feat: add grpc transcoding + tests

google/api_core/path_template.py

@@ -25,6 +25,8 @@
 
 from __future__ import unicode_literals
 
+from collections import deque
+import copy
 import functools
 import re
 
@@ -64,7 +66,7 @@ def _expand_variable_match(positional_vars, named_vars, match):
  """Expand a matched variable with its value.
 
  Args:
- positional_vars (list): A list of positonal variables. This list will
+ positional_vars (list): A list of positional variables. This list will
  be modified.
  named_vars (dict): A dictionary of named variables.
  match (re.Match): A regular expression match.
@@ -170,6 +172,46 @@ def _generate_pattern_for_template(tmpl):
  return _VARIABLE_RE.sub(_replace_variable_with_pattern, tmpl)
 
 
+def get_field(request, field):
+ """Get the value of a field from a given dictionary.
+
+ Args:
+ request (dict): A dictionary object.
+ field (str): The key to the request in dot notation.
+
+ Returns:
+ The value of the field.
+ """
+ parts = field.split(".")
+ value = request
+ for part in parts:
+ if not isinstance(value, dict):
+ return
+ value = value.get(part)
+ if isinstance(value, dict):
+ return
+ return value
+
+
+def delete_field(request, field):
+ """Delete the value of a field from a given dictionary.
+
+ Args:
+ request (dict): A dictionary object.
+ field (str): The key to the request in dot notation.
+ """
+ parts = deque(field.split("."))
+ while len(parts) > 1:
+ if not isinstance(request, dict):
+ return
+ part = parts.popleft()
+ request = request.get(part)
+ part = parts.popleft()
+ if not isinstance(request, dict):
+ return
+ request.pop(part, None)
+
+
 def validate(tmpl, path):
  """Validate a path against the path template.
 
@@ -193,3 +235,66 @@ def validate(tmpl, path):
  """
  pattern = _generate_pattern_for_template(tmpl) + "$"
  return True if re.match(pattern, path) is not None else False
+
+
+def transcode(http_options, **request_kwargs):
+ """Transcodes a grpc request pattern into a proper HTTP request following the rules outlined here,
+ https://github.com/googleapis/googleapis/blob/master/google/api/http.proto#L44-L312
+
+ Args:
+ http_options (list(dict)): A list of dicts which consist of these keys,
+ 'method' (str): The http method
+ 'uri' (str): The path template
+ 'body' (str): The body field name (optional)
+ (This is a simplified representation of the proto option `google.api.http`)
+
+ request_kwargs (dict) : A dict representing the request object
+
+ Returns:
+ dict: The transcoded request with these keys,
+ 'method' (str) : The http method
+ 'uri' (str) : The expanded uri
+ 'body' (dict) : A dict representing the body (optional)
+ 'query_params' (dict) : A dict mapping query parameter variables and values
+
+ Raises:
+ ValueError: If the request does not match the given template.
+ """
+ for http_option in http_options:
+ request = {}
+
+ # Assign path
+ uri_template = http_option["uri"]
+ path_fields = [
+ match.group("name") for match in _VARIABLE_RE.finditer(uri_template)
+ ]
+ path_args = {field: get_field(request_kwargs, field) for field in path_fields}
+ request["uri"] = expand(uri_template, **path_args)
+
+ # Remove fields used in uri path from request
+ leftovers = copy.deepcopy(request_kwargs)
+ for path_field in path_fields:
+ delete_field(leftovers, path_field)
+
+ if not validate(uri_template, request["uri"]) or not all(path_args.values()):
+ continue
+
+ # Assign body and query params
+ body = http_option.get("body")
+
+ if body:
+ if body == "*":
+ request["body"] = leftovers
+ request["query_params"] = {}
+ else:
+ try:
+ request["body"] = leftovers.pop(body)
+ except KeyError:
+ continue
+ request["query_params"] = leftovers
+ else:
+ request["query_params"] = leftovers
+ request["method"] = http_option["method"]
+ return request
+
+ raise ValueError("Request obj does not match any template")