package main

import (
	"html/template"
	"io/fs"
	"os"
	"sync"
)

var devMode bool

// assetFS defaults to the embedded FS so package-level initializers (e.g. icon
// vars in render.go) can read assets before main() runs. initAssets() swaps it
// for os.DirFS when -dev is set.
var assetFS fs.FS = assets

func initAssets(dev bool) {
	devMode = dev
	if dev {
		assetFS = os.DirFS(".")
	}
}

// readAsset reads a file from the asset FS (embedded in prod, live disk in dev).
func readAsset(path string) ([]byte, error) {
	return fs.ReadFile(assetFS, path)
}

// tmplLoader holds a lazily-parsed template. In dev mode it re-parses on every
// get() call so HTML changes are visible without recompiling.
type tmplLoader struct {
	name     string
	patterns []string
	once     sync.Once
	t        *template.Template
}

// newTemplate creates a tmplLoader. name is the root template name passed to
// template.New; patterns are the glob/path arguments forwarded to ParseFS.
func newTemplate(name string, patterns ...string) *tmplLoader {
	return &tmplLoader{name: name, patterns: patterns}
}

func (l *tmplLoader) get() *template.Template {
	if devMode {
		return template.Must(template.New(l.name).ParseFS(assetFS, l.patterns...))
	}
	l.once.Do(func() {
		l.t = template.Must(template.New(l.name).ParseFS(assetFS, l.patterns...))
	})
	return l.t
}