vk: move file i/o to a separate module

3 files changed, 77 insertions, 63 deletions

diff --git a/vk/tracking/db/backend/csv.py b/vk/tracking/db/backend/csv.py
index e607774..5b2cc7d 100644
--- a/vk/tracking/db/backend/csv.py
+++ b/vk/tracking/db/backend/csv.py
@@ -4,23 +4,20 @@
 # Distributed under the MIT License.
 
 from collections.abc import Iterable
-import csv
 
+from ..io import InputReaderCSV, OutputWriterCSV
 from ..record import Record
 from ..timestamp import Timestamp
 
 class Writer:
     def __init__(self, fd):
-        self._fd = fd
-        self._writer = csv.writer(fd, lineterminator='\n')
+        self._writer = OutputWriterCSV(fd)
 
     def on_initial_status(self, user):
         self._write_record(user)
-        self._fd.flush()
 
     def on_status_update(self, user):
         self._write_record(user)
-        self._fd.flush()
 
     def on_connection_error(self, e):
         pass
@@ -28,10 +25,7 @@ class Writer:
     def _write_record(self, user):
         if not self:
             return
-        self._write_row(self._record_to_row(Record.from_user(user)))
-
-    def _write_row(self, row):
-        self._writer.writerow(row)
+        self._writer.write_row(self._record_to_row(Record.from_user(user)))
 
     @staticmethod
     def _record_to_row(record):
@@ -39,7 +33,7 @@ class Writer:
 
 class Reader(Iterable):
     def __init__(self, fd):
-        self._reader = csv.reader(fd)
+        self._reader = InputReaderCSV(fd)
 
     def __iter__(self):
         return map(Reader._record_from_row, self._reader)
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))
diff --git a/vk/tracking/db/io.py b/vk/tracking/db/io.py
new file mode 100644
index 0000000..04bab3d
--- /dev/null
+++ b/vk/tracking/db/io.py
@@ -0,0 +1,43 @@
+# Copyright (c) 2017 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
+import csv
+import sys
+
+class OutputWriterCSV:
+    def __init__(self, fd=sys.stdout):
+        self._fd = fd
+        self._writer = csv.writer(fd, lineterminator='\n')
+
+    def write_row(self, row):
+        self._writer.writerow(row)
+        self._fd.flush()
+
+class InputReaderCSV:
+    def __init__(self, fd=sys.stdin):
+        self._reader = csv.reader(fd)
+
+    def __iter__(self):
+        return iter(self._reader)
+
+@contextmanager
+def _open_file(path=None, default=None, **kwargs):
+    fd = default
+    if path is None:
+        pass
+    else:
+        fd = open(path, **kwargs)
+    try:
+        yield fd
+    finally:
+        if fd is not default:
+            fd.close()
+
+def open_output_text_file(path=None):
+    return _open_file(path, default=sys.stdout, mode='w', encoding='utf-8')
+
+def open_input_text_file(path=None):
+    return _open_file(path, default=sys.stdin, mode='r', encoding='utf-8')