[feature] User-selectable preset CSS themes for accounts (#2777)

* [feature] User-selectable preset themes

* docs, more theme stuff

* lint, tests

* fix css name

* correct some little issues

* add another theme

* fix poll background

* okay last theme i swear

* make retrieval of apimodel themes more conventional

* preallocate stylesheet slices

7 files changed, 122 insertions, 2 deletions

diff --git a/internal/api/client/accounts/accounts.go b/internal/api/client/accounts/accounts.go
index c94fbfbaa..8b92bd7a5 100644
--- a/internal/api/client/accounts/accounts.go
+++ b/internal/api/client/accounts/accounts.go
@@ -55,6 +55,7 @@ const (
 	VerifyPath        = BasePath + "/verify_credentials"
 	MovePath          = BasePath + "/move"
 	AliasPath         = BasePath + "/alias"
+	ThemesPath        = BasePath + "/themes"
 )
 
 type Module struct {
@@ -114,4 +115,7 @@ func (m *Module) Route(attachHandler func(method string, path string, f ...gin.H
 	// migration handlers
 	attachHandler(http.MethodPost, AliasPath, m.AccountAliasPOSTHandler)
 	attachHandler(http.MethodPost, MovePath, m.AccountMovePOSTHandler)
+
+	// account themes
+	attachHandler(http.MethodGet, ThemesPath, m.AccountThemesGETHandler)
 }
diff --git a/internal/api/client/accounts/accountupdate.go b/internal/api/client/accounts/accountupdate.go
index 02c0fc5ac..905d11479 100644
--- a/internal/api/client/accounts/accountupdate.go
+++ b/internal/api/client/accounts/accountupdate.go
@@ -309,6 +309,7 @@ func parseUpdateAccountForm(c *gin.Context) (*apimodel.UpdateCredentialsRequest,
 			form.Source.Language == nil &&
 			form.Source.StatusContentType == nil &&
 			form.FieldsAttributes == nil &&
+			form.Theme == nil &&
 			form.CustomCSS == nil &&
 			form.EnableRSS == nil) {
 		return nil, errors.New("empty form submitted")
diff --git a/internal/api/client/accounts/lists.go b/internal/api/client/accounts/lists.go
index d42fdd3f9..7bd1227a8 100644
--- a/internal/api/client/accounts/lists.go
+++ b/internal/api/client/accounts/lists.go
@@ -69,7 +69,7 @@ import (
 //		'500':
 //			description: internal server error
 func (m *Module) AccountListsGETHandler(c *gin.Context) {
-	authed, err := oauth.Authed(c, false, false, false, false)
+	authed, err := oauth.Authed(c, true, true, true, true)
 	if err != nil {
 		apiutil.ErrorHandler(c, gtserror.NewErrorUnauthorized(err, err.Error()), m.processor.InstanceGetV1)
 		return
diff --git a/internal/api/client/accounts/statuses.go b/internal/api/client/accounts/statuses.go
index 7dd4cbe37..a72a464ed 100644
--- a/internal/api/client/accounts/statuses.go
+++ b/internal/api/client/accounts/statuses.go
@@ -134,7 +134,7 @@ import (
 //		'500':
 //			description: internal server error
 func (m *Module) AccountStatusesGETHandler(c *gin.Context) {
-	authed, err := oauth.Authed(c, false, false, false, false)
+	authed, err := oauth.Authed(c, true, true, true, true)
 	if err != nil {
 		apiutil.ErrorHandler(c, gtserror.NewErrorUnauthorized(err, err.Error()), m.processor.InstanceGetV1)
 		return
diff --git a/internal/api/client/accounts/themesget.go b/internal/api/client/accounts/themesget.go
new file mode 100644
index 000000000..5a0cb6d94
--- /dev/null
+++ b/internal/api/client/accounts/themesget.go
@@ -0,0 +1,77 @@
+// 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 accounts
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	apiutil "github.com/superseriousbusiness/gotosocial/internal/api/util"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/oauth"
+)
+
+// AccountThemesGETHandler swagger:operation GET /api/v1/accounts/themes accountThemes
+//
+// See preset CSS themes available to accounts on this instance.
+//
+//	---
+//	tags:
+//	- accounts
+//
+//	produces:
+//	- application/json
+//
+//	security:
+//	- OAuth2 Bearer:
+//		- read:accounts
+//
+//	responses:
+//		'200':
+//			name: statuses
+//			description: Array of themes.
+//			schema:
+//				type: array
+//				items:
+//					"$ref": "#/definitions/theme"
+//		'400':
+//			description: bad request
+//		'401':
+//			description: unauthorized
+//		'404':
+//			description: not found
+//		'406':
+//			description: not acceptable
+//		'500':
+//			description: internal server error
+func (m *Module) AccountThemesGETHandler(c *gin.Context) {
+	_, err := oauth.Authed(c, true, true, true, true)
+	if err != nil {
+		apiutil.ErrorHandler(c, gtserror.NewErrorUnauthorized(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
+	}
+
+	// Retrieve available themes.
+	themes := m.processor.Account().ThemesGet()
+	apiutil.JSON(c, http.StatusOK, themes)
+}
diff --git a/internal/api/model/account.go b/internal/api/model/account.go
index 7d3fa4b62..af2a394af 100644
--- a/internal/api/model/account.go
+++ b/internal/api/model/account.go
@@ -89,6 +89,8 @@ type Account struct {
 	MuteExpiresAt string `json:"mute_expires_at,omitempty"`
 	// Extra profile information. Shown only if the requester owns the account being requested.
 	Source *Source `json:"source,omitempty"`
+	// Filename of user-selected CSS theme to include when rendering this account's profile or statuses. Eg., `blurple-light.css`.
+	Theme string `json:"theme,omitempty"`
 	// CustomCSS to include when rendering this account's profile or statuses.
 	CustomCSS string `json:"custom_css,omitempty"`
 	// Account has enabled RSS feed.
@@ -162,7 +164,11 @@ type UpdateCredentialsRequest struct {
 	FieldsAttributes *[]UpdateField `form:"fields_attributes" json:"-"`
 	// Profile metadata names and values, parsed from JSON.
 	JSONFieldsAttributes *map[string]UpdateField `form:"-" json:"fields_attributes"`
+	// Theme file name to be used when rendering this account's profile or statuses.
+	// Use empty string to unset.
+	Theme *string `form:"theme" json:"theme"`
 	// Custom CSS to be included when rendering this account's profile or statuses.
+	// Use empty string to unset.
 	CustomCSS *string `form:"custom_css" json:"custom_css"`
 	// Enable RSS feed of public toots for this account at /@[username]/feed.rss
 	EnableRSS *bool `form:"enable_rss" json:"enable_rss"`
diff --git a/internal/api/model/theme.go b/internal/api/model/theme.go
new file mode 100644
index 000000000..b98e7395a
--- /dev/null
+++ b/internal/api/model/theme.go
@@ -0,0 +1,32 @@
+// 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 model
+
+// Theme represents one user-selectable preset CSS theme.
+//
+// swagger:model theme
+type Theme struct {
+	// User-facing title of this theme.
+	Title string `json:"title"`
+
+	// User-facing description of this theme.
+	Description string `json:"description"`
+
+	// FileName of this theme in the themes directory.
+	FileName string `json:"file_name"`
+}