package status

import (
	"embed"
	"html/template"
	"io/fs"
	"net/http"
	"sync"
	"sync/atomic"

	"github.com/pkg/errors"
	"gitlab.com/wpetit/goweb/logger"
)

//go:embed templates/*.gotpl
var templates embed.FS

//go:embed public/*
var public embed.FS

type Handler struct {
	status *atomic.Value

	public    http.Handler
	templates *template.Template

	init    sync.Once
	initErr error
}

// ServeHTTP implements http.Handler.
func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	h.init.Do(func() {
		root, err := fs.Sub(public, "public")
		if err != nil {
			h.initErr = errors.WithStack(err)
			return
		}

		h.public = http.FileServer(http.FS(root))

		tmpl, err := template.ParseFS(templates, "templates/*.gotpl")
		if err != nil {
			h.initErr = errors.WithStack(err)
			return
		}

		h.templates = tmpl
	})
	if h.initErr != nil {
		logger.Error(r.Context(), "could not initialize handler", logger.E(h.initErr))
		http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)

		return
	}

	switch r.URL.Path {
	case "/":
		h.serveIndex(w, r)
	default:
		h.public.ServeHTTP(w, r)
	}
}

func (h *Handler) serveIndex(w http.ResponseWriter, r *http.Request) {
	data := h.status.Load()

	if err := h.templates.ExecuteTemplate(w, "index.html.gotpl", data); err != nil {
		logger.Error(r.Context(), "could not render template", logger.E(errors.WithStack(err)))
		return
	}
}

var _ http.Handler = &Handler{}