/*
Copyright 2026.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package controller

import databasev1alpha1 "git.ddupan.top/panxiao81/postgresql-tenant-operator/api/v1alpha1"

type instancePhaseResult struct {
	phase              databasev1alpha1.PostgreSQLInstancePhase
	reconcilingMessage string
}

type instancePhaseHandler func(*databasev1alpha1.PostgreSQLInstance) instancePhaseResult

type instanceStateMachine struct {
	handlers map[databasev1alpha1.PostgreSQLInstancePhase]instancePhaseHandler
}

func newInstanceStateMachine() instanceStateMachine {
	return instanceStateMachine{handlers: map[databasev1alpha1.PostgreSQLInstancePhase]instancePhaseHandler{
		databasev1alpha1.PostgreSQLInstancePhasePending:              reconcileInstancePending,
		databasev1alpha1.PostgreSQLInstancePhaseValidating:           keepInstancePhase,
		databasev1alpha1.PostgreSQLInstancePhaseInitializingRegistry: keepInstancePhase,
		databasev1alpha1.PostgreSQLInstancePhaseReady:                keepInstancePhase,
		databasev1alpha1.PostgreSQLInstancePhaseDeleting:             reconcileInstanceDeleting,
	}}
}

func (m instanceStateMachine) reconcile(instance *databasev1alpha1.PostgreSQLInstance) instancePhaseResult {
	phase := instance.Status.Phase
	if !instance.DeletionTimestamp.IsZero() {
		phase = databasev1alpha1.PostgreSQLInstancePhaseDeleting
	} else if phase == "" {
		phase = databasev1alpha1.PostgreSQLInstancePhasePending
	}

	handler, found := m.handlers[phase]
	if !found {
		return instancePhaseResult{phase: phase}
	}
	return handler(instance)
}

func reconcileInstancePending(*databasev1alpha1.PostgreSQLInstance) instancePhaseResult {
	return instancePhaseResult{
		phase:              databasev1alpha1.PostgreSQLInstancePhaseValidating,
		reconcilingMessage: "instance dependencies are being validated",
	}
}

func reconcileInstanceDeleting(*databasev1alpha1.PostgreSQLInstance) instancePhaseResult {
	return instancePhaseResult{
		phase:              databasev1alpha1.PostgreSQLInstancePhaseDeleting,
		reconcilingMessage: "instance deletion is reconciling",
	}
}

func keepInstancePhase(instance *databasev1alpha1.PostgreSQLInstance) instancePhaseResult {
	return instancePhaseResult{phase: instance.Status.Phase}
}