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pkg/httpx/json.go

@@ -0,0 +1,45 @@
+package httpx
+
+import (
+	"encoding/json"
+	"net/http"
+)
+
+var jsonInternalServerErr = []byte(`{"status":"internal server error"}`)
+var jsonNotFound = []byte(`{"status":"not found"}`)
+
+// JSON creates a new JSONHandler
+func JSON[T any](f func(r *http.Request) (T, error)) JSONHandler[T] {
+	return JSONHandler[T](f)
+}
+
+// JSONHandler implements [http.Handler] by returning values as json to the caller.
+// In case of an error, a generic "internal server error" message is returned.
+type JSONHandler[T any] func(r *http.Request) (T, error)
+
+// ServeHTTP calls j(r) and returns json
+func (j JSONHandler[T]) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	// call the function
+	result, err := j(r)
+
+	// entity not found
+	if err == ErrNotFound {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusNotFound)
+		w.Write(jsonNotFound)
+		return
+	}
+
+	// handle other errors
+	if err != nil {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write(jsonInternalServerErr)
+		return
+	}
+
+	// write out the response as json
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusOK)
+	json.NewEncoder(w).Encode(result)
+}