package mpd

import (
	"encoding/xml"
	"fmt"
	"regexp"
	"strings"
)

var reDefaultKID = regexp.MustCompile(`(?i)default_KID="([^"]+)"`)

// KIDToUUID normalizes any hex-ish KID spelling to dashed UUID form.
func KIDToUUID(kid string) (string, error) {
	var b strings.Builder
	for _, r := range kid {
		if (r >= '0' && r <= '9') || (r >= 'a' && r <= 'f') || (r >= 'A' && r <= 'F') {
			b.WriteRune(r)
		}
	}
	h := strings.ToLower(b.String())
	if len(h) != 32 {
		return "", fmt.Errorf("invalid KID %q", kid)
	}
	return fmt.Sprintf("%s-%s-%s-%s-%s", h[0:8], h[8:12], h[12:16], h[16:20], h[20:32]), nil
}

// KIDHex strips dashes and lowercases a KID (the form used as a map key).
func KIDHex(kid string) string {
	return strings.ToLower(strings.ReplaceAll(kid, "-", ""))
}

// ExtractDefaultKID pulls cenc:default_KID out of an MPD, as dashed UUID.
func ExtractDefaultKID(xmlText string) string {
	m := reDefaultKID.FindStringSubmatch(xmlText)
	if len(m) < 2 {
		return ""
	}
	u, err := KIDToUUID(m[1])
	if err != nil {
		return ""
	}
	return u
}

// XMLEscape escapes text for inclusion in an XML element body.
func XMLEscape(s string) string {
	var b strings.Builder
	_ = xml.EscapeText(&b, []byte(s))
	return b.String()
}