snippet.go

// -*- mode:go;mode:go-playground -*-
// snippet of code @ 2020-11-14 14:23:30

// === Go Playground ===
// Execute the snippet with Ctl-Return
// Provide custom arguments to compile with Alt-Return
// Remove the snippet completely with its dir and all files M-x `go-playground-rm`
package main

import (
	"crypto/rand"
	"time"

	"github.com/cnf/structhash"
	"github.com/google/uuid"
	"github.com/rs/zerolog/log"
)

type State struct {
	Clock time.Time
	Hash  string `hash:"~"`
}

type ParticipantList struct {
	Participants []string
	State        State
}

func (p *ParticipantList) Modify(modifier func(p *ParticipantList)) error {
	modifier(p)
	return p.Rehash()
}

func (p *ParticipantList) Rehash() error {
	var err error
	p.State.Clock = time.Now()
	p.State.Hash, err = structhash.Hash(p, 0)

	return err
}

func Generate(times int) []string {
	data := make([]string, 0)

	for ii := 0; ii < times; ii++ {
		id, err := uuid.NewRandomFromReader(rand.Reader)

		if err != nil {
			continue
		}

		data = append(data, id.String())
	}

	return data
}

func main() {
	participants := ParticipantList{
		Participants: Generate(10),
	}

	log.Debug().Interface("participants", participants).Msg("before rehash")

	err := participants.Rehash()

	if err != nil {
		log.Fatal().Err(err).Send()
	}

	log.Debug().Interface("participants", participants).Msg("after rehash")

	participants.Participants = append(
		participants.Participants,
		Generate(1)...,
	)

	err = participants.Rehash()

	if err != nil {
		log.Fatal().Err(err).Send()
	}

	err = participants.Modify(func(p *ParticipantList) {
		p.Participants = append(
			p.Participants,
			Generate(2)...,
		)
	})

	if err != nil {
		log.Fatal().Err(err).Send()
	}

	log.Debug().Interface("participants", participants).Msg("after modification")

}