1 files changed, 108 insertions, 0 deletions
diff --git a/yarnlib/scenario_step_connector.py b/yarnlib/scenario_step_connector.py
new file mode 100644
index 0000000..3e0712f
--- /dev/null
+++ b/yarnlib/scenario_step_connector.py
@@ -0,0 +1,108 @@
+# Copyright 2014  Lars Wirzenius and Codethink Limited
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+# =*= License: GPL-3+ =*=
+
+
+import cliapp
+import re
+
+
+def implements_matches_step(implements, step):
+    '''Return re.Match if implements matches the step.
+
+    Otherwise, return None.
+
+    '''
+
+    m = re.match(implements.regexp, step.text, re.I)
+    if m and m.end() != len(step.text):
+        return None
+    return m
+
+
+class StepNotImplementedError(cliapp.AppException):
+
+    def __init__(self, scenario, step):
+        cliapp.AppException.__init__(
+            self, 'Scenario "%s", step "%s %s" has no matching '
+                  'implementation' %
+                  (scenario.name, step.what, step.text))
+
+
+class StepMultipleImplementationsError(cliapp.AppException):
+
+    def __init__(self, scenario, step, matching):
+        s = '\n'.join(
+            'IMPLEMENTS %s %s' % (i.what, i.regexp)
+            for i in matching)
+        cliapp.AppException.__init__(
+            self, 'Scenario "%s", step "%s %s" has more than one '
+                  'matching implementations:\n%s' %
+                  (scenario.name, step.what, step.text, s))
+
+
+class ScenarioStepConnector(object):
+    '''Connect scenario steps to their implementations.'''
+
+    def __init__(self, implementations, missing_step_cb=lambda sc, st: None):
+        self.implementations = implementations
+        self.missing_step_cb = missing_step_cb
+
+    def connect_implementations(self, scenarios):
+        '''Connect scenario steps, returning implemented scenarios.
+
+        For each scenario given, connect known implementations to
+        the steps.
+
+        This returns only scenarios that were fully implemented.
+        Unless ``missing_step_cb`` is provided and returns true for all
+        missing steps, an exception is raised instead.
+
+        '''
+        implemented_scenarios = []
+        for scenario in scenarios:
+            missing_step = False
+            for step in scenario.steps:
+                self.connect_implementation(scenario, step)
+                if step.implementation is None:
+                    missing_step = True
+            if not missing_step:
+                implemented_scenarios.append(scenario)
+        return implemented_scenarios
+
+    def connect_implementation(self, scenario, step):
+        '''Connect the step of a scenario to its implementation.
+
+        Always raises an exception if there are multiple matching
+        implementations.
+
+        Raises an exception if there are no matching implementations
+        unless ``missing_step_cb`` returns true.
+
+        '''
+        matching = [i for i in self.implementations
+                    if step.what == i.what and
+                       implements_matches_step(i, step)]
+
+        if len(matching) == 0:
+            if self.missing_step_cb(scenario, step):
+                return
+            raise StepNotImplementedError(scenario, step)
+        if len(matching) > 1:
+            raise StepMultipleImplementationsError(scenario, step, matching)
+
+        assert step.implementation is None
+        step.implementation = matching[0]