feat(smalltrip,problems): http handler for problems (wip)

smalltrip/problem/http.go

@@ -0,0 +1,125 @@
+package problem
+
+import (
+	"encoding/json"
+	"encoding/xml"
+	"fmt"
+	"net/http"
+	"strings"
+)
+
+func ProblemHandler(p any) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		h := r.Header.Get("Accept")
+		if strings.Contains(h, "application/xml") || strings.Contains(h, ProblemMediaTypeXML) {
+			ProblemHandlerXML(p).ServeHTTP(w, r)
+			return
+		}
+		ProblemHandlerJSON(p).ServeHTTP(w, r)
+	})
+}
+
+func ProblemHandlerXML(p any) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// w.Header().Set("Content-Type", ProblemMediaTypeXML)
+		w.Header().Set("Content-Type", "application/xml")
+
+		b, err := xml.Marshal(p)
+		if err != nil {
+			ProblemHandlerJSON(p).ServeHTTP(w, r)
+			return
+		}
+
+		w.WriteHeader(GetStatus(p))
+
+		_, err = w.Write(b)
+		if err != nil {
+			ProblemHandlerJSON(p).ServeHTTP(w, r)
+		}
+	})
+}
+
+func ProblemHandlerJSON(p any) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", ProblemMediaTypeJSON)
+
+		b, err := json.Marshal(p)
+		if err != nil {
+			ProblemHandlerText(p).ServeHTTP(w, r)
+			return
+		}
+
+		w.WriteHeader(GetStatus(p))
+
+		_, err = w.Write(b)
+		if err != nil {
+			ProblemHandlerText(p).ServeHTTP(w, r)
+		}
+	})
+}
+
+func ProblemHandlerText(p any) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "text/plain")
+
+		w.WriteHeader(GetStatus(p))
+
+		var s string
+		if p, ok := p.(Problem); ok {
+			s = fmt.Sprintf(
+				"Type: %s\n"+
+					"Status: %3d\n"+
+					"Title: %s\n"+
+					"Detail: %s\n"+
+					"Instance: %s\n\n"+
+					p.Type,
+				p.Status,
+				p.Title,
+				p.Detail,
+				p.Instance,
+			)
+		}
+		if p, ok := p.(*Problem); ok {
+			s = fmt.Sprintf(
+				"Type: %s\n"+
+					"Status: %3d\n"+
+					"Title: %s\n"+
+					"Detail: %s\n"+
+					"Instance: %s\n\n"+
+					p.Type,
+				p.Status,
+				p.Title,
+				p.Detail,
+				p.Instance,
+			)
+		}
+
+		_, err := w.Write(fmt.Appendf([]byte{}, "%s%+v\n\n%#v", s, p, p))
+		if err != nil {
+			_, _ = w.Write(fmt.Append([]byte{},
+				"Ok, what should we do at this point? You fucked up so bad that this message "+
+					"shouldn't even be able to be sent in the first place. If you are a normal user I'm "+
+					"so sorry for you to be reading this. If you're a developer, go fix your ResponseWriter "+
+					"implementation, because this should never happen in any normal codebase. "+
+					"I hope for the life of anyone you love you don't use this message in some "+
+					"error checking or any sort of API-contract, because there will be no more hope "+
+					"for you or your project. May God or any other divinity that you may "+
+					"or may not believe be with you when trying to fix this mistake, you will need it.",
+				// If someone use this as part of the API-contract I'll not even be surprised.
+				// So any change to this message is still considered a breaking change.
+			))
+		}
+	})
+}
+
+func GetStatus(p any) int {
+	if p, ok := p.(interface{ StatusCode() int }); ok {
+		return p.StatusCode()
+	}
+	return http.StatusInternalServerError
+}
+
+const (
+	ProblemMediaTypeJSON = "application/problem+json"
+	ProblemMediaTypeXML  = "application/problem+xml"
+)

smalltrip/problem/problem.go

@@ -3,6 +3,7 @@ package problem
 import (
 	"encoding/xml"
 	"fmt"
+	"net/http"
 	"slices"
 )
 
@@ -43,6 +44,10 @@ func (p Problem) StatusCode() int {
 	return p.Status
 }
 
+func (p Problem) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	p.handler(p).ServeHTTP(w, r)
+}
+
 func WithType(t string) Option {
 	return func(p *Problem) {
 		p.Type = t