[feature] Account alias / move API + db models (#2518)

* [feature] Account alias / move API + db models

* go fmt

* fix little cherry-pick issues

* update error checking, formatting

* add and use new util functions to simplify alias logic

internal/processing/account/alias.go

@@ -0,0 +1,149 @@
+// 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 account
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/url"
+	"slices"
+
+	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+	"github.com/superseriousbusiness/gotosocial/internal/util"
+)
+
+func (p *Processor) Alias(
+	ctx context.Context,
+	account *gtsmodel.Account,
+	newAKAURIStrs []string,
+) (*apimodel.Account, gtserror.WithCode) {
+	if slices.Equal(
+		newAKAURIStrs,
+		account.AlsoKnownAsURIs,
+	) {
+		// No changes to do
+		// here. Return early.
+		return p.c.GetAPIAccountSensitive(ctx, account)
+	}
+
+	newLen := len(newAKAURIStrs)
+	if newLen == 0 {
+		// Simply unset existing
+		// aliases and return early.
+		account.AlsoKnownAsURIs = nil
+		account.AlsoKnownAs = nil
+
+		err := p.state.DB.UpdateAccount(ctx, account, "also_known_as_uris")
+		if err != nil {
+			err := gtserror.Newf("db error updating also_known_as_uri: %w", err)
+			return nil, gtserror.NewErrorInternalError(err)
+		}
+
+		return p.c.GetAPIAccountSensitive(ctx, account)
+	}
+
+	// We need to set new AKA URIs!
+	//
+	// First parse them to URI ptrs and
+	// normalized string representations.
+	//
+	// Use this cheeky type to avoid
+	// repeatedly calling uri.String().
+	type uri struct {
+		uri *url.URL // Parsed URI.
+		str string   // uri.String().
+	}
+
+	newAKAs := make([]uri, newLen)
+	for i, newAKAURIStr := range newAKAURIStrs {
+		newAKAURI, err := url.Parse(newAKAURIStr)
+		if err != nil {
+			err := fmt.Errorf(
+				"invalid also_known_as_uri (%s) provided in account alias request: %w",
+				newAKAURIStr, err,
+			)
+			return nil, gtserror.NewErrorBadRequest(err, err.Error())
+		}
+
+		// We only deref http or https, so check this.
+		if newAKAURI.Scheme != "https" && newAKAURI.Scheme != "http" {
+			err := fmt.Errorf(
+				"invalid also_known_as_uri (%s) provided in account alias request: %w",
+				newAKAURIStr, errors.New("uri must not be empty and scheme must be http or https"),
+			)
+			return nil, gtserror.NewErrorBadRequest(err, err.Error())
+		}
+
+		newAKAs[i].uri = newAKAURI
+		newAKAs[i].str = newAKAURI.String()
+	}
+
+	// Dedupe the URI/string pairs.
+	newAKAs = util.DeduplicateFunc(
+		newAKAs,
+		func(v uri) string {
+			return v.str
+		},
+	)
+
+	// For each deduped entry, get and
+	// check the target account, and set.
+	for _, newAKA := range newAKAs {
+		// Don't let account do anything
+		// daft by aliasing to itself.
+		if newAKA.str == account.URI {
+			continue
+		}
+
+		// Ensure we have a valid, up-to-date
+		// representation of the target account.
+		targetAccount, _, err := p.federator.GetAccountByURI(ctx, account.Username, newAKA.uri)
+		if err != nil {
+			err := fmt.Errorf(
+				"error dereferencing also_known_as_uri (%s) account: %w",
+				newAKA.str, err,
+			)
+			return nil, gtserror.NewErrorUnprocessableEntity(err, err.Error())
+		}
+
+		// Alias target must not be suspended.
+		if !targetAccount.SuspendedAt.IsZero() {
+			err := fmt.Errorf(
+				"target account %s is suspended from this instance; "+
+					"you will not be able to set alsoKnownAs to that account",
+				newAKA.str,
+			)
+			return nil, gtserror.NewErrorUnprocessableEntity(err, err.Error())
+		}
+
+		// Alrighty-roo, looks good, add this one.
+		account.AlsoKnownAsURIs = append(account.AlsoKnownAsURIs, newAKA.str)
+		account.AlsoKnownAs = append(account.AlsoKnownAs, targetAccount)
+	}
+
+	err := p.state.DB.UpdateAccount(ctx, account, "also_known_as_uris")
+	if err != nil {
+		err := gtserror.Newf("db error updating also_known_as_uri: %w", err)
+		return nil, gtserror.NewErrorInternalError(err)
+	}
+
+	return p.c.GetAPIAccountSensitive(ctx, account)
+}