package pop3

import (
    "errors"
    "fmt"
)

var (
    // Package pop3 will never transmit credentials in the clear.
    ErrNoTLS = errors.New("no TLS")

    // E.g. maximum line length violated or unknown status indicator sent.
    ErrProtocol = errors.New("pop3: protocol not followed")

    // E.g. "+OK 5 oktets" instead of "+OK 5 octets".
    ErrSyntax = errors.New("pop3: wrong syntax")

    // POP3 semantics were not followed, e.g. message numbers are duplicated.
    ErrSemantics = errors.New("pop3: semantically incoherent")
)

// ERR encapsulates a "-ERR" POP3 response line.
type ERR struct { Diagnostics string }
func (err *ERR) Error() string {
    return fmt.Sprintf("pop3 -ERR: %q", string(err.Diagnostics))
}