lavender/server/pages/pages.go

package pages

import (
	"embed"
	_ "embed"
	"errors"
	"github.com/1f349/overlapfs"
	"html/template"
	"io"
	"io/fs"
	"log"
	"os"
	"path/filepath"
	"sync"
)

var (
	//go:embed *.go.html
	flowPages     embed.FS
	flowTemplates *template.Template
	loadOnce      sync.Once
)

func LoadPages(wd string) (err error) {
	loadOnce.Do(func() {
		var o fs.FS = flowPages
		if wd != "" {
			wwwDir := filepath.Join(wd, "www")
			err = os.Mkdir(wwwDir, os.ModePerm)
			if err != nil && !errors.Is(err, os.ErrExist) {
				return
			}
			wdFs := os.DirFS(wwwDir)
			o = overlapfs.OverlapFS{A: flowPages, B: wdFs}
		}
		flowTemplates, err = template.ParseFS(o, "*.go.html")
	})
	return err
}

func RenderPageTemplate(wr io.Writer, name string, data any) {
	err := flowTemplates.ExecuteTemplate(wr, name+".go.html", data)
	if err != nil {
		log.Printf("Failed to render page: %s: %s\n", name, err)
	}
}