package main

import (
	"encoding/binary"
	"fmt"
	"time"

	"github.com/oklog/ulid/v2"
	"golang.org/x/crypto/sha3"
)

type Event struct {
	id        int64
	createdAt time.Time
	Foo       string
	Bar       string
}

type IDEntropy int64

func (ide IDEntropy) Read(p []byte) (n int, err error) {
	data := make([]byte, 8)
	binary.LittleEndian.PutUint64(data, uint64(ide))

	hash := make([]byte, len(p))
	sha3.ShakeSum256(hash, data)

	p = append(p[:0], hash...)

	return len(p), nil
}

func main() {
	t := time.Unix(123, 567)

	uniq := make(map[string]struct{})

	for i := 0; i < 1000000000; i++ {
		e := Event{
			id:        int64(i),
			createdAt: t,
			Foo:       "foo",
			Bar:       "bar",
		}

		id, err := ulid.New(ulid.Timestamp(e.createdAt), IDEntropy(e.id))
		if err != nil {
			panic(err)
		}

		fmt.Printf("%d -> %s\n", e.id, id.String())

		if _, ok := uniq[id.String()]; ok {
			fmt.Printf("%d -> %s\n", e.id, id.String())
			panic("duplicate id")
		} else {
			uniq[id.String()] = struct{}{}
		}
	}
}