package imapx

import (
	"crypto/md5"
	"fmt"
	"strings"

	"github.com/emersion/go-imap/v2"
)

func MessageKey(env *imap.Envelope, size int64) string {
	if env != nil && env.MessageID != "" {
		return env.MessageID
	}
	var b strings.Builder
	if env != nil {
		b.WriteString(addrList(env.From))
		b.WriteByte('|')
		b.WriteString(addrList(env.To))
		b.WriteByte('|')
		b.WriteString(env.Subject)
		b.WriteByte('|')
		b.WriteString(env.Date.UTC().Format("2006-01-02T15:04:05Z"))
	}
	b.WriteByte('|')
	fmt.Fprintf(&b, "%d", size)
	sum := md5.Sum([]byte(b.String()))
	return fmt.Sprintf("h:%x", sum)
}

func addrList(addrs []imap.Address) string {
	parts := make([]string, 0, len(addrs))
	for _, a := range addrs {
		parts = append(parts, a.Mailbox+"@"+a.Host)
	}
	return strings.Join(parts, ",")
}