const (
	RespAccept   = SimpleResponse(ActAccept)
	RespContinue = SimpleResponse(ActContinue)
	RespDiscard  = SimpleResponse(ActDiscard)
	RespReject   = SimpleResponse(ActReject)
	RespTempFail = SimpleResponse(ActTempFail)
)

const MaxBodyChunk = 65535

var ErrServerClosed = errors.New("milter: server closed")

var ErrUnsupportedMilterVersion = fmt.Errorf("milter: negotiate: unsupported milter version")

type Action struct {
	Code ActionCode

	// SMTP code if Code == ActReplyCode.
	SMTPCode int
	// Reply text if Code == ActReplyCode.
	SMTPText string
}

type ActionCode byte

const (
	ActAccept    ActionCode = 'a' // SMFIR_ACCEPT
	ActContinue  ActionCode = 'c' // SMFIR_CONTINUE
	ActDiscard   ActionCode = 'd' // SMFIR_DISCARD
	ActReject    ActionCode = 'r' // SMFIR_REJECT
	ActTempFail  ActionCode = 't' // SMFIR_TEMPFAIL
	ActReplyCode ActionCode = 'y' // SMFIR_REPLYCODE

	// [v6]
	ActSkip ActionCode = 's' // SMFIR_SKIP
)

type Client struct {
	// contains filtered or unexported fields
}

type ClientOptions struct {
	Dialer       Dialer
	ReadTimeout  time.Duration
	WriteTimeout time.Duration
	ActionMask   OptAction
	ProtocolMask OptProtocol
}

type ClientSession struct {

	// Bitmask of negotiated action options.
	ActionOpts OptAction

	// Bitmask of negotiated protocol options.
	ProtocolOpts OptProtocol
	// contains filtered or unexported fields
}

type Code byte

const (
	CodeOptNeg Code = 'O' // SMFIC_OPTNEG
	CodeMacro  Code = 'D' // SMFIC_MACRO
	CodeConn   Code = 'C' // SMFIC_CONNECT
	CodeQuit   Code = 'Q' // SMFIC_QUIT
	CodeHelo   Code = 'H' // SMFIC_HELO
	CodeMail   Code = 'M' // SMFIC_MAIL
	CodeRcpt   Code = 'R' // SMFIC_RCPT
	CodeHeader Code = 'L' // SMFIC_HEADER
	CodeEOH    Code = 'N' // SMFIC_EOH
	CodeBody   Code = 'B' // SMFIC_BODY
	CodeEOB    Code = 'E' // SMFIC_BODYEOB
	CodeAbort  Code = 'A' // SMFIC_ABORT
	CodeData   Code = 'T' // SMFIC_DATA

	// [v6]
	CodeQuitNewConn Code = 'K' // SMFIC_QUIT_NC
)

type CustomResponse struct {
	// contains filtered or unexported fields
}

type Dialer interface {
	Dial(network string, addr string) (net.Conn, error)
}

type Message struct {
	Code byte
	Data []byte
}

type Milter interface {
	// Connect is called to provide SMTP connection data for incoming message.
	// Suppress with OptNoConnect.
	Connect(host string, family string, port uint16, addr net.IP, m *Modifier) (Response, error)

	// Helo is called to process any HELO/EHLO related filters. Suppress with
	// OptNoHelo.
	Helo(name string, m *Modifier) (Response, error)

	// MailFrom is called to process filters on envelope FROM address. Suppress
	// with OptNoMailFrom.
	MailFrom(from string, m *Modifier) (Response, error)

	// RcptTo is called to process filters on envelope TO address. Suppress with
	// OptNoRcptTo.
	RcptTo(rcptTo string, m *Modifier) (Response, error)

	// Header is called once for each header in incoming message. Suppress with
	// OptNoHeaders.
	Header(name string, value string, m *Modifier) (Response, error)

	// Headers is called when all message headers have been processed. Suppress
	// with OptNoEOH.
	Headers(h textproto.MIMEHeader, m *Modifier) (Response, error)

	// BodyChunk is called to process next message body chunk data (up to 64KB
	// in size). Suppress with OptNoBody.
	BodyChunk(chunk []byte, m *Modifier) (Response, error)

	// Body is called at the end of each message. All changes to message's
	// content & attributes must be done here.
	Body(m *Modifier) (Response, error)

	// Abort is called is the current message has been aborted. All message data
	// should be reset to prior to the Helo callback. Connection data should be
	// preserved.
	Abort(m *Modifier) error
}

type Modifier struct {
	Macros  map[string]string
	Headers textproto.MIMEHeader
	// contains filtered or unexported fields
}

type ModifyActCode byte

const (
	ActAddRcpt      ModifyActCode = '+' // SMFIR_ADDRCPT
	ActDelRcpt      ModifyActCode = '-' // SMFIR_DELRCPT
	ActReplBody     ModifyActCode = 'b' // SMFIR_ACCEPT
	ActAddHeader    ModifyActCode = 'h' // SMFIR_ADDHEADER
	ActChangeHeader ModifyActCode = 'm' // SMFIR_CHGHEADER
	ActInsertHeader ModifyActCode = 'i' // SMFIR_INSHEADER
	ActQuarantine   ModifyActCode = 'q' // SMFIR_QUARANTINE

	// [v6]
	ActChangeFrom ModifyActCode = 'e' // SMFIR_CHGFROM
)

type ModifyAction struct {
	Code ModifyActCode

	// Recipient to add/remove if Code == ActAddRcpt or ActDelRcpt.
	Rcpt string

	// New envelope sender if Code = ActChangeFrom.
	From string

	// ESMTP arguments for envelope sender if Code = ActChangeFrom.
	FromArgs []string

	// Portion of body to be replaced if Code == ActReplBody.
	Body []byte

	// Index of the header field to be changed if Code = ActChangeHeader or Code = ActInsertHeader.
	// Index is 1-based and is per value of HdrName.
	// E.g. HeaderIndex = 3 and HdrName = "DKIM-Signature" mean "change third
	// DKIM-Signature field". Order is the same as of HeaderField calls.
	HeaderIndex uint32

	// Header field name to be added/changed if Code == ActAddHeader or
	// ActChangeHeader or ActInsertHeader.
	HeaderName string

	// Header field value to be added/changed if Code == ActAddHeader or
	// ActChangeHeader or ActInsertHeader. If set to empty string - the field
	// should be removed.
	HeaderValue string

	// Quarantine reason if Code == ActQuarantine.
	Reason string
}

type NoOpMilter struct{}

type OptAction uint32

const (
	OptAddHeader    OptAction = 1 << 0 // SMFIF_ADDHDRS
	OptChangeBody   OptAction = 1 << 1 // SMFIF_CHGBODY
	OptAddRcpt      OptAction = 1 << 2 // SMFIF_ADDRCPT
	OptRemoveRcpt   OptAction = 1 << 3 // SMFIF_DELRCPT
	OptChangeHeader OptAction = 1 << 4 // SMFIF_CHGHDRS
	OptQuarantine   OptAction = 1 << 5 // SMFIF_QUARANTINE

	// [v6]
	OptChangeFrom      OptAction = 1 << 6 // SMFIF_CHGFROM
	OptAddRcptWithArgs OptAction = 1 << 7 // SMFIF_ADDRCPT_PAR
	OptSetSymList      OptAction = 1 << 8 // SMFIF_SETSYMLIST
)

type OptProtocol uint32

const (
	OptNoConnect  OptProtocol = 1 << 0 // SMFIP_NOCONNECT
	OptNoHelo     OptProtocol = 1 << 1 // SMFIP_NOHELO
	OptNoMailFrom OptProtocol = 1 << 2 // SMFIP_NOMAIL
	OptNoRcptTo   OptProtocol = 1 << 3 // SMFIP_NORCPT
	OptNoBody     OptProtocol = 1 << 4 // SMFIP_NOBODY
	OptNoHeaders  OptProtocol = 1 << 5 // SMFIP_NOHDRS
	OptNoEOH      OptProtocol = 1 << 6 // SMFIP_NOEOH
	OptNoUnknown  OptProtocol = 1 << 8 // SMFIP_NOUNKNOWN
	OptNoData     OptProtocol = 1 << 9 // SMFIP_NODATA

	// [v6] MTA supports ActSkip
	OptSkip OptProtocol = 1 << 10 // SMFIP_SKIP
	// [v6] Filter wants rejected RCPTs
	OptRcptRej OptProtocol = 1 << 11 // SMFIP_RCPT_REJ

	// Milter will not send action response for the following MTA messages
	OptNoHeaderReply OptProtocol = 1 << 7 // SMFIP_NR_HDR, SMFIP_NOHREPL
	// [v6]
	OptNoConnReply    OptProtocol = 1 << 12 // SMFIP_NR_CONN
	OptNoHeloReply    OptProtocol = 1 << 13 // SMFIP_NR_HELO
	OptNoMailReply    OptProtocol = 1 << 14 // SMFIP_NR_MAIL
	OptNoRcptReply    OptProtocol = 1 << 15 // SMFIP_NR_RCPT
	OptNoDataReply    OptProtocol = 1 << 16 // SMFIP_NR_DATA
	OptNoUnknownReply OptProtocol = 1 << 17 // SMFIP_NR_UNKN
	OptNoEOHReply     OptProtocol = 1 << 18 // SMFIP_NR_EOH
	OptNoBodyReply    OptProtocol = 1 << 19 // SMFIP_NR_BODY

	// [v6]
	OptHeaderLeadingSpace OptProtocol = 1 << 20 // SMFIP_HDR_LEADSPC
)

type ProtoFamily byte

const (
	FamilyUnknown ProtoFamily = 'U' // SMFIA_UNKNOWN
	FamilyUnix    ProtoFamily = 'L' // SMFIA_UNIX
	FamilyInet    ProtoFamily = '4' // SMFIA_INET
	FamilyInet6   ProtoFamily = '6' // SMFIA_INET6
)

type Response interface {
	Response() *Message
	Continue() bool
}

type Server struct {
	NewMilter func() Milter
	Actions   OptAction
	Protocol  OptProtocol
	// contains filtered or unexported fields
}

type SimpleResponse byte