package web

import (
	"fmt"
	"html/template"
	"log/slog"
	"net/http"
)

// PageData is the view model passed to every HTML template.
type PageData struct {
	Active string
	Build  BuildInfo
}

// Renderer parses and executes HTML templates from the embedded FS.
type Renderer struct {
	tmpls map[string]*template.Template
}

var pageNames = []string{"adults", "juniors", "payments", "sync", "flush_cache"}

// NewRenderer parses all templates from the embedded FS.
// A parse failure should be treated as a startup-time fatal error.
func NewRenderer() (*Renderer, error) {
	tmpls := make(map[string]*template.Template, len(pageNames))
	for _, name := range pageNames {
		t, err := template.New("").ParseFS(templateFS,
			"templates/base.tmpl",
			"templates/partials/nav.tmpl",
			"templates/partials/footer.tmpl",
			"templates/"+name+".tmpl",
		)
		if err != nil {
			return nil, fmt.Errorf("parse template %q: %w", name, err)
		}
		tmpls[name] = t
	}
	return &Renderer{tmpls: tmpls}, nil
}

// Render executes the named template with data, writing to w.
func (r *Renderer) Render(w http.ResponseWriter, name string, data any) {
	t, ok := r.tmpls[name]
	if !ok {
		http.Error(w, "template not found: "+name, http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	if err := t.ExecuteTemplate(w, "base", data); err != nil {
		slog.Error("render template", "name", name, "err", err)
	}
}