/*
Copyright 2026 The Cozystack Authors.

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 model

import (
	"strings"

	"github.com/go-logr/logr"
	corev1 "k8s.io/api/core/v1"
)

// systemTaintPrefix marks the taints Kubernetes sets for a cordon or a
// node that is not Ready, which Cordoned and Ready already decide.
const systemTaintPrefix = "node.kubernetes.io/"

// Cordoned reports whether the node is cordoned. Only spec.unschedulable
// counts: a taint, such as the one Fence Agents Remediation sets, is not a
// cordon and does not trigger the class's onCordon policy.
func Cordoned(n *corev1.Node) bool {
	return n.Spec.Unschedulable
}

// Ready reports whether the node's Ready condition is True.
func Ready(n *corev1.Node) bool {
	for _, c := range n.Status.Conditions {
		if c.Type == corev1.NodeReady {
			return c.Status == corev1.ConditionTrue
		}
	}
	return false
}

// UntoleratedTaint returns the first NoSchedule or NoExecute taint outside
// node.kubernetes.io/ that tolerations do not tolerate, or nil. Gt and Lt
// tolerations never match: where their feature gate is off the scheduler
// does not honour them, and a node is better skipped than bound to in vain.
func UntoleratedTaint(n *corev1.Node, tolerations []corev1.Toleration) *corev1.Taint {
	for i := range n.Spec.Taints {
		taint := &n.Spec.Taints[i]
		if taint.Effect != corev1.TaintEffectNoSchedule && taint.Effect != corev1.TaintEffectNoExecute {
			continue
		}
		if strings.HasPrefix(taint.Key, systemTaintPrefix) {
			continue
		}
		tolerated := false
		for j := range tolerations {
			if tolerations[j].ToleratesTaint(logr.Discard(), taint, false) {
				tolerated = true
				break
			}
		}
		if !tolerated {
			return taint
		}
	}
	return nil
}

// Eligible reports whether new binds, moves, rebinds and gathers may use
// the node, and whether its units count in a class's capacity.
// tolerations are those of the virt-launcher pod, nil when no VMI is
// known.
func Eligible(n *corev1.Node, tolerations []corev1.Toleration) bool {
	return !Cordoned(n) && Ready(n) && UntoleratedTaint(n, tolerations) == nil
}