[feature] Set/show instance language(s); show post language on frontend (#2362)

* update go text, include text/display

* [feature] Set instance langs, show post lang on frontend

* go fmt

* WebGet

* set language for whole article, don't use FA icon

* mention instance languages + other optional config vars

* little tweak

* put languages in config properly

* warn log language parse

* change some naming around

* tidy up validate a bit

* lint

* rename LanguageTmpl in template

20 files changed, 586 insertions, 81 deletions

diff --git a/internal/api/client/instance/instancepatch_test.go b/internal/api/client/instance/instancepatch_test.go
index 2fc045855..1f8b691be 100644
--- a/internal/api/client/instance/instancepatch_test.go
+++ b/internal/api/client/instance/instancepatch_test.go
@@ -82,7 +82,10 @@ func (suite *InstancePatchTestSuite) TestInstancePatch1() {
   "short_description": "\u003cp\u003eThis is the GoToSocial testrig. It doesn't federate or anything.\u003c/p\u003e\u003cp\u003eWhen the testrig is shut down, all data on it will be deleted.\u003c/p\u003e\u003cp\u003eDon't use this in production!\u003c/p\u003e",
   "email": "someone@example.org",
   "version": "0.0.0-testrig",
-  "languages": [],
+  "languages": [
+    "nl",
+    "en-gb"
+  ],
   "registrations": true,
   "approval_required": true,
   "invites_enabled": false,
@@ -196,7 +199,10 @@ func (suite *InstancePatchTestSuite) TestInstancePatch2() {
   "short_description": "\u003cp\u003eThis is the GoToSocial testrig. It doesn't federate or anything.\u003c/p\u003e\u003cp\u003eWhen the testrig is shut down, all data on it will be deleted.\u003c/p\u003e\u003cp\u003eDon't use this in production!\u003c/p\u003e",
   "email": "admin@example.org",
   "version": "0.0.0-testrig",
-  "languages": [],
+  "languages": [
+    "nl",
+    "en-gb"
+  ],
   "registrations": true,
   "approval_required": true,
   "invites_enabled": false,
@@ -310,7 +316,10 @@ func (suite *InstancePatchTestSuite) TestInstancePatch3() {
   "short_description": "\u003cp\u003eThis is some html, which is \u003cem\u003eallowed\u003c/em\u003e in short descriptions.\u003c/p\u003e",
   "email": "admin@example.org",
   "version": "0.0.0-testrig",
-  "languages": [],
+  "languages": [
+    "nl",
+    "en-gb"
+  ],
   "registrations": true,
   "approval_required": true,
   "invites_enabled": false,
@@ -475,7 +484,10 @@ func (suite *InstancePatchTestSuite) TestInstancePatch6() {
   "short_description": "\u003cp\u003eThis is the GoToSocial testrig. It doesn't federate or anything.\u003c/p\u003e\u003cp\u003eWhen the testrig is shut down, all data on it will be deleted.\u003c/p\u003e\u003cp\u003eDon't use this in production!\u003c/p\u003e",
   "email": "",
   "version": "0.0.0-testrig",
-  "languages": [],
+  "languages": [
+    "nl",
+    "en-gb"
+  ],
   "registrations": true,
   "approval_required": true,
   "invites_enabled": false,
@@ -611,7 +623,10 @@ func (suite *InstancePatchTestSuite) TestInstancePatch8() {
   "short_description": "\u003cp\u003eThis is the GoToSocial testrig. It doesn't federate or anything.\u003c/p\u003e\u003cp\u003eWhen the testrig is shut down, all data on it will be deleted.\u003c/p\u003e\u003cp\u003eDon't use this in production!\u003c/p\u003e",
   "email": "admin@example.org",
   "version": "0.0.0-testrig",
-  "languages": [],
+  "languages": [
+    "nl",
+    "en-gb"
+  ],
   "registrations": true,
   "approval_required": true,
   "invites_enabled": false,
@@ -762,7 +777,10 @@ func (suite *InstancePatchTestSuite) TestInstancePatch9() {
   "short_description": "\u003cp\u003eThis is the GoToSocial testrig. It doesn't federate or anything.\u003c/p\u003e\u003cp\u003eWhen the testrig is shut down, all data on it will be deleted.\u003c/p\u003e\u003cp\u003eDon't use this in production!\u003c/p\u003e",
   "email": "admin@example.org",
   "version": "0.0.0-testrig",
-  "languages": [],
+  "languages": [
+    "nl",
+    "en-gb"
+  ],
   "registrations": true,
   "approval_required": true,
   "invites_enabled": false,
diff --git a/internal/api/model/status.go b/internal/api/model/status.go
index a6c7f43a4..1efae9cfc 100644
--- a/internal/api/model/status.go
+++ b/internal/api/model/status.go
@@ -17,6 +17,8 @@
 
 package model
 
+import "github.com/superseriousbusiness/gotosocial/internal/language"
+
 // Status models a status or post.
 //
 // swagger:model status
@@ -98,6 +100,13 @@ type Status struct {
 	// so the user may redraft from the source text without the client having to reverse-engineer
 	// the original text from the HTML content.
 	Text string `json:"text,omitempty"`
+
+	// Additional fields not exposed via JSON
+	// (used only internally for templating etc).
+
+	// Template-ready language tag + string, based
+	// on *status.Language. Nil for non-web statuses
+	LanguageTag *language.Language `json:"-"`
 }
 
 /*
diff --git a/internal/config/config.go b/internal/config/config.go
index 7cb31d0a1..b7d2eff36 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -23,6 +23,7 @@ import (
 
 	"codeberg.org/gruf/go-bytesize"
 	"github.com/mitchellh/mapstructure"
+	"github.com/superseriousbusiness/gotosocial/internal/language"
 )
 
 // cfgtype is the reflected type information of Configuration{}.
@@ -76,13 +77,14 @@ type Configuration struct {
 	WebTemplateBaseDir string `name:"web-template-base-dir" usage:"Basedir for html templating files for rendering pages and composing emails."`
 	WebAssetBaseDir    string `name:"web-asset-base-dir" usage:"Directory to serve static assets from, accessible at example.org/assets/"`
 
-	InstanceFederationMode         string `name:"instance-federation-mode" usage:"Set instance federation mode."`
-	InstanceExposePeers            bool   `name:"instance-expose-peers" usage:"Allow unauthenticated users to query /api/v1/instance/peers?filter=open"`
-	InstanceExposeSuspended        bool   `name:"instance-expose-suspended" usage:"Expose suspended instances via web UI, and allow unauthenticated users to query /api/v1/instance/peers?filter=suspended"`
-	InstanceExposeSuspendedWeb     bool   `name:"instance-expose-suspended-web" usage:"Expose list of suspended instances as webpage on /about/suspended"`
-	InstanceExposePublicTimeline   bool   `name:"instance-expose-public-timeline" usage:"Allow unauthenticated users to query /api/v1/timelines/public"`
-	InstanceDeliverToSharedInboxes bool   `name:"instance-deliver-to-shared-inboxes" usage:"Deliver federated messages to shared inboxes, if they're available."`
-	InstanceInjectMastodonVersion  bool   `name:"instance-inject-mastodon-version" usage:"This injects a Mastodon compatible version in /api/v1/instance to help Mastodon clients that use that version for feature detection"`
+	InstanceFederationMode         string             `name:"instance-federation-mode" usage:"Set instance federation mode."`
+	InstanceExposePeers            bool               `name:"instance-expose-peers" usage:"Allow unauthenticated users to query /api/v1/instance/peers?filter=open"`
+	InstanceExposeSuspended        bool               `name:"instance-expose-suspended" usage:"Expose suspended instances via web UI, and allow unauthenticated users to query /api/v1/instance/peers?filter=suspended"`
+	InstanceExposeSuspendedWeb     bool               `name:"instance-expose-suspended-web" usage:"Expose list of suspended instances as webpage on /about/suspended"`
+	InstanceExposePublicTimeline   bool               `name:"instance-expose-public-timeline" usage:"Allow unauthenticated users to query /api/v1/timelines/public"`
+	InstanceDeliverToSharedInboxes bool               `name:"instance-deliver-to-shared-inboxes" usage:"Deliver federated messages to shared inboxes, if they're available."`
+	InstanceInjectMastodonVersion  bool               `name:"instance-inject-mastodon-version" usage:"This injects a Mastodon compatible version in /api/v1/instance to help Mastodon clients that use that version for feature detection"`
+	InstanceLanguages              language.Languages `name:"instance-languages" usage:"BCP47 language tags for the instance. Used to indicate the preferred languages of instance residents (in order from most-preferred to least-preferred)."`
 
 	AccountsRegistrationOpen bool `name:"accounts-registration-open" usage:"Allow anyone to submit an account signup request. If false, server will be invite-only."`
 	AccountsApprovalRequired bool `name:"accounts-approval-required" usage:"Do account signups require approval by an admin or moderator before user can log in? If false, new registrations will be automatically approved."`
diff --git a/internal/config/defaults.go b/internal/config/defaults.go
index 2a7c6f9db..3da489501 100644
--- a/internal/config/defaults.go
+++ b/internal/config/defaults.go
@@ -22,6 +22,7 @@ import (
 
 	"codeberg.org/gruf/go-bytesize"
 	"github.com/coreos/go-oidc/v3/oidc"
+	"github.com/superseriousbusiness/gotosocial/internal/language"
 )
 
 // Defaults contains a populated Configuration with reasonable defaults. Note that
@@ -62,6 +63,7 @@ var Defaults = Configuration{
 	InstanceExposeSuspended:        false,
 	InstanceExposeSuspendedWeb:     false,
 	InstanceDeliverToSharedInboxes: true,
+	InstanceLanguages:              make(language.Languages, 0),
 
 	AccountsRegistrationOpen: true,
 	AccountsApprovalRequired: true,
diff --git a/internal/config/flags.go b/internal/config/flags.go
index b29d0fe04..2dc583abc 100644
--- a/internal/config/flags.go
+++ b/internal/config/flags.go
@@ -88,6 +88,7 @@ func (s *ConfigState) AddServerFlags(cmd *cobra.Command) {
 		cmd.Flags().Bool(InstanceExposeSuspendedFlag(), cfg.InstanceExposeSuspended, fieldtag("InstanceExposeSuspended", "usage"))
 		cmd.Flags().Bool(InstanceExposeSuspendedWebFlag(), cfg.InstanceExposeSuspendedWeb, fieldtag("InstanceExposeSuspendedWeb", "usage"))
 		cmd.Flags().Bool(InstanceDeliverToSharedInboxesFlag(), cfg.InstanceDeliverToSharedInboxes, fieldtag("InstanceDeliverToSharedInboxes", "usage"))
+		// cmd.Flags().StringSlice(InstanceLanguagesFlag(), cfg.InstanceLanguages.TagStrs(), fieldtag("InstanceLanguages", "usage"))
 
 		// Accounts
 		cmd.Flags().Bool(AccountsRegistrationOpenFlag(), cfg.AccountsRegistrationOpen, fieldtag("AccountsRegistrationOpen", "usage"))
diff --git a/internal/config/gen/gen.go b/internal/config/gen/gen.go
index d9fb30904..96e036d98 100644
--- a/internal/config/gen/gen.go
+++ b/internal/config/gen/gen.go
@@ -67,6 +67,7 @@ func main() {
 	fmt.Fprint(output, "import (\n")
 	fmt.Fprint(output, "\t\"time\"\n\n")
 	fmt.Fprint(output, "\t\"codeberg.org/gruf/go-bytesize\"\n")
+	fmt.Fprint(output, "\t\"github.com/superseriousbusiness/gotosocial/internal/langs\"\n")
 	fmt.Fprint(output, ")\n\n")
 	generateFields(output, nil, reflect.TypeOf(config.Configuration{}))
 	_ = output.Close()
diff --git a/internal/config/helpers.gen.go b/internal/config/helpers.gen.go
index 6e9b71812..a008092d3 100644
--- a/internal/config/helpers.gen.go
+++ b/internal/config/helpers.gen.go
@@ -22,6 +22,7 @@ import (
 	"time"
 
 	"codeberg.org/gruf/go-bytesize"
+	"github.com/superseriousbusiness/gotosocial/internal/language"
 )
 
 // GetLogLevel safely fetches the Configuration value for state's 'LogLevel' field
@@ -924,6 +925,31 @@ func GetInstanceInjectMastodonVersion() bool { return global.GetInstanceInjectMa
 // SetInstanceInjectMastodonVersion safely sets the value for global configuration 'InstanceInjectMastodonVersion' field
 func SetInstanceInjectMastodonVersion(v bool) { global.SetInstanceInjectMastodonVersion(v) }
 
+// GetInstanceLanguages safely fetches the Configuration value for state's 'InstanceLanguages' field
+func (st *ConfigState) GetInstanceLanguages() (v language.Languages) {
+	st.mutex.RLock()
+	v = st.config.InstanceLanguages
+	st.mutex.RUnlock()
+	return
+}
+
+// SetInstanceLanguages safely sets the Configuration value for state's 'InstanceLanguages' field
+func (st *ConfigState) SetInstanceLanguages(v language.Languages) {
+	st.mutex.Lock()
+	defer st.mutex.Unlock()
+	st.config.InstanceLanguages = v
+	st.reloadToViper()
+}
+
+// InstanceLanguagesFlag returns the flag name for the 'InstanceLanguages' field
+func InstanceLanguagesFlag() string { return "instance-languages" }
+
+// GetInstanceLanguages safely fetches the value for global configuration 'InstanceLanguages' field
+func GetInstanceLanguages() language.Languages { return global.GetInstanceLanguages() }
+
+// SetInstanceLanguages safely sets the value for global configuration 'InstanceLanguages' field
+func SetInstanceLanguages(v language.Languages) { global.SetInstanceLanguages(v) }
+
 // GetAccountsRegistrationOpen safely fetches the Configuration value for state's 'AccountsRegistrationOpen' field
 func (st *ConfigState) GetAccountsRegistrationOpen() (v bool) {
 	st.mutex.RLock()
diff --git a/internal/config/validate.go b/internal/config/validate.go
index 45cdc4eee..d79d83b9d 100644
--- a/internal/config/validate.go
+++ b/internal/config/validate.go
@@ -18,85 +18,131 @@
 package config
 
 import (
-	"errors"
 	"fmt"
-	"strings"
 
 	"github.com/miekg/dns"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/language"
 	"github.com/superseriousbusiness/gotosocial/internal/log"
 )
 
-// Validate validates global config settings which don't have defaults, to make sure they are set sensibly.
+// Validate validates global config settings.
 func Validate() error {
-	errs := []error{}
+	// Gather all validation errors in
+	// easily readable format for admins.
+	var (
+		errs gtserror.MultiError
+		errf = func(format string, a ...any) {
+			errs = append(errs, fmt.Errorf(format, a...))
+		}
+	)
 
-	// host
+	// `host`
 	host := GetHost()
 	if host == "" {
-		errs = append(errs, fmt.Errorf("%s must be set", HostFlag()))
+		errf("%s must be set", HostFlag())
 	}
 
-	// accountDomain; only check if host was set, otherwise there's no point
+	// If `account-domain` and `host`
+	// are set, `host` must be a valid
+	// subdomain of `account-domain`.
 	if host != "" {
-		switch ad := GetAccountDomain(); ad {
-		case "":
+		ad := GetAccountDomain()
+		if ad == "" {
+			// `account-domain` not set, fall
+			// back by setting it to `host`.
 			SetAccountDomain(GetHost())
-		default:
-			if !dns.IsSubDomain(ad, host) {
-				errs = append(errs, fmt.Errorf("%s was %s and %s was %s, but %s is not a valid subdomain of %s", HostFlag(), host, AccountDomainFlag(), ad, host, ad))
-			}
+		} else if !dns.IsSubDomain(ad, host) {
+			errf(
+				"%s %s is not a valid subdomain of %s %s",
+				AccountDomainFlag(), ad, HostFlag(), host,
+			)
 		}
 	}
 
-	// protocol
+	// Ensure `protocol` sensibly set.
 	switch proto := GetProtocol(); proto {
 	case "https":
-		// no problem
-		break
+		// No problem.
+
 	case "http":
-		log.Warnf(nil, "%s was set to 'http'; this should *only* be used for debugging and tests!", ProtocolFlag())
+		log.Warnf(
+			nil,
+			"%s was set to 'http'; this should *only* be used for debugging and tests!",
+			ProtocolFlag(),
+		)
+
 	case "":
-		errs = append(errs, fmt.Errorf("%s must be set", ProtocolFlag()))
+		errf("%s must be set", ProtocolFlag())
+
 	default:
-		errs = append(errs, fmt.Errorf("%s must be set to either http or https, provided value was %s", ProtocolFlag(), proto))
+		errf(
+			"%s must be set to either http or https, provided value was %s",
+			ProtocolFlag(), proto,
+		)
 	}
 
-	// federation mode
-	switch federationMode := GetInstanceFederationMode(); federationMode {
+	// `federation-mode` should be
+	// "blocklist" or "allowlist".
+	switch fediMode := GetInstanceFederationMode(); fediMode {
 	case InstanceFederationModeBlocklist, InstanceFederationModeAllowlist:
-		// no problem
-		break
+		// No problem.
+
 	case "":
-		errs = append(errs, fmt.Errorf("%s must be set", InstanceFederationModeFlag()))
+		errf("%s must be set", InstanceFederationModeFlag())
+
 	default:
-		errs = append(errs, fmt.Errorf("%s must be set to either blocklist or allowlist, provided value was %s", InstanceFederationModeFlag(), federationMode))
+		errf(
+			"%s must be set to either blocklist or allowlist, provided value was %s",
+			InstanceFederationModeFlag(), fediMode,
+		)
 	}
 
+	// Parse `instance-languages`, and
+	// set enriched version into config.
+	parsedLangs, err := language.InitLangs(GetInstanceLanguages().TagStrs())
+	if err != nil {
+		errf(
+			"%s could not be parsed as an array of valid BCP47 language tags: %v",
+			InstanceLanguagesFlag(), err,
+		)
+	} else {
+		// Parsed successfully, put enriched
+		// versions in config immediately.
+		SetInstanceLanguages(parsedLangs)
+	}
+
+	// `web-assets-base-dir`.
 	webAssetsBaseDir := GetWebAssetBaseDir()
 	if webAssetsBaseDir == "" {
-		errs = append(errs, fmt.Errorf("%s must be set", WebAssetBaseDirFlag()))
+		errf("%s must be set", WebAssetBaseDirFlag())
 	}
 
-	tlsChain := GetTLSCertificateChain()
-	tlsKey := GetTLSCertificateKey()
-	tlsChainFlag := TLSCertificateChainFlag()
-	tlsKeyFlag := TLSCertificateKeyFlag()
+	// Custom / LE TLS settings.
+	//
+	// Only one of custom certs or LE can be set,
+	// and if using custom certs then all relevant
+	// values must be provided.
+	var (
+		tlsChain     = GetTLSCertificateChain()
+		tlsKey       = GetTLSCertificateKey()
+		tlsChainFlag = TLSCertificateChainFlag()
+		tlsKeyFlag   = TLSCertificateKeyFlag()
+	)
 
 	if GetLetsEncryptEnabled() && (tlsChain != "" || tlsKey != "") {
-		errs = append(errs, fmt.Errorf("%s cannot be enabled when %s and/or %s are also set", LetsEncryptEnabledFlag(), tlsChainFlag, tlsKeyFlag))
+		errf(
+			"%s cannot be true when %s and/or %s are also set",
+			LetsEncryptEnabledFlag(), tlsChainFlag, tlsKeyFlag,
+		)
 	}
 
 	if (tlsChain != "" && tlsKey == "") || (tlsChain == "" && tlsKey != "") {
-		errs = append(errs, fmt.Errorf("%s and %s need to both be set or unset", tlsChainFlag, tlsKeyFlag))
-	}
-
-	if len(errs) > 0 {
-		errStrings := []string{}
-		for _, err := range errs {
-			errStrings = append(errStrings, err.Error())
-		}
-		return errors.New(strings.Join(errStrings, "; "))
+		errf(
+			"%s and %s need to both be set or unset",
+			tlsChainFlag, tlsKeyFlag,
+		)
 	}
 
-	return nil
+	return errs.Combine()
 }
diff --git a/internal/config/validate_test.go b/internal/config/validate_test.go
index 72c268c16..1ae3d6c78 100644
--- a/internal/config/validate_test.go
+++ b/internal/config/validate_test.go
@@ -80,7 +80,7 @@ func (suite *ConfigValidateTestSuite) TestValidateAccountDomainNotSubdomain1() {
 	config.SetAccountDomain("example.com")
 
 	err := config.Validate()
-	suite.EqualError(err, "host was gts.example.org and account-domain was example.com, but gts.example.org is not a valid subdomain of example.com")
+	suite.EqualError(err, "account-domain example.com is not a valid subdomain of host gts.example.org")
 }
 
 func (suite *ConfigValidateTestSuite) TestValidateAccountDomainNotSubdomain2() {
@@ -90,7 +90,7 @@ func (suite *ConfigValidateTestSuite) TestValidateAccountDomainNotSubdomain2() {
 	config.SetAccountDomain("gts.example.org")
 
 	err := config.Validate()
-	suite.EqualError(err, "host was example.org and account-domain was gts.example.org, but example.org is not a valid subdomain of gts.example.org")
+	suite.EqualError(err, "account-domain gts.example.org is not a valid subdomain of host example.org")
 }
 
 func (suite *ConfigValidateTestSuite) TestValidateConfigNoProtocol() {
@@ -118,7 +118,7 @@ func (suite *ConfigValidateTestSuite) TestValidateConfigNoProtocolOrHost() {
 	config.SetProtocol("")
 
 	err := config.Validate()
-	suite.EqualError(err, "host must be set; protocol must be set")
+	suite.EqualError(err, "host must be set\nprotocol must be set")
 }
 
 func (suite *ConfigValidateTestSuite) TestValidateConfigBadProtocol() {
@@ -137,7 +137,7 @@ func (suite *ConfigValidateTestSuite) TestValidateConfigBadProtocolNoHost() {
 	config.SetProtocol("foo")
 
 	err := config.Validate()
-	suite.EqualError(err, "host must be set; protocol must be set to either http or https, provided value was foo")
+	suite.EqualError(err, "host must be set\nprotocol must be set to either http or https, provided value was foo")
 }
 
 func TestConfigValidateTestSuite(t *testing.T) {
diff --git a/internal/language/language.go b/internal/language/language.go
new file mode 100644
index 000000000..d91e3a4db
--- /dev/null
+++ b/internal/language/language.go
@@ -0,0 +1,184 @@
+// 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 language
+
+import (
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"golang.org/x/text/language"
+	"golang.org/x/text/language/display"
+)
+
+var namer display.Namer
+
+// InitLangs parses languages from the
+// given slice of tags, and sets the `namer`
+// display.Namer for the instance.
+//
+// This function should only be called once,
+// since setting the namer is not thread safe.
+func InitLangs(tagStrs []string) (Languages, error) {
+	var (
+		languages = make(Languages, len(tagStrs))
+		tags      = make([]language.Tag, len(tagStrs))
+	)
+
+	// Reset namer.
+	namer = nil
+
+	// Parse all tags first.
+	for i, tagStr := range tagStrs {
+		tag, err := language.Parse(tagStr)
+		if err != nil {
+			return nil, gtserror.Newf(
+				"error parsing %s as BCP47 language tag: %w",
+				tagStr, err,
+			)
+		}
+		tags[i] = tag
+	}
+
+	// Check if we can set a namer.
+	if len(tags) != 0 {
+		namer = display.Languages(tags[0])
+	}
+
+	// Fall namer back to English.
+	if namer == nil {
+		namer = display.Languages(language.English)
+	}
+
+	// Parse nice language models from tags
+	// (this will use the namer we just set).
+	for i, tag := range tags {
+		languages[i] = ParseTag(tag)
+	}
+
+	return languages, nil
+}
+
+// Language models a BCP47 language tag
+// along with helper strings for the tag.
+type Language struct {
+	// BCP47 language tag
+	Tag language.Tag
+	// Normalized string
+	// of BCP47 tag.
+	TagStr string
+	// Human-readable
+	// language name(s).
+	DisplayStr string
+}
+
+// MarshalText implements encoding.TextMarshaler{}.
+func (l *Language) MarshalText() ([]byte, error) {
+	return []byte(l.TagStr), nil
+}
+
+// UnmarshalText implements encoding.TextUnmarshaler{}.
+func (l *Language) UnmarshalText(text []byte) error {
+	lang, err := Parse(string(text))
+	if err != nil {
+		return err
+	}
+
+	*l = *lang
+	return nil
+}
+
+type Languages []*Language
+
+func (l Languages) Tags() []language.Tag {
+	tags := make([]language.Tag, len(l))
+	for i, lang := range l {
+		tags[i] = lang.Tag
+	}
+
+	return tags
+}
+
+func (l Languages) TagStrs() []string {
+	tagStrs := make([]string, len(l))
+	for i, lang := range l {
+		tagStrs[i] = lang.TagStr
+	}
+
+	return tagStrs
+}
+
+func (l Languages) DisplayStrs() []string {
+	displayStrs := make([]string, len(l))
+	for i, lang := range l {
+		displayStrs[i] = lang.DisplayStr
+	}
+
+	return displayStrs
+}
+
+// ParseTag parses and nicely formats the input language BCP47 tag,
+// returning a Language with ready-to-use display and tag strings.
+func ParseTag(tag language.Tag) *Language {
+	l := new(Language)
+	l.Tag = tag
+	l.TagStr = tag.String()
+
+	var (
+		// Our name for the language.
+		name string
+		// Language's name for itself.
+		selfName = display.Self.Name(tag)
+	)
+
+	// Try to use namer
+	// (if initialized).
+	if namer != nil {
+		name = namer.Name(tag)
+	}
+
+	switch {
+	case name == "":
+		// We don't have a name for
+		// this language, just use
+		// its own name for itself.
+		l.DisplayStr = selfName
+
+	case name == selfName:
+		// Avoid repeating ourselves:
+		// showing "English (English)"
+		// is not useful.
+		l.DisplayStr = name
+
+	default:
+		// Include our name for the
+		// language, and its own
+		// name for itself.
+		l.DisplayStr = name + " " + "(" + selfName + ")"
+	}
+
+	return l
+}
+
+// Parse parses and nicely formats the input language BCP47 tag,
+// returning a Language with ready-to-use display and tag strings.
+func Parse(lang string) (*Language, error) {
+	tag, err := language.Parse(lang)
+	if err != nil {
+		return nil, err
+	}
+
+	return ParseTag(tag), nil
+}
diff --git a/internal/language/language_test.go b/internal/language/language_test.go
new file mode 100644
index 000000000..024448ab4
--- /dev/null
+++ b/internal/language/language_test.go
@@ -0,0 +1,142 @@
+// 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 language_test
+
+import (
+	"slices"
+	"testing"
+
+	"github.com/superseriousbusiness/gotosocial/internal/language"
+	golanguage "golang.org/x/text/language"
+)
+
+func TestInstanceLangs(t *testing.T) {
+	for i, test := range []struct {
+		InstanceLangs       []string
+		expectedLangs       []golanguage.Tag
+		expectedLangStrs    []string
+		expectedErr         error
+		parseDisplayLang    string
+		expectedDisplayLang string
+	}{
+		{
+			InstanceLangs: []string{"en-us", "fr"},
+			expectedLangs: []golanguage.Tag{
+				golanguage.AmericanEnglish,
+				golanguage.French,
+			},
+			expectedLangStrs: []string{
+				"American English",
+				"French (français)",
+			},
+			parseDisplayLang:    "de",
+			expectedDisplayLang: "German (Deutsch)",
+		},
+		{
+			InstanceLangs: []string{"fr", "en-us"},
+			expectedLangs: []golanguage.Tag{
+				golanguage.French,
+				golanguage.AmericanEnglish,
+			},
+			expectedLangStrs: []string{
+				"français",
+				"anglais américain (American English)",
+			},
+			parseDisplayLang:    "de",
+			expectedDisplayLang: "allemand (Deutsch)",
+		},
+		{
+			InstanceLangs:       []string{},
+			expectedLangs:       []golanguage.Tag{},
+			expectedLangStrs:    []string{},
+			parseDisplayLang:    "de",
+			expectedDisplayLang: "German (Deutsch)",
+		},
+		{
+			InstanceLangs: []string{"zh"},
+			expectedLangs: []golanguage.Tag{
+				golanguage.Chinese,
+			},
+			expectedLangStrs: []string{
+				"中文",
+			},
+			parseDisplayLang:    "de",
+			expectedDisplayLang: "德语 (Deutsch)",
+		},
+		{
+			InstanceLangs: []string{"ar", "en"},
+			expectedLangs: []golanguage.Tag{
+				golanguage.Arabic,
+				golanguage.English,
+			},
+			expectedLangStrs: []string{
+				"العربية",
+				"الإنجليزية (English)",
+			},
+			parseDisplayLang:    "fi",
+			expectedDisplayLang: "الفنلندية (suomi)",
+		},
+		{
+			InstanceLangs: []string{"en-us"},
+			expectedLangs: []golanguage.Tag{
+				golanguage.AmericanEnglish,
+			},
+			expectedLangStrs: []string{
+				"American English",
+			},
+			parseDisplayLang:    "en-us",
+			expectedDisplayLang: "American English",
+		},
+		{
+			InstanceLangs: []string{"en-us"},
+			expectedLangs: []golanguage.Tag{
+				golanguage.AmericanEnglish,
+			},
+			expectedLangStrs: []string{
+				"American English",
+			},
+			parseDisplayLang:    "en-gb",
+			expectedDisplayLang: "British English",
+		},
+	} {
+		languages, err := language.InitLangs(test.InstanceLangs)
+		if err != test.expectedErr {
+			t.Errorf("test %d expected error %v, got %v", i, test.expectedErr, err)
+		}
+
+		parsedTags := languages.Tags()
+		if !slices.Equal(test.expectedLangs, parsedTags) {
+			t.Errorf("test %d expected language tags %v, got %v", i, test.expectedLangs, parsedTags)
+		}
+
+		parsedLangStrs := languages.DisplayStrs()
+		if !slices.Equal(test.expectedLangStrs, parsedLangStrs) {
+			t.Errorf("test %d expected language strings %v, got %v", i, test.expectedLangStrs, parsedLangStrs)
+		}
+
+		parsedLang, err := language.Parse(test.parseDisplayLang)
+		if err != nil {
+			t.Errorf("unexpected error %v", err)
+			return
+		}
+
+		if test.expectedDisplayLang != parsedLang.DisplayStr {
+			t.Errorf("test %d expected to parse language %v, got %v", i, test.expectedDisplayLang, parsedLang.DisplayStr)
+		}
+	}
+}
diff --git a/internal/processing/account/statuses.go b/internal/processing/account/statuses.go
index 1bdd3906b..0985bb4ef 100644
--- a/internal/processing/account/statuses.go
+++ b/internal/processing/account/statuses.go
@@ -133,7 +133,11 @@ func (p *Processor) StatusesGet(
 // WebStatusesGet fetches a number of statuses (in descending order)
 // from the given account. It selects only statuses which are suitable
 // for showing on the public web profile of an account.
-func (p *Processor) WebStatusesGet(ctx context.Context, targetAccountID string, maxID string) (*apimodel.PageableResponse, gtserror.WithCode) {
+func (p *Processor) WebStatusesGet(
+	ctx context.Context,
+	targetAccountID string,
+	maxID string,
+) (*apimodel.PageableResponse, gtserror.WithCode) {
 	account, err := p.state.DB.GetAccountByID(ctx, targetAccountID)
 	if err != nil {
 		if errors.Is(err, db.ErrNoEntries) {
@@ -167,10 +171,10 @@ func (p *Processor) WebStatusesGet(ctx context.Context, targetAccountID string,
 	)
 
 	for _, s := range statuses {
-		// Convert fetched statuses to API statuses.
-		item, err := p.converter.StatusToAPIStatus(ctx, s, nil)
+		// Convert fetched statuses to web view statuses.
+		item, err := p.converter.StatusToWebStatus(ctx, s, nil)
 		if err != nil {
-			log.Errorf(ctx, "error convering to api status: %v", err)
+			log.Errorf(ctx, "error convering to web status: %v", err)
 			continue
 		}
 		items = append(items, item)
@@ -183,8 +187,39 @@ func (p *Processor) WebStatusesGet(ctx context.Context, targetAccountID string,
 	})
 }
 
-// PinnedStatusesGet is a shortcut for getting just an account's pinned statuses.
-// Under the hood, it just calls StatusesGet using mostly default parameters.
-func (p *Processor) PinnedStatusesGet(ctx context.Context, requestingAccount *gtsmodel.Account, targetAccountID string) (*apimodel.PageableResponse, gtserror.WithCode) {
-	return p.StatusesGet(ctx, requestingAccount, targetAccountID, 0, false, false, "", "", true, false, false)
+// WebStatusesGetPinned returns web versions of pinned statuses.
+func (p *Processor) WebStatusesGetPinned(
+	ctx context.Context,
+	targetAccountID string,
+) ([]*apimodel.Status, gtserror.WithCode) {
+	statuses, err := p.state.DB.GetAccountPinnedStatuses(ctx, targetAccountID)
+	if err != nil && !errors.Is(err, db.ErrNoEntries) {
+		return nil, gtserror.NewErrorInternalError(err)
+	}
+
+	webStatuses := make([]*apimodel.Status, 0, len(statuses))
+	for _, status := range statuses {
+		if status.Visibility != gtsmodel.VisibilityPublic {
+			// Skip non-public
+			// pinned status.
+			continue
+		}
+
+		webStatus, err := p.converter.StatusToWebStatus(ctx, status, nil)
+		if err != nil {
+			log.Errorf(ctx, "error convering to web status: %v", err)
+			continue
+		}
+
+		// Normally when viewed via the API, 'pinned' is
+		// only true if the *viewing account* has pinned
+		// the status being viewed. For web statuses,
+		// however, we still want to be able to indicate
+		// a pinned status, so bodge this in here.
+		webStatus.Pinned = true
+
+		webStatuses = append(webStatuses, webStatus)
+	}
+
+	return webStatuses, nil
 }
diff --git a/internal/processing/admin/admin_test.go b/internal/processing/admin/admin_test.go
index 367924664..01a3a88ff 100644
--- a/internal/processing/admin/admin_test.go
+++ b/internal/processing/admin/admin_test.go
@@ -80,7 +80,6 @@ func (suite *AdminStandardTestSuite) SetupSuite() {
 
 func (suite *AdminStandardTestSuite) SetupTest() {
 	suite.state.Caches.Init()
-	
 
 	testrig.InitTestConfig()
 	testrig.InitTestLog()
diff --git a/internal/processing/status/get.go b/internal/processing/status/get.go
index 170dd0e53..ae6918e3f 100644
--- a/internal/processing/status/get.go
+++ b/internal/processing/status/get.go
@@ -36,6 +36,21 @@ func (p *Processor) Get(ctx context.Context, requestingAccount *gtsmodel.Account
 	return p.c.GetAPIStatus(ctx, requestingAccount, targetStatus)
 }
 
+// WebGet gets the given status for web use, taking account of privacy settings.
+func (p *Processor) WebGet(ctx context.Context, targetStatusID string) (*apimodel.Status, gtserror.WithCode) {
+	targetStatus, errWithCode := p.c.GetVisibleTargetStatus(ctx, nil, targetStatusID)
+	if errWithCode != nil {
+		return nil, errWithCode
+	}
+
+	webStatus, err := p.converter.StatusToWebStatus(ctx, targetStatus, nil)
+	if err != nil {
+		err = gtserror.Newf("error converting status: %w", err)
+		return nil, gtserror.NewErrorInternalError(err)
+	}
+	return webStatus, nil
+}
+
 func (p *Processor) contextGet(
 	ctx context.Context,
 	requestingAccount *gtsmodel.Account,
diff --git a/internal/typeutils/converter_test.go b/internal/typeutils/converter_test.go
index 122b98d4c..0195a6889 100644
--- a/internal/typeutils/converter_test.go
+++ b/internal/typeutils/converter_test.go
@@ -526,7 +526,7 @@ func (suite *TypeUtilsTestSuite) GetProcessor() *processing.Processor {
 	mediaManager := testrig.NewTestMediaManager(&suite.state)
 	federator := testrig.NewTestFederator(&suite.state, transportController, mediaManager)
 	emailSender := testrig.NewEmailSender("../../web/template/", nil)
-	
+
 	processor := testrig.NewTestProcessor(&suite.state, federator, emailSender, mediaManager)
 	testrig.StartWorkers(&suite.state, processor.Workers())
 
diff --git a/internal/typeutils/internaltofrontend.go b/internal/typeutils/internaltofrontend.go
index 1a2c321f5..8138ee7b4 100644
--- a/internal/typeutils/internaltofrontend.go
+++ b/internal/typeutils/internaltofrontend.go
@@ -30,6 +30,7 @@ import (
 	"github.com/superseriousbusiness/gotosocial/internal/db"
 	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
 	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+	"github.com/superseriousbusiness/gotosocial/internal/language"
 	"github.com/superseriousbusiness/gotosocial/internal/log"
 	"github.com/superseriousbusiness/gotosocial/internal/media"
 	"github.com/superseriousbusiness/gotosocial/internal/uris"
@@ -656,7 +657,28 @@ func (c *Converter) StatusToWebStatus(
 	s *gtsmodel.Status,
 	requestingAccount *gtsmodel.Account,
 ) (*apimodel.Status, error) {
-	return c.statusToFrontend(ctx, s, requestingAccount)
+	webStatus, err := c.statusToFrontend(ctx, s, requestingAccount)
+	if err != nil {
+		return nil, err
+	}
+
+	// Add additional information for template.
+	// Assume empty langs, hope for not empty language.
+	webStatus.LanguageTag = new(language.Language)
+	if lang := webStatus.Language; lang != nil {
+		langTag, err := language.Parse(*lang)
+		if err != nil {
+			log.Warnf(
+				ctx,
+				"error parsing %s as language tag: %v",
+				*lang, err,
+			)
+		} else {
+			webStatus.LanguageTag = langTag
+		}
+	}
+
+	return webStatus, nil
 }
 
 // statusToFrontend is a package internal function for
@@ -873,7 +895,7 @@ func (c *Converter) InstanceToAPIV1Instance(ctx context.Context, i *gtsmodel.Ins
 		ShortDescription: i.ShortDescription,
 		Email:            i.ContactEmail,
 		Version:          config.GetSoftwareVersion(),
-		Languages:        []string{}, // todo: not supported yet
+		Languages:        config.GetInstanceLanguages().TagStrs(),
 		Registrations:    config.GetAccountsRegistrationOpen(),
 		ApprovalRequired: config.GetAccountsApprovalRequired(),
 		InvitesEnabled:   false, // todo: not supported yet
@@ -982,7 +1004,7 @@ func (c *Converter) InstanceToAPIV2Instance(ctx context.Context, i *gtsmodel.Ins
 		SourceURL:     instanceSourceURL,
 		Description:   i.Description,
 		Usage:         apimodel.InstanceV2Usage{}, // todo: not implemented
-		Languages:     []string{},                 // todo: not implemented
+		Languages:     config.GetInstanceLanguages().TagStrs(),
 		Rules:         c.InstanceRulesToAPIRules(i.Rules),
 		Terms:         i.Terms,
 	}
diff --git a/internal/typeutils/internaltofrontend_test.go b/internal/typeutils/internaltofrontend_test.go
index d386c180e..ee8216e8f 100644
--- a/internal/typeutils/internaltofrontend_test.go
+++ b/internal/typeutils/internaltofrontend_test.go
@@ -712,7 +712,10 @@ func (suite *InternalToFrontendTestSuite) TestInstanceV1ToFrontend() {
   "short_description": "\u003cp\u003eThis is the GoToSocial testrig. It doesn't federate or anything.\u003c/p\u003e\u003cp\u003eWhen the testrig is shut down, all data on it will be deleted.\u003c/p\u003e\u003cp\u003eDon't use this in production!\u003c/p\u003e",
   "email": "admin@example.org",
   "version": "0.0.0-testrig",
-  "languages": [],
+  "languages": [
+    "nl",
+    "en-gb"
+  ],
   "registrations": true,
   "approval_required": true,
   "invites_enabled": false,
@@ -826,7 +829,10 @@ func (suite *InternalToFrontendTestSuite) TestInstanceV2ToFrontend() {
   "thumbnail": {
     "url": "http://localhost:8080/assets/logo.png"
   },
-  "languages": [],
+  "languages": [
+    "nl",
+    "en-gb"
+  ],
   "configuration": {
     "urls": {
       "streaming": "wss://localhost:8080"
diff --git a/internal/web/about.go b/internal/web/about.go
index ebb1ceefa..89bb13f0d 100644
--- a/internal/web/about.go
+++ b/internal/web/about.go
@@ -39,6 +39,7 @@ func (m *Module) aboutGETHandler(c *gin.Context) {
 
 	c.HTML(http.StatusOK, "about.tmpl", gin.H{
 		"instance":         instance,
+		"languages":        config.GetInstanceLanguages().DisplayStrs(),
 		"ogMeta":           ogBase(instance),
 		"blocklistExposed": config.GetInstanceExposeSuspendedWeb(),
 		"stylesheets": []string{
diff --git a/internal/web/profile.go b/internal/web/profile.go
index c16965adc..b2c3bb944 100644
--- a/internal/web/profile.go
+++ b/internal/web/profile.go
@@ -121,21 +121,17 @@ func (m *Module) profileGETHandler(c *gin.Context) {
 	var (
 		maxStatusID    = apiutil.ParseMaxID(c.Query(apiutil.MaxIDKey), "")
 		paging         = maxStatusID != ""
-		pinnedStatuses *apimodel.PageableResponse
+		pinnedStatuses []*apimodel.Status
 	)
 
 	if !paging {
 		// Client opened bare profile (from the top)
 		// so load + display pinned statuses.
-		pinnedStatuses, errWithCode = m.processor.Account().PinnedStatusesGet(ctx, authed.Account, targetAccount.ID)
+		pinnedStatuses, errWithCode = m.processor.Account().WebStatusesGetPinned(ctx, targetAccount.ID)
 		if errWithCode != nil {
 			apiutil.WebErrorHandler(c, errWithCode, instanceGet)
 			return
 		}
-	} else {
-		// Don't load pinned statuses at
-		// the top of profile while paging.
-		pinnedStatuses = new(apimodel.PageableResponse)
 	}
 
 	// Get statuses from maxStatusID onwards (or from top if empty string).
@@ -162,7 +158,7 @@ func (m *Module) profileGETHandler(c *gin.Context) {
 		"robotsMeta":       robotsMeta,
 		"statuses":         statusResp.Items,
 		"statuses_next":    statusResp.NextLink,
-		"pinned_statuses":  pinnedStatuses.Items,
+		"pinned_statuses":  pinnedStatuses,
 		"show_back_to_top": paging,
 		"stylesheets":      stylesheets,
 		"javascript":       []string{distPathPrefix + "/frontend.js"},
diff --git a/internal/web/thread.go b/internal/web/thread.go
index 13dd5877d..523cf7579 100644
--- a/internal/web/thread.go
+++ b/internal/web/thread.go
@@ -111,7 +111,7 @@ func (m *Module) threadGETHandler(c *gin.Context) {
 	}
 
 	// Get the status itself from the processor using provided ID and authorization (if any).
-	status, errWithCode := m.processor.Status().Get(ctx, authed.Account, targetStatusID)
+	status, errWithCode := m.processor.Status().WebGet(ctx, targetStatusID)
 	if errWithCode != nil {
 		apiutil.WebErrorHandler(c, errWithCode, instanceGet)
 		return