package voiceroomredpacket

import (
	"math/rand"
	"net/http"
	"time"
)

// splitRandomAmounts 按二倍均值法预拆拼手气金额。
func splitRandomAmounts(total int64, count int, seed int64) ([]int64, error) {
	if total <= 0 {
		return nil, NewAppError(http.StatusBadRequest, "voice_room_red_packet_amount_invalid", "totalAmount must be greater than 0")
	}
	if count <= 0 {
		return nil, NewAppError(http.StatusBadRequest, "voice_room_red_packet_count_invalid", "totalCount must be greater than 0")
	}
	if total < int64(count) {
		return nil, NewAppError(http.StatusBadRequest, "voice_room_red_packet_amount_invalid", "totalAmount must be greater than or equal to totalCount")
	}
	if seed == 0 {
		seed = time.Now().UnixNano()
	}

	random := rand.New(rand.NewSource(seed))
	amounts := make([]int64, 0, count)
	remainAmount := total
	remainCount := count
	for remainCount > 1 {
		avg := remainAmount / int64(remainCount)
		maxAmount := avg * 2
		keepForRest := int64(remainCount - 1)
		if maxAmount > remainAmount-keepForRest {
			maxAmount = remainAmount - keepForRest
		}
		if maxAmount < 1 {
			maxAmount = 1
		}
		amount := int64(1)
		if maxAmount > 1 {
			amount = random.Int63n(maxAmount) + 1
		}
		amounts = append(amounts, amount)
		remainAmount -= amount
		remainCount--
	}
	amounts = append(amounts, remainAmount)
	random.Shuffle(len(amounts), func(i, j int) {
		amounts[i], amounts[j] = amounts[j], amounts[i]
	})
	return amounts, nil
}

func sumAmounts(values []int64) int64 {
	var total int64
	for _, value := range values {
		total += value
	}
	return total
}