// Copyright 2023 The etcd 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 random

import (
	"math/rand"
	"strings"
)

func RandString(size int) string {
	data := strings.Builder{}
	data.Grow(size)
	for i := 0; i < size; i++ {
		data.WriteByte(byte(int('a') + rand.Intn(26)))
	}
	return data.String()
}

func RandRange(start, end int64) int64 {
	return rand.Int63n(end-start) + start
}

type ChoiceWeight[T any] struct {
	Choice T
	Weight int
}

func PickRandom[T any](choices []ChoiceWeight[T]) T {
	sum := 0
	for _, op := range choices {
		sum += op.Weight
	}
	roll := rand.Int() % sum
	for _, op := range choices {
		if roll < op.Weight {
			return op.Choice
		}
		roll -= op.Weight
	}
	panic("unexpected")
}