// Package util holds small shared helpers used across internal packages to
// avoid divergent same-named copies.
package util

import (
	"crypto/rand"
	"fmt"
	"strings"
	"time"
)

// FirstNonEmpty returns the first trimmed-non-empty value, or "" when none of
// the values are non-empty. Callers that need a specific fallback for the
// all-empty case should apply it explicitly at the call site.
func FirstNonEmpty(values ...string) string {
	for _, v := range values {
		if strings.TrimSpace(v) != "" {
			return v
		}
	}
	return ""
}

// RandomRequestID returns a random v4 UUID string, matching the format the
// Zhanlu plugin sends in the `request` header of every gateway call
// (crypto.randomUUID()). Extracted so the login and phone-code paths share
// one implementation.
func RandomRequestID() string {
	b := make([]byte, 16)
	if _, err := rand.Read(b); err != nil {
		return fmt.Sprintf("%d", time.Now().UnixNano())
	}
	b[6] = (b[6] & 0x0f) | 0x40
	b[8] = (b[8] & 0x3f) | 0x80
	return fmt.Sprintf("%x-%x-%x-%x-%x", b[0:4], b[4:6], b[6:8], b[8:10], b[10:])
}