vk: move file i/o to a separate module

1 files changed, 30 insertions, 53 deletions

diff --git a/vk/tracking/db/format.py b/vk/tracking/db/format.py
index e1b34a1..7b3f312 100644
--- a/vk/tracking/db/format.py
+++ b/vk/tracking/db/format.py
@@ -3,76 +3,53 @@
 # 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
+from . import backend, io
 
 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))
+    def __str__(self):
+        return self.value
 
-    @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')
+    def create_writer(self, fd=sys.stdout):
+        if self is Format.CSV:
+            return backend.csv.Writer(fd)
+        elif self is Format.LOG:
+            return backend.log.Writer(fd)
         elif self is Format.NULL:
-            pass
+            return backend.null.Writer()
         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))
+    def open_output_file(self, path=None):
+        if self is Format.CSV or self is Format.LOG:
+            return io.open_output_text_file(path)
+        elif self is Format.NULL:
+            return io.open_output_text_file(None)
+        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')
+    def create_reader(self, fd=sys.stdin):
+        if self is Format.CSV:
+            return backend.csv.Reader(fd)
         elif self is Format.LOG:
-            raise NotImplementedError('cannot read from a log file')
+            return NotImplementedError('cannot read from a log file')
         elif self is Format.NULL:
-            pass
+            return backend.null.Reader()
         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
+    def open_input_file(self, path=None):
+        if self is Format.CSV:
+            return io.open_input_text_file(path)
+        elif self is Format.LOG:
+            raise NotImplementedError('cannot read from a log file')
+        elif self is Format.NULL:
+            return io.open_input_text_file(None)
+        else:
+            raise NotImplementedError('unsupported database format: ' + str(self))