schedule & diffusions check/update + cleanup Schedule methods

aircox/admin/program.py

@@ -1,20 +1,33 @@
 from copy import copy
 
 from django.contrib import admin
+from django.forms import ModelForm
 from django.utils.translation import gettext_lazy as _
 
 from ..models import Program, Schedule, Stream
 from .page import PageAdmin
 
 
+# In order to simplify schedule_post_save algorithm, an existing schedule can't
+# update the following fields: "frequency", "date"
+class ScheduleInlineForm(ModelForm):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        if self.initial:
+            self.fields['date'].disabled = True
+            self.fields['frequency'].disabled = True
+
+
 class ScheduleInline(admin.TabularInline):
     model = Schedule
+    form = ScheduleInlineForm
+    readonly_fields = ('timezone',)
     extra = 1
 
 
 class StreamInline(admin.TabularInline):
-    fields = ['delay', 'begin', 'end']
     model = Stream
+    fields = ['delay', 'begin', 'end']
     extra = 1
 
 
@@ -71,4 +84,3 @@ class StreamAdmin(admin.ModelAdmin):
     list_display = ('id', 'program', 'delay', 'begin', 'end')
 
 
-