@startuml

actor "Buyer=Taker \n[frontend]" as Buyer
participant "Buyer \n[daemon]" as BuyerApp
participant "Buyer Offer Feed \n[in daemon]" as BuyerOfferFeed
participant "Buyer CFD Feed \n[in daemon]" as BuyerCfdFeed
participant "Seller CFD Feed \n[in daemon]" as SellerCfdFeed
participant "Seller Offer Feed \n[in daemon]" as SellerOfferFeed
participant "Seller \n[daemon]" as SellerApp
actor "Seller=Maker \n[frontend]" as Seller
participant Oracle as Oracle

note over Seller : currently static offer in the frontend
Seller -> SellerOfferFeed: Subscribe
note over Seller: The seller should see the current active offer \nInitially there is none (until one POSTed)
Seller -> SellerApp: POST sell offer

group Oracle stuff?
SellerApp -> Oracle: Attestation for sell offer
Oracle --> SellerApp: Attestation pubkey
end group

SellerApp -> SellerApp: Store current offer
SellerApp -> SellerOfferFeed: Push offer
SellerOfferFeed --> Seller: offer [Untaken]

Buyer -> BuyerApp: Start daemon & UI
BuyerApp -> BuyerOfferFeed: Subscribe
BuyerApp -> BuyerCfdFeed: Subscribe
BuyerApp -> SellerApp: Open TCP (socket) connection
SellerApp -> SellerApp: New connection
SellerApp -> BuyerApp: {TCP} Current offer

note over SellerOfferFeed : Assumption: Current offer \nalways available for new subscriptions
BuyerApp -> BuyerOfferFeed: push offer
BuyerOfferFeed --> Buyer: offer

Buyer -> Buyer: Click BUY
Buyer -> BuyerApp: POST cfd_take_request
BuyerApp -> BuyerApp: Create cfd [TakeRequested]
note over BuyerApp: Must include offer_id

BuyerApp -> BuyerCfdFeed: Push cfd
BuyerCfdFeed --> Buyer: cfd [TakeRequested]

BuyerApp -> SellerApp: {TCP} cfd_take_request (offer_id, quantity)
SellerApp -> SellerApp: Create cfd [TakeRequested]
SellerApp -> SellerCfdFeed: cfd [TakeRequested]
SellerCfdFeed --> Seller: cfd [TakeRequested]
Seller -> Seller: Accept cfd
Seller -> SellerApp: POST cfd [Accepted]
SellerApp -> BuyerApp: {TCP} cfd [Accepted]
SellerApp -> SellerCfdFeed: cfd [Accepted]
SellerCfdFeed --> Seller: cfd [Accepted]
BuyerApp -> BuyerCfdFeed: cfd [Accepted]
BuyerCfdFeed --> Buyer: cfd [Accepted]

ref over BuyerApp, SellerApp: {TCP} protocol setup messaging & contract publication on Bitcoin\n-> cfd in state [ContractSetup]

SellerApp -> SellerCfdFeed: cfd [Open]
SellerCfdFeed --> Seller: cfd [Open]
BuyerApp -> BuyerCfdFeed: cfd [Open]
BuyerCfdFeed --> Buyer: cfd [Open]



@enduml