# HG changeset patch
# User Sean Farley <sean.michael.farley@gmail.com>
# Date 1395678044 18000
# Node ID eb4c7bc23f9e486e4de055326125d27acee13705
# Parent  cdad3b3e4a09957e06211ce9d562a2674e5d74b6
svnmeta: add generator for cached svn configuration properties

This will allow use to unify the reading and writing of configuration options
into a central object to simplify their use sprinkled throughout the codebase.

The idea is that after this patch, we will move each option to the svnmeta
class thereby allowing us to remove lots of I/O cruft. Once the cruft is gone,
we'll refactor objects where necessary. After refactoring, we'll have a
framework for easily adding new configuration options.

diff --git a/hgsubversion/svnmeta.py b/hgsubversion/svnmeta.py
--- a/hgsubversion/svnmeta.py
+++ b/hgsubversion/svnmeta.py
@@ -67,6 +67,81 @@ class SVNMeta(object):
         self.addedtags = {}
         self.deletedtags = {}
 
+    def _get_cachedconfig(self, name, filename, configname, default):
+        """Return a cached value for a config option. If the cache is uninitialized
+        then try to read its value from disk. Option can be overridden by the
+        commandline.
+            name: property name, e.g. 'lastpulled'
+            filename: name of file in .hg/svn
+            configname: commandline option name
+            default: default value
+        """
+        varname = '_' + name
+        if getattr(self, varname) is None:
+            # construct the file path from metapath (e.g. .hg/svn) plus the
+            # filename
+            f = os.path.join(self.metapath, filename)
+
+            # load the config property (i.e. command-line or .hgrc)
+            c = None
+            if configname:
+                # a little awkward but we need to convert the option from a
+                # string to whatever type the default value is, so we use the
+                # type of `default` to determine with ui.config method to call
+                c = None
+                if isinstance(default, bool):
+                    c = self.ui.configbool('hgsubversion', configname, default)
+                elif isinstance(default, int):
+                    c = self.ui.configint('hgsubversion', configname, default)
+                elif isinstance(default, list):
+                    c = self.ui.configlist('hgsubversion', configname, default)
+                else:
+                    c = self.ui.config('hgsubversion', configname, default)
+
+            # load the value from disk
+            val = util.load(f, default=default)
+
+            # prefer the non-default, and the one sent from command-line
+            if c and c != val and c != default:
+                val = c
+
+            # set the value as the one from disk (or default if not found)
+            setattr(self, varname, val)
+
+            # save the value to disk by using the setter property
+            setattr(self, name, val)
+
+        return getattr(self, varname)
+
+    def _set_cachedconfig(self, value, name, filename):
+        varname = '_' + name
+        f = os.path.join(self.metapath, filename)
+        setattr(self, varname, value)
+        util.dump(value, f)
+
+    def _gen_cachedconfig(self, name, default=None, filename=None,
+                          configname=None):
+        """Generate an attribute for reading (and caching) config data.
+
+        This method constructs a new attribute on self with the given name.
+        The actual value from the config file will be read lazily, and then
+        cached once that read has occurred. No cache invalidation will happen,
+        so within a session these values shouldn't be required to mutate.
+        """
+        setattr(SVNMeta, '_' + name, None)
+        if filename is None:
+            filename = name
+        if configname is None:
+            configname = name
+        prop = property(lambda x: x._get_cachedconfig(name,
+                                                      filename,
+                                                      configname,
+                                                      default),
+                        lambda x, y: x._set_cachedconfig(y,
+                                                         name,
+                                                         filename))
+        setattr(SVNMeta, name, prop)
+
     @property
     def layout(self):
         # this method can't determine the layout, but it needs to be