Add psuedocode/boilerplate for intent manager

This won't run. Don't try to import this class yet. It's outlining what we need to implement to get intents per stack.

It does no form of caching at this point. Build first, optimise later, right.

Contributes to issue CURA-6091.

cura/Machines/Models/IntentCategoryModel.py

@@ -0,0 +1,14 @@
+#Copyright (c) 2019 Ultimaker B.V.
+#Cura is released under the terms of the LGPLv3 or higher.
+
+from UM.Qt.ListModel import ListModel
+from cura.Settings.IntentManager import IntentManager
+
+class IntentCategoryModel(ListModel):
+    def __init__(self, intent_category: str):
+        self._intent_category = intent_category
+
+    def update(self):
+        available_intents = IntentManager.getInstance().currentAvailableIntents()
+        result = filter(lambda intent: intent.getMetaDataEntry("intent_category") == self._intent_category, available_intents)
+        super().update(result)

cura/Settings/IntentManager.py

@@ -0,0 +1,95 @@
+#Copyright (c) 2019 Ultimaker B.V.
+#Cura is released under the terms of the LGPLv3 or higher.
+
+from PyQt5.QtCore import pyqtProperty, pyqtSignal
+from typing import List, Tuple, TYPE_CHECKING
+from cura.CuraApplication import CuraApplication
+from cura.Machines.QualityManager import QualityManager
+from cura.Settings.MachineManager import MachineManager
+from UM.Settings.ContainerRegistry import ContainerRegistry
+
+if TYPE_CHECKING:
+    from UM.Settings.InstanceContainer import InstanceContainer
+
+##  Front-end for querying which intents are available for a certain
+#   configuration.
+#
+#   CURRENTLY THIS CLASS CONTAINS ONLY SOME PSEUDOCODE OF WHAT WE ARE SUPPOSED
+#   TO IMPLEMENT.
+class IntentManager:
+    __instance = None
+
+    def __init__(self) -> None:
+        MachineManager.activeStackChanged.connect(self.configurationChanged)
+        self.configurationChanged.connect(self.selectDefaultIntent)
+        pass
+
+    @classmethod
+    def getInstance(cls):
+        if not cls.__instance:
+            cls.__instance = IntentManager()
+        return cls.__instance
+
+    configurationChanged = pyqtSignal
+
+    def intentMetadatas(self, definition_id: str, nozzle_id: str, material_id: str) -> List[str]:
+        #Return list of available intent profiles for any configuration.
+        #Use ContainerRegistry.findContainersMetadata for this.
+        return []
+
+    def intentCategories(self, definition_id: str, nozzle_id: str, material_id: str) -> List[str]:
+        categories = set()
+        for intent in self.intentMetadatas(definition_id, nozzle_id, material_id):
+            categories.add(intent["intent_category"])
+        return list(categories)
+
+    ##  List of intents to be displayed in the interface.
+    #
+    #   For the interface this will have to be broken up into the different
+    #   intent categories. That is up to the model there.
+    #
+    #   \return A list of tuples of intent_category and quality_type. The actual
+    #   instance may vary per extruder.
+    @pyqtProperty("QVariantList", notify = configurationChanged)
+    def currentAvailableIntents(self) -> List[Tuple[str, str]]:
+        final_intent_ids = {metadata["id"] for metadata in ContainerRegistry.getInstance().findContainersMetadata(type = "intent", definition = current_definition_id)} #All intents that match the global stack.
+        for extruder in all_extruders:
+            extruder_intent_ids = {metadata["id"] for metadata in self.intentMetadatas(current_definition_id, extruder_nozzle_id, extruder_material_id)}
+            final_intent_ids = final_intent_ids.intersection(extruder_intent_ids)
+
+        result = set()
+        for intent_id in final_intent_ids:
+            intent = ContainerRegistry.getInstance().findContainers(id = intent_id)[0]
+            result.add((intent.getMetaDataEntry("intent_category"), intent.getMetaDataEntry("quality_type")))
+        return list(result)
+
+    ##  List of intent categories to be displayed in the interface.
+    @pyqtProperty("QVariantList", notify = configurationChanged)
+    def currentAvailableIntentCategories(self) -> List[str]:
+        final_intent_categories = {metadata["intent_category"] for metadata in ContainerRegistry.getInstance().findContainersMetadata(type = "intent", definition = current_definition_id)}
+        for extruder in all_extruders:
+            final_intent_categories = final_intent_categories.intersection(self.intentCategories())
+        return list(final_intent_categories)
+
+    def defaultIntent(self) -> Tuple[str, str]:
+        default_quality_type = QualityManager.getInstance().getDefaultQualityType().quality_type
+        for intent in self.currentAvailableIntents():
+            if intent.getMetaDataEntry("intent_category") == "default" and intent.getMetaDataEntry("quality_type") == default_quality_type:
+                return intent
+        else: #Fallback: Preferred quality type is not available for default category.
+            for intent in self.currentAvailableIntents():
+                if intent.getMetaDataEntry("intent_category") == "default":
+                    return intent
+            else: #Fallback: No default category.
+                if self.currentAvailableIntents():
+                    return self.currentAvailableIntents()[0]
+                else:
+                    return CuraApplication.empty_intent_container
+
+    def selectIntent(self, intent_category, quality_type):
+        for extruder in all_extruders:
+            extruder_stack.intent = ContainerRegistry.getInstance().findContainers(type = "intent", definition = current_definition_id, variant = extruder_nozzle_id, material = extruder_material_id)[0]
+
+    def selectDefaultIntent(self) -> None:
+        category, quality_type = self.defaultIntent()
+        self.selectIntent(category, quality_type)