[feature] Add GET endpoint for single notification (#1719)

docs/api/swagger.yaml

@@ -4535,6 +4535,32 @@ paths:
             summary: Update a media attachment.
             tags:
                 - media
+    /api/v1/notification/{id}:
+        get:
+            operationId: notification
+            produces:
+                - application/json
+            responses:
+                "200":
+                    description: Requested notification.
+                    schema:
+                        $ref: '#/definitions/notification'
+                "400":
+                    description: bad request
+                "401":
+                    description: unauthorized
+                "404":
+                    description: not found
+                "406":
+                    description: not acceptable
+                "500":
+                    description: internal server error
+            security:
+                - OAuth2 Bearer:
+                    - read:notifications
+            summary: Get a single notification with the given ID.
+            tags:
+                - notifications
     /api/v1/notifications:
         get:
             description: |-

internal/api/client/notifications/notificationget.go

@@ -0,0 +1,87 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package notifications
+
+import (
+	"errors"
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	apiutil "github.com/superseriousbusiness/gotosocial/internal/api/util"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/oauth"
+)
+
+// NotificationGETHandler swagger:operation GET /api/v1/notification/{id} notification
+//
+// Get a single notification with the given ID.
+//
+//	---
+//	tags:
+//	- notifications
+//
+//	produces:
+//	- application/json
+//
+//	security:
+//	- OAuth2 Bearer:
+//		- read:notifications
+//
+//	responses:
+//		'200':
+//			name: notifications
+//			description: Requested notification.
+//			schema:
+//				"$ref": "#/definitions/notification"
+//		'400':
+//			description: bad request
+//		'401':
+//			description: unauthorized
+//		'404':
+//			description: not found
+//		'406':
+//			description: not acceptable
+//		'500':
+//			description: internal server error
+func (m *Module) NotificationGETHandler(c *gin.Context) {
+	authed, err := oauth.Authed(c, true, true, true, true)
+	if err != nil {
+		apiutil.ErrorHandler(c, gtserror.NewErrorUnauthorized(err, err.Error()), m.processor.InstanceGetV1)
+		return
+	}
+
+	if _, err := apiutil.NegotiateAccept(c, apiutil.JSONAcceptHeaders...); err != nil {
+		apiutil.ErrorHandler(c, gtserror.NewErrorNotAcceptable(err, err.Error()), m.processor.InstanceGetV1)
+		return
+	}
+
+	targetNotifID := c.Param(IDKey)
+	if targetNotifID == "" {
+		err := errors.New("no notification id specified")
+		apiutil.ErrorHandler(c, gtserror.NewErrorBadRequest(err, err.Error()), m.processor.InstanceGetV1)
+		return
+	}
+
+	resp, errWithCode := m.processor.NotificationGet(c.Request.Context(), authed.Account, targetNotifID)
+	if errWithCode != nil {
+		apiutil.ErrorHandler(c, errWithCode, m.processor.InstanceGetV1)
+		return
+	}
+
+	c.JSON(http.StatusOK, resp)
+}

internal/api/client/notifications/notifications.go

@@ -56,5 +56,6 @@ func New(processor *processing.Processor) *Module {
 
 func (m *Module) Route(attachHandler func(method string, path string, f ...gin.HandlerFunc) gin.IRoutes) {
 	attachHandler(http.MethodGet, BasePath, m.NotificationsGETHandler)
+	attachHandler(http.MethodGet, BasePathWithID, m.NotificationGETHandler)
 	attachHandler(http.MethodPost, BasePathWithClear, m.NotificationsClearPOSTHandler)
 }

internal/processing/notification.go

@@ -20,10 +20,12 @@
 import (
 	"context"
 	"errors"
+	"fmt"
 
 	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
 	"github.com/superseriousbusiness/gotosocial/internal/db"
 	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
 	"github.com/superseriousbusiness/gotosocial/internal/log"
 	"github.com/superseriousbusiness/gotosocial/internal/oauth"
 	"github.com/superseriousbusiness/gotosocial/internal/util"
@@ -72,6 +74,35 @@ func (p *Processor) NotificationsGet(ctx context.Context, authed *oauth.Auth, ex
 	})
 }
 
+func (p *Processor) NotificationGet(ctx context.Context, account *gtsmodel.Account, targetNotifID string) (*apimodel.Notification, gtserror.WithCode) {
+	notif, err := p.state.DB.GetNotificationByID(ctx, targetNotifID)
+	if err != nil {
+		if errors.Is(err, db.ErrNoEntries) {
+			return nil, gtserror.NewErrorNotFound(err)
+		}
+
+		// Real error.
+		return nil, gtserror.NewErrorInternalError(err)
+	}
+
+	if notifTargetAccountID := notif.TargetAccountID; notifTargetAccountID != account.ID {
+		err = fmt.Errorf("account %s does not have permission to view notification belong to account %s", account.ID, notifTargetAccountID)
+		return nil, gtserror.NewErrorNotFound(err)
+	}
+
+	apiNotif, err := p.tc.NotificationToAPINotification(ctx, notif)
+	if err != nil {
+		if errors.Is(err, db.ErrNoEntries) {
+			return nil, gtserror.NewErrorNotFound(err)
+		}
+
+		// Real error.
+		return nil, gtserror.NewErrorInternalError(err)
+	}
+
+	return apiNotif, nil
+}
+
 func (p *Processor) NotificationsClear(ctx context.Context, authed *oauth.Auth) gtserror.WithCode {
 	// Delete all notifications of all types that target the authorized account.
 	if err := p.state.DB.DeleteNotifications(ctx, nil, authed.Account.ID, ""); err != nil && !errors.Is(err, db.ErrNoEntries) {