summercms/modules/wristband/redirect_html.go

package wristband

import (
	"net/http"
	"strings"
)

// htmlEscapePHP ports PHP's htmlspecialchars($s, ENT_QUOTES, 'UTF-8') byte
// for byte: Go's stdlib html.EscapeString differs on the quote entities
// ('/" vs PHP's '/"), which would diverge from the
// recorded redirect body whenever a redirect_uri or state value contains a
// quote character.
func htmlEscapePHP(s string) string {
	var b strings.Builder
	b.Grow(len(s))
	for _, r := range s {
		switch r {
		case '&':
			b.WriteString("&")
		case '"':
			b.WriteString(""")
		case '\'':
			b.WriteString("'")
		case '<':
			b.WriteString("&lt;")
		case '>':
			b.WriteString("&gt;")
		default:
			b.WriteRune(r)
		}
	}
	return b.String()
}

// writeRedirectHTML ports Laravel/Symfony's RedirectResponse default HTML
// body byte-for-byte (T-08-OPEN-REDIRECT/D-04). Go's net/http never emits a
// body for a 3xx Location redirect; every wristband redirect needs this
// exact body plus Content-Type because real recorded PHP traffic includes
// it, and an unchanged browser-based client (the Nuxt /connect handoff)
// observes it. Cache-Control is the caller's responsibility -- callers set
// it before invoking this helper because its value differs between the
// authorize success path and error redirects versus other endpoints.
func writeRedirectHTML(w http.ResponseWriter, status int, target string) {
	escaped := htmlEscapePHP(target)
	var b strings.Builder
	b.WriteString("<!DOCTYPE html>\n<html>\n    <head>\n        <meta charset=\"UTF-8\" />\n        <meta http-equiv=\"refresh\" content=\"0;url='")
	b.WriteString(escaped)
	b.WriteString("'\" />\n\n        <title>Redirecting to ")
	b.WriteString(escaped)
	b.WriteString("</title>\n    </head>\n    <body>\n        Redirecting to <a href=\"")
	b.WriteString(escaped)
	b.WriteString("\">")
	b.WriteString(escaped)
	b.WriteString("</a>.\n    </body>\n</html>")

	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.Header().Set("Location", target)
	w.WriteHeader(status)
	_, _ = w.Write([]byte(b.String()))
}