from __future__ import with_statement

import logging
import os

from alembic import context
from alembic.revision import ResolutionError
from alembic.util import CommandError
from sqlalchemy import engine_from_config, pool
from logging.config import fileConfig
from urllib import unquote, quote
from peewee import SqliteDatabase

from data.database import all_models, db
from app import app
from data.model.sqlalchemybridge import gen_sqlalchemy_metadata
from release import GIT_HEAD, REGION, SERVICE
from util.morecollections import AttrDict

config = context.config
config.set_main_option('sqlalchemy.url', unquote(app.config['DB_URI']))

# Interpret the config file for Python logging.
# This line sets up loggers basically.
if config.config_file_name:
    fileConfig(config.config_file_name)

logger = logging.getLogger(__name__)

# add your model's MetaData object here
# for 'autogenerate' support
# from myapp import mymodel
# target_metadata = mymodel.Base.metadata
target_metadata = gen_sqlalchemy_metadata(all_models)
tables = AttrDict(target_metadata.tables)

# other values from the config, defined by the needs of env.py,
# can be acquired:
# my_important_option = config.get_main_option("my_important_option")
# ... etc.

def run_migrations_offline():
    """Run migrations in 'offline' mode.

    This configures the context with just a URL
    and not an Engine, though an Engine is acceptable
    here as well.  By skipping the Engine creation
    we don't even need a DBAPI to be available.

    Calls to context.execute() here emit the given string to the
    script output.

    """
    url = unquote(app.config['DB_URI'])
    context.configure(url=url, target_metadata=target_metadata, transactional_ddl=True)

    with context.begin_transaction():
        context.run_migrations(tables=tables)

def run_migrations_online():
    """Run migrations in 'online' mode.

    In this scenario we need to create an Engine
    and associate a connection with the context.

    """

    if isinstance(db.obj, SqliteDatabase) and not 'GENMIGRATE' in os.environ and not 'DB_URI' in os.environ:
        print ('Skipping Sqlite migration!')
        return

    engine = engine_from_config(
                config.get_section(config.config_ini_section),
                prefix='sqlalchemy.',
                poolclass=pool.NullPool)

    connection = engine.connect()
    context.configure(
                connection=connection,
                target_metadata=target_metadata,
                transactional_ddl=False,
                )

    try:
        with context.begin_transaction():
            try:
                context.run_migrations(tables=tables)
            except (CommandError, ResolutionError) as ex:
                if 'No such revision' not in str(ex):
                    raise

                if not REGION or not GIT_HEAD:
                    raise

                from data.model.release import get_recent_releases

                # ignore revision error if we're running the previous release
                releases = list(get_recent_releases(SERVICE, REGION).offset(1).limit(1))
                if releases and releases[0].version == GIT_HEAD:
                    logger.warn('Skipping database migration because revision not found')
                else:
                    raise
    finally:
        connection.close()

if context.is_offline_mode():
    run_migrations_offline()
else:
    run_migrations_online()