khatru/basic/main.go

package main

import (
	"encoding/json"
	"fmt"
	"time"

	"github.com/fiatjaf/go-nostr"
	"github.com/fiatjaf/relayer"
	"github.com/fiatjaf/relayer/storage/postgresql"
	"github.com/kelseyhightower/envconfig"
)

type Relay struct {
	PostgresDatabase string `envconfig:"POSTGRESQL_DATABASE"`
}

func (r *Relay) Name() string {
	return "BasicRelay"
}

func (r *Relay) Storage() relayer.Storage {
	return &postgresql.PostgresBackend{DatabaseURL: r.PostgresDatabase}
}

func (r *Relay) OnInitialized() {}

func (r *Relay) Init() error {
	err := envconfig.Process("", r)
	if err != nil {
		return fmt.Errorf("couldn't process envconfig: %w", err)
	}

	// every hour, delete all very old events
	go func() {
		db := r.Storage().(*postgresql.PostgresBackend)

		for {
			time.Sleep(60 * time.Minute)
			db.DB.Exec(`DELETE FROM event WHERE created_at < $1`, time.Now().AddDate(0, -3, 0)) // 3 months
		}
	}()

	return nil
}

func (r *Relay) AcceptEvent(evt *nostr.Event) bool {
	// block events that are too large
	jsonb, _ := json.Marshal(evt)
	if len(jsonb) > 10000 {
		return false
	}

	return true
}

func (r *Relay) BeforeSave(evt *nostr.Event) {
	// do nothing
}

func (r *Relay) AfterSave(evt *nostr.Event) {
	// delete all but the 100 most recent ones for each key
	r.Storage().(*postgresql.PostgresBackend).DB.Exec(`DELETE FROM event WHERE pubkey = $1 AND kind = $2 AND created_at < (
      SELECT created_at FROM event WHERE pubkey = $1
      ORDER BY created_at DESC OFFSET 100 LIMIT 1
    )`, evt.PubKey, evt.Kind)
}

func main() {
	relayer.Start(&Relay{})
}