connections.close_all()
        return return_value
    except OperationalError:
        return False

def get_migration_status(**options):
    # type: (**Any) -> str
    verbosity = options.get('verbosity', 1)

    for app_config in apps.get_app_configs():
        if module_has_submodule(app_config.module, "management"):
            import_module('.management', app_config.name)

    app_labels = [options['app_label']] if options.get('app_label') else None
    db = options.get('database', DEFAULT_DB_ALIAS)
    out = StringIO()
    call_command(
        'showmigrations',
        '--list',
        app_labels=app_labels,
        database=db,
        no_color=options.get('no_color', False),
        settings=options.get('settings', os.environ['DJANGO_SETTINGS_MODULE']),
        stdout=out,
        traceback=options.get('traceback', True),
        verbosity=verbosity,
    )
    connections.close_all()
    out.seek(0)
    output = out.read()
    return re.sub('\x1b\[(1|0)m', '', output)

def are_migrations_the_same(migration_file, **options):
    # type: (Text, **Any) -> bool
    if not os.path.exists(migration_file):
        return False

    with open(migration_file) as f:
        migration_content = f.read()
    return migration_content == get_migration_status(**options)

def _get_hash_file_path(source_file_path):
    # type: (str) -> str
    basename = os.path.basename(source_file_path)
    filename = '_'.join(FILENAME_SPLITTER.split(basename)).lower()
    return os.path.join(TEST_DB_STATUS_DIR, filename)

def _check_hash(target_hash_file, **options):
    # type: (str, **Any) -> bool
    """
    This function has a side effect of creating a new hash file or
    updating the old hash file.
    """
    source_hash_file = _get_hash_file_path(target_hash_file)

    with open(target_hash_file) as f:
        target_hash_content = hashlib.sha1(f.read().encode('utf8')).hexdigest()

    if os.path.exists(source_hash_file):
        with open(source_hash_file) as f:
            source_hash_content = f.read().strip()
    else:
        source_hash_content = None

    with open(source_hash_file, 'w') as f:
        f.write(target_hash_content)

    return source_hash_content == target_hash_content

def is_template_database_current(
        database_name='zulip_test_template',
        migration_status='var/migration-status',
        settings='zproject.test_settings',
        check_files=None):
    # type: (Optional[Text], Optional[Text], Optional[Text], Optional[List[str]]) -> bool
    # Using str type for check_files because re.split doesn't accept unicode
    if check_files is None:
        check_files = [
            'zilencer/management/commands/populate_db.py',
            'tools/setup/postgres-init-test-db',
            'tools/setup/postgres-init-dev-db',
        ]

    if not os.path.exists(TEST_DB_STATUS_DIR):
        os.mkdir(TEST_DB_STATUS_DIR)

    if database_exists(database_name):
        # To ensure Python evaluates all the hash tests (and thus creates the
        # hash files about the current state), we evaluate them in a
        # list and then process the result
        hash_status = all([_check_hash(fn) for fn in check_files])
        return are_migrations_the_same(migration_status, settings=settings) and hash_status

    return False