package main

import (
	"embed"
	"encoding/json"
	"fmt"
	"html/template"
	"log"
	"net/http"
)

//go:embed static
var staticFS embed.FS

//go:embed templates
var templatesFS embed.FS

// Error model
type Error struct {
	Title   string `json:"title"`
	Message string `json:"message"`
}

func main() {
	port := "5900"

	http.Handle("/static/", http.FileServer(http.FS(staticFS)))
	http.HandleFunc("/", errorHandler)

	log.Printf("Listening on :%s...", port)
	err := http.ListenAndServe(fmt.Sprintf(":%s", port), nil)
	if err != nil {
		log.Fatal(err)
	}
}

func errorHandler(w http.ResponseWriter, r *http.Request) {
	errorCode := r.URL.Query().Get("error")

	// Load error messages from JSON file
	jsonData, err := templatesFS.ReadFile("templates/errors.json")
	if err != nil {
		generateInternalServerError(w, err)
		return
	}
	errors := make(map[string]Error)
	err = json.Unmarshal(jsonData, &errors)
	if err != nil {
		generateInternalServerError(w, err)
		return
	}
	errorData := errors[errorCode]
	if errorData.Title == "" {
		errorData.Title = "Error"
		errorData.Message = "An error occurred."
	}

	// Render error page
	tmpl, err := templatesFS.ReadFile("templates/error.html")
	if err != nil {
		generateInternalServerError(w, err)
		return
	}
	t, err := template.New("error").Parse(string(tmpl))
	if err != nil {
		generateInternalServerError(w, err)
		return
	}
	t.Execute(w, errorData)
}

func generateInternalServerError(w http.ResponseWriter, err error) {
	log.Println(err)
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(http.StatusInternalServerError)
	w.Write([]byte(`{"error": "Internal Server Error"}`))
}