bin: move file i/o to a separate module

3 files changed, 113 insertions, 95 deletions

diff --git a/bin/mutual_friends.py b/bin/mutual_friends.py
index 76bf00f..3b0576f 100644
--- a/bin/mutual_friends.py
+++ b/bin/mutual_friends.py
@@ -3,17 +3,17 @@
 # For details, see https://github.com/egor-tensin/vk-scripts.
 # Distributed under the MIT License.
 
+import abc
 import argparse
 from collections import OrderedDict
-from contextlib import contextmanager
-import csv
 from enum import Enum
-import json
 import sys
 
 from vk.api import API, Language
 from vk.user import UserField
 
+from .utils import output
+
 _OUTPUT_USER_FIELDS = UserField.UID, UserField.FIRST_NAME, UserField.LAST_NAME
 
 def _query_friend_list(api, user):
@@ -25,25 +25,25 @@ def _filter_user_fields(user):
         new_user[str(field)] = user[field] if field in user else None
     return new_user
 
-class OutputWriterCSV:
+class OutputSinkMutualFriends(metaclass=abc.ABCMeta):
+    @abc.abstractmethod
+    def write_mutual_friends(self, friend_list):
+        pass
+
+class OutputSinkCSV(OutputSinkMutualFriends):
     def __init__(self, fd=sys.stdout):
-        self._writer = csv.writer(fd, lineterminator='\n')
+        self._writer = output.OutputWriterCSV(fd)
 
     def write_mutual_friends(self, friend_list):
         for user in friend_list:
-            user = _filter_user_fields(user)
-            self._writer.writerow(user.values())
+            self._writer.write_row(user.values())
 
-class OutputWriterJSON:
+class OutputSinkJSON(OutputSinkMutualFriends):
     def __init__(self, fd=sys.stdout):
-        self._fd = fd
+        self._writer = output.OutputWriterJSON(fd)
 
     def write_mutual_friends(self, friend_list):
-        arr = []
-        for user in friend_list:
-            arr.append(_filter_user_fields(user))
-        self._fd.write(json.dumps(arr, indent=3, ensure_ascii=False))
-        self._fd.write('\n')
+        self._writer.write(friend_list)
 
 class OutputFormat(Enum):
     CSV = 'csv'
@@ -52,29 +52,17 @@ class OutputFormat(Enum):
     def __str__(self):
         return self.value
 
-    @contextmanager
-    def create_writer(self, path=None):
-        with self._open_file(path) as fd:
-            if self is OutputFormat.CSV:
-                yield OutputWriterCSV(fd)
-            elif self is OutputFormat.JSON:
-                yield OutputWriterJSON(fd)
-            else:
-                raise NotImplementedError('unsupported output format: ' + str(self))
-
     @staticmethod
-    @contextmanager
-    def _open_file(path=None):
-        fd = sys.stdout
-        if path is None:
-            pass
+    def open_file(path=None):
+        return output.open_text_file(path)
+
+    def create_sink(self, fd=sys.stdout):
+        if self is OutputFormat.CSV:
+            return OutputSinkCSV(fd)
+        elif self is OutputFormat.JSON:
+            return OutputSinkJSON(fd)
         else:
-            fd = open(path, 'w', encoding='utf-8')
-        try:
-            yield fd
-        finally:
-            if fd is not sys.stdout:
-                fd.close()
+            raise NotImplementedError('unsupported output format: ' + str(self))
 
 def _parse_output_format(s):
     try:
@@ -107,9 +95,11 @@ def write_mutual_friends(uids, out_path=None, out_fmt=OutputFormat.CSV):
 
     friend_lists = (frozenset(_query_friend_list(api, user)) for user in users)
     mutual_friends = frozenset.intersection(*friend_lists)
+    mutual_friends = [_filter_user_fields(user) for user in mutual_friends]
 
-    with out_fmt.create_writer(out_path) as writer:
-        writer.write_mutual_friends(mutual_friends)
+    with out_fmt.open_file(out_path) as out_fd:
+        sink = out_fmt.create_sink(out_fd)
+        sink.write_mutual_friends(mutual_friends)
 
 def main(args=None):
     write_mutual_friends(**vars(_parse_args(args)))
diff --git a/bin/online_sessions.py b/bin/online_sessions.py
index 5a9bdc8..cb3f4bf 100644
--- a/bin/online_sessions.py
+++ b/bin/online_sessions.py
@@ -3,13 +3,11 @@
 # For details, see https://github.com/egor-tensin/vk-scripts.
 # Distributed under the MIT License.
 
+import abc
 import argparse
-import csv
 from collections import OrderedDict
-from contextlib import contextmanager
 from datetime import datetime, timedelta, timezone
 from enum import Enum
-import json
 import sys
 
 from vk.tracking import OnlineSessionEnumerator
@@ -17,6 +15,7 @@ from vk.tracking.db import Format as DatabaseFormat
 from vk.user import UserField
 
 from .utils.bar_chart import BarChartBuilder
+from .utils import output
 
 class GroupBy(Enum):
     USER = 'user'
@@ -24,6 +23,9 @@ class GroupBy(Enum):
     WEEKDAY = 'weekday'
     HOUR = 'hour'
 
+    def __str__(self):
+        return self.value
+
     def group(self, db_reader, time_from=None, time_to=None):
         online_streaks = OnlineSessionEnumerator(time_from, time_to)
         if self is GroupBy.USER:
@@ -37,9 +39,6 @@ class GroupBy(Enum):
         else:
             raise NotImplementedError('unsupported grouping: ' + str(self))
 
-    def __str__(self):
-        return self.value
-
 _OUTPUT_USER_FIELDS = (
     UserField.UID,
     UserField.FIRST_NAME,
@@ -47,6 +46,11 @@ _OUTPUT_USER_FIELDS = (
     UserField.DOMAIN,
 )
 
+class OutputSinkOnlineSessions(metaclass=abc.ABCMeta):
+    @abc.abstractmethod
+    def process_database(self, group_by, db_reader, time_from=None, time_to=None):
+        pass
+
 class OutputConverterCSV:
     @staticmethod
     def convert_user(user):
@@ -64,9 +68,9 @@ class OutputConverterCSV:
     def convert_hour(hour):
         return [str(timedelta(hours=hour))]
 
-class OutputWriterCSV:
+class OutputSinkCSV(OutputSinkOnlineSessions):
     def __init__(self, fd=sys.stdout):
-        self._writer = csv.writer(fd, lineterminator='\n')
+        self._writer = output.OutputWriterCSV(fd)
 
     _CONVERT_KEY = {
         GroupBy.USER: OutputConverterCSV.convert_user,
@@ -77,18 +81,15 @@ class OutputWriterCSV:
 
     @staticmethod
     def _key_to_row(group_by, key):
-        if group_by not in OutputWriterCSV._CONVERT_KEY:
+        if group_by not in OutputSinkCSV._CONVERT_KEY:
             raise NotImplementedError('unsupported grouping: ' + str(group_by))
-        return OutputWriterCSV._CONVERT_KEY[group_by](key)
+        return OutputSinkCSV._CONVERT_KEY[group_by](key)
 
     def process_database(self, group_by, db_reader, time_from=None, time_to=None):
         for key, duration in group_by.group(db_reader, time_from, time_to).items():
             row = self._key_to_row(group_by, key)
             row.append(str(duration))
-            self._write_row(row)
-
-    def _write_row(self, row):
-        self._writer.writerow(row)
+            self._writer.write_row(row)
 
 class OutputConverterJSON:
     _DATE_FIELD = 'date'
@@ -124,9 +125,9 @@ class OutputConverterJSON:
         obj[OutputConverterJSON._HOUR_FIELD] = str(timedelta(hours=hour))
         return obj
 
-class OutputWriterJSON:
+class OutputSinkJSON(OutputSinkOnlineSessions):
     def __init__(self, fd=sys.stdout):
-        self._fd = fd
+        self._writer = output.OutputWriterJSON(fd)
 
     _DURATION_FIELD = 'duration'
 
@@ -141,13 +142,9 @@ class OutputWriterJSON:
 
     @staticmethod
     def _key_to_object(group_by, key):
-        if not group_by in OutputWriterJSON._CONVERT_KEY:
+        if not group_by in OutputSinkJSON._CONVERT_KEY:
             raise NotImplementedError('unsupported grouping: ' + str(group_by))
-        return OutputWriterJSON._CONVERT_KEY[group_by](key)
-
-    def _write(self, entries):
-        self._fd.write(json.dumps(entries, indent=3, ensure_ascii=False))
-        self._fd.write('\n')
+        return OutputSinkJSON._CONVERT_KEY[group_by](key)
 
     def process_database(self, group_by, db_reader, time_from=None, time_to=None):
         entries = []
@@ -155,7 +152,7 @@ class OutputWriterJSON:
             entry = self._key_to_object(group_by, key)
             entry[self._DURATION_FIELD] = str(duration)
             entries.append(entry)
-        self._write(entries)
+        self._writer.write(entries)
 
 class OutputConverterPlot:
     @staticmethod
@@ -174,7 +171,7 @@ class OutputConverterPlot:
     def convert_hour(hour):
         return '{}:00'.format(hour)
 
-class OutputWriterPlot:
+class OutputSinkPlot(OutputSinkOnlineSessions):
     def __init__(self, fd=sys.stdout):
         self._fd = fd
 
@@ -189,9 +186,9 @@ class OutputWriterPlot:
 
     @staticmethod
     def _format_key(group_by, key):
-        if group_by not in OutputWriterPlot._FORMAT_KEY:
+        if group_by not in OutputSinkPlot._FORMAT_KEY:
             raise NotImplementedError('unsupported grouping: ' + str(group_by))
-        return OutputWriterPlot._FORMAT_KEY[group_by](key)
+        return OutputSinkPlot._FORMAT_KEY[group_by](key)
 
     @staticmethod
     def _format_duration(seconds, _):
@@ -203,11 +200,11 @@ class OutputWriterPlot:
 
     @staticmethod
     def _extract_labels(group_by, durations):
-        return tuple(map(lambda key: OutputWriterPlot._format_key(group_by, key), durations.keys()))
+        return tuple(map(lambda key: OutputSinkPlot._format_key(group_by, key), durations.keys()))
 
     @staticmethod
     def _extract_values(durations):
-        return tuple(map(OutputWriterPlot._duration_to_seconds, durations.values()))
+        return tuple(map(OutputSinkPlot._duration_to_seconds, durations.values()))
 
     def process_database(
             self, group_by, db_reader, time_from=None, time_to=None):
@@ -215,7 +212,7 @@ class OutputWriterPlot:
         durations = group_by.group(db_reader, time_from, time_to)
 
         bar_chart = BarChartBuilder()
-        bar_chart.set_title(OutputWriterPlot.TITLE)
+        bar_chart.set_title(OutputSinkPlot.TITLE)
         bar_chart.enable_grid_for_values()
         bar_chart.only_integer_values()
         bar_chart.set_property(bar_chart.get_values_labels(),
@@ -245,37 +242,24 @@ class OutputFormat(Enum):
     JSON = 'json'
     PLOT = 'plot'
 
-    @contextmanager
-    def create_writer(self, path=None):
-        with self._open_file(path) as fd:
-            if self is OutputFormat.CSV:
-                yield OutputWriterCSV(fd)
-            elif self is OutputFormat.JSON:
-                yield OutputWriterJSON(fd)
-            elif self is OutputFormat.PLOT:
-                yield OutputWriterPlot(fd)
-            else:
-                raise NotImplementedError('unsupported output format: ' + str(self))
-
-    @contextmanager
-    def _open_file(self, path=None):
-        fd = sys.stdout
-        if path is None:
-            pass
-        elif self is OutputFormat.CSV or self is OutputFormat.JSON:
-            fd = open(path, 'w', encoding='utf-8')
+    def __str__(self):
+        return self.value
+
+    def create_sink(self, fd=sys.stdout):
+        if self is OutputFormat.CSV:
+            return OutputSinkCSV(fd)
+        elif self is OutputFormat.JSON:
+            return OutputSinkJSON(fd)
         elif self is OutputFormat.PLOT:
-            fd = open(path, 'wb')
+            return OutputSinkPlot(fd)
         else:
             raise NotImplementedError('unsupported output format: ' + str(self))
-        try:
-            yield fd
-        finally:
-            if fd is not sys.stdout:
-                fd.close()
 
-    def __str__(self):
-        return self.value
+    def open_file(self, path=None):
+        if self is OutputFormat.PLOT:
+            return output.open_binary_file(path)
+        else:
+            return output.open_text_file(path)
 
 def _parse_group_by(s):
     try:
@@ -352,8 +336,9 @@ def process_online_sessions(
             time_from, time_to = time_to, time_from
 
     with db_fmt.create_reader(db_path) as db_reader:
-        with out_fmt.create_writer(out_path) as out_writer:
-            out_writer.process_database(
+        with out_fmt.open_file(out_path) as out_fd:
+            out_sink = out_fmt.create_sink(out_fd)
+            out_sink.process_database(
                 group_by, db_reader,
                 time_from=time_from,
                 time_to=time_to)
diff --git a/bin/utils/output.py b/bin/utils/output.py
new file mode 100644
index 0000000..8954c8b
--- /dev/null
+++ b/bin/utils/output.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 json
+import sys
+
+class OutputWriterJSON:
+    def __init__(self, fd=sys.stdout):
+        self._fd = fd
+
+    def write(self, something):
+        self._fd.write(json.dumps(something, indent=3, ensure_ascii=False))
+        self._fd.write('\n')
+
+class OutputWriterCSV:
+    def __init__(self, fd=sys.stdout):
+        self._writer = csv.writer(fd, lineterminator='\n')
+
+    def write_row(self, row):
+        self._writer.writerow(row)
+
+@contextmanager
+def _open_file(path=None, **kwargs):
+    fd = sys.stdout
+    if path is None:
+        pass
+    else:
+        fd = open(path, **kwargs)
+    try:
+        yield fd
+    finally:
+        if fd is not sys.stdout:
+            fd.close()
+
+def open_text_file(path=None):
+    return _open_file(path, mode='w', encoding='utf-8')
+
+def open_binary_file(path=None):
+    return _open_file(path, mode='wb')