package imap

import (
	"strings"

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

func isAllowedFlag(flag imap.Flag) bool {
	if len(flag) == 0 { // RFC 9051 requires one or more characters
		return false
	}
	// system flags start with "\" and are defined per RFC 9051
	if strings.HasPrefix(string(flag), "\\") {
		switch flag {
		// \Recent was deprecated in IMAP 4 rev.2
		case imap.FlagSeen, imap.FlagAnswered, imap.FlagFlagged, imap.FlagDeleted, imap.FlagDraft:
			return true
		default:
			return false
		}
	}

	// Clients are generally free in adding keywords
	return true
}

func toIMAPFlags(flags []string) []imap.Flag {
	out := make([]imap.Flag, 0, len(flags))
	for _, flag := range flags {
		if flag == "" {
			continue
		}
		out = append(out, imap.Flag(flag))
	}
	if len(out) == 0 {
		return nil
	}
	return out
}

func fromIMAPFlags(flags []imap.Flag) []string {
	out := make([]string, 0, len(flags))
	for _, f := range flags {
		if string(f) == "" {
			continue
		}
		out = append(out, string(f))
	}
	return out
}