package outpost

import (
	"crypto/rand"
	"encoding/base32"
	"time"
)

// crockford is the Crockford base32 alphabet: no I, L, O, or U, so identifiers
// read aloud unambiguously and compare case-insensitively.
const crockford = "0123456789ABCDEFGHJKMNPQRSTVWXYZ"

var idEncoding = base32.NewEncoding(crockford).WithPadding(base32.NoPadding)

// newID returns a 26-character identifier: 48 bits of millisecond timestamp
// followed by 80 bits of randomness, encoded as Crockford base32. The timestamp
// makes identifiers roughly sortable and readable in logs; uniqueness rests on
// the 80 random bits.
func newID() (string, error) {
	var b [16]byte
	ms := time.Now().UnixMilli()
	for i := 5; i >= 0; i-- {
		b[i] = byte(ms >> (8 * (5 - i)))
	}
	if _, err := rand.Read(b[6:]); err != nil {
		return "", err
	}
	return idEncoding.EncodeToString(b[:]), nil
}