config: Begin Configuration class.

oxrlib/config.py

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+import argparse
+import configparser
+import datetime
+import os.path
+import pathlib
+
+from . import loaders
+
+HOME_PATH = pathlib.Path(os.path.expanduser('~'))
+CONFFILE_SEED = """
+[Historical]
+base=USD
+"""
+
+def currency_code(s):
+    if not (len(s) == 3) and s.isalpha():
+        raise ValueError("bad currency code: {!r}".format(s))
+    return s.upper()
+
+def date_from(fmt_s):
+    def date_from_fmt(s):
+        return datetime.datetime.strptime(s, fmt_s).date
+    return date_from_fmt
+
+class Configuration:
+    DEFAULT_CONFIG_PATH = pathlib.Path(HOME_PATH, '.config', 'oxrlib.ini')
+
+    def __init__(self, arglist):
+        argparser = self._build_argparser()
+        self.error = argparser.error
+        self.args = argparser.parse_args(arglist)
+
+        if self.args.config_file is None:
+            self.args.config_file = [self.DEFAULT_CONFIG_PATH]
+        self.conffile = self._build_conffile()
+        conffile_paths = [path.as_posix() for path in self.args.config_file]
+        read_files = self.conffile.read(conffile_paths)
+        for expected_path, read_path in zip(conffile_paths, read_files):
+            if read_path != expected_path:
+                self.error("failed to read configuration file {!r}".format(expected_path))
+
+        try:
+            post_hook = getattr(self, '_post_hook_' + self.args.command)
+        except AttributeError:
+            pass
+        else:
+            post_hook()
+
+    def _build_argparser(self):
+        prog_parser = argparse.ArgumentParser()
+        prog_parser.add_argument(
+            '--config-file', '-c',
+            action='append', type=pathlib.Path,
+            help="Path of a configuration file to read",
+        )
+        subparsers = prog_parser.add_subparsers()
+
+        hist_parser = subparsers.add_parser('historical', aliases=['hist'])
+        hist_parser.set_defaults(command='historical')
+        hist_parser.add_argument(
+            '--base',
+            help="Base currency (default USD)",
+        )
+        hist_parser.add_argument(
+            'date',
+            type=date_from('%Y-%m-%d'), metavar='YYYY-MM-DD',
+        )
+
+        return prog_parser
+
+    def _build_conffile(self):
+        conffile = configparser.ConfigParser()
+        conffile.read_string(CONFFILE_SEED)
+        return conffile
+
+    def _post_hook_historical(self):
+        if self.args.base is None:
+            self.args.base = self.conffile.get('Historical', 'base')
+
+    def _build_cache_loader(self):
+        kwargs = dict(self.conffile.items('Cache'))
+        try:
+            kwargs['dir_path'] = kwargs.pop('directory')
+        except KeyError:
+            pass
+        return loaders.FileCache(**kwargs)
+
+    def _build_oxrapi_loader(self):
+        kwargs = dict(self.conffile.items('OXR'))
+        return loaders.OXRAPIRequest(**kwargs)
+
+    def get_loaders(self):
+        loader_chain = loaders.LoaderChain()
+        for build_func in [
+                self._build_cache_loader,
+                self._build_oxrapi_loader,
+        ]:
+            try:
+                loader = build_func()
+            except (TypeError, ValueError, configparser.NoSectionError):
+                pass
+            else:
+                loader_chain.add_loader(loader)
+        return loader_chain

tests/config_ini/full.ini

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+[Cache]
+directory = /tmp
+historical = {date}_{base}_rates.json
+
+[OXR]
+app_id = 1234567890abcdef1234567890abcdef
+api_root = http://[100::]/oxrlibtest/
+
+[Historical]
+base = INI

tests/config_ini/incomplete.ini

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+[Cache]
+# No directory.
+# FIXME: Write pattern-validating code, and then make this the section:
+# directory = /tmp
+# historical = rates.json
+
+[OXR]
+# No app_id.
+api_root = http://[100::]/oxrlibtest/

tests/test_Configuration.py

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+import os
+
+import pytest
+
+from . import any_date, relpath
+
+import oxrlib.config
+import oxrlib.loaders
+
+INI_DIR_PATH = relpath('config_ini')
+
+def config_from(ini_filename, arglist=None):
+    if arglist is None:
+        arglist = ['historical', any_date().isoformat()]
+    ini_path = INI_DIR_PATH / ini_filename
+    return oxrlib.config.Configuration(['--config-file', ini_path.as_posix()] + arglist)
+
+def test_full_config():
+    config = config_from('full.ini')
+    loaders = config.get_loaders().loaders
+    assert type(loaders[0]) is oxrlib.loaders.FileCache
+    assert type(loaders[1]) is oxrlib.loaders.OXRAPIRequest
+    assert len(loaders) == 2
+
+def test_incomplete_config():
+    config = config_from('incomplete.ini')
+    assert not config.get_loaders().loaders
+
+def test_empty_config():
+    config = config_from(os.devnull)
+    assert not config.get_loaders().loaders
+
+@pytest.mark.parametrize('ini_filename,expected_currency,use_switch', [
+    (os.devnull, 'USD', False),
+    ('full.ini', 'INI', False),
+    ('full.ini', 'EUR', True),
+])
+def test_historical_default_base(ini_filename, expected_currency, use_switch, any_date):
+    arglist = ['historical']
+    if use_switch:
+        arglist.extend(['--base', expected_currency])
+    arglist.append(any_date.isoformat())
+    config = config_from(ini_filename, arglist)
+    assert config.args.base == expected_currency