package handlers

import (
	"html/template"
	"log/slog"
	"net/http"
	"path/filepath"

	"qbank/internal/auth"
)

var tmplFuncs = template.FuncMap{
	"inc": func(i int) int { return i + 1 },
}

// Renderer parses and executes HTML templates from a directory.
type Renderer struct {
	dir string
}

func NewRenderer(dir string) *Renderer { return &Renderer{dir: dir} }

// Render executes layout.html + <name>.html, passing data to the "layout" template.
func (r *Renderer) Render(w http.ResponseWriter, status int, name string, data any) {
	t, err := template.New("").Funcs(tmplFuncs).ParseFiles(
		filepath.Join(r.dir, "layout.html"),
		filepath.Join(r.dir, name+".html"),
	)
	if err != nil {
		slog.Error("parse template", "name", name, "err", err)
		http.Error(w, "internal error", http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.WriteHeader(status)
	if err := t.ExecuteTemplate(w, "layout", data); err != nil {
		slog.Error("execute template", "name", name, "err", err)
	}
}

// HTTPError writes a plain-text HTTP error.
func HTTPError(w http.ResponseWriter, status int) {
	http.Error(w, http.StatusText(status), status)
}

// BaseData builds the common template map (User, CSRFToken, Flash).
func BaseData(a *auth.Manager, r *http.Request) map[string]any {
	return map[string]any{
		"User":      auth.UserFromCtx(r.Context()),
		"CSRFToken": a.CSRFToken(r),
		"Flash":     a.PopFlash(r),
	}
}