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# Copyright (c) 2016 Egor Tensin <Egor.Tensin@gmail.com>
# This file is part of the "VK scripts" project.
# For details, see https://github.com/egor-tensin/vk-scripts.
# Distributed under the MIT License.
from contextlib import contextmanager
from enum import Enum
import sys
from . import backend
class Format(Enum):
CSV = 'csv'
LOG = 'log'
NULL = 'null'
@contextmanager
def create_writer(self, path=None):
with self._open_output_file(path) as fd:
if self is Format.CSV:
yield backend.csv.Writer(fd)
elif self is Format.LOG:
yield backend.log.Writer(fd)
elif self is Format.NULL:
yield backend.null.Writer()
else:
raise NotImplementedError('unsupported database format: ' + str(self))
@contextmanager
def _open_output_file(self, path=None):
fd = sys.stdout
if path is None:
pass
elif self is Format.CSV or self is Format.LOG:
fd = open(path, 'w', encoding='utf-8')
elif self is Format.NULL:
pass
else:
raise NotImplementedError('unsupported database format: ' + str(self))
try:
yield fd
finally:
if fd is not sys.stdout:
fd.close()
@contextmanager
def create_reader(self, path=None):
with self._open_input_file(path) as fd:
if self is Format.CSV:
yield backend.csv.Reader(fd)
elif self is Format.LOG:
raise NotImplementedError('cannot read from a log file')
elif self is Format.NULL:
yield backend.null.Reader()
else:
raise NotImplementedError('unsupported database format: ' + str(self))
@contextmanager
def _open_input_file(self, path=None):
fd = sys.stdin
if path is None:
pass
elif self is Format.CSV:
fd = open(path, encoding='utf-8')
elif self is Format.LOG:
raise NotImplementedError('cannot read from a log file')
elif self is Format.NULL:
pass
else:
raise NotImplementedError('unsupported database format: ' + str(self))
try:
yield fd
finally:
if fd is not sys.stdin:
fd.close()
def __str__(self):
return self.value
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