website/api/v1: implement request route

templates: added HasField method that indicates if the first argument has
a field named after the second.

util: implement RedirectToServer that uses http.ServerContextKey to get
the *http.Server used for the request and passes its arguments back into
its srv.Handler.ServeHTTP method.

templates: theme middleware now uses util.RedirectToServer

util: implement ChangeRequestMethod

templates/functions.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"html/template"
+	"reflect"
 	"time"
 
 	radio "github.com/R-a-dio/valkyrie"
@@ -30,6 +31,13 @@ var fnMap = map[string]any{
 	"Sub":                         func(a, b int64) int64 { return a - b },
 	"CalculateSubmissionCooldown": radio.CalculateSubmissionCooldown,
 	"AllUserPermissions":          radio.AllUserPermissions,
+	"HasField":                    HasField,
+}
+
+func HasField(v any, name string) bool {
+	rv := reflect.ValueOf(v)
+	rv = reflect.Indirect(rv)
+	return rv.FieldByName(name).IsValid()
 }
 
 func PrintJSON(v any) (template.HTML, error) {

templates/middleware.go

@@ -95,13 +95,11 @@ func SetThemeHandler(cookieName string, resolve func(string) string) http.Handle
 		// and change the theme so the new page actually uses our new theme set
 		r = r.WithContext(SetTheme(r.Context(), theme, true))
 
-		srv := r.Context().Value(http.ServerContextKey)
-		if srv == nil {
-			hlog.FromRequest(r).Error().Msg("SetThemeHandler used with no server")
+		err := util.RedirectToServer(w, r)
+		if err != nil {
+			hlog.FromRequest(r).Error().Err(err).Msg("SetThemeHandler")
 			w.WriteHeader(http.StatusOK)
 			return
 		}
-
-		srv.(*http.Server).Handler.ServeHTTP(w, r)
 	})
 }

util/util.go

@@ -11,6 +11,7 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/R-a-dio/valkyrie/errors"
 	"github.com/R-a-dio/valkyrie/util/eventstream"
 	"github.com/go-chi/chi/v5"
 	"github.com/rs/zerolog"
@@ -33,13 +34,21 @@ func IsHTMX(r *http.Request) bool {
 }
 
 func RedirectBack(r *http.Request) *http.Request {
-	current, err := url.Parse(r.Header.Get("Hx-Current-Url"))
-	if err == nil {
-		r.URL = current
-	} else {
-		current, err = url.Parse(r.Referer())
+	var changed bool
+
+	if hxHeader := r.Header.Get("Hx-Current-Url"); hxHeader != "" {
+		current, err := url.Parse(hxHeader)
 		if err == nil {
 			r.URL = current
+			changed = true
+		}
+	}
+
+	if !changed {
+		current, err := url.Parse(r.Referer())
+		if err == nil {
+			r.URL = current
+			changed = true
 		}
 	}
 
@@ -56,6 +65,50 @@ func RedirectBack(r *http.Request) *http.Request {
 	return r
 }
 
+func ChangeRequestMethod(r *http.Request, method string) *http.Request {
+	r.Method = method
+
+	rCtx := r.Context().Value(chi.RouteCtxKey)
+	if rCtx != nil {
+		if chiCtx, ok := rCtx.(*chi.Context); ok {
+			chiCtx.RouteMethod = method
+		}
+	}
+
+	return r
+}
+
+type alreadyRedirectedKey struct{}
+
+// RedirectToServer looks up the http.Server associated with this request
+// and calls ServeHTTP again
+func RedirectToServer(w http.ResponseWriter, r *http.Request) error {
+	const op errors.Op = "util.RedirectToServer"
+	ctx := r.Context()
+
+	alreadyRedirected := ctx.Value(alreadyRedirectedKey{})
+	if alreadyRedirected != nil {
+		return errors.E(op, "request was already redirected once")
+	}
+
+	srv := ctx.Value(http.ServerContextKey)
+	if srv == nil {
+		return errors.E(op, "no server context key found")
+	}
+
+	httpSrv, ok := srv.(*http.Server)
+	if !ok {
+		return errors.E(op, "server context key did not contain *http.Server")
+	}
+
+	// add a context value so we know we've redirected internally
+	ctx = context.WithValue(r.Context(), alreadyRedirectedKey{}, struct{}{})
+
+	// and then send them off to be handled again
+	httpSrv.Handler.ServeHTTP(w, r.WithContext(ctx))
+	return nil
+}
+
 func AbsolutePath(dir string, path string) string {
 	if filepath.IsAbs(path) {
 		return path

website/api/v1/router.go

@@ -62,4 +62,5 @@ func (a *API) Route(r chi.Router) {
 	r.Get("/sse", a.sse.ServeHTTP)
 	r.Get("/search", a.SearchHTML)
 	r.Get("/song", a.GetSong)
+	r.Post("/request", a.PostRequest)
 }