package artifacts

import (
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"io"
	"time"
)

// NewRunID returns a run ID in format: YYYYMMDDTHHMMSSZ-xxxxxxxx.
func NewRunID() (string, error) {
	return NewRunIDWith(time.Now().UTC(), rand.Reader)
}

// NewRunIDWith returns a run ID in format: YYYYMMDDTHHMMSSZ-xxxxxxxx
// using an injected timestamp and randomness source.
func NewRunIDWith(now time.Time, random io.Reader) (string, error) {
	if random == nil {
		random = rand.Reader
	}

	var suffix [4]byte
	if _, err := io.ReadFull(random, suffix[:]); err != nil {
		return "", fmt.Errorf("generate run id random suffix: %w", err)
	}

	ts := now.UTC().Format("20060102T150405Z")
	return ts + "-" + hex.EncodeToString(suffix[:]), nil
}