Revamped FileIO (#262)

Handles backups, way tidier with different functions, backwards compatible. Should fix the corrupted json issues.

cogs/utils/dataIO.py

@@ -1,20 +1,83 @@
 import json
+import os
+import logging
+from shutil import copy
 
-def fileIO(filename, IO, data=None):
-    if IO == "save" and data != None:
-        with open(filename, encoding='utf-8', mode="w") as f:
-            f.write(json.dumps(data,indent=4,sort_keys=True,separators=(',',' : ')))
-    elif IO == "load" and data == None:
-        with open(filename, encoding='utf-8', mode="r") as f:
-            return json.loads(f.read())
-    elif IO == "check" and data == None:
+class InvalidFileIO(Exception):
+    pass
+
+class CorruptedJSON(Exception):
+    pass
+
+class DataIO():
+    def __init__(self):
+        self.logger = logging.getLogger("red")
+
+    def save_json(self, filename, data):
+        """Saves and backups json file"""
+        bak_file = os.path.splitext(filename)[0]+'.bak'
+        self._save_json(filename, data)
+        copy(filename, bak_file) # Backup copy
+
+    def load_json(self, filename):
+        """Loads json file and restores backup copy in case of corrupted file"""
         try:
-            with open(filename, encoding='utf-8', mode="r") as f:
-                return True
-        except:
+            return self._read_json(filename)
+        except json.decoder.JSONDecodeError:
+            result = self._restore_json(filename)
+            if result:
+                return self._read_json(filename) # Which hopefully will work
+            else:
+                raise CorruptedJSON("{} is corrupted and no backup copy is"
+                                    " available.".format(filename))
+
+    def is_valid_json(self, filename):
+        """Returns True if readable json file, False if not existing.
+           Tries to restore backup copy if corrupted"""
+        try:
+            data = self._read_json(filename)
+        except FileNotFoundError:
             return False
-    else:
-        raise("Invalid fileIO call")
+        except json.decoder.JSONDecodeError:
+            result = self._restore_json(filename)
+            return result # If False, no backup copy, might as well
+        else:             # allow the overwrite
+            return True
+
+    def _read_json(self, filename):
+        with open(filename, encoding='utf-8', mode="r") as f:
+            data = json.loads(f.read())
+        return data
+
+    def _save_json(self, filename, data):
+        with open(filename, encoding='utf-8', mode="w") as f:
+            f.write(json.dumps(data,indent=4,sort_keys=True,
+                separators=(',',' : ')))
+        return data
+
+    def _restore_json(self, filename):
+        bak_file = os.path.splitext(filename)[0]+'.bak'
+        if os.path.isfile(bak_file):
+            copy(bak_file, filename) # Restore last working copy
+            self.logger.warning("{} was corrupted. Restored "
+                    "backup copy.".format(filename))
+            return True
+        else:
+            self.logger.critical("{} is corrupted and there is no "
+                    "backup copy available.".format(filename))
+            return False
+
+    def _legacy_fileio(self, filename, IO, data=None):
+        """Old fileIO provided for backwards compatibility"""
+        if IO == "save" and data != None:
+            return self.save_json(filename, data)
+        elif IO == "load" and data == None:
+            return self.load_json(filename)
+        elif IO == "check" and data == None:
+            return self.is_valid_json(filename)
+        else:
+            raise InvalidFileIO("FileIO was called with invalid"
+                " parameters")
 
 def get_value(filename, key):
     with open(filename, encoding='utf-8', mode="r") as f:
@@ -25,4 +88,7 @@ def set_value(filename, key, value):
     data = fileIO(filename, "load")
     data[key] = value
     fileIO(filename, "save", data)
-    return True
+    return True
+
+dataIO = DataIO()
+fileIO = dataIO._legacy_fileio # backwards compatibility