Revamp undo API

bulk_reminders/undo.py

@@ -1,25 +1,67 @@
 import json
 import os
-
-stages = []
+from typing import List
 
 
-def load() -> None:
-    """Load data from the undo history file"""
-    with open('history.json', 'r') as history:
-        stages = json.load(history)
+class HistoryManager(object):
+    def __init__(self, file: str) -> None:
+        self.file = file
+        self.stages: List[Stage] = []
+
+        # Immediately load data if possible
+        if os.path.exists(self.file):
+            self.load()
+
+    def pop(self) -> 'Stage':
+        """Remove the latest Stage and return it"""
+        return self.stages.pop(0)
+
+    def load(self) -> None:
+        """Load data from the undo history file"""
+        with open(self.file, 'r') as history:
+            self.stages = json.load(history)
+
+    def save(self) -> None:
+        """Save data to the undo history file."""
+        with open(self.file, 'w') as history:
+            json.dump(self.stages, history)
+
+    def getTotal(self) -> int:
+        """Returns the total number of undoable events known."""
+        return sum(len(stage) for stage in self.stages)
+
+    def exists(self, id: 'IDPair') -> int:
+        """Check if a given ID exists anywhere in the undo history data. Returns the stage index or -1 if it wasn't found."""
+        for stage in self.stages:
+            for stageID in stage.events:
+                if id == stageID:
+                    return stage.index
+        return -1
 
 
-def save() -> None:
-    """Save data to the undo history file."""
-    with open('history.json', 'w') as history:
-        stages = json.dump(history)
+class Stage(object):
+    def __init__(self, index: int) -> None:
+        self.index = index
+        self.events: List[IDPair] = []
+
+    def __contains__(self, item) -> bool:
+        if type(item) is IDPair:
+            return item in self.events
+        return False
+
+    def __len__(self) -> int:
+        """The len function on a Stage object returns the number of events in the stage."""
+        return len(self.events)
 
 
-if os.path.exists('history.json'):
-    load()
+class IDPair(object):
+    def __init__(self, calendarID: str, eventID: str) -> None:
+        self.calendarID, self.eventID = calendarID, eventID
 
-
-def getTotal() -> int:
-    """Returns the total number of undoable events known."""
-    return sum(len(stage) for stage in stages)
+    def __eq__(self, other):
+        """Check equality between two IDPair objects or two item tuple."""
+        if type(other) is IDPair:
+            return self.calendarID == other.calendarID and self.eventID == other.calendarID
+        elif type(other) is tuple:
+            return len(other) == 2 and other == (self.calendarID, self.eventID)
+        return False