import logging
import os

from logging.config import fileConfig
from urllib import unquote

from alembic import context
from alembic.script.revision import ResolutionError
from alembic.util import CommandError
from sqlalchemy import engine_from_config, pool
from peewee import SqliteDatabase

from data.database import all_models, db
from data.migrations.tester import NoopTester, PopulateTestDataTester
from data.model.sqlalchemybridge import gen_sqlalchemy_metadata
from release import GIT_HEAD, REGION, SERVICE
from util.morecollections import AttrDict
from data.migrations.progress import PrometheusReporter, NullReporter


config = context.config
DB_URI = config.get_main_option('db_uri', 'sqlite:///test/data/test.db')
PROM_LABEL_PREFIX = 'DBA_OP_LABEL_'


# This option exists because alembic needs the db proxy to be configured in order
# to perform migrations. The app import does the init of the proxy, but we don't
# want that in the case of the config app, as we are explicitly connecting to a
# db that the user has passed in, and we can't have import dependency on app
if config.get_main_option('alembic_setup_app', 'True') == 'True':
  from app import app
  DB_URI = app.config['DB_URI']

config.set_main_option('sqlalchemy.url', unquote(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 get_tester():
  """ Returns the tester to use. We only return the tester that populates data
      if the TEST_MIGRATE env var is set to `true` AND we make sure we're not
      connecting to a production database.
  """
  if os.environ.get('TEST_MIGRATE', '') == 'true':
    url = unquote(DB_URI)
    if url.find('amazonaws.com') < 0:
      return PopulateTestDataTester()

  return NoopTester()

def get_progress_reporter():
  prom_addr = os.environ.get('DBA_OP_PROMETHEUS_PUSH_GATEWAY_ADDR', None)

  if prom_addr is not None:
    prom_job = os.environ.get('DBA_OP_JOB_ID')

    def _process_label_key(label_key):
      return label_key[len(PROM_LABEL_PREFIX):].lower()
    labels = {_process_label_key(k): v for k, v in os.environ.items()
              if k.startswith(PROM_LABEL_PREFIX)}

    return PrometheusReporter(prom_addr, prom_job, labels)
  else:
      return NullReporter()

def report_success(ctx=None, step=None, heads=None, run_args=None):
  progress_reporter = run_args['progress_reporter']
  progress_reporter.report_version_complete(success=True)

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(DB_URI)
  context.configure(url=url, target_metadata=target_metadata, transactional_ddl=True)

  with context.begin_transaction():
    context.run_migrations(tables=tables, tester=get_tester(), progress_reporter=NullReporter())

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

  progress_reporter = get_progress_reporter()
  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,
                    on_version_apply=report_success)

  try:
    with context.begin_transaction():
      try:
        context.run_migrations(tables=tables, tester=get_tester(),
                               progress_reporter=progress_reporter)
      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()