package web

import (
	"bytes"
	"fmt"
	"html/template"

	"git.fabledsword.com/bvandeusen/minstrel/internal/config"
)

// applyBrandingTemplate parses the given HTML source as an html/template,
// substitutes the branding fields, and returns the rendered bytes. Used
// by Handler at construction time so each request serves cached output
// rather than re-rendering. The Vite build (T4) injects the {{ .AppName }}
// and similar tokens into the head of build/index.html; in dev (vite dev)
// no tokens are present and the template effectively returns the source
// unchanged.
//
// html/template's context-aware escaping handles XSS for both the
// HTML-attribute contexts (e.g. <meta content="...">) and the JS-string
// context inside <script>window.__MINSTREL__ = { appName: "..." }</script>.
func applyBrandingTemplate(htmlSrc string, branding config.BrandingConfig) ([]byte, error) {
	tpl, err := template.New("index").Parse(htmlSrc)
	if err != nil {
		return nil, fmt.Errorf("parse index template: %w", err)
	}
	var buf bytes.Buffer
	if err := tpl.Execute(&buf, branding); err != nil {
		return nil, fmt.Errorf("execute index template: %w", err)
	}
	return buf.Bytes(), nil
}