statemachine.go

package dicompot

// Implements the network statemachine, as defined in P3.8 9.2.3.
// http://dicom.nema.org/medical/dicom/current/output/pdf/part08.pdf

import (
	"fmt"
	"io"
	"net"
	"strings"
	"time"

	"github.com/grailbio/go-dicom/dicomio"
	"github.com/grailbio/go-dicom/dicomuid"
	"github.com/nsmfoo/dicompot/dimse"
	"github.com/nsmfoo/dicompot/pdu"
	"github.com/sirupsen/logrus"
)

type stateType int

const (
	sta01 = stateType(1)
	sta02 = stateType(2)
	sta03 = stateType(3)
	sta04 = stateType(4)
	sta05 = stateType(5)
	sta06 = stateType(6)
	sta07 = stateType(7)
	sta08 = stateType(8)
	sta09 = stateType(9)
	sta10 = stateType(10)
	sta11 = stateType(11)
	sta12 = stateType(12)
	sta13 = stateType(13)
)

func (s *stateType) String() string {
	var description string
	switch *s {
	case sta01:
		description = "Idle"
	case sta02:
		description = "Transport connection open (Awaiting A-ASSOCIATE-RQ PDU)"
	case sta03:
		description = "Awaiting local A-ASSOCIATE response primitive (from local user)"
	case sta04:
		description = "Awaiting transport connection opening to complete (from local transport service)"
	case sta05:
		description = "Awaiting A-ASSOCIATE-AC or A-ASSOCIATE-RJ PDU"
	case sta06:
		description = "Association established and ready for data transfer"
	case sta07:
		description = "Awaiting A-RELEASE-RP PDU"
	case sta08:
		description = "Awaiting local A-RELEASE response primitive (from local user)"
	case sta09:
		description = "Release collision requestor side; awaiting A-RELEASE response (from local user)"
	case sta10:
		description = "Release collision acceptor side; awaiting A-RELEASE-RP PDU"
	case sta11:
		description = "Release collision requestor side; awaiting A-RELEASE-RP PDU"
	case sta12:
		description = "Release collision acceptor side; awaiting A-RELEASE response primitive (from local user)"
	case sta13:
		description = "Awaiting Transport Connection Close Indication (Association no longer exists)"
	}
	return fmt.Sprintf("sta%02d(%s)", *s, description)
}

type eventType int

const (
	evt01 = eventType(1)
	evt02 = eventType(2)
	evt03 = eventType(3)
	evt04 = eventType(4)
	evt05 = eventType(5)
	evt06 = eventType(6)
	evt07 = eventType(7)
	evt08 = eventType(8)
	evt09 = eventType(9)
	evt10 = eventType(10)
	evt11 = eventType(11)
	evt12 = eventType(12)
	evt13 = eventType(13)
	evt14 = eventType(14)
	evt15 = eventType(15)
	evt16 = eventType(16)
	evt17 = eventType(17)
	evt18 = eventType(18)
	evt19 = eventType(19)
)

func (e *eventType) String() string {
	var description string
	switch *e {
	case evt01:
		description = "A-ASSOCIATE request (local user)"
	case evt02:
		description = "Connection established (for service user)"
	case evt03:
		description = "A-ASSOCIATE-AC PDU (received on transport connection)"
	case evt04:
		description = "A-ASSOCIATE-RJ PDU (received on transport connection)"
	case evt05:
		description = "Connection accepted (for service provider)"
	case evt06:
		description = "A-ASSOCIATE-RQ PDU (on tranport connection)"
	case evt07:
		description = "A-ASSOCIATE response primitive (accept)"
	case evt08:
		description = "A-ASSOCIATE response primitive (reject)"
	case evt09:
		description = "P-DATA request primitive"
	case evt10:
		description = "P-DATA-TF PDU (on transport connection)"
	case evt11:
		description = "A-RELEASE request primitive"
	case evt12:
		description = "A-RELEASE-RQ PDU (on transport)"
	case evt13:
		description = "A-RELEASE-RP PDU (on transport)"
	case evt14:
		description = "A-RELEASE response primitive"
	case evt15:
		description = "A-ABORT request primitive"
	case evt16:
		description = "A-ABORT PDU (on transport)"
	case evt17:
		description = "Transport connection closed indication (local transport service)"
	case evt18:
		description = "ARTIM timer expired (Association reject/release timer)"
	case evt19:
		description = "Unrecognized or invalid PDU received"
	default:
		panic(fmt.Sprintf("dicom.stateMachine: Unknown event type %v", int(*e)))
	}
	return fmt.Sprintf("evt%02d(%s)", *e, description)
}

type stateAction struct {
	Name        string
	Description string
	Callback    func(sm *stateMachine, event stateEvent) stateType
}

func (s *stateAction) String() string {
	return fmt.Sprintf("%s(%s)", s.Name, s.Description)
}

var actionAe1 = &stateAction{"AE-1",
	"Issue TRANSPORT CONNECT request primitive to local transport service",
	func(sm *stateMachine, event stateEvent) stateType {
		return sta04
	}}

var actionAe2 = &stateAction{"AE-2", "Connection established on the user side. Send A-ASSOCIATE-RQ-PDU",
	func(sm *stateMachine, event stateEvent) stateType {
		doassert(event.conn != nil)
		sm.conn = event.conn
		go networkReaderThread(sm.netCh, event.conn, DefaultMaxPDUSize, sm.label)
		items := sm.contextManager.generateAssociateRequest(
			sm.userParams.SOPClasses,
			sm.userParams.TransferSyntaxes)

		pdu := &pdu.AAssociate{
			Type:            pdu.TypeAAssociateRq,
			ProtocolVersion: pdu.CurrentProtocolVersion,
			CalledAETitle:   sm.userParams.CalledAETitle,
			CallingAETitle:  sm.userParams.CallingAETitle,
			Items:           items,
		}

		sendPDU(sm, pdu)
		startTimer(sm)
		return sta05
	}}

var actionAe3 = &stateAction{"AE-3", "Issue A-ASSOCIATE confirmation (accept) primitive",
	func(sm *stateMachine, event stateEvent) stateType {
		stopTimer(sm)
		v := event.pdu.(*pdu.AAssociate)
		doassert(v.Type == pdu.TypeAAssociateAc)
		err := sm.contextManager.onAssociateResponse(v.Items)

		if err == nil {
			sm.upcallCh <- upcallEvent{
				eventType: upcallEventHandshakeCompleted,
				cm:        sm.contextManager,
			}
			return sta06
		}
		return actionAa8.Callback(sm, event)
	}}

var actionAe4 = &stateAction{"AE-4", "Issue A-ASSOCIATE confirmation (reject) primitive and close transport connection",
	func(sm *stateMachine, event stateEvent) stateType {
		closeConnection(sm)
		return sta01
	}}

var actionAe5 = &stateAction{"AE-5", "Issue Transport connection response primitive; start ARTIM timer",
	func(sm *stateMachine, event stateEvent) stateType {
		doassert(event.conn != nil)
		startTimer(sm)
		go func(ch chan stateEvent, conn net.Conn) {
			networkReaderThread(ch, conn, DefaultMaxPDUSize, sm.label)
		}(sm.netCh, event.conn)
		return sta02
	}}

var actionAe6 = &stateAction{"AE-6", `Stop ARTIM timer and if A-ASSOCIATE-RQ acceptable by "
service-dul: issue A-ASSOCIATE indication primitive
otherwise issue A-ASSOCIATE-RJ-PDU and start ARTIM timer`,
	func(sm *stateMachine, event stateEvent) stateType {
		stopTimer(sm)
		v := event.pdu.(*pdu.AAssociate)

		if sm.enforceStatus != "no" {
			if strings.TrimSpace(v.CalledAETitle) != strings.TrimSpace(sm.clientAETitleStatus) {

				logrus.WithFields(logrus.Fields{
					"AETitle": strings.TrimSpace(v.CalledAETitle),
					"ID":      sm.label,
				}).Error("Connection")
				// Sleep to prevent overload in case of an extended brutefoce attempt
				time.Sleep(5 * time.Second)

				rj := pdu.AAssociateRj{Result: 1, Source: 2, Reason: 2}
				sendPDU(sm, &rj)
				startTimer(sm)
				return sta13
			} else {

				logrus.WithFields(logrus.Fields{
					"AETitle": strings.TrimSpace(v.CalledAETitle),
					"ID":      sm.label,
				}).Info("Client")
				logrus.WithFields(logrus.Fields{
					"Identifier": strings.TrimSpace(v.CallingAETitle),
					"ID":         sm.label,
				}).Info("Client")
			}
		}

		if v.ProtocolVersion != 0x0001 {
			rj := pdu.AAssociateRj{Result: 1, Source: 2, Reason: 2}

			sendPDU(sm, &rj)
			startTimer(sm)

			return sta13
		}
		responses, err := sm.contextManager.onAssociateRequest(v.Items)
		if err != nil {
			sm.downcallCh <- stateEvent{
				event: evt08,
				pdu: &pdu.AAssociateRj{
					Result: pdu.ResultRejectedPermanent,
					Source: pdu.SourceULServiceProviderACSE,
					Reason: 1,
				},
			}
		} else {
			doassert(len(responses) > 0)
			doassert(v.CalledAETitle != "")
			doassert(v.CallingAETitle != "")
			sm.downcallCh <- stateEvent{
				event: evt07,
				pdu: &pdu.AAssociate{
					Type:            pdu.TypeAAssociateAc,
					ProtocolVersion: pdu.CurrentProtocolVersion,
					CalledAETitle:   v.CalledAETitle,
					CallingAETitle:  v.CallingAETitle,
					Items:           responses,
				},
			}
		}
		return sta03
	}}
var actionAe7 = &stateAction{"AE-7", "Send A-ASSOCIATE-AC PDU",
	func(sm *stateMachine, event stateEvent) stateType {

		sendPDU(sm, event.pdu.(*pdu.AAssociate))

		sm.upcallCh <- upcallEvent{
			eventType: upcallEventHandshakeCompleted,
			cm:        sm.contextManager,
		}

		return sta06
	}}

var actionAe8 = &stateAction{"AE-8", "Send A-ASSOCIATE-RJ PDU and start ARTIM timer",
	func(sm *stateMachine, event stateEvent) stateType {
		sendPDU(sm, event.pdu.(*pdu.AAssociateRj))
		startTimer(sm)

		return sta13
	}}

// Produce a list of P_DATA_TF PDUs that collective store "data".
func splitDataIntoPDUs(sm *stateMachine, abstractSyntaxName string, command bool, data []byte) []pdu.PDataTf {
	doassert(len(data) > 0)
	context, err := sm.contextManager.lookupByAbstractSyntaxUID(abstractSyntaxName)
	if err != nil {
		panic(fmt.Sprintf("dicom.stateMachine(%s): Illegal syntax name %s: %s", sm.label, dicomuid.UIDString(abstractSyntaxName), err))
	}
	var pdus []pdu.PDataTf
	// two byte header overhead.
	var maxChunkSize = sm.contextManager.peerMaxPDUSize - 8
	for len(data) > 0 {
		chunkSize := len(data)
		if chunkSize > maxChunkSize {
			chunkSize = maxChunkSize
		}
		chunk := data[0:chunkSize]
		data = data[chunkSize:]
		pdus = append(pdus, pdu.PDataTf{Items: []pdu.PresentationDataValueItem{
			pdu.PresentationDataValueItem{
				ContextID: context.contextID,
				Command:   command,
				Last:      false, // Set later.
				Value:     chunk,
			}}})
	}
	if len(pdus) > 0 {
		pdus[len(pdus)-1].Items[0].Last = true
	}
	return pdus
}

// Data transfer related actions
var actionDt1 = &stateAction{"DT-1", "Send P-DATA-TF PDU",
	func(sm *stateMachine, event stateEvent) stateType {
		doassert(event.dimsePayload != nil)
		command := event.dimsePayload.command
		doassert(command != nil)
		e := dicomio.NewBytesEncoder(nil, dicomio.UnknownVR)
		dimse.EncodeMessage(e, command)
		if e.Error() != nil {
			panic(fmt.Sprintf("Failed to encode DIMSE cmd %v: %v", command, e.Error()))
		}
		pdus := splitDataIntoPDUs(sm, event.dimsePayload.abstractSyntaxName, true /*command*/, e.Bytes())
		for _, pdu := range pdus {
			sendPDU(sm, &pdu)
		}
		if command.HasData() {
			pdus := splitDataIntoPDUs(sm, event.dimsePayload.abstractSyntaxName, false /*data*/, event.dimsePayload.data)
			for _, pdu := range pdus {
				sendPDU(sm, &pdu)
			}
		} else if len(event.dimsePayload.data) > 0 {
			panic(fmt.Sprintf("dicom.stateMachine(%s): Found DIMSE data of %db, command: %v", sm.label, len(event.dimsePayload.data), command))
		}
		return sta06
	}}

var actionDt2 = &stateAction{"DT-2", "Send P-DATA indication primitive",
	func(sm *stateMachine, event stateEvent) stateType {
		contextID, command, data, err := sm.commandAssembler.AddDataPDU(event.pdu.(*pdu.PDataTf))
		if err == nil {
			if command != nil { // All fragments received
				sm.upcallCh <- upcallEvent{
					eventType: upcallEventData,
					cm:        sm.contextManager,
					contextID: contextID,
					command:   command,
					data:      data}
			}
			return sta06
		}
		return actionAa8.Callback(sm, event)
	}}

// Assocation Release related actions
var actionAr1 = &stateAction{"AR-1", "Send A-RELEASE-RQ PDU",
	func(sm *stateMachine, event stateEvent) stateType {
		sendPDU(sm, &pdu.AReleaseRq{})
		return sta07
	}}
var actionAr2 = &stateAction{"AR-2", "Issue A-RELEASE indication primitive",
	func(sm *stateMachine, event stateEvent) stateType {
		sm.downcallCh <- stateEvent{event: evt14}
		return sta08
	}}

var actionAr3 = &stateAction{"AR-3", "Issue A-RELEASE confirmation primitive and close transport connection",
	func(sm *stateMachine, event stateEvent) stateType {
		sendPDU(sm, &pdu.AReleaseRp{})
		closeConnection(sm)
		return sta01
	}}
var actionAr4 = &stateAction{"AR-4", "Issue A-RELEASE-RP PDU and start ARTIM timer",
	func(sm *stateMachine, event stateEvent) stateType {
		sendPDU(sm, &pdu.AReleaseRp{})
		startTimer(sm)
		return sta13
	}}

var actionAr5 = &stateAction{"AR-5", "Stop ARTIM timer",
	func(sm *stateMachine, event stateEvent) stateType {
		stopTimer(sm)
		return sta01
	}}

var actionAr6 = &stateAction{"AR-6", "Issue P-DATA indication",
	func(sm *stateMachine, event stateEvent) stateType {
		return sta07
	}}

var actionAr7 = &stateAction{"AR-7", "Issue P-DATA-TF PDU",
	func(sm *stateMachine, event stateEvent) stateType {
		doassert(event.dimsePayload != nil)
		command := event.dimsePayload.command
		doassert(command != nil)
		e := dicomio.NewBytesEncoder(nil, dicomio.UnknownVR)
		dimse.EncodeMessage(e, command)
		if e.Error() != nil {
			panic(fmt.Sprintf("dicom.StateMachine %s: Failed to encode DIMSE cmd %v: %v", sm.label, command, e.Error()))
		}
		pdus := splitDataIntoPDUs(sm, event.dimsePayload.abstractSyntaxName, true /*command*/, e.Bytes())
		for _, pdu := range pdus {
			sendPDU(sm, &pdu)
		}
		if command.HasData() {
			pdus := splitDataIntoPDUs(sm, event.dimsePayload.abstractSyntaxName, false /*data*/, event.dimsePayload.data)
			for _, pdu := range pdus {
				sendPDU(sm, &pdu)
			}
		} else {
			doassert(len(event.dimsePayload.data) == 0)
		}
		sm.downcallCh <- stateEvent{event: evt14}
		return sta08
	}}

var actionAr8 = &stateAction{"AR-8", "Issue A-RELEASE indication (release collision): if association-requestor, next state is Sta09, if not next state is Sta10",
	func(sm *stateMachine, event stateEvent) stateType {
		if sm.isUser {
			return sta09
		}
		return sta10
	}}

var actionAr9 = &stateAction{"AR-9", "Send A-RELEASE-RP PDU",
	func(sm *stateMachine, event stateEvent) stateType {
		sendPDU(sm, &pdu.AReleaseRp{})
		return sta11
	}}

var actionAr10 = &stateAction{"AR-10", "Issue A-RELEASE confimation primitive",
	func(sm *stateMachine, event stateEvent) stateType {
		return sta12
	}}

// Association abort related actions
var actionAa1 = &stateAction{"AA-1", "Send A-ABORT PDU (service-user source) and start (or restart if already started) ARTIM timer",
	func(sm *stateMachine, event stateEvent) stateType {
		diagnostic := pdu.AbortReasonType(0)
		if sm.currentState == sta02 {
			diagnostic = pdu.AbortReasonUnexpectedPDU
		}
		sendPDU(sm, &pdu.AAbort{Source: 0, Reason: diagnostic})
		restartTimer(sm)
		return sta13
	}}

var actionAa2 = &stateAction{"AA-2", "Stop ARTIM timer if running. Close transport connection",
	func(sm *stateMachine, event stateEvent) stateType {
		stopTimer(sm)
		closeConnection(sm)
		return sta01
	}}

var actionAa3 = &stateAction{"AA-3", "If (service-user initiated abort): issue A-ABORT indication and close transport connection, otherwise (service-dul initiated abort): issue A-P-ABORT indication and close transport connection",
	func(sm *stateMachine, event stateEvent) stateType {
		closeConnection(sm)
		return sta01
	}}

var actionAa4 = &stateAction{"AA-4", "Issue A-P-ABORT indication primitive",
	func(sm *stateMachine, event stateEvent) stateType {
		return sta01
	}}

var actionAa5 = &stateAction{"AA-5", "Stop ARTIM timer",
	func(sm *stateMachine, event stateEvent) stateType {
		stopTimer(sm)
		return sta01
	}}

var actionAa6 = &stateAction{"AA-6", "Ignore PDU",
	func(sm *stateMachine, event stateEvent) stateType {
		return sta13
	}}

var actionAa7 = &stateAction{"AA-7", "Send A-ABORT PDU",
	func(sm *stateMachine, event stateEvent) stateType {
		sendPDU(sm, &pdu.AAbort{Source: 0, Reason: 0})
		return sta13
	}}

var actionAa8 = &stateAction{"AA-8", "Send A-ABORT PDU (service-dul source), issue an A-P-ABORT indication and start ARTIM timer",
	func(sm *stateMachine, event stateEvent) stateType {
		sendPDU(sm, &pdu.AAbort{Source: 2, Reason: 0})
		startTimer(sm)
		return sta13
	}}

type upcallEventType int

const (
	upcallEventHandshakeCompleted = upcallEventType(100)
	upcallEventData               = upcallEventType(101)
	// Note: connection shutdown and any error will result in channel
	// closure, so they don't have event types.
)

func (e *upcallEventType) String() string {
	var description string
	switch *e {
	case upcallEventHandshakeCompleted:
		description = "Handshake completed"
	case upcallEventData:
		description = "P_DATA_TF PDU received"
	default:
		panic(fmt.Sprintf("dicom.StateMachine: Unknown event type %v", int(*e)))
	}
	return fmt.Sprintf("upcall%02d(%s)", *e, description)
}

type upcallEvent struct {
	eventType upcallEventType

	// The context ID -> <abstract syntax uid, transefr syntax uid> mappings.
	// Sent for upcallEventHandshakeCompleted and upcallEventData.
	cm *contextManager

	// abstractSyntaxUID is extracted from the P_DATA_TF packet.
	// transferSyntaxUID is the value agreed on for the abstractSyntaxUID
	// during protocol handshake. Both are nonempty iff
	// eventType==upcallEventData.
	//abstractSyntaxUID string
	//transferSyntaxUID string

	// The context of the request. It can be mapped backto <abstract syntax, transfer syntax> by consulting the
	// context manager. Set only in upcallEventData event.
	contextID byte

	command dimse.Message
	data    []byte
}

type stateEventDIMSEPayload struct {
	// The syntax UID of the data to be sent.
	abstractSyntaxName string

	// Command to send. len(command) may exceed the max PDU size, in which case it
	// will be split into multiple PresentationDataValueItems.
	command dimse.Message

	// Ditto, but for the data payload. The data PDU is sent iff.
	// command.HasData()==true.
	data []byte
}

type stateEventDebugInfo struct {
	state stateType // the state the system was in when timer was created.
}

type stateEvent struct {
	event eventType
	pdu   pdu.PDU
	err   error
	conn  net.Conn

	dimsePayload *stateEventDIMSEPayload // set iff event==evt09.
	debug        *stateEventDebugInfo
}

func (e *stateEvent) String() string {
	debug := ""
	if e.debug != nil {
		debug = e.debug.state.String()
	}
	return fmt.Sprintf("type:%s err:%v debug:%v pdu:%v",
		e.event.String(), e.err, debug, e.pdu)
}

type stateTransition struct {
	current stateType
	event   eventType
	action  *stateAction
}

var stateTransitions = []stateTransition{
	stateTransition{sta01, evt01, actionAe1},
	stateTransition{sta01, evt05, actionAe5},
	stateTransition{sta02, evt03, actionAa1},
	stateTransition{sta02, evt04, actionAa1},
	stateTransition{sta02, evt06, actionAe6},
	stateTransition{sta02, evt10, actionAa1},
	stateTransition{sta02, evt12, actionAa1},
	stateTransition{sta02, evt13, actionAa1},
	stateTransition{sta02, evt16, actionAa2},
	stateTransition{sta02, evt17, actionAa5},
	stateTransition{sta02, evt18, actionAa2},
	stateTransition{sta02, evt19, actionAa1},
	stateTransition{sta03, evt03, actionAa8},
	stateTransition{sta03, evt04, actionAa8},
	stateTransition{sta03, evt06, actionAa8},
	stateTransition{sta03, evt07, actionAe7},
	stateTransition{sta03, evt08, actionAe8},
	stateTransition{sta03, evt10, actionAa8},
	stateTransition{sta03, evt12, actionAa8},
	stateTransition{sta03, evt13, actionAa8},
	stateTransition{sta03, evt15, actionAa1},
	stateTransition{sta03, evt16, actionAa3},
	stateTransition{sta03, evt17, actionAa4},
	stateTransition{sta03, evt19, actionAa8},
	stateTransition{sta04, evt02, actionAe2},
	stateTransition{sta04, evt15, actionAa2},
	stateTransition{sta04, evt17, actionAa4},
	stateTransition{sta05, evt03, actionAe3},
	stateTransition{sta05, evt04, actionAe4},
	stateTransition{sta05, evt06, actionAa8},
	stateTransition{sta05, evt10, actionAa8},
	stateTransition{sta05, evt12, actionAa8},
	stateTransition{sta05, evt13, actionAa8},
	stateTransition{sta05, evt15, actionAa1},
	stateTransition{sta05, evt16, actionAa3},
	stateTransition{sta05, evt17, actionAa4},
	stateTransition{sta05, evt18, actionAa8},
	stateTransition{sta05, evt19, actionAa8},

	stateTransition{sta06, evt03, actionAa8},
	stateTransition{sta06, evt04, actionAa8},
	stateTransition{sta06, evt06, actionAa8},
	stateTransition{sta06, evt09, actionDt1},
	stateTransition{sta06, evt10, actionDt2},
	stateTransition{sta06, evt11, actionAr1},
	stateTransition{sta06, evt12, actionAr2},
	stateTransition{sta06, evt13, actionAa8},
	stateTransition{sta06, evt15, actionAa1},
	stateTransition{sta06, evt16, actionAa3},
	stateTransition{sta06, evt17, actionAa4},
	stateTransition{sta06, evt19, actionAa8},
	stateTransition{sta07, evt03, actionAa8},
	stateTransition{sta07, evt04, actionAa8},
	stateTransition{sta07, evt06, actionAa8},
	stateTransition{sta07, evt10, actionAr6},
	stateTransition{sta07, evt12, actionAr8},
	stateTransition{sta07, evt13, actionAr3},
	stateTransition{sta07, evt15, actionAa1},
	stateTransition{sta07, evt16, actionAa3},
	stateTransition{sta07, evt17, actionAa4},
	stateTransition{sta07, evt19, actionAa8},
	stateTransition{sta08, evt03, actionAa8},
	stateTransition{sta08, evt04, actionAa8},
	stateTransition{sta08, evt06, actionAa8},
	stateTransition{sta08, evt09, actionAr7},
	stateTransition{sta08, evt10, actionAa8},
	stateTransition{sta08, evt12, actionAa8},
	stateTransition{sta08, evt13, actionAa8},
	stateTransition{sta08, evt14, actionAr4},
	stateTransition{sta08, evt15, actionAa1},
	stateTransition{sta08, evt16, actionAa3},
	stateTransition{sta08, evt17, actionAa4},
	stateTransition{sta08, evt19, actionAa8},
	stateTransition{sta09, evt03, actionAa8},
	stateTransition{sta09, evt04, actionAa8},
	stateTransition{sta09, evt06, actionAa8},
	stateTransition{sta09, evt10, actionAa8},
	stateTransition{sta09, evt12, actionAa8},
	stateTransition{sta09, evt13, actionAa8},
	stateTransition{sta09, evt14, actionAr9},
	stateTransition{sta09, evt15, actionAa1},
	stateTransition{sta09, evt16, actionAa3},
	stateTransition{sta09, evt17, actionAa4},
	stateTransition{sta09, evt19, actionAa8},
	stateTransition{sta10, evt03, actionAa8},
	stateTransition{sta10, evt04, actionAa8},
	stateTransition{sta10, evt06, actionAa8},
	stateTransition{sta10, evt10, actionAa8},
	stateTransition{sta10, evt12, actionAa8},
	stateTransition{sta10, evt13, actionAr10},
	stateTransition{sta10, evt15, actionAa1},
	stateTransition{sta10, evt16, actionAa3},
	stateTransition{sta10, evt17, actionAa4},
	stateTransition{sta10, evt19, actionAa8},
	stateTransition{sta11, evt03, actionAa8},
	stateTransition{sta11, evt04, actionAa8},
	stateTransition{sta11, evt06, actionAa8},
	stateTransition{sta11, evt10, actionAa8},
	stateTransition{sta11, evt12, actionAa8},
	stateTransition{sta11, evt13, actionAr3},
	stateTransition{sta11, evt15, actionAa1},
	stateTransition{sta11, evt16, actionAa3},
	stateTransition{sta11, evt17, actionAa4},
	stateTransition{sta11, evt19, actionAa8},
	stateTransition{sta12, evt03, actionAa8},
	stateTransition{sta12, evt04, actionAa8},
	stateTransition{sta12, evt06, actionAa8},
	stateTransition{sta12, evt10, actionAa8},
	stateTransition{sta12, evt12, actionAa8},
	stateTransition{sta12, evt13, actionAa8},
	stateTransition{sta12, evt14, actionAr4},
	stateTransition{sta12, evt15, actionAa1},
	stateTransition{sta12, evt16, actionAa3},
	stateTransition{sta12, evt17, actionAa4},
	stateTransition{sta12, evt19, actionAa8},

	stateTransition{sta13, evt03, actionAa6},
	stateTransition{sta13, evt04, actionAa6},
	stateTransition{sta13, evt06, actionAa7},
	stateTransition{sta13, evt07, actionAa7},
	stateTransition{sta13, evt08, actionAa7},
	stateTransition{sta13, evt09, actionAa7},
	stateTransition{sta13, evt10, actionAa6},
	stateTransition{sta13, evt11, actionAa6},
	stateTransition{sta13, evt12, actionAa6},
	stateTransition{sta13, evt13, actionAa6},
	stateTransition{sta13, evt14, actionAa6},
	stateTransition{sta13, evt15, actionAa2},
	stateTransition{sta13, evt16, actionAa2},
	stateTransition{sta13, evt17, actionAr5},
	stateTransition{sta13, evt18, actionAa2},
	stateTransition{sta13, evt19, actionAa7},
}

// Per-TCP-connection state.
type stateMachine struct {
	label  string // For logging only
	isUser bool   // true if service user, false if provider

	clientAETitleStatus string
	enforceStatus       string

	// userParams is set only for a client-side statemachine
	userParams ServiceUserParams

	// Manages mappings between one-byte contextID to the
	// <abstractsyntaxUID, transfersyntaxuid> pair.  Filled during A_ACCEPT
	// handshake.
	contextManager *contextManager

	// For receiving PDU and network status events.
	// Owned by networkReaderThread.
	netCh chan stateEvent

	// For reporting errors to this event.  Owned by the statemachine.
	errorCh chan stateEvent

	// For receiving commands from the upper layer
	// Owned by the upper layer.
	downcallCh chan stateEvent

	// For sending indications to the the upper layer. Owned by the
	// statemachine.
	upcallCh chan upcallEvent

	// For Timer expiration event
	timerCh chan stateEvent

	// The socket to the remote peer.
	conn         net.Conn
	currentState stateType

	// For assembling DIMSE command from multiple P_DATA_TF fragments.
	commandAssembler dimse.CommandAssembler
}

func closeConnection(sm *stateMachine) {
	close(sm.upcallCh)
	if sm.conn != nil {
		sm.conn.Close()
	}
}

func sendPDU(sm *stateMachine, v pdu.PDU) {
	doassert(sm.conn != nil)
	data, err := pdu.EncodePDU(v)
	if err != nil {
		sm.conn.Close()
		sm.errorCh <- stateEvent{event: evt17, err: err}
		return
	}

	n, err := sm.conn.Write(data)
	if n != len(data) || err != nil {
		sm.conn.Close()
		sm.errorCh <- stateEvent{event: evt17, err: err}
		return
	}
}

func startTimer(sm *stateMachine) {
	ch := make(chan stateEvent, 1)
	sm.timerCh = ch
	currentState := sm.currentState
	time.AfterFunc(time.Duration(10)*time.Second,
		func() {
			ch <- stateEvent{event: evt18, debug: &stateEventDebugInfo{currentState}}
			close(ch)
		})
}

func restartTimer(sm *stateMachine) {
	startTimer(sm)
}

func stopTimer(sm *stateMachine) {
	sm.timerCh = make(chan stateEvent, 1)
}

func networkReaderThread(ch chan stateEvent, conn net.Conn, maxPDUSize int, smName string) {
	doassert(maxPDUSize > 16*1024)
	for {
		v, err := pdu.ReadPDU(conn, maxPDUSize)
		if err != nil {
			if err == io.EOF {
				ch <- stateEvent{event: evt17, pdu: nil, err: nil}
			} else {
				ch <- stateEvent{event: evt19, pdu: nil, err: err}
			}
			close(ch)
			break
		}
		doassert(v != nil)
		switch n := v.(type) {
		case *pdu.AAssociate:

			if n.Type == pdu.TypeAAssociateRq {
				ch <- stateEvent{event: evt06, pdu: n, err: nil}
			} else {
				doassert(n.Type == pdu.TypeAAssociateAc)
				ch <- stateEvent{event: evt03, pdu: n, err: nil}
			}
			continue
		case *pdu.AAssociateRj:
			ch <- stateEvent{event: evt04, pdu: n, err: nil}
			continue
		case *pdu.PDataTf:
			ch <- stateEvent{event: evt10, pdu: n, err: nil}
			continue
		case *pdu.AReleaseRq:
			ch <- stateEvent{event: evt12, pdu: n, err: nil}
			continue
		case *pdu.AReleaseRp:
			ch <- stateEvent{event: evt13, pdu: n, err: nil}
			continue
		case *pdu.AAbort:
			ch <- stateEvent{event: evt16, pdu: n, err: nil}
			continue
		default:
			err := fmt.Errorf("dicom.StateMachine %s: Unknown PDU type: %v", v.String(), smName)
			ch <- stateEvent{event: evt19, pdu: v, err: err}
			continue
		}
	}
}

func getNextEvent(sm *stateMachine) stateEvent {
	var ok bool
	var event stateEvent
	for event.event == 0 {
		select {
		case event, ok = <-sm.netCh:
			if !ok {
				sm.netCh = nil
			}
		case event = <-sm.errorCh:
			// this channel shall never close.
		case event, ok = <-sm.timerCh:
			if !ok {
				sm.timerCh = nil
			}
		case event, ok = <-sm.downcallCh:
			if !ok {
				sm.downcallCh = nil
			}
		}
	}
	switch event.event {
	case evt02:
		doassert(event.conn != nil)
		sm.conn = event.conn
	case evt17:
		close(sm.upcallCh)
		sm.conn = nil
	}
	return event
}

func findAction(currentState stateType, event *stateEvent, smName string) *stateAction {
	for _, t := range stateTransitions {
		if t.current == currentState && t.event == event.event {
			return t.action
		}
	}
	return nil
}

func runOneStep(sm *stateMachine) {
	event := getNextEvent(sm)
	action := findAction(sm.currentState, &event, sm.label)

	if action == nil {
		action = actionAa2 // This will force connection abortion
	}
	newState := action.Callback(sm, event)
	sm.currentState = newState
}

func runStateMachineForServiceUser(
	params ServiceUserParams,
	upcallCh chan upcallEvent,
	downcallCh chan stateEvent,
	label string) {
	doassert(params.CallingAETitle != "")
	doassert(len(params.SOPClasses) > 0)
	doassert(len(params.TransferSyntaxes) > 0)
	sm := &stateMachine{
		label:          label,
		isUser:         true,
		contextManager: newContextManager(label),
		userParams:     params,
		netCh:          make(chan stateEvent, 128),
		errorCh:        make(chan stateEvent, 128),
		downcallCh:     downcallCh,
		upcallCh:       upcallCh,
	}

	event := stateEvent{event: evt01}
	action := findAction(sta01, &event, sm.label)
	sm.currentState = action.Callback(sm, event)
	for sm.currentState != sta01 {
		runOneStep(sm)
	}
}

func runStateMachineForServiceProvider(
	conn net.Conn,
	upcallCh chan upcallEvent,
	downcallCh chan stateEvent,
	label string,
	clientAETitle string,
	enforce string,
) {
	sm := &stateMachine{
		clientAETitleStatus: clientAETitle,
		enforceStatus:       enforce,
		label:               label,
		isUser:              false,
		contextManager:      newContextManager(label),
		conn:                conn,
		netCh:               make(chan stateEvent, 128),
		errorCh:             make(chan stateEvent, 128),
		downcallCh:          downcallCh,
		upcallCh:            upcallCh,
	}

	event := stateEvent{event: evt05, conn: conn}
	action := findAction(sta01, &event, sm.label)
	sm.currentState = action.Callback(sm, event)

	for sm.currentState != sta01 {
		runOneStep(sm)
	}
}