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dialog.go
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dialog.go
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package fbbot
import (
log "github.com/Sirupsen/logrus"
)
// Event represents event triggered in a step
type Event string
const ResetEvent Event = "reset"
const NilEvent Event = ""
type Step interface {
Name() string
Enter(*Bot, *Message) Event
Process(*Bot, *Message) Event
Leave(*Bot, *Message) Event
}
// BaseStep is base struct for steps
type BaseStep struct{}
func (s BaseStep) Name() string { return "unnamed step" }
func (s BaseStep) Enter(bot *Bot, msg *Message) (e Event) { return e } // Do nothing
func (s BaseStep) Process(bot *Bot, msg *Message) (e Event) { return e } // Do nothing
func (s BaseStep) Leave(bot *Bot, msg *Message) (e Event) { return e } // Do nothing
type Dialog struct {
beginStep Step
endStep Step
currentStepMap map[string]Step // maps an user ID to his current step
p2pTransMap map[Step]map[Event]Step
globalTransMap map[Event]Step
// Hooks
PreHandleMessageHook func(*Bot, *Message) bool
PostHandleMessageHook func(*Bot, *Message)
PreHandlePostbackHook func(*Bot, *Postback) bool
PostHandlePostbackHook func(*Bot, *Postback)
}
func NewDialog() *Dialog {
var d Dialog
d.currentStepMap = make(map[string]Step)
d.p2pTransMap = make(map[Step]map[Event]Step)
d.globalTransMap = make(map[Event]Step)
return &d
}
func (d *Dialog) SetBeginStep(s Step) {
d.beginStep = s
}
func (d *Dialog) SetEndStep(s Step) {
d.endStep = s
}
func (d *Dialog) AddTransition(event Event, steps ...Step) {
n := len(steps)
if n == 0 {
return
}
if n == 1 { // global transition
d.globalTransMap[event] = steps[0]
return
}
// point-to-point transition
srcs := steps[:n-1]
dst := steps[n-1]
for _, src := range srcs {
d.addP2PTransition(src, event, dst)
}
}
// Add point-to-point transition
func (d *Dialog) addP2PTransition(src Step, event Event, dst Step) {
_, exist := d.p2pTransMap[src]
if !exist {
d.p2pTransMap[src] = make(map[Event]Step)
}
d.p2pTransMap[src][event] = dst
}
func (d *Dialog) HandleMessage(bot *Bot, msg *Message) {
if d.PreHandleMessageHook != nil {
isBreak := d.PreHandleMessageHook(bot, msg)
if isBreak {
return
}
}
if d.beginStep == nil || d.endStep == nil {
log.Fatal("BeginStep and EndStep are not set.")
}
var event Event
step := d.getStep(msg.Sender.ID)
if step == nil || step == d.endStep {
bot.STMemory.Delete(msg.Sender.ID)
d.setStep(msg.Sender.ID, d.beginStep)
step = d.getStep(msg.Sender.ID)
event = step.Enter(bot, msg)
} else {
event = step.Process(bot, msg)
}
d.transition(bot, msg, step, event)
if d.PostHandleMessageHook != nil {
d.PostHandleMessageHook(bot, msg)
}
}
func (d *Dialog) HandlePostback(bot *Bot, pbk *Postback) {
if d.PreHandlePostbackHook != nil {
isBreak := d.PreHandlePostbackHook(bot, pbk)
if isBreak {
return
}
}
msg := &Message{Sender: pbk.Sender, Text: pbk.Payload}
d.HandleMessage(bot, msg)
if d.PostHandlePostbackHook != nil {
d.PostHandlePostbackHook(bot, pbk)
}
}
func (d *Dialog) transition(bot *Bot, msg *Message, src Step, event Event) {
if event == ResetEvent {
d.Reset(msg.Sender.ID)
return
}
var dst Step
var exist bool
// check point-to-point transition first
dst, exist = d.p2pTransMap[src][event]
if !exist { // if doesn't have point-to-point transition
// then check global transition
dst, exist = d.globalTransMap[event]
if !exist { // if doesn't have global transition too
return // then do nothing
}
}
// if have destination step
src.Leave(bot, msg)
d.setStep(msg.Sender.ID, dst)
event = d.getStep(msg.Sender.ID).Enter(bot, msg)
d.transition(bot, msg, dst, event)
}
func (d *Dialog) setStep(user_id string, step Step) {
d.currentStepMap[user_id] = step
}
func (d *Dialog) getStep(user_id string) Step {
return d.currentStepMap[user_id]
}
func (d *Dialog) Reset(user_id string) {
delete(d.currentStepMap, user_id)
}
// This function used for moving dialog to any step.
// It should be used with caution for adhoc cases only, since it breaks already defined dialog flow.
func (d *Dialog) Move(msg *Message, dst Step) {
// Get out of current step nicely
currentStep := d.getStep(msg.Sender.ID)
if currentStep != nil {
currentStep.Leave(bot, msg)
}
if dst == nil || dst == d.endStep {
// Follow current logic for end step
bot.STMemory.Delete(msg.Sender.ID)
dst = d.beginStep
}
d.setStep(msg.Sender.ID, dst)
event := dst.Enter(bot, msg)
d.transition(bot, msg, dst, event)
}