[feature] Allow admins to send test emails (#1620)

* [feature] Allow admins to send test emails

* implement unwrap on new error type

* add + use gtserror types

* GoToSocial Email Test -> GoToSocial Test Email

* add + use getInstance db call

* removed unused "unknown" error type

15 files changed, 394 insertions, 81 deletions

diff --git a/internal/api/client/admin/admin.go b/internal/api/client/admin/admin.go
index 2193ce545..4079dd979 100644
--- a/internal/api/client/admin/admin.go
+++ b/internal/api/client/admin/admin.go
@@ -25,60 +25,37 @@ import (
 )
 
 const (
-	// BasePath is the base API path for this module, excluding the api prefix
-	BasePath = "/v1/admin"
-	// EmojiPath is used for posting/deleting custom emojis.
-	EmojiPath = BasePath + "/custom_emojis"
-	// EmojiPathWithID is used for interacting with a single emoji.
-	EmojiPathWithID = EmojiPath + "/:" + IDKey
-	// EmojiCategoriesPath is used for interacting with emoji categories.
-	EmojiCategoriesPath = EmojiPath + "/categories"
-	// DomainBlocksPath is used for posting domain blocks.
-	DomainBlocksPath = BasePath + "/domain_blocks"
-	// DomainBlocksPathWithID is used for interacting with a single domain block.
+	BasePath               = "/v1/admin"
+	EmojiPath              = BasePath + "/custom_emojis"
+	EmojiPathWithID        = EmojiPath + "/:" + IDKey
+	EmojiCategoriesPath    = EmojiPath + "/categories"
+	DomainBlocksPath       = BasePath + "/domain_blocks"
 	DomainBlocksPathWithID = DomainBlocksPath + "/:" + IDKey
-	// AccountsPath is used for listing + acting on accounts.
-	AccountsPath = BasePath + "/accounts"
-	// AccountsPathWithID is used for interacting with a single account.
-	AccountsPathWithID = AccountsPath + "/:" + IDKey
-	// AccountsActionPath is used for taking action on a single account.
-	AccountsActionPath = AccountsPathWithID + "/action"
-	MediaCleanupPath   = BasePath + "/media_cleanup"
-	MediaRefetchPath   = BasePath + "/media_refetch"
-	// ReportsPath is for serving admin view of user reports.
-	ReportsPath = BasePath + "/reports"
-	// ReportsPathWithID is for viewing/acting on one report.
-	ReportsPathWithID = ReportsPath + "/:" + IDKey
-	// ReportsResolvePath is for marking one report as resolved.
-	ReportsResolvePath = ReportsPathWithID + "/resolve"
+	AccountsPath           = BasePath + "/accounts"
+	AccountsPathWithID     = AccountsPath + "/:" + IDKey
+	AccountsActionPath     = AccountsPathWithID + "/action"
+	MediaCleanupPath       = BasePath + "/media_cleanup"
+	MediaRefetchPath       = BasePath + "/media_refetch"
+	ReportsPath            = BasePath + "/reports"
+	ReportsPathWithID      = ReportsPath + "/:" + IDKey
+	ReportsResolvePath     = ReportsPathWithID + "/resolve"
+	EmailPath              = BasePath + "/email"
+	EmailTestPath          = EmailPath + "/test"
 
-	// ExportQueryKey is for requesting a public export of some data.
-	ExportQueryKey = "export"
-	// ImportQueryKey is for submitting an import of some data.
-	ImportQueryKey = "import"
-	// IDKey specifies the ID of a single item being interacted with.
-	IDKey = "id"
-	// FilterKey is for applying filters to admin views of accounts, emojis, etc.
-	FilterQueryKey = "filter"
-	// MaxShortcodeDomainKey is the url query for returning emoji results lower (alphabetically)
-	// than the given `[shortcode]@[domain]` parameter.
+	ExportQueryKey        = "export"
+	ImportQueryKey        = "import"
+	IDKey                 = "id"
+	FilterQueryKey        = "filter"
 	MaxShortcodeDomainKey = "max_shortcode_domain"
-	// MaxShortcodeDomainKey is the url query for returning emoji results higher (alphabetically)
-	// than the given `[shortcode]@[domain]` parameter.
 	MinShortcodeDomainKey = "min_shortcode_domain"
-	// LimitKey is for specifying maximum number of results to return.
-	LimitKey = "limit"
-	// DomainQueryKey is for specifying a domain during admin actions.
-	DomainQueryKey = "domain"
-	// ResolvedKey is for filtering reports by their resolved status
-	ResolvedKey = "resolved"
-	// AccountIDKey is for selecting account in API paths.
-	AccountIDKey = "account_id"
-	// TargetAccountIDKey is for selecting target account in API paths.
-	TargetAccountIDKey = "target_account_id"
-	MaxIDKey           = "max_id"
-	SinceIDKey         = "since_id"
-	MinIDKey           = "min_id"
+	LimitKey              = "limit"
+	DomainQueryKey        = "domain"
+	ResolvedKey           = "resolved"
+	AccountIDKey          = "account_id"
+	TargetAccountIDKey    = "target_account_id"
+	MaxIDKey              = "max_id"
+	SinceIDKey            = "since_id"
+	MinIDKey              = "min_id"
 )
 
 type Module struct {
@@ -117,4 +94,7 @@ func (m *Module) Route(attachHandler func(method string, path string, f ...gin.H
 	attachHandler(http.MethodGet, ReportsPath, m.ReportsGETHandler)
 	attachHandler(http.MethodGet, ReportsPathWithID, m.ReportGETHandler)
 	attachHandler(http.MethodPost, ReportsResolvePath, m.ReportResolvePOSTHandler)
+
+	// email stuff
+	attachHandler(http.MethodPost, EmailTestPath, m.EmailTestPOSTHandler)
 }
diff --git a/internal/api/client/admin/emailtest.go b/internal/api/client/admin/emailtest.go
new file mode 100644
index 000000000..5c5330679
--- /dev/null
+++ b/internal/api/client/admin/emailtest.go
@@ -0,0 +1,120 @@
+// 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 admin
+
+import (
+	"fmt"
+	"net/http"
+	"net/mail"
+
+	"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/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/oauth"
+)
+
+// EmailTestPostHandler swagger:operation POST /api/v1/admin/email/test testEmailSend
+//
+// Send a generic test email to a specified email address.
+//
+// This can be used to validate an instance's SMTP configuration, and to debug any potential issues.
+//
+// If an error is returned by the SMTP connection, this handler will return code 422 to indicate that
+// the request could not be processed, and the SMTP error will be returned to the caller.
+//
+//	---
+//	tags:
+//	- admin
+//
+//	consumes:
+//	- multipart/form-data
+//
+//	produces:
+//	- application/json
+//
+//	parameters:
+//	-
+//		name: email
+//		in: formData
+//		description: The email address that the test email should be sent to.
+//		type: string
+//
+//	security:
+//	- OAuth2 Bearer:
+//		- admin
+//
+//	responses:
+//		'202':
+//			description: Test email was sent.
+//		'400':
+//			description: bad request
+//		'401':
+//			description: unauthorized
+//		'403':
+//			description: forbidden
+//		'404':
+//			description: not found
+//		'406':
+//			description: not acceptable
+//		'422':
+//			description: >-
+//				An smtp occurred while the email attempt was in progress.
+//				Check the returned json for more information. The smtp error
+//				will be included, to help you debug communication with the
+//				smtp server.
+//		'500':
+//			description: internal server error
+func (m *Module) EmailTestPOSTHandler(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 !*authed.User.Admin {
+		err := fmt.Errorf("user %s not an admin", authed.User.ID)
+		apiutil.ErrorHandler(c, gtserror.NewErrorForbidden(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
+	}
+
+	form := &apimodel.AdminSendTestEmailRequest{}
+	if err := c.ShouldBind(form); err != nil {
+		apiutil.ErrorHandler(c, gtserror.NewErrorBadRequest(err, err.Error()), m.processor.InstanceGetV1)
+		return
+	}
+
+	email, err := mail.ParseAddress(form.Email)
+	if err != nil {
+		apiutil.ErrorHandler(c, gtserror.NewErrorBadRequest(err, err.Error()), m.processor.InstanceGetV1)
+		return
+	}
+
+	errWithCode := m.processor.Admin().EmailTest(c.Request.Context(), authed.Account, email.Address)
+	if errWithCode != nil {
+		apiutil.ErrorHandler(c, errWithCode, m.processor.InstanceGetV1)
+		return
+	}
+
+	c.JSON(http.StatusAccepted, gin.H{"status": "test email sent"})
+}
diff --git a/internal/api/model/admin.go b/internal/api/model/admin.go
index 7d1590b34..cc449ab82 100644
--- a/internal/api/model/admin.go
+++ b/internal/api/model/admin.go
@@ -183,3 +183,9 @@ type MediaCleanupRequest struct {
 	// If value is not specified, the value of media-remote-cache-days in the server config will be used.
 	RemoteCacheDays *int `form:"remote_cache_days" json:"remote_cache_days" xml:"remote_cache_days"`
 }
+
+// AdminSendTestEmailRequest models a test email send request (woah).
+type AdminSendTestEmailRequest struct {
+	// Email address to send the test email to.
+	Email string `form:"email" json:"email" xml:"email"`
+}
diff --git a/internal/db/bundb/instance.go b/internal/db/bundb/instance.go
index c40551212..b4bdeb1d9 100644
--- a/internal/db/bundb/instance.go
+++ b/internal/db/bundb/instance.go
@@ -97,6 +97,20 @@ func (i *instanceDB) CountInstanceDomains(ctx context.Context, domain string) (i
 	return count, nil
 }
 
+func (i *instanceDB) GetInstance(ctx context.Context, domain string) (*gtsmodel.Instance, db.Error) {
+	instance := &gtsmodel.Instance{}
+
+	if err := i.conn.
+		NewSelect().
+		Model(instance).
+		Where("? = ?", bun.Ident("instance.domain"), domain).
+		Scan(ctx); err != nil {
+		return nil, i.conn.ProcessError(err)
+	}
+
+	return instance, nil
+}
+
 func (i *instanceDB) GetInstancePeers(ctx context.Context, includeSuspended bool) ([]*gtsmodel.Instance, db.Error) {
 	instances := []*gtsmodel.Instance{}
 
diff --git a/internal/db/bundb/instance_test.go b/internal/db/bundb/instance_test.go
index 3edb68370..4269df5ca 100644
--- a/internal/db/bundb/instance_test.go
+++ b/internal/db/bundb/instance_test.go
@@ -23,6 +23,7 @@ import (
 
 	"github.com/stretchr/testify/suite"
 	"github.com/superseriousbusiness/gotosocial/internal/config"
+	"github.com/superseriousbusiness/gotosocial/internal/db"
 )
 
 type InstanceTestSuite struct {
@@ -59,6 +60,18 @@ func (suite *InstanceTestSuite) TestCountInstanceDomains() {
 	suite.Equal(2, count)
 }
 
+func (suite *InstanceTestSuite) TestGetInstanceOK() {
+	instance, err := suite.db.GetInstance(context.Background(), "localhost:8080")
+	suite.NoError(err)
+	suite.NotNil(instance)
+}
+
+func (suite *InstanceTestSuite) TestGetInstanceNonexistent() {
+	instance, err := suite.db.GetInstance(context.Background(), "doesnt.exist.com")
+	suite.ErrorIs(err, db.ErrNoEntries)
+	suite.Nil(instance)
+}
+
 func (suite *InstanceTestSuite) TestGetInstancePeers() {
 	peers, err := suite.db.GetInstancePeers(context.Background(), false)
 	suite.NoError(err)
diff --git a/internal/db/instance.go b/internal/db/instance.go
index 85d094d96..dff471193 100644
--- a/internal/db/instance.go
+++ b/internal/db/instance.go
@@ -34,6 +34,9 @@ type Instance interface {
 	// CountInstanceDomains returns the number of known instances known that the given domain federates with.
 	CountInstanceDomains(ctx context.Context, domain string) (int, Error)
 
+	// GetInstance returns the instance entry for the given domain, if it exists.
+	GetInstance(ctx context.Context, domain string) (*gtsmodel.Instance, Error)
+
 	// GetInstanceAccounts returns a slice of accounts from the given instance, arranged by ID.
 	GetInstanceAccounts(ctx context.Context, domain string, maxID string, limit int) ([]*gtsmodel.Account, Error)
 
diff --git a/internal/email/confirm.go b/internal/email/confirm.go
index 94aebc61f..a6548e7d1 100644
--- a/internal/email/confirm.go
+++ b/internal/email/confirm.go
@@ -21,8 +21,7 @@ import (
 	"bytes"
 	"net/smtp"
 
-	"github.com/superseriousbusiness/gotosocial/internal/config"
-	"github.com/superseriousbusiness/gotosocial/internal/log"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
 )
 
 const (
@@ -30,6 +29,19 @@ const (
 	confirmSubject  = "GoToSocial Email Confirmation"
 )
 
+// ConfirmData represents data passed into the confirm email address template.
+type ConfirmData struct {
+	// Username to be addressed.
+	Username string
+	// URL of the instance to present to the receiver.
+	InstanceURL string
+	// Name of the instance to present to the receiver.
+	InstanceName string
+	// Link to present to the receiver to click on and do the confirmation.
+	// Should be a full link with protocol eg., https://example.org/confirm_email?token=some-long-token
+	ConfirmLink string
+}
+
 func (s *sender) SendConfirmEmail(toAddress string, data ConfirmData) error {
 	buf := &bytes.Buffer{}
 	if err := s.template.ExecuteTemplate(buf, confirmTemplate, data); err != nil {
@@ -41,19 +53,10 @@ func (s *sender) SendConfirmEmail(toAddress string, data ConfirmData) error {
 	if err != nil {
 		return err
 	}
-	log.Trace(nil, s.hostAddress+"\n"+config.GetSMTPUsername()+":password"+"\n"+s.from+"\n"+toAddress+"\n\n"+string(msg)+"\n")
-	return smtp.SendMail(s.hostAddress, s.auth, s.from, []string{toAddress}, msg)
-}
 
-// ConfirmData represents data passed into the confirm email address template.
-type ConfirmData struct {
-	// Username to be addressed.
-	Username string
-	// URL of the instance to present to the receiver.
-	InstanceURL string
-	// Name of the instance to present to the receiver.
-	InstanceName string
-	// Link to present to the receiver to click on and do the confirmation.
-	// Should be a full link with protocol eg., https://example.org/confirm_email?token=some-long-token
-	ConfirmLink string
+	if err := smtp.SendMail(s.hostAddress, s.auth, s.from, []string{toAddress}, msg); err != nil {
+		return gtserror.SetType(err, gtserror.TypeSMTP)
+	}
+
+	return nil
 }
diff --git a/internal/email/noopsender.go b/internal/email/noopsender.go
index 435ffb04c..7164440f3 100644
--- a/internal/email/noopsender.go
+++ b/internal/email/noopsender.go
@@ -88,3 +88,24 @@ func (s *noopSender) SendResetEmail(toAddress string, data ResetData) error {
 
 	return nil
 }
+
+func (s *noopSender) SendTestEmail(toAddress string, data TestData) error {
+	buf := &bytes.Buffer{}
+	if err := s.template.ExecuteTemplate(buf, testTemplate, data); err != nil {
+		return err
+	}
+	testBody := buf.String()
+
+	msg, err := assembleMessage(testSubject, testBody, toAddress, "test@example.org")
+	if err != nil {
+		return err
+	}
+
+	log.Tracef(nil, "NOT SENDING test email to %s with contents: %s", toAddress, msg)
+
+	if s.sendCallback != nil {
+		s.sendCallback(toAddress, string(msg))
+	}
+
+	return nil
+}
diff --git a/internal/email/reset.go b/internal/email/reset.go
index 0b950c1c9..cb1da9fee 100644
--- a/internal/email/reset.go
+++ b/internal/email/reset.go
@@ -20,6 +20,8 @@ package email
 import (
 	"bytes"
 	"net/smtp"
+
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
 )
 
 const (
@@ -27,6 +29,19 @@ const (
 	resetSubject  = "GoToSocial Password Reset"
 )
 
+// ResetData represents data passed into the reset email address template.
+type ResetData struct {
+	// Username to be addressed.
+	Username string
+	// URL of the instance to present to the receiver.
+	InstanceURL string
+	// Name of the instance to present to the receiver.
+	InstanceName string
+	// Link to present to the receiver to click on and begin the reset process.
+	// Should be a full link with protocol eg., https://example.org/reset_password?token=some-reset-password-token
+	ResetLink string
+}
+
 func (s *sender) SendResetEmail(toAddress string, data ResetData) error {
 	buf := &bytes.Buffer{}
 	if err := s.template.ExecuteTemplate(buf, resetTemplate, data); err != nil {
@@ -38,18 +53,10 @@ func (s *sender) SendResetEmail(toAddress string, data ResetData) error {
 	if err != nil {
 		return err
 	}
-	return smtp.SendMail(s.hostAddress, s.auth, s.from, []string{toAddress}, msg)
-}
 
-// ResetData represents data passed into the reset email address template.
-type ResetData struct {
-	// Username to be addressed.
-	Username string
-	// URL of the instance to present to the receiver.
-	InstanceURL string
-	// Name of the instance to present to the receiver.
-	InstanceName string
-	// Link to present to the receiver to click on and begin the reset process.
-	// Should be a full link with protocol eg., https://example.org/reset_password?token=some-reset-password-token
-	ResetLink string
+	if err := smtp.SendMail(s.hostAddress, s.auth, s.from, []string{toAddress}, msg); err != nil {
+		return gtserror.SetType(err, gtserror.TypeSMTP)
+	}
+
+	return nil
 }
diff --git a/internal/email/sender.go b/internal/email/sender.go
index 3d188011f..13dd26531 100644
--- a/internal/email/sender.go
+++ b/internal/email/sender.go
@@ -32,6 +32,9 @@ type Sender interface {
 
 	// SendResetEmail sends a 'reset your password' style email to the given toAddress, with the given data.
 	SendResetEmail(toAddress string, data ResetData) error
+
+	// SendTestEmail sends a 'testing email sending' style email to the given toAddress, with the given data.
+	SendTestEmail(toAddress string, data TestData) error
 }
 
 // NewSender returns a new email Sender interface with the given configuration, or an error if something goes wrong.
diff --git a/internal/email/test.go b/internal/email/test.go
new file mode 100644
index 000000000..1e411f161
--- /dev/null
+++ b/internal/email/test.go
@@ -0,0 +1,58 @@
+// 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 email
+
+import (
+	"bytes"
+	"net/smtp"
+
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+)
+
+const (
+	testTemplate = "email_test_text.tmpl"
+	testSubject  = "GoToSocial Test Email"
+)
+
+type TestData struct {
+	// Username of admin user who sent the test.
+	SendingUsername string
+	// URL of the instance to present to the receiver.
+	InstanceURL string
+	// Name of the instance to present to the receiver.
+	InstanceName string
+}
+
+func (s *sender) SendTestEmail(toAddress string, data TestData) error {
+	buf := &bytes.Buffer{}
+	if err := s.template.ExecuteTemplate(buf, testTemplate, data); err != nil {
+		return err
+	}
+	testBody := buf.String()
+
+	msg, err := assembleMessage(testSubject, testBody, toAddress, s.from)
+	if err != nil {
+		return err
+	}
+
+	if err := smtp.SendMail(s.hostAddress, s.auth, s.from, []string{toAddress}, msg); err != nil {
+		return gtserror.SetType(err, gtserror.TypeSMTP)
+	}
+
+	return nil
+}
diff --git a/internal/gtserror/error.go b/internal/gtserror/error.go
index 981b987cb..56e546cf1 100644
--- a/internal/gtserror/error.go
+++ b/internal/gtserror/error.go
@@ -24,11 +24,18 @@ import (
 // package private error key type.
 type errkey int
 
+// ErrorType denotes the type of an error, if set.
+type ErrorType string
+
 const (
 	// error value keys.
 	_ errkey = iota
 	statusCodeKey
 	notFoundKey
+	errorTypeKey
+
+	// error types
+	TypeSMTP ErrorType = "smtp" // smtp (mail) error
 )
 
 // StatusCode checks error for a stored status code value. For example
@@ -57,3 +64,17 @@ func NotFound(err error) bool {
 func SetNotFound(err error) error {
 	return errors.WithValue(err, notFoundKey, struct{}{})
 }
+
+// Type checks error for a stored "type" value. For example
+// an error from sending an email may set a value of "smtp"
+// to indicate this was an SMTP error.
+func Type(err error) ErrorType {
+	s, _ := errors.Value(err, errorTypeKey).(ErrorType)
+	return s
+}
+
+// SetType will wrap the given error to store a "type" value,
+// returning wrapped error. See Type() for example use-cases.
+func SetType(err error, errType ErrorType) error {
+	return errors.WithValue(err, errorTypeKey, errType)
+}
diff --git a/internal/processing/admin/admin.go b/internal/processing/admin/admin.go
index 83dbc5f5b..ad0279dbf 100644
--- a/internal/processing/admin/admin.go
+++ b/internal/processing/admin/admin.go
@@ -18,6 +18,7 @@
 package admin
 
 import (
+	"github.com/superseriousbusiness/gotosocial/internal/email"
 	"github.com/superseriousbusiness/gotosocial/internal/media"
 	"github.com/superseriousbusiness/gotosocial/internal/state"
 	"github.com/superseriousbusiness/gotosocial/internal/transport"
@@ -29,14 +30,16 @@ type Processor struct {
 	tc                  typeutils.TypeConverter
 	mediaManager        media.Manager
 	transportController transport.Controller
+	emailSender         email.Sender
 }
 
 // New returns a new admin processor.
-func New(state *state.State, tc typeutils.TypeConverter, mediaManager media.Manager, transportController transport.Controller) Processor {
+func New(state *state.State, tc typeutils.TypeConverter, mediaManager media.Manager, transportController transport.Controller, emailSender email.Sender) Processor {
 	return Processor{
 		state:               state,
 		tc:                  tc,
 		mediaManager:        mediaManager,
 		transportController: transportController,
+		emailSender:         emailSender,
 	}
 }
diff --git a/internal/processing/admin/email.go b/internal/processing/admin/email.go
new file mode 100644
index 000000000..88396db76
--- /dev/null
+++ b/internal/processing/admin/email.go
@@ -0,0 +1,61 @@
+// 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 admin
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/superseriousbusiness/gotosocial/internal/config"
+	"github.com/superseriousbusiness/gotosocial/internal/email"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+)
+
+// EmailTest sends a generic test email to the given toAddress (which
+// should be a valid email address). To help callers differentiate between
+// proper errors and the smtp errors they're likely fishing for, will return
+// 422 + help text on an SMTP error, or error 500 otherwise.
+func (p *Processor) EmailTest(ctx context.Context, account *gtsmodel.Account, toAddress string) gtserror.WithCode {
+	// Pull our instance entry from the database,
+	// so we can greet the email recipient nicely.
+	instance, err := p.state.DB.GetInstance(ctx, config.GetHost())
+	if err != nil {
+		err = fmt.Errorf("SendConfirmEmail: error getting instance: %s", err)
+		return gtserror.NewErrorInternalError(err)
+	}
+
+	testData := email.TestData{
+		SendingUsername: account.Username,
+		InstanceURL:     instance.URI,
+		InstanceName:    instance.Title,
+	}
+
+	if err := p.emailSender.SendTestEmail(toAddress, testData); err != nil {
+		if errorType := gtserror.Type(err); errorType == gtserror.TypeSMTP {
+			// An error occurred during the SMTP part.
+			// We should indicate this to the caller, as
+			// it will likely help them debug the issue.
+			return gtserror.NewErrorUnprocessableEntity(err, err.Error())
+		}
+		// An actual error has occurred.
+		return gtserror.NewErrorInternalError(err)
+	}
+
+	return nil
+}
diff --git a/internal/processing/processor.go b/internal/processing/processor.go
index 6f5e7a124..98b417ba3 100644
--- a/internal/processing/processor.go
+++ b/internal/processing/processor.go
@@ -125,7 +125,7 @@ func NewProcessor(
 
 	// sub processors
 	processor.account = account.New(state, tc, mediaManager, oauthServer, federator, parseMentionFunc)
-	processor.admin = admin.New(state, tc, mediaManager, federator.TransportController())
+	processor.admin = admin.New(state, tc, mediaManager, federator.TransportController(), emailSender)
 	processor.fedi = fedi.New(state, tc, federator)
 	processor.media = media.New(state, tc, mediaManager, federator.TransportController())
 	processor.report = report.New(state, tc)