(core) move data engine code to core

Summary:
this moves sandbox/grist to core, and adds a requirements.txt
file for reconstructing the content of sandbox/thirdparty.

Test Plan:
existing tests pass.
Tested core functionality manually.  Tested docker build manually.

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2563

sandbox/grist/action_obj.py

@@ -0,0 +1,79 @@
+"""
+This module defines ActionGroup, ActionEnvelope, and ActionBundle -- classes that together
+represent the result of applying a UserAction to a document.
+
+In general, UserActions refer to logical actions performed by the user. DocActions are the
+individual steps to which UserActions translate.
+
+A list of UserActions applied together translates to multiple DocActions, packaged into an
+ActionGroup. In a separate step, this ActionGroup is split up according to ACL rules into and
+ActionBundle consisting of ActionEnvelopes, each containing a smaller set of actions associated
+with the set of recipients who should receive them.
+"""
+
+import actions
+
+
+class ActionGroup(object):
+  """
+  ActionGroup packages different types of doc actions for returning them to the instance.
+
+  The ActionGroup stores actions produced by the engine in the course of processing one or more
+  UserActions, plus an array of return values, one for each UserAction.
+  """
+  def __init__(self):
+    self.calc     = []
+    self.stored   = []
+    self.undo     = []
+    self.retValues = []
+
+  def get_repr(self):
+    return {
+      "calc":     map(actions.get_action_repr, self.calc),
+      "stored":   map(actions.get_action_repr, self.stored),
+      "undo":     map(actions.get_action_repr, self.undo),
+      "retValues": self.retValues
+    }
+
+  @classmethod
+  def from_json_obj(cls, data):
+    ag = ActionGroup()
+    ag.calc   = map(actions.action_from_repr, data.get('calc', []))
+    ag.stored = map(actions.action_from_repr, data.get('stored', []))
+    ag.undo   = map(actions.action_from_repr, data.get('undo', []))
+    ag.retValues = data.get('retValues', [])
+    return ag
+
+
+class Envelope(object):
+  """
+  Envelope contains information about recipients as a set (or frozenset) of instanceIds.
+  """
+  def __init__(self, recipient_set):
+    self.recipients = recipient_set
+
+  def to_json_obj(self):
+    return {"recipients": sorted(self.recipients)}
+
+class ActionBundle(object):
+  """
+  ActionBundle contains actions arranged into envelopes, i.e. split up by sets of recipients.
+  Note that different Envelopes contain different sets of recipients (which may overlap however).
+  """
+  def __init__(self):
+    self.envelopes = []
+    self.stored = []          # Pairs of (envIndex, docAction)
+    self.calc = []            # Pairs of (envIndex, docAction)
+    self.undo = []            # Pairs of (envIndex, docAction)
+    self.retValues = []
+    self.rules = set()        # RowIds of ACLRule records used to construct this ActionBundle.
+
+  def to_json_obj(self):
+    return {
+      "envelopes": [e.to_json_obj() for e in self.envelopes],
+      "stored":    [(env, actions.get_action_repr(a)) for (env, a) in self.stored],
+      "calc":      [(env, actions.get_action_repr(a)) for (env, a) in self.calc],
+      "undo":      [(env, actions.get_action_repr(a)) for (env, a) in self.undo],
+      "retValues": self.retValues,
+      "rules":     sorted(self.rules)
+    }