config parsing in pure python

1 files changed, 161 insertions, 63 deletions

diff --git a/talerbank/talerconfig.py b/talerbank/talerconfig.py
index 9b258e2..4a8d45a 100644
--- a/talerbank/talerconfig.py
+++ b/talerbank/talerconfig.py
@@ -1,68 +1,166 @@
-#  This file is part of TALER
-#  (C) 2016 INRIA
-#
-#  TALER is free software; you can redistribute it and/or modify it under the
-#  terms of the GNU Affero General Public License as published by the Free Software
-#  Foundation; either version 3, or (at your option) any later version.
-#
-#  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
-#  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
-#  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
-#
-#  You should have received a copy of the GNU General Public License along with
-#  TALER; see the file COPYING.  If not, If not, see <http://www.gnu.org/licenses/>
-#
-#  @author Florian Dold
-
-"""
-Access to GNUnet-style configuration for Taler.
-
-Requires the taler-config utility from the
-GNU Taler exchange to be available in $PATH
-"""
-
-import shutil
-import subprocess
-
-# FIXME: eventually this should use a python
-# parser and not shell out to taler-config
-
-cmd = "taler-config"
+import logging
+import collections
+import os
 
+logger = logging.getLogger(__name__)
 
-class TalerConfig:
-    def __init__(self, filename=None):
-        self.filename = filename
+__all__ = ["TalerConfig"]
+
+taler_datadir = None
+try:
+    # not clear if this is a good idea ...
+    from talerpaths import taler_datadir as t
+    taler_datadir = t
+except ImportError:
+    pass
+
+
+class OptionDict(collections.defaultdict):
+    def __init__(self):
+        super().__init__()
+    def __missing__(self, key):
+        raise KeyError(key)
 
-    def _check_prog(self):
-        prog = shutil.which(cmd)
-        if prog is None:
-            raise Exception("taler-config command not found in $PATH")
-
-    def _run(self, *args):
-        p = subprocess.Popen([cmd] + list(args), stdout=subprocess.PIPE)
-        (out, err) = p.communicate()
-        r = p.wait()
-        return r, out.decode('utf-8').rstrip('\n')
-
-    def get_string(self, section, option):
-        self._check_prog()
-        args = ['-s', section, '-o', option]
-        if self.filename is not None:
-            args.append('-c')
-            args.append(self.filename)
-        r, v = self._run(*args)
-        if r != 0:
-            raise Exception("error running taler-config")
-        return v
 
-    def get_filename(self, section, option):
-        self._check_prog()
-        args = ['-f', '-s', section, '-o', option]
-        if self.filename is not None:
-            args.append('-c')
-            args.append(self.filename)
-        r, v = self._run(*args)
-        if r != 0:
-            raise Exception("error running taler-config")
+class SectionDict(collections.defaultdict):
+    def __init__(self):
+        super().__init__()
+    def __missing__(self, key):
+        v = OptionDict()
+        self[key] = v
         return v
+
+class Entry:
+    def __init__(self, section, option, value=None, filename=None, lineno=None):
+        self.value = value
+        self.filename = filename
+        self.lineno = lineno
+        self.section = section
+        self.option = option
+
+    def __repr__(self):
+        return "<Entry section=%s, option=%s, value=%s>" % (self.section, self.option, repr(self.value),)
+
+    def __str__(self):
+        return self.value
+
+    def value_string(self, default=None, warn=False):
+        if self.value is None:
+            if warn:
+                if default is not None:
+                    logger.warn("Configuration is missing option %s in section %s, falling back to '%s'", default)
+                else:
+                    logger.warn("Configuration is missing option %s in section %s", default)
+            return default
+        return self.value
+
+    def location(self):
+        if self.filename is None or self.lineno is None:
+            return "<unknown>"
+        return "%s:%s" % (self.filename, self.lineno)
+
+
+class TalerConfig:
+    """
+    One loaded taler configuration, including base configuration
+    files and included files.
+    """
+    def __init__(self):
+        """
+        Initialize an empty configuration
+        """
+        self.sections = SectionDict()
+
+    @staticmethod
+    def from_file(filename=None, load_defaults=True):
+        cfg = TalerConfig()
+        if filename is None:
+            xdg = os.environ.get("XDG_CONFIG_HOME")
+            if xdg:
+                filename = os.path.join(xdg, "taler.conf")
+            else:
+                filename = os.path.expanduser("~/.config/taler.conf")
+        if load_defaults:
+            cfg.load_defaults()
+        cfg.load_file(filename)
+        return cfg
+
+    def load_defaults(self):
+        base_dir = os.environ.get("TALER_BASE_CONFIG")
+        if base_dir:
+            self.load_dir(base_dir)
+            return
+        prefix = os.environ.get("TALER_PREFIX")
+        if prefix:
+            self.load_dir(os.path.join(prefix, "share/config.d"))
+            return
+        if taler_datadir:
+            self.load_dir(os.path.join(taler_datadir, "config.d"))
+            return
+        logger.warn("no base directory found")
+
+    def load_dir(self, dirname):
+        try:
+            files = os.listdir(dirname)
+        except FileNotFoundError:
+            logger.warn("can't read config directory '%s'", dirname)
+            return
+        for file in files:
+            if not file.endswith(".conf"):
+                continue
+            self.load_file(os.path.join(dirname, file))
+
+    def load_file(self, filename):
+        sections = self.sections
+        with open(filename, "r") as file:
+            lineno = 0
+            current_section = None
+            for line in file:
+                lineno += 1
+                line = line.strip()
+                if len(line) == 0:
+                    # empty line
+                    continue
+                if line.startswith("#"):
+                    # comment
+                    continue
+                if line.startswith("["):
+                    if not line.endswith("]"):
+                        logger.error("invalid section header in line %s: %s", lineno, repr(line))
+                    section_name = line.strip("[]").strip().strip('"')
+                    current_section = section_name
+                    continue
+                if current_section is None:
+                    logger.error("option outside of section in line %s: %s", lineno, repr(line))
+                    continue
+                kv = line.split("=", 2)
+                if len(kv) != 2:
+                    logger.error("invalid option in line %s: %s", lineno, repr(line))
+                key = kv[0].strip()
+                value = kv[1].strip()
+                if value.startswith('"'):
+                    value = value[1:]
+                    if not value.endswith('"'):
+                        logger.error("mismatched quotes in line %s: %s", lineno, repr(line))
+                    else:
+                        value = value[:-1]
+                e = Entry(current_section, key, value, filename, lineno)
+                sections[current_section][key] = e
+
+
+    def dump(self):
+        for section_name, section in self.sections.items():
+            print("[%s]" % (section_name,))
+            for option_name, option in section.items():
+                print("%s = %s # %s" % (option_name, option, option.location()))
+
+    def __getitem__(self, slice):
+        if isinstance(slice, str):
+            return self.sections[slice]
+        raise TypeError("index must be string")
+
+
+if __name__ == "__main__":
+    import sys
+    tc = TalerConfig.from_file(sys.argv[1])
+    tc.dump()