1 files changed, 54 insertions, 0 deletions
diff --git a/catapult/telemetry/telemetry/util/js_template.py b/catapult/telemetry/telemetry/util/js_template.py
new file mode 100644
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+++ b/catapult/telemetry/telemetry/util/js_template.py
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+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import json
+import re
+
+
+RE_REPLACEMENT_FIELD = re.compile(r'{{(?P<field_spec>[^}]*)}}')
+RE_FIELD_IDENTIFIER = re.compile(r'(?P<modifier>@)?(?P<name>\w+)$')
+
+
+def RenderValue(value):
+  """Convert a Python value to a string with its JavaScript representation."""
+  return json.dumps(value, sort_keys=True)
+
+
+def Render(template, **kwargs):
+  """Helper method to interpolate Python values into JavaScript snippets.
+
+  Placeholders in the template, field names enclosed in double curly braces,
+  are replaced with the value of the corresponding named argument. Prefixing
+  a field name with '@' causes the value to be inserted literally.
+
+
+  For example:
+
+    js_template.Render(
+      'var {{ @var_name }} = f({{ x }}, {{ y }});',
+      var_name='foo', x=42, y='hello')
+
+  Returns:
+
+    'var foo = f(42, "hello");'
+
+  Args:
+    template: A string with a JavaScript template, tagged with {{ fields }}
+      to interpolate with values.
+    **kwargs: Values to be interpolated in the template.
+  """
+  def interpolate(m):
+    field_spec = m.group('field_spec').strip()
+    field = RE_FIELD_IDENTIFIER.match(field_spec)
+    if not field:
+      raise KeyError(field_spec)
+    value = kwargs[field.group('name')]
+    if field.group('modifier') == '@':
+      if not isinstance(value, str):
+        raise ValueError('Literal value for %s must be a string' % field_spec)
+      return value
+    else:
+      return RenderValue(value)
+
+  return RE_REPLACEMENT_FIELD.sub(interpolate, template)