- add generic Filter class for Get() requests: eases filtering on one

  or more columns of a table, for a specific value for each column, or a
  list of possible values for each column

diff --git a/PLC/Filter.py b/PLC/Filter.py
new file mode 100644 (file)
index 0000000..66e9aee
--- /dev/null
+++ b/PLC/Filter.py
@@ -0,0 +1,76 @@
+from PLC.Faults import *
+from PLC.Parameter import Parameter, Mixed, python_type
+
+class Filter(Parameter, dict):
+    """
+    A type of parameter that represents a filter on one or more
+    columns of a database table. fields should be a dictionary of
+    field names and types, e.g.
+
+    {'node_id': Parameter(int, "Node identifier"),
+     'hostname': Parameter(int, "Fully qualified hostname", max = 255),
+     ...}
+
+    Only filters on non-sequence type fields are supported.
+
+    filter should be a dictionary of field names and values
+    representing an intersection (if join_with is AND) or union (if
+    join_with is OR) filter. If a value is a sequence type, then it
+    should represent a list of possible values for that field.
+    """
+
+    def __init__(self, fields = {}, filter = {}, doc = "Attribute filter"):
+        # Store the filter in our dict instance
+        dict.__init__(self, filter)
+
+        # Declare ourselves as a type of parameter that can take
+        # either a value or a list of values for each of the specified
+        # fields.
+        self.fields = {}
+
+        for field, expected in fields.iteritems():
+            # Cannot filter on sequences
+            if python_type(expected) in (list, tuple, set):
+                continue
+            
+            # Accept either a value or a list of values of the specified type
+            self.fields[field] = Mixed(expected, [expected])
+
+        Parameter.__init__(self, self.fields, doc = doc)
+
+    def sql(self, api, join_with = "AND"):
+        """
+        Returns a SQL conditional that represents this filter.
+        """
+
+        # So that we always return something
+        if join_with == "AND":
+            conditionals = ["True"]
+        elif join_with == "OR":
+            conditionals = ["False"]
+        else:
+            assert join_with in ("AND", "OR")
+
+        for field, value in self.iteritems():
+            if field not in self.fields:
+                raise PLCInvalidArgument, "Invalid filter field '%s'" % field
+
+            if isinstance(value, (list, tuple, set)):
+                # Turn empty list into (NULL) instead of invalid ()
+                if not value:
+                    value = [None]
+
+                operator = "IN"
+                value = map(str, map(api.db.quote, value))
+                value = "(%s)" % ", ".join(value)
+            else:
+                if value is None:
+                    operator = "IS"
+                    value = "NULL"
+                else:
+                    operator = "="
+                    value = str(api.db.quote(value))
+
+            conditionals.append("%s %s %s" % (field, operator, value))
+
+        return (" %s " % join_with).join(conditionals)