package main

import (
	"bytes"
	"encoding/json"
	"encoding/xml"
	"html/template"
	"log"
	"net/http"
)

func renderTemplate[T any](w http.ResponseWriter, r *http.Request, status int, templates *template.Template, template string, response T) error {
	buffer := bytes.Buffer{}
	if err := templates.Lookup(template).Execute(&buffer, response); err == nil {
		w.Header().Add("content-type", "text/html; charset=utf-8")
		w.WriteHeader(status)
		_, err = w.Write(buffer.Bytes())
		return err
	} else {
		return onError(w, err)
	}
}

func onError(w http.ResponseWriter, err error) error {
	w.WriteHeader(http.StatusInternalServerError)
	log.Printf("failed writing response: %v", err)
	_, _ = w.Write([]byte{})
	return err
}

func render[T any](w http.ResponseWriter, r *http.Request, status int, response T) error {
	switch r.Header.Get("accept") {
	case "application/xml":
		fallthrough
	case "text/xml":
		if body, err := xml.MarshalIndent(response, "", "  "); err == nil {
			// we return the same type as requested
			w.Header().Add("content-type", r.Header.Get("accept")+"; charset=utf-8")
			w.WriteHeader(status)
			_, err = w.Write([]byte(xml.Header))
			_, err = w.Write(body)
			return err
		} else {
			return onError(w, err)
		}
	case "application/json":
		fallthrough
	default:
		if body, err := json.MarshalIndent(response, "", "  "); err == nil {
			w.Header().Add("content-type", "application/json; charset=utf-8")
			w.WriteHeader(status)
			_, err = w.Write(body)
			return err
		} else {
			return onError(w, err)
		}
	}
}