Fix capacity extraction for generators

Also add hstore text representation parser

entsoe/abstraction.sql

@@ -125,7 +125,7 @@ insert into network_link (link_id, src_bus_id, dst_bus_id, voltage, circuits, dc
 insert into network_generator (generator_id, bus_id, symbol, capacity, tags, geometry)
      select g.generator_id,
             (select network_bus_id from station_terminal t where g.station_id = t.station_id order by voltage asc limit 1),
-            p.tags->'symbol', (p.tags->'capacity')::numeric, p.tags - array['symbol','numeric'],
+            p.tags->'symbol', (p.tags->'mw')::numeric, p.tags - array['symbol','mw'],
             st_astext(st_transform(p.location, 4326))
        from topology_generators g
        join power_generator p on p.generator_id = g.generator_id;

util/hstore.py

@@ -0,0 +1,48 @@
+import re
+
+class hstore(dict):
+    class parser(object):
+        word   = re.compile(r'"([^"]+)"')
+        arrow  = re.compile(r'\s*=>\s*')
+        comma  = re.compile(r',\s*')
+
+        def __init__(self, text):
+            self.position = 0
+            self.text     = text
+
+        def __iter__(self):
+            while self.peek(self.word):
+                key   = self.read(self.word, 1)
+                self.read(self.arrow)
+                value = self.read(self.word, 1)
+                yield key, value
+                if self.peek(self.comma):
+                    self.read(self.comma)
+                else:
+                    break
+
+        def read(self, expect, group=0):
+            match = expect.match(self.text, self.position)
+            if match is None:
+                raise Exception('parse error at ' + position)
+            self.position = match.end()
+            return match.group(group)
+
+        def peek(self, expect):
+            return expect.match(self.text, self.position) is not None
+
+    def __init__(self, text):
+        super(hstore,self).__init__(self.parser(text))
+
+    def __str__(self):
+        return ', '.join('"{0}"=>"{1}"'.format(k,v) for k,v in self.items())
+
+def _main():
+    hstore_str = '"foo" => "bar"'
+    hstore_dct = hstore(hstore_str)
+    assert hstore_dct['foo'] == 'bar'
+    assert str(hstore_dct) == '"foo"=>"bar"'
+    assert repr(hstore_dct) == "{'foo': 'bar'}"
+
+if __name__ == '__main__':
+    _main()