[chore] The Big Middleware and API Refactor (tm) (#1250)

* interim commit: start refactoring middlewares into package under router

* another interim commit, this is becoming a big job

* another fucking massive interim commit

* refactor bookmarks to new style

* ambassador, wiz zeze commits you are spoiling uz

* she compiles, we're getting there

* we're just normal men; we're just innocent men

* apiutil

* whoopsie

* i'm glad noone reads commit msgs haha :blob_sweat:

* use that weirdo go-bytesize library for maxMultipartMemory

* fix media module paths

1 files changed, 115 insertions, 0 deletions

diff --git a/internal/api/auth/token.go b/internal/api/auth/token.go
new file mode 100644
index 000000000..17c4d8d8b
--- /dev/null
+++ b/internal/api/auth/token.go
@@ -0,0 +1,115 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
+
+   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 (
+	"net/http"
+	"net/url"
+
+	apiutil "github.com/superseriousbusiness/gotosocial/internal/api/util"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/oauth"
+
+	"github.com/gin-gonic/gin"
+)
+
+type tokenRequestForm struct {
+	GrantType    *string `form:"grant_type" json:"grant_type" xml:"grant_type"`
+	Code         *string `form:"code" json:"code" xml:"code"`
+	RedirectURI  *string `form:"redirect_uri" json:"redirect_uri" xml:"redirect_uri"`
+	ClientID     *string `form:"client_id" json:"client_id" xml:"client_id"`
+	ClientSecret *string `form:"client_secret" json:"client_secret" xml:"client_secret"`
+	Scope        *string `form:"scope" json:"scope" xml:"scope"`
+}
+
+// TokenPOSTHandler should be served as a POST at https://example.org/oauth/token
+// The idea here is to serve an oauth access token to a user, which can be used for authorizing against non-public APIs.
+func (m *Module) TokenPOSTHandler(c *gin.Context) {
+	if _, err := apiutil.NegotiateAccept(c, apiutil.JSONAcceptHeaders...); err != nil {
+		apiutil.ErrorHandler(c, gtserror.NewErrorNotAcceptable(err, err.Error()), m.processor.InstanceGet)
+		return
+	}
+
+	help := []string{}
+
+	form := &tokenRequestForm{}
+	if err := c.ShouldBind(form); err != nil {
+		apiutil.OAuthErrorHandler(c, gtserror.NewErrorBadRequest(oauth.InvalidRequest(), err.Error()))
+		return
+	}
+
+	c.Request.Form = url.Values{}
+
+	var grantType string
+	if form.GrantType != nil {
+		grantType = *form.GrantType
+		c.Request.Form.Set("grant_type", grantType)
+	} else {
+		help = append(help, "grant_type was not set in the token request form, but must be set to authorization_code or client_credentials")
+	}
+
+	if form.ClientID != nil {
+		c.Request.Form.Set("client_id", *form.ClientID)
+	} else {
+		help = append(help, "client_id was not set in the token request form")
+	}
+
+	if form.ClientSecret != nil {
+		c.Request.Form.Set("client_secret", *form.ClientSecret)
+	} else {
+		help = append(help, "client_secret was not set in the token request form")
+	}
+
+	if form.RedirectURI != nil {
+		c.Request.Form.Set("redirect_uri", *form.RedirectURI)
+	} else {
+		help = append(help, "redirect_uri was not set in the token request form")
+	}
+
+	var code string
+	if form.Code != nil {
+		if grantType != "authorization_code" {
+			help = append(help, "a code was provided in the token request form, but grant_type was not set to authorization_code")
+		} else {
+			code = *form.Code
+			c.Request.Form.Set("code", code)
+		}
+	} else if grantType == "authorization_code" {
+		help = append(help, "code was not set in the token request form, but must be set since grant_type is authorization_code")
+	}
+
+	if form.Scope != nil {
+		c.Request.Form.Set("scope", *form.Scope)
+	}
+
+	if len(help) != 0 {
+		apiutil.OAuthErrorHandler(c, gtserror.NewErrorBadRequest(oauth.InvalidRequest(), help...))
+		return
+	}
+
+	token, errWithCode := m.processor.OAuthHandleTokenRequest(c.Request)
+	if errWithCode != nil {
+		apiutil.OAuthErrorHandler(c, errWithCode)
+		return
+	}
+
+	c.Header("Cache-Control", "no-store")
+	c.Header("Pragma", "no-cache")
+	c.JSON(http.StatusOK, token)
+}