add follow accept code

models/user_keypair.go

@@ -1,7 +1,13 @@
 package models
 
+import "sample/db"
+
 type UserKeyPair struct {
 	ID         string `gorm:"primaryKey"`
 	PublicKey  string `gorm:"not null;type:text"`
 	PrivateKey string `gorm:"not null;type:text"`
 }
+
+func (u *UserKeyPair) GetByID() error {
+	return db.DB.First(&u, "id = ?", u.ID).Error
+}

router/user/inbox/follow_accept.go

@@ -0,0 +1,72 @@
+package inbox
+
+import (
+	"crypto"
+	"encoding/json"
+	"fmt"
+	"net/url"
+	"sample/constants"
+	"sample/models"
+
+	signature_header "github.com/cloudmatelabs/go-activitypub-signature-header"
+	"github.com/gofiber/fiber/v2"
+)
+
+func followAccept(body []byte, id string, actor string) error {
+	var followRequest map[string]interface{}
+	json.Unmarshal(body, &followRequest)
+	delete(followRequest, "@context")
+
+	userURL := fmt.Sprintf(constants.USER_JSON_URL_FORMAT, constants.APP_ADDRESS, id)
+
+	acceptBody, _ := json.Marshal(fiber.Map{
+		"@context": "https://www.w3.org/ns/activitystreams",
+		"object":   followRequest,
+		"type":     "Accept",
+		"id":       userURL,
+		"actor":    userURL,
+	})
+
+	actorURL, _ := url.Parse(actor)
+	path := actorURL.Path + "/inbox"
+	keyID := userURL + "#main-key"
+
+	keyPair := models.UserKeyPair{ID: id}
+	keyPair.GetByID()
+
+	privateKey, err := signature_header.PrivateKeyFromBytes([]byte(keyPair.PrivateKey))
+	if err != nil {
+		panic(err)
+	}
+
+	algorithm := crypto.SHA256
+	date := signature_header.Date()
+	digest := signature_header.Digest(algorithm, acceptBody)
+	signature, err := signature_header.Signature{
+		PrivateKey: privateKey,
+		Algorithm:  algorithm,
+		Date:       date,
+		Digest:     digest,
+		Host:       actorURL.Host,
+		Path:       path,
+		KeyID:      keyID,
+	}.String()
+	if err != nil {
+		panic(err)
+	}
+
+	agent := fiber.Post(actor + "/inbox")
+	agent.Request().Header.Set("Date", date)
+	agent.Request().Header.Set("Digest", digest)
+	agent.Request().Header.Set("Host", actorURL.Host)
+	agent.Request().Header.Set("Signature", signature)
+	agent.ContentType("application/activity+json")
+	agent.Body(acceptBody)
+
+	_, _, errs := agent.Bytes()
+	if len(errs) > 0 {
+		return errs[0]
+	}
+
+	return nil
+}

router/user/inbox/router.go

@@ -28,6 +28,10 @@ func Route(c *fiber.Ctx) error {
 		return c.SendStatus(fiber.StatusBadRequest)
 	}
 
+	if messageType == "Follow" {
+		followAccept(originBody, id, actor)
+	}
+
 	db.DB.Save(&models.UserInbox{
 		ID:      uuid.New(),
 		From:    actor,

router/user/inbox/verify_signature.go

@@ -75,7 +75,7 @@ func fetchActorPublicKey(actor string) (string, error) {
 	agent.Request().Header.Set("Accept", "application/ld+json")
 
 	statusCode, response, errs := agent.Bytes()
-	if errs != nil {
+	if len(errs) > 0 {
 		return "", errs[0]
 	}