// This is Free Software under GNU Affero General Public License v >= 3.0
// without warranty, see README.md and license for details.
//
// SPDX-License-Identifier: AGPL-3.0-or-later
// License-Filename: LICENSES/AGPL-3.0.txt
//
// Copyright (C) 2018 by via donau
//   – Österreichische Wasserstraßen-Gesellschaft mbH
// Software engineering by Intevation GmbH
//
// Author(s):
//  * Sascha Wilde <wilde@sha-bang.de>

package common

import (
	"math"
	"sort"
	"time"
)

type Rest struct {
	Key  int
	Rest float64
}

// Simple sum preserving rounding method:
func SumPreservingRound(arr []float64) []int {
	var (
		sum   float64
		rests []Rest
	)
	result := make([]int, len(arr))

	// floor all values
	for i, v := range arr {
		sum += v
		result[i] = int(v)
		rests = append(rests, Rest{Key: i, Rest: v - float64(result[i])})
	}

	// find the difference in summs
	var newSum int
	for _, v := range result {
		newSum += v
	}
	delta := int(math.Round(sum)) - newSum

	// spread delta over values with highest rest
	sort.Slice(rests, func(i, j int) bool {
		return rests[i].Rest > rests[j].Rest
	})
	for _, v := range rests {
		if delta <= 0 {
			break
		}
		result[v.Key]++
		delta--
	}

	return result
}

// Round anarray of Duratons to full days
func RoundToFullDays(durations []time.Duration) []int {
	days := make([]float64, len(durations))
	for i, v := range durations {
		days[i] = v.Hours() / 24
	}
	return SumPreservingRound(days)
}