status-im/status-go

package walletevent

import (
    "context"

    "github.com/ethereum/go-ethereum/event"
    "github.com/ethereum/go-ethereum/log"
    "github.com/status-im/status-go/services/wallet/async"
)

type EventCb func(event Event)

// Watcher executes a given callback whenever a wallet event gets sent
type Watcher struct {
    feed     *event.Feed
    group    *async.Group
    callback EventCb
}

func NewWatcher(feed *event.Feed, callback EventCb) *Watcher {
    return &Watcher{
        feed:     feed,
        callback: callback,
    }
}

func (w *Watcher) Start() {
    if w.group != nil {
        return
    }

    w.group = async.NewGroup(context.Background())
    w.group.Add(func(ctx context.Context) error {
        return watch(ctx, w.feed, w.callback)
    })
}

func (w *Watcher) Stop() {
    if w.group != nil {
        w.group.Stop()
        w.group.Wait()
        w.group = nil
    }
}

func watch(ctx context.Context, feed *event.Feed, callback EventCb) error {
    ch := make(chan Event, 10)
    sub := feed.Subscribe(ch)
    defer sub.Unsubscribe()

    for {
        select {
        case <-ctx.Done():
            return nil
        case err := <-sub.Err():
            if err != nil {
                log.Error("wallet event watcher subscription failed", "error", err)
            }
        case ev := <-ch:
            if callback != nil {
                callback(ev)
            }
        }
    }
}