implemented federation

internal/domain/federation/actor.go

@@ -0,0 +1,84 @@
+package federation
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/pem"
+	"fmt"
+	"strings"
+
+	"xorm.io/xorm"
+
+	"github.com/forgeo/forgebucket/internal/models"
+)
+
+// APID returns the canonical ActivityPub actor ID for a local username.
+func APID(instanceURL, username string) string {
+	return strings.TrimRight(instanceURL, "/") + "/users/" + username
+}
+
+// GetOrCreate fetches the FederationActor for a user, creating it with a fresh
+// RSA-2048 key pair if none exists. Actor URLs are derived from instanceURL.
+func GetOrCreate(db *xorm.Engine, userID int64, username, instanceURL string) (*models.FederationActor, error) {
+	var actor models.FederationActor
+	if found, _ := db.Where("user_id = ?", userID).Get(&actor); found {
+		return &actor, nil
+	}
+
+	priv, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		return nil, fmt.Errorf("generate rsa key: %w", err)
+	}
+
+	privPEM := pem.EncodeToMemory(&pem.Block{
+		Type:  "RSA PRIVATE KEY",
+		Bytes: x509.MarshalPKCS1PrivateKey(priv),
+	})
+	pubDER, err := x509.MarshalPKIXPublicKey(&priv.PublicKey)
+	if err != nil {
+		return nil, fmt.Errorf("marshal public key: %w", err)
+	}
+	pubPEM := pem.EncodeToMemory(&pem.Block{Type: "PUBLIC KEY", Bytes: pubDER})
+
+	base := APID(instanceURL, username)
+	actor = models.FederationActor{
+		UserID:     userID,
+		APID:       base,
+		InboxURL:   base + "/inbox",
+		OutboxURL:  base + "/outbox",
+		PublicKey:  string(pubPEM),
+		PrivateKey: string(privPEM),
+	}
+	if _, err := db.Insert(&actor); err != nil {
+		// Race condition: another goroutine may have just created it.
+		if found, _ := db.Where("user_id = ?", userID).Get(&actor); found {
+			return &actor, nil
+		}
+		return nil, fmt.Errorf("insert actor: %w", err)
+	}
+	return &actor, nil
+}
+
+// ActorJSON builds the JSON-LD actor document returned by GET /users/{username}.
+func ActorJSON(actor *models.FederationActor, username, displayName string) map[string]any {
+	return map[string]any{
+		"@context": []any{
+			"https://www.w3.org/ns/activitystreams",
+			"https://w3id.org/security/v1",
+		},
+		"id":                actor.APID,
+		"type":              "Person",
+		"preferredUsername": username,
+		"name":              displayName,
+		"inbox":             actor.InboxURL,
+		"outbox":            actor.OutboxURL,
+		"followers":         actor.APID + "/followers",
+		"following":         actor.APID + "/following",
+		"publicKey": map[string]any{
+			"id":           actor.APID + "#main-key",
+			"owner":        actor.APID,
+			"publicKeyPem": actor.PublicKey,
+		},
+	}
+}