save_variables: Support saving variables to a disk file

Signed-off-by: Dushyant Ahuja dusht.ahuja@gmail.com
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/extras/save_variables.py

@@ -0,0 +1,63 @@
+# Save arbitrary variables so that values can be kept across restarts.
+#
+# Copyright (C) 2020 Dushyant Ahuja <dusht.ahuja@gmail.com>
+# Copyright (C) 2016-2020  Kevin O'Connor <kevin@koconnor.net>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+import os, logging, ast, ConfigParser
+
+class SaveVariables:
+    def __init__(self, config):
+        self.printer = config.get_printer()
+        self.filename = os.path.expanduser(config.get('filename'))
+        self.allVariables = {}
+        try:
+            self.loadVariables()
+        except self.printer.command_error as e:
+            raise config.error(str(e))
+        gcode = self.printer.lookup_object('gcode')
+        gcode.register_command('SAVE_VARIABLE', self.cmd_SAVE_VARIABLE,
+                               desc=self.cmd_SAVE_VARIABLE_help)
+    def loadVariables(self):
+        allvars = {}
+        varfile = ConfigParser.ConfigParser()
+        try:
+            varfile.read(self.filename)
+            if varfile.has_section('Variables'):
+                for name, val in varfile.items('Variables'):
+                    allvars[name] = ast.literal_eval(val)
+        except:
+            msg = "Unable to parse existing variable file"
+            logging.exception(msg)
+            raise self.printer.command_error(msg)
+        self.allVariables = allvars
+    cmd_SAVE_VARIABLE_help = "Save arbitrary variables to disk"
+    def cmd_SAVE_VARIABLE(self, gcmd):
+        varname = gcmd.get('VARIABLE')
+        value = gcmd.get('VALUE')
+        try:
+            value = ast.literal_eval(value)
+        except ValueError as e:
+            raise gcmd.error("Unable to parse '%s' as a literal" % (value,))
+        newvars = dict(self.allVariables)
+        newvars[varname] = value
+        # Write file
+        varfile = ConfigParser.ConfigParser()
+        varfile.add_section('Variables')
+        for name, val in sorted(newvars.items()):
+            varfile.set('Variables', name, repr(val))
+        try:
+            f = open(self.filename, "w")
+            varfile.write(f)
+            f.close()
+        except:
+            msg = "Unable to save variable"
+            logging.exception(msg)
+            raise gcmd.error(msg)
+        gcmd.respond_info("Variable Saved")
+        self.loadVariables()
+    def get_status(self, eventtime):
+        return {'variables': dict(self.allVariables)}
+
+def load_config(config):
+    return SaveVariables(config)