move nostr-sdk repository into here because why not?

sdk/outbox.go

@@ -0,0 +1,89 @@
+package sdk
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/nbd-wtf/go-nostr"
+)
+
+func (sys *System) FetchOutboxRelays(ctx context.Context, pubkey string, n int) []string {
+	if relays, ok := sys.outboxShortTermCache.Get(pubkey); ok {
+		if len(relays) > n {
+			relays = relays[0:n]
+		}
+		return relays
+	}
+
+	if rl, ok := sys.RelayListCache.Get(pubkey); !ok || (rl.Event != nil && rl.Event.CreatedAt < nostr.Now()-60*60*24*7) {
+		// try to fetch relays list again if we don't have one or if ours is a week old
+		fetchGenericList(sys, ctx, pubkey, 10002, parseRelayFromKind10002, sys.RelayListCache, false)
+	}
+
+	relays := sys.Hints.TopN(pubkey, 6)
+
+	if len(relays) == 0 {
+		return []string{"wss://relay.damus.io", "wss://nos.lol"}
+	}
+
+	sys.outboxShortTermCache.SetWithTTL(pubkey, relays, time.Minute*2)
+
+	if len(relays) > n {
+		relays = relays[0:n]
+	}
+
+	return relays
+}
+
+func (sys *System) ExpandQueriesByAuthorAndRelays(
+	ctx context.Context,
+	filter nostr.Filter,
+) (map[string]nostr.Filter, error) {
+	n := len(filter.Authors)
+	if n == 0 {
+		return nil, fmt.Errorf("no authors in filter")
+	}
+
+	relaysForPubkey := make(map[string][]string, n)
+	mu := sync.Mutex{}
+
+	wg := sync.WaitGroup{}
+	wg.Add(n)
+	for _, pubkey := range filter.Authors {
+		go func(pubkey string) {
+			defer wg.Done()
+			relayURLs := sys.FetchOutboxRelays(ctx, pubkey, 3)
+			c := 0
+			for _, r := range relayURLs {
+				relay, err := sys.Pool.EnsureRelay(r)
+				if err != nil {
+					continue
+				}
+				mu.Lock()
+				relaysForPubkey[pubkey] = append(relaysForPubkey[pubkey], relay.URL)
+				mu.Unlock()
+				c++
+				if c == 3 {
+					return
+				}
+			}
+		}(pubkey)
+	}
+	wg.Wait()
+
+	filterForRelay := make(map[string]nostr.Filter, n) // { [relay]: filter }
+	for pubkey, relays := range relaysForPubkey {
+		for _, relay := range relays {
+			flt, ok := filterForRelay[relay]
+			if !ok {
+				flt = filter.Clone()
+				filterForRelay[relay] = flt
+			}
+			flt.Authors = append(flt.Authors, pubkey)
+		}
+	}
+
+	return filterForRelay, nil
+}