Add more code for creating/processing diffs

config/impl.go

@@ -146,12 +146,40 @@ func (this *config) saveUser () error {
 	return nil
 }
 
-func (this *config) processUserDiff (changed []string) {
-	// TODO
+func (this *config) processUserDiff (changed map[string] struct { }) {
+	for key := range changed {
+		// this is the user file, and nothing has precedence over it, so
+		// the change always matters
+		this.broadcastChange(key)
+	}
 }
 
-func (this *config) processSystemDiff (index int, changed []string) {
-	// TODO
+func (this *config) processSystemDiff (index int, changed map[string] struct { }) {
+	for key := range changed {
+		// if specified in the user file, the change doesn't matter
+		if this.data.user != nil {
+			if has, _ := this.data.user.Has(key); has {
+				continue
+			}
+		}
+		
+		// if specified in any system files with precedence greater than
+		// this one, the change doesn't matter
+		for _, system := range this.data.system[:index] {
+			if _, has := system[key]; has {
+				continue
+			}
+		}
+
+		// the change does matter
+		this.broadcastChange(key)
+	}
+}
+
+func (this *config) broadcastChange (key string) {
+	for _, listener := range this.on.change.Listeners() {
+		listener(key)
+	}
 }
 
 func (this *config) get (key string, fallback Value) (Value, error) {
@@ -246,3 +274,29 @@ func (this *config) OnChange (callback func (string)) event.Cookie {
 	defer this.lock.Unlock()
 	return this.on.change.Connect(callback)
 }
+
+func diffValueMaps (first, second map[string] Value) map[string] struct { } {
+	diff := make(map[string] struct { })
+	
+	// - keys only first has
+	// - keys both have, but are different
+	for key, firstValue := range first {
+		secondValue, ok := second[key]
+		if !ok {
+			diff[key] = struct { } { }
+			continue
+		}
+		if !firstValue.Equals(secondValue) {
+			diff[key] = struct { } { }
+		}
+	}
+
+	// - keys only second has
+	for key := range second {
+		if _, has := first[key]; !has {
+			diff[key] = struct { } { }
+		}
+	}
+
+	return diff
+}