from __future__ import unicode_literals

import contextlib
import io
import logging
import os.path
import sqlite3
import tempfile

from cached_property import cached_property

import pre_commit.constants as C
from pre_commit import file_lock
from pre_commit.prefixed_command_runner import PrefixedCommandRunner
from pre_commit.util import clean_path_on_failure
from pre_commit.util import cmd_output
from pre_commit.util import copy_tree_to_path
from pre_commit.util import cwd
from pre_commit.util import no_git_env
from pre_commit.util import resource_filename


logger = logging.getLogger('pre_commit')


def _get_default_directory():
    """Returns the default directory for the Store.  This is intentionally
    underscored to indicate that `Store.get_default_directory` is the intended
    way to get this information.  This is also done so
    `Store.get_default_directory` can be mocked in tests and
    `_get_default_directory` can be tested.
    """
    return os.environ.get(
        'PRE_COMMIT_HOME',
        os.path.join(os.path.expanduser('~'), '.pre-commit'),
    )


class Store(object):
    get_default_directory = staticmethod(_get_default_directory)
    __created = False

    def __init__(self, directory=None):
        if directory is None:
            directory = self.get_default_directory()

        self.directory = directory

    @contextlib.contextmanager
    def exclusive_lock(self, quiet=False):
        if not quiet:
            logger.info('Locking pre-commit directory')
        with file_lock.lock(os.path.join(self.directory, '.lock')):
            yield

    def _write_readme(self):
        with io.open(os.path.join(self.directory, 'README'), 'w') as readme:
            readme.write(
                'This directory is maintained by the pre-commit project.\n'
                'Learn more: https://github.com/pre-commit/pre-commit\n',
            )

    def _write_sqlite_db(self):
        # To avoid a race where someone ^Cs between db creation and execution
        # of the CREATE TABLE statement
        fd, tmpfile = tempfile.mkstemp(dir=self.directory)
        # We'll be managing this file ourselves
        os.close(fd)
        # sqlite doesn't close its fd with its contextmanager >.<
        # contextlib.closing fixes this.
        # See: http://stackoverflow.com/a/28032829/812183
        with contextlib.closing(sqlite3.connect(tmpfile)) as db:
            db.executescript(
                'CREATE TABLE repos ('
                '    repo CHAR(255) NOT NULL,'
                '    ref CHAR(255) NOT NULL,'
                '    path CHAR(255) NOT NULL,'
                '    PRIMARY KEY (repo, ref)'
                ');',
            )

        # Atomic file move
        os.rename(tmpfile, self.db_path)

    def _create(self):
        if not os.path.exists(self.directory):
            os.makedirs(self.directory)
            self._write_readme()

        if os.path.exists(self.db_path):
            return
        with self.exclusive_lock(quiet=True):
            # Another process may have already completed this work
            if os.path.exists(self.db_path):  # pragma: no cover (race)
                return
            self._write_sqlite_db()

    def require_created(self):
        """Require the pre-commit file store to be created."""
        if not self.__created:
            self._create()
            self.__created = True

    def _new_repo(self, repo, ref, make_strategy):
        self.require_created()

        def _get_result():
            # Check if we already exist
            with sqlite3.connect(self.db_path) as db:
                result = db.execute(
                    'SELECT path FROM repos WHERE repo = ? AND ref = ?',
                    [repo, ref],
                ).fetchone()
                if result:
                    return result[0]

        result = _get_result()
        if result:
            return result
        with self.exclusive_lock():
            # Another process may have already completed this work
            result = _get_result()
            if result:  # pragma: no cover (race)
                return result

            logger.info('Initializing environment for {}.'.format(repo))

            directory = tempfile.mkdtemp(prefix='repo', dir=self.directory)
            with clean_path_on_failure(directory):
                make_strategy(directory)

            # Update our db with the created repo
            with sqlite3.connect(self.db_path) as db:
                db.execute(
                    'INSERT INTO repos (repo, ref, path) VALUES (?, ?, ?)',
                    [repo, ref, directory],
                )
        return directory

    def clone(self, repo, ref):
        """Clone the given url and checkout the specific ref."""
        def clone_strategy(directory):
            cmd_output(
                'git', 'clone', '--no-checkout', repo, directory,
                env=no_git_env(),
            )
            with cwd(directory):
                cmd_output('git', 'reset', ref, '--hard', env=no_git_env())
                cmd_output(
                    'git', 'submodule', 'update', '--init', '--recursive',
                    env=no_git_env(),
                )

        return self._new_repo(repo, ref, clone_strategy)

    def make_local(self, deps):
        def make_local_strategy(directory):
            copy_tree_to_path(resource_filename('empty_template'), directory)
        return self._new_repo(
            'local:{}'.format(','.join(sorted(deps))), C.LOCAL_REPO_VERSION,
            make_local_strategy,
        )

    @cached_property
    def cmd_runner(self):
        return PrefixedCommandRunner(self.directory)

    @cached_property
    def db_path(self):
        return os.path.join(self.directory, 'db.db')