[feature] Application creation + management via API + settings panel (#3906)

* [feature] Application creation + management via API + settings panel

* fix docs links

* add errnorows test

* use known application as shorter

* add comment about side effects

internal/processing/application/get.go

@@ -0,0 +1,104 @@
+// 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 application
+
+import (
+	"context"
+	"errors"
+
+	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/log"
+	"github.com/superseriousbusiness/gotosocial/internal/paging"
+)
+
+func (p *Processor) Get(
+	ctx context.Context,
+	userID string,
+	appID string,
+) (*apimodel.Application, gtserror.WithCode) {
+	app, err := p.state.DB.GetApplicationByID(ctx, appID)
+	if err != nil && !errors.Is(err, db.ErrNoEntries) {
+		err := gtserror.Newf("db error getting app %s: %w", appID, err)
+		return nil, gtserror.NewErrorInternalError(err)
+	}
+
+	if app == nil {
+		err := gtserror.Newf("app %s not found in the db", appID)
+		return nil, gtserror.NewErrorNotFound(err)
+	}
+
+	if app.ManagedByUserID != userID {
+		err := gtserror.Newf("app %s not managed by user %s", appID, userID)
+		return nil, gtserror.NewErrorNotFound(err)
+	}
+
+	apiApp, err := p.converter.AppToAPIAppSensitive(ctx, app)
+	if err != nil {
+		err := gtserror.Newf("error converting app to api app: %w", err)
+		return nil, gtserror.NewErrorInternalError(err)
+	}
+
+	return apiApp, nil
+}
+
+func (p *Processor) GetPage(
+	ctx context.Context,
+	userID string,
+	page *paging.Page,
+) (*apimodel.PageableResponse, gtserror.WithCode) {
+	apps, err := p.state.DB.GetApplicationsManagedByUserID(ctx, userID, page)
+	if err != nil && !errors.Is(err, db.ErrNoEntries) {
+		err := gtserror.Newf("db error getting apps: %w", err)
+		return nil, gtserror.NewErrorInternalError(err)
+	}
+
+	count := len(apps)
+	if count == 0 {
+		return paging.EmptyResponse(), nil
+	}
+
+	var (
+		// Get the lowest and highest
+		// ID values, used for paging.
+		lo = apps[count-1].ID
+		hi = apps[0].ID
+
+		// Best-guess items length.
+		items = make([]interface{}, 0, count)
+	)
+
+	for _, app := range apps {
+		apiApp, err := p.converter.AppToAPIAppSensitive(ctx, app)
+		if err != nil {
+			log.Errorf(ctx, "error converting app to api app: %v", err)
+			continue
+		}
+
+		// Append req to return items.
+		items = append(items, apiApp)
+	}
+
+	return paging.PackageResponse(paging.ResponseParams{
+		Items: items,
+		Path:  "/api/v1/apps",
+		Next:  page.Next(lo, hi),
+		Prev:  page.Prev(lo, hi),
+	}), nil
+}