// Copyright (c) 2020-2026 Tigera, Inc. All rights reserved.

// 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 common

// GetExpectedTyphaScale will return the number of Typhas needed for the number of nodes.
//
// Nodes       	Replicas
//
//	  1-2              1
//	  3-4              2
//	 <200              3
//	 >400              4
//	 >600              5
//	 >800              6
//	>1000              7
//	...
//	>2000             12
//	...
//	>3600             20
func GetExpectedTyphaScale(nodes int) int {
	maxNodesPerTypha := 200

	// This gives a count of how many 200s so we need 1+ this number to get at least
	// 1 typha for every 200 nodes.
	typhas := (nodes / maxNodesPerTypha) + 1

	// We add one more to ensure there is always 1 extra for high availability purposes.
	typhas += 1

	// We have a couple special cases for small clusters. We want to ensure that we run one fewer
	// Typha instances than there are nodes, so that there is room for rescheduling. We also want
	// to ensure we have at least two, where possible, so that we have redundancy.
	if nodes <= 2 {
		// For one and two node clusters, we only need a single typha.
		typhas = 1
	} else if nodes <= 4 {
		// For three and four node clusters, we can run an additional typha.
		typhas = 2
	} else if typhas < 3 {
		// For clusters with more than 4 nodes, make sure we have a minimum of three for redundancy.
		typhas = 3
	}
	return typhas
}