You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: oob.go
    path of file: ./repos/gotosocial/internal/api/auth
    
    the code of the file until where you have to start completion: // 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 auth

import (
	"context"
	"errors"
	"fmt"

	"github.com/gin-contrib/sessions"
	"github.com/gin-gonic/gin"
	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
	apiutil "github.com/superseriousbusiness/gotosocial/internal/api/util"
	"github.com/superseriousbusiness/gotosocial/internal/db"
	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
	"github.com/superseriousbusiness/gotosocial/internal/oauth"
)

func (m *Module) OobHandler(c *gin.Context) {
	instance, errWithCode := m.processor.InstanceGetV1(c.Request.Context())
	if errWithCode != nil {
		apiutil.ErrorHandler(c, errWithCode, m.processor.InstanceGetV1)
		return
	}

	instanceGet := func(ctx context.Context) (*apimodel.InstanceV1, gtserror.WithCode) {
		return instance, nil
	}

	oobToken := c.Query("code")
	if oobToken == "" {
		err := errors.New("no 'code' query value provided in callback redirect")
		apiutil.ErrorHandler(c, gtserror.NewErrorBadRequest(err, err.Error(), oauth.HelpfulAdvice), instanceGet)
		return
	}

	s := sessions.Default(c)

	errs := []string{}

	scope, ok := s.Get(sessionScope).(string)
	if !ok {
		errs = append(errs, fmt.Sprintf("key %s was not found in session", sessionScope))
	}

	userID, ok := s.Get(sessionUserID).(string)
	if !ok {
		errs = append(errs, fmt.Sprintf("key %s was not found in session", sessionUserID))
	}

	if len(errs) != 0 {
		errs = append(errs, oauth.HelpfulAdvice)
		apiutil.ErrorHandler(c, gtserror.NewErrorBadRequest(errors.New("one or more missing keys on session during OobHandler"), errs...), m.processor.InstanceGetV1)
	
    
func (m *Module) OobHandler(c *gin.Context) {
	instance, errWithCode := m.processor.InstanceGetV1(c.Request.Context())
	if errWithCode != nil {
		apiutil.ErrorHandler(c, errWithCode, m.processor.InstanceGetV1)
		return
	}

	instanceGet := func(ctx context.Context) (*apimodel.InstanceV1, gtserror.WithCode) {
		return instance, nil
	}

	oobToken := c.Query("code")
	if oobToken == "" {
		err := errors.New("no 'code' query value provided in callback redirect")
		apiutil.ErrorHandler(c, gtserror.NewErrorBadRequest(err, err.Error(), oauth.HelpfulAdvice), instanceGet)
		return
	}

	s := sessions.Default(c)

	errs := []string{}

	scope, ok := s.Get(sessionScope).(string)
	if !ok {
		errs = append(errs, fmt.Sprintf("key %s was not found in session", sessionScope))
	}

	userID, ok := s.Get(sessionUserID).(string)
	if !ok {
		errs = append(errs, fmt.Sprintf("key %s was not found in session", sessionUserID))
	}

	if len(errs) != 0 {
		errs = append(errs, oauth.HelpfulAdvice)
		apiutil.ErrorHandler(c, gtserror.NewErrorBadRequest(errors.New("one or more missing keys on session during OobHandler"), errs...), m.processor.InstanceGetV1)
		return
	}

	user, err := m.db.GetUserByID(c.Request.Context(), userID)
	if err != nil {
		m.clearSession(s)
		safe := fmt.Sprintf("user with id %s could not be retrieved", userID)
		var errWithCode gtserror.WithCode
		if err == db.ErrNoEntries {
			errWithCode = gtserror.NewErrorBadRequest(err, safe, oauth.HelpfulAdvice)
		} else {
			errWithCode = gtserror.NewErrorInternalError(err, safe, oauth.HelpfulAdvice)
		}
		apiutil.ErrorHandler(c, errWithCode, instanceGet)
		return
	}

	acct, err := m.db.GetAccountByID(c.Request.Context(), user.AccountID)
	if err != nil {
		m.clearSession(s)
		safe := fmt.Sprintf("account with id %s could not be retrieved", user.AccountID)
		var errWithCode gtserror.WithCode
		if err == db.ErrNoEntries {
			errWithCode = gtserror.NewErrorBadRequest(err, safe, oauth.HelpfulAdvice)
		} else {
			errWithCode = gtserror.NewErrorInternalError(err, safe, oauth.HelpfulAdvice)
		}
		apiutil.ErrorHandler(c, errWithCode, instanceGet)
		return
	}

	// we're done with the session now, so just clear it out
	m.clearSession(s)

	page := apiutil.WebPage{
		Template: "oob.tmpl",
		Instance: instance,
		Extra: map[string]any{
			"user":     acct.Username,
			"oobToken": oobToken,
			"scope":    scope,
		},
	}

	apiutil.TemplateWebPage(c, page)
}