robosats/api/logics.py

from datetime import timedelta
from django.utils import timezone
from .lightning import LNNode

from .models import Order, LNPayment, MarketTick, User
from decouple import config
from .utils import get_exchange_rate

FEE = float(config('FEE'))
BOND_SIZE = float(config('BOND_SIZE'))
MARKET_PRICE_API = config('MARKET_PRICE_API')
ESCROW_USERNAME = config('ESCROW_USERNAME')

MIN_TRADE = int(config('MIN_TRADE'))
MAX_TRADE = int(config('MAX_TRADE'))

EXP_MAKER_BOND_INVOICE = int(config('EXP_MAKER_BOND_INVOICE'))
EXP_TAKER_BOND_INVOICE = int(config('EXP_TAKER_BOND_INVOICE'))
EXP_TRADE_ESCR_INVOICE = int(config('EXP_TRADE_ESCR_INVOICE'))

BOND_EXPIRY = int(config('BOND_EXPIRY'))
ESCROW_EXPIRY = int(config('ESCROW_EXPIRY'))

class Logics():

    def validate_already_maker_or_taker(user):
        '''Checks if the user is already partipant of an order'''
        queryset = Order.objects.filter(maker=user)
        if queryset.exists():
            return False, {'bad_request':'You are already maker of an order'}
        queryset = Order.objects.filter(taker=user)
        if queryset.exists():
            return False, {'bad_request':'You are already taker of an order'}
        return True, None

    def validate_order_size(order):
        '''Checks if order is withing limits at t0'''
        if order.t0_satoshis > MAX_TRADE:
            return False, {'bad_request': f'Your order is too big. It is worth {order.t0_satoshis} now. But maximum is {MAX_TRADE}'}
        if order.t0_satoshis < MIN_TRADE:
            return False, {'bad_request': f'Your order is too small. It is worth {order.t0_satoshis} now. But minimum is {MIN_TRADE}'}
        return True, None
        
    def take(order, user):
        order.taker = user
        order.status = Order.Status.TAK
        order.save()

    def is_buyer(order, user):
        is_maker = order.maker == user
        is_taker = order.taker == user
        return (is_maker and order.type == Order.Types.BUY) or (is_taker and order.type == Order.Types.SELL)

    def is_seller(order, user):
        is_maker = order.maker == user
        is_taker = order.taker == user
        return (is_maker and order.type == Order.Types.SELL) or (is_taker and order.type == Order.Types.BUY)
    
    def satoshis_now(order):
        ''' checks trade amount in sats '''
        if order.is_explicit:
            satoshis_now = order.satoshis
        else:
            exchange_rate = get_exchange_rate(Order.currency_dict[str(order.currency)])
            premium_rate = exchange_rate * (1+float(order.premium)/100)
            satoshis_now = (float(order.amount) / premium_rate) * 100*1000*1000

        return int(satoshis_now)
    
    def order_expires(order):
        order.status = Order.Status.EXP
        order.maker = None
        order.taker = None
        order.save()

    @classmethod
    def buyer_invoice_amount(cls, order, user):
        ''' Computes buyer invoice amount. Uses order.last_satoshis, 
        that is the final trade amount set at Taker Bond time'''

        if cls.is_buyer(order, user):
            invoice_amount = int(order.last_satoshis * (1-FEE)) # Trading FEE is charged here.

        return True, {'invoice_amount': invoice_amount}

    @classmethod
    def update_invoice(cls, order, user, invoice):
        
        # only the buyer can post a buyer invoice
        if not cls.is_buyer(order, user):
            return False, {'bad_request':'Only the buyer of this order can provide a buyer invoice.'}
        if not order.taker_bond:
            return False, {'bad_request':'Wait for your order to be taken.'}
        if not (order.taker_bond.status == order.maker_bond.status == LNPayment.Status.LOCKED):
            return False, {'bad_request':'You cannot a invoice while bonds are not posted.'}

        num_satoshis = cls.buyer_invoice_amount(order, user)[1]['invoice_amount']
        valid, context, description, payment_hash, expires_at = LNNode.validate_ln_invoice(invoice, num_satoshis)
        if not valid:
            return False, context

        order.buyer_invoice, _ = LNPayment.objects.update_or_create(
            concept = LNPayment.Concepts.PAYBUYER, 
            type = LNPayment.Types.NORM, 
            sender = User.objects.get(username=ESCROW_USERNAME),
            receiver= user, 
            # if there is a LNPayment matching these above, it updates that one with defaults below.
            defaults={
                'invoice' : invoice,
                'status' : LNPayment.Status.VALIDI,
                'num_satoshis' : num_satoshis,
                'description' :  description,
                'payment_hash' : payment_hash,
                'expires_at' : expires_at}
            )

        # If the order status is 'Waiting for invoice'. Move forward to 'waiting for invoice'
        if order.status == Order.Status.WFE: order.status = Order.Status.CHA

        # If the order status is 'Waiting for both'. Move forward to 'waiting for escrow' or to 'chat'
        if order.status == Order.Status.WF2:
            print(order.trade_escrow)
            if order.trade_escrow:
                if order.trade_escrow.status == LNPayment.Status.LOCKED:
                    order.status = Order.Status.CHA
            else:
                order.status = Order.Status.WFE

        order.save()
        return True, None

    @classmethod
    def rate_counterparty(cls, order, user, rating):

        # If the trade is finished
        if order.status > Order.Status.PAY:

            # if maker, rates taker
            if order.maker == user:
                order.taker.profile.total_ratings = order.taker.profile.total_ratings + 1
                last_ratings = list(order.taker.profile.last_ratings).append(rating)
                order.taker.profile.total_ratings = sum(last_ratings) / len(last_ratings)

            # if taker, rates maker
            if order.taker == user:
                order.maker.profile.total_ratings = order.maker.profile.total_ratings + 1
                last_ratings = list(order.maker.profile.last_ratings).append(rating)
                order.maker.profile.total_ratings = sum(last_ratings) / len(last_ratings)
        else:
            return False, {'bad_request':'You cannot rate your counterparty yet.'}

        order.save()
        return True, None

    @classmethod
    def cancel_order(cls, order, user, state=None):

        # 1) When maker cancels before bond
        '''The order never shows up on the book and order 
        status becomes "cancelled". That's it.'''
        if order.status == Order.Status.WFB and order.maker == user:
            order.maker = None
            order.status = Order.Status.UCA
            order.save()
            return True, None

        # 2) When maker cancels after bond
            '''The order dissapears from book and goes to cancelled. 
            Maker is charged a small amount of sats, to prevent DDOS 
            on the LN node and order book'''

        # 3) When taker cancels before bond
            ''' The order goes back to the book as public.
            LNPayment "order.taker_bond" is deleted() '''

        # 4) When taker or maker cancel after bond (before escrow)
            '''The order goes into cancelled status if maker cancels.
            The order goes into the public book if taker cancels.
            In both cases there is a small fee.'''

        # 5) When trade collateral has been posted (after escrow)
            '''Always goes to cancelled status. Collaboration  is needed.
            When a user asks for cancel, 'order.is_pending_cancel' goes True.
            When the second user asks for cancel. Order is totally cancelled.
            Has a small cost for both parties to prevent node DDOS.'''
        
        else:
            return False, {'bad_request':'You cannot cancel this order'}

    @classmethod
    def gen_maker_hold_invoice(cls, order, user):

        # Do not gen and cancel if order is more than 5 minutes old
        if order.expires_at < timezone.now():
            cls.order_expires(order)
            return False, {'bad_request':'Invoice expired. You did not confirm publishing the order in time. Make a new order.'}

        # Return the previous invoice if there was one and is still unpaid
        if order.maker_bond:
            if order.maker_bond.status == LNPayment.Status.INVGEN:
                return True, {'bond_invoice':order.maker_bond.invoice,'bond_satoshis':order.maker_bond.num_satoshis}
            else:
                return False, None

        order.last_satoshis = cls.satoshis_now(order)
        bond_satoshis = int(order.last_satoshis * BOND_SIZE)
        description = f'RoboSats - Publishing {str(order)} - This bond will return to you if you do not cheat.'

        # Gen hold Invoice
        invoice, payment_hash, expires_at = LNNode.gen_hold_invoice(bond_satoshis, description, BOND_EXPIRY*3600)
        
        order.maker_bond = LNPayment.objects.create(
            concept = LNPayment.Concepts.MAKEBOND, 
            type = LNPayment.Types.hold, 
            sender = user,
            receiver = User.objects.get(username=ESCROW_USERNAME),
            invoice = invoice,
            status = LNPayment.Status.INVGEN,
            num_satoshis = bond_satoshis,
            description =  description,
            payment_hash = payment_hash,
            expires_at = expires_at)

        order.save()
        return True, {'bond_invoice':invoice,'bond_satoshis':bond_satoshis}

    @classmethod
    def gen_taker_hold_invoice(cls, order, user):

        # Do not gen and cancel if a taker invoice is there and older than X minutes and unpaid still
        if order.taker_bond:
            # Check if status is INVGEN and still not expired
            if order.taker_bond.status == LNPayment.Status.INVGEN:
                if order.taker_bond.created_at > (timezone.now()+timedelta(minutes=EXP_TAKER_BOND_INVOICE)):
                    cls.cancel_order(order, user, 3) # State 3, cancel order before taker bond
                    return False, {'bad_request':'Invoice expired. You did not confirm taking the order in time.'}
                # Return the previous invoice there was with INVGEN status
                else:
                    return True, {'bond_invoice':order.taker_bond.invoice,'bond_satoshis':order.taker_bond.num_satoshis}
            # Invoice exists, but was already locked or settled
            else:
                return False, None

        order.last_satoshis = cls.satoshis_now(order)  # LOCKS THE AMOUNT OF SATOSHIS FOR THE TRADE
        bond_satoshis = int(order.last_satoshis * BOND_SIZE)
        description = f'RoboSats - Taking {str(order)} - This bond will return to you if you do not cheat.'

        # Gen hold Invoice
        invoice, payment_hash, expires_at = LNNode.gen_hold_invoice(bond_satoshis, description, BOND_EXPIRY*3600)
        
        order.taker_bond = LNPayment.objects.create(
            concept = LNPayment.Concepts.TAKEBOND, 
            type = LNPayment.Types.hold, 
            sender = user,
            receiver = User.objects.get(username=ESCROW_USERNAME),
            invoice = invoice,
            status = LNPayment.Status.INVGEN,
            num_satoshis = bond_satoshis,
            description =  description,
            payment_hash = payment_hash,
            expires_at = expires_at)

        # Extend expiry time to allow for escrow deposit
        ## Not here, on func for confirming taker collar. order.expires_at = timezone.now() + timedelta(minutes=EXP_TRADE_ESCR_INVOICE)
        
        order.save()
        return True, {'bond_invoice':invoice,'bond_satoshis': bond_satoshis}

    @classmethod
    def gen_escrow_hold_invoice(cls, order, user):
        # Do not generate and cancel if an invoice is there and older than X minutes and unpaid still
        if order.trade_escrow:
            # Check if status is INVGEN and still not expired
            if order.trade_escrow.status == LNPayment.Status.INVGEN:
                if order.trade_escrow.created_at > (timezone.now()+timedelta(minutes=EXP_TRADE_ESCR_INVOICE)): # Expired
                    cls.cancel_order(order, user, 4) # State 4, cancel order before trade escrow locked
                    return False, {'bad_request':'Invoice expired. You did not lock the trade escrow in time.'}
                # Return the previous invoice there was with INVGEN status
                else:
                    return True, {'escrow_invoice': order.trade_escrow.invoice, 'escrow_satoshis':order.trade_escrow.num_satoshis}
            # Invoice exists, but was already locked or settled
            else:
                return False, None # Does not return any context of a healthy locked escrow

        escrow_satoshis = order.last_satoshis # Trade sats amount was fixed at the time of taker bond generation (order.last_satoshis)
        description = f'RoboSats - Escrow amount for {str(order)} - This escrow will be released to the buyer once you confirm you received the fiat.'

        # Gen hold Invoice
        invoice, payment_hash, expires_at = LNNode.gen_hold_invoice(escrow_satoshis, description, ESCROW_EXPIRY*3600)
        
        order.trade_escrow = LNPayment.objects.create(
            concept = LNPayment.Concepts.TRESCROW, 
            type = LNPayment.Types.hold, 
            sender = user,
            receiver = User.objects.get(username=ESCROW_USERNAME),
            invoice = invoice,
            status = LNPayment.Status.INVGEN,
            num_satoshis = escrow_satoshis,
            description =  description,
            payment_hash = payment_hash,
            expires_at = expires_at)

        order.save()
        return True, {'escrow_invoice':invoice,'escrow_satoshis': escrow_satoshis}
    
    def settle_escrow(order):
        ''' Settles the trade escrow HTLC'''
        # TODO ERROR HANDLING

        valid = LNNode.settle_hold_htlcs(order.trade_escrow.payment_hash)
        return valid

    def pay_buyer_invoice(order):
        ''' Settles the trade escrow HTLC'''
        # TODO ERROR HANDLING

        valid = LNNode.pay_invoice(order.buyer_invoice.payment_hash)
        return valid

    @classmethod
    def confirm_fiat(cls, order, user):
        ''' If Order is in the CHAT states:
        If user is buyer: mark FIAT SENT and settle escrow!
        If User is the seller and FIAT is SENT: Pay buyer invoice!'''

        if order.status == Order.Status.CHA or order.status == Order.Status.FSE: # TODO Alternatively, if all collateral is locked? test out
            
            # If buyer, settle escrow and mark fiat sent
            if cls.is_buyer(order, user):
                if cls.settle_escrow(order): ##### !!! KEY LINE - SETTLES THE TRADE ESCROW !!!
                    order.trade_escrow.status = LNPayment.Status.SETLED
                    order.status = Order.Status.FSE
                    order.is_fiat_sent = True

            # If seller and fiat sent, pay buyer invoice
            elif cls.is_seller(order, user):
                if not order.is_fiat_sent:
                    return False, {'bad_request':'You cannot confirm to have received the fiat before it is confirmed to be sent by the buyer.'}
                
                # Make sure the trade escrow is at least as big as the buyer invoice 
                if order.trade_escrow.num_satoshis > order.buyer_invoice.num_satoshis:
                    return False, {'bad_request':'Woah, something broke badly. Report in the public channels, or open a Github Issue.'}
                
                # Double check the escrow is settled.
                if LNNode.double_check_htlc_is_settled(order.trade_escrow.payment_hash): 
                    if cls.pay_buyer_invoice(order): ##### !!! KEY LINE - PAYS THE BUYER INVOICE !!!
                        order.status = Order.Status.PAY
                        order.buyer_invoice.status = LNPayment.Status.PAYING
        else:
            return False, {'bad_request':'You cannot confirm the fiat payment at this stage'}

        order.save()
        return True, None