// Copyright (C) The Arvados Authors. All rights reserved.
//
// SPDX-License-Identifier: Apache-2.0

package keepclient

import (
	"sort"
)

type RootSorter struct {
	root   []string
	weight []string
	order  []int
}

func NewRootSorter(serviceRoots map[string]string, hash string) *RootSorter {
	rs := new(RootSorter)
	rs.root = make([]string, len(serviceRoots))
	rs.weight = make([]string, len(serviceRoots))
	rs.order = make([]int, len(serviceRoots))
	i := 0
	for uuid, root := range serviceRoots {
		rs.root[i] = root
		rs.weight[i] = rs.getWeight(hash, uuid)
		rs.order[i] = i
		i++
	}
	sort.Sort(rs)
	return rs
}

func (rs RootSorter) getWeight(hash string, uuid string) string {
	if len(uuid) == 27 {
		return Md5String(hash + uuid[12:])
	}
	// Only useful for testing, a set of one service root, etc.
	return Md5String(hash + uuid)
}

func (rs RootSorter) GetSortedRoots() []string {
	sorted := make([]string, len(rs.order))
	for i := range rs.order {
		sorted[i] = rs.root[rs.order[i]]
	}
	return sorted
}

// Less is really More here: the heaviest root will be at the front of the list.
func (rs RootSorter) Less(i, j int) bool {
	return rs.weight[rs.order[j]] < rs.weight[rs.order[i]]
}

func (rs RootSorter) Len() int {
	return len(rs.order)
}

func (rs RootSorter) Swap(i, j int) {
	sort.IntSlice(rs.order).Swap(i, j)
}
