robosats/api/logics.py

from datetime import time, timedelta
from django.utils import timezone
from .lightning.node import LNNode

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

import math

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

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'))

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

PUBLIC_ORDER_DURATION = int(config('PUBLIC_ORDER_DURATION'))
INVOICE_AND_ESCROW_DURATION = int(config('INVOICE_AND_ESCROW_DURATION'))
FIAT_EXCHANGE_DURATION = int(config('FIAT_EXCHANGE_DURATION'))

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': 'Your order is too big. It is worth '+'{:,}'.format(order.t0_satoshis)+' Sats now. But limit is '+'{:,}'.format(MAX_TRADE)+ ' Sats'}
        if order.t0_satoshis < MIN_TRADE:
            return False, {'bad_request': 'Your order is too small. It is worth '+'{:,}'.format(order.t0_satoshis)+' Sats now. But limit is '+'{:,}'.format(MIN_TRADE)+ ' Sats'}
        return True, None

    @classmethod    
    def take(cls, order, user):
        is_penalized, time_out = cls.is_penalized(user)
        if is_penalized:
            return False, {'bad_request',f'You need to wait {time_out} seconds to take an order'}
        else:
            order.taker = user
            order.status = Order.Status.TAK
            order.expires_at = timezone.now() + timedelta(minutes=EXP_TAKER_BOND_INVOICE)
            order.save()
            return True, None

    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 price_and_premium_now(order):
        ''' computes order premium live '''
        exchange_rate = get_exchange_rate(Order.currency_dict[str(order.currency)])
        if not order.is_explicit:
            premium = order.premium
            price = exchange_rate * (1+float(premium)/100)
        else:
            exchange_rate = get_exchange_rate(Order.currency_dict[str(order.currency)])
            order_rate = float(order.amount) / (float(order.satoshis) / 100000000)
            premium = order_rate / exchange_rate - 1
            premium = int(premium*100)  # 2 decimals left
            price = order_rate

        significant_digits = 6
        price = round(price, significant_digits - int(math.floor(math.log10(abs(price)))) - 1)
        
        return price, premium

    def order_expires(order):
        ''' General case when time runs out. Only 
        used when the maker does not lock a publishing bond'''
        order.status = Order.Status.EXP
        order.maker = None
        order.taker = None
        order.save()

    def kick_taker(order):
        ''' The taker did not lock the taker_bond. Now he has to go'''
        # Add a time out to the taker
        profile = order.taker.profile
        profile.penalty_expiration = timezone.now() + timedelta(seconds=PENALTY_TIMEOUT)
        profile.save()

        # Delete the taker_bond payment request, and make order public again
        if LNNode.cancel_return_hold_invoice(order.taker_bond.payment_hash):
            order.status = Order.Status.PUB
            order.taker = None
            order.taker_bond = None
            order.expires_at = timezone.now() + timedelta(hours=PUBLIC_ORDER_DURATION) ## TO FIX. Restore the remaining order durantion, not all of it!
            order.save()
            return True

    @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']
        buyer_invoice = LNNode.validate_ln_invoice(invoice, num_satoshis)

        if not buyer_invoice['valid']:
            return False, buyer_invoice['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' :  buyer_invoice['description'],
                'payment_hash' : buyer_invoice['payment_hash'],
                'created_at' : buyer_invoice['created_at'],
                'expires_at' : buyer_invoice['expires_at']}
            )

        # If the order status is 'Waiting for invoice'. Move forward to 'chat'
        if order.status == Order.Status.WFI: 
            order.status = Order.Status.CHA
            order.expires_at = timezone.now() + timedelta(hours=FIAT_EXCHANGE_DURATION)

        # If the order status is 'Waiting for both'. Move forward to 'waiting for escrow'
        if order.status == Order.Status.WF2:
            # If the escrow is lock move to Chat.
            if order.trade_escrow.status == LNPayment.Status.LOCKED:
                order.status = Order.Status.CHA
                order.expires_at = timezone.now() + timedelta(hours=FIAT_EXCHANGE_DURATION)
            else:
                order.status = Order.Status.WFE

        order.save()
        return True, None

    def add_profile_rating(profile, rating):
        ''' adds a new rating to a user profile'''

        profile.total_ratings = profile.total_ratings + 1
        latest_ratings = profile.latest_ratings
        if len(latest_ratings) <= 1:
            profile.latest_ratings = [rating]
            profile.avg_rating = rating

        else:
            latest_ratings = list(latest_ratings).append(rating)
            profile.latest_ratings = latest_ratings
            profile.avg_rating = sum(latest_ratings) / len(latest_ratings)

        profile.save()

    def is_penalized(user):
        ''' Checks if a user that is not participant of orders
        has a limit on taking or making a order'''
        
        if user.profile.penalty_expiration:
            if user.profile.penalty_expiration > timezone.now():
                time_out = (user.profile.penalty_expiration - timezone.now()).seconds
                return True, time_out

        return False, 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 the bond to prevent DDOS 
            on the LN node and order book. TODO Only charge a small part of the bond (requires maker submitting an invoice)'''
        elif order.status == Order.Status.PUB and order.maker == user:
            #Settle the maker bond (Maker loses the bond for cancelling public order)
            if cls.settle_maker_bond(order):
                order.maker = None
                order.status = Order.Status.UCA
                order.save()
                return True, None

        # 3) When taker cancels before bond
            ''' The order goes back to the book as public.
            LNPayment "order.taker_bond" is deleted() '''
        elif order.status == Order.Status.TAK and order.taker == user:
            # adds a timeout penalty
            user.profile.penalty_expiration = timezone.now() + timedelta(seconds=PENALTY_TIMEOUT)
            user.profile.save()

            order.taker = None
            order.status = Order.Status.PUB
            order.save()

            return True, None

        # 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.'''

        # 4.a) When maker cancel after bond (before escrow)
            '''The order into cancelled status if maker cancels.'''
        elif order.status > Order.Status.PUB and order.status < Order.Status.CHA and order.maker == user:
            #Settle the maker bond (Maker loses the bond for canceling an ongoing trade)
            valid = cls.settle_maker_bond(order)
            if valid:
                order.maker = None
                order.status = Order.Status.UCA
                order.save()
                return True, None

        # 4.b) When taker cancel after bond (before escrow)
            '''The order into cancelled status if maker cancels.'''
        elif order.status > Order.Status.TAK and order.status < Order.Status.CHA and order.taker == user:
            # Settle the maker bond (Maker loses the bond for canceling an ongoing trade)
            valid = cls.settle_taker_bond(order)
            if valid:
                order.taker = None
                order.status = Order.Status.PUB
                # order.taker_bond = None # TODO fix this, it overrides the information about the settled taker bond. Might make admin tasks hard.
                order.save()
                return True, None

        # 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 is_maker_bond_locked(cls, order):
        if LNNode.validate_hold_invoice_locked(order.maker_bond.payment_hash):
            order.maker_bond.status = LNPayment.Status.LOCKED
            order.maker_bond.save()
            order.status = Order.Status.PUB
            # With the bond confirmation the order is extended 'public_order_duration' hours
            order.expires_at = timezone.now() + timedelta(hours=PUBLIC_ORDER_DURATION)
            order.save()
            return True
        return False

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

        # Do not gen and cancel if order is older than expiry time
        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 cls.is_maker_bond_locked(order):
                return False, None
            elif order.maker_bond.status == LNPayment.Status.INVGEN:
                return True, {'bond_invoice':order.maker_bond.invoice,'bond_satoshis':order.maker_bond.num_satoshis}

        # If there was no maker_bond object yet, generates one
        order.last_satoshis = cls.satoshis_now(order)
        bond_satoshis = int(order.last_satoshis * BOND_SIZE)

        description = f"RoboSats - Publishing '{str(order)}' - This is a maker bond, it will freeze in your wallet temporarily and automatically return. It will be charged if you cheat or cancel."

        # Gen hold Invoice
        hold_payment = 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 = hold_payment['invoice'],
            preimage = hold_payment['preimage'],
            status = LNPayment.Status.INVGEN,
            num_satoshis = bond_satoshis,
            description =  description,
            payment_hash = hold_payment['payment_hash'],
            created_at = hold_payment['created_at'],
            expires_at = hold_payment['expires_at'])

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

    @classmethod
    def is_taker_bond_locked(cls, order):
        if LNNode.validate_hold_invoice_locked(order.taker_bond.payment_hash):
            # THE TRADE AMOUNT IS FINAL WITH THE CONFIRMATION OF THE TAKER BOND! 
            # (This is the last update to "last_satoshis", it becomes the escrow amount next!)
            order.last_satoshis = cls.satoshis_now(order)
            order.taker_bond.status = LNPayment.Status.LOCKED
            order.taker_bond.save()

            # Log a market tick
            MarketTick.log_a_tick(order) 

            # With the bond confirmation the order is extended 'public_order_duration' hours
            order.expires_at = timezone.now() + timedelta(minutes=INVOICE_AND_ESCROW_DURATION)
            order.status = Order.Status.WF2
            order.save()
            return True
        return False

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

        # Do not gen and kick out the taker if order is older than expiry time
        if order.expires_at < timezone.now():
            cls.kick_taker(order)
            return False, {'bad_request':'Invoice expired. You did not confirm taking the order in time.'}

        # Do not gen if a taker invoice exist. Do not return if it is already locked. Return the old one if still waiting.
        if order.taker_bond:
            # Check if status is INVGEN and still not expired
            if cls.is_taker_bond_locked(order):
                return False, None
            elif order.taker_bond.status == LNPayment.Status.INVGEN:
                return True, {'bond_invoice':order.taker_bond.invoice,'bond_satoshis':order.taker_bond.num_satoshis}

        # If there was no taker_bond object yet, generates one
        order.last_satoshis = cls.satoshis_now(order)
        bond_satoshis = int(order.last_satoshis * BOND_SIZE)
        description = f"RoboSats - Taking '{str(order)}' - This is a taker bond, it will freeze in your wallet temporarily and automatically return. It will be charged if you cheat or cancel."

        # Gen hold Invoice
        hold_payment = 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 = hold_payment['invoice'],
            preimage = hold_payment['preimage'],
            status = LNPayment.Status.INVGEN,
            num_satoshis = bond_satoshis,
            description =  description,
            payment_hash = hold_payment['payment_hash'],
            created_at = hold_payment['created_at'],
            expires_at = hold_payment['expires_at'])

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


    @classmethod
    def is_trade_escrow_locked(cls, order):
        if LNNode.validate_hold_invoice_locked(order.trade_escrow.payment_hash):
            order.trade_escrow.status = LNPayment.Status.LOCKED
            order.trade_escrow.save()
            # If status is 'Waiting for both' move to Waiting for invoice
            if order.status == Order.Status.WF2:
                order.status = Order.Status.WFI
            # If status is 'Waiting for invoice' move to Chat
            elif order.status == Order.Status.WFE:
                order.status = Order.Status.CHA
                order.expires_at = timezone.now() + timedelta(hours=FIAT_EXCHANGE_DURATION)
            order.save()
            return True
        return False

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

        # Do not generate if escrow deposit time has expired
        if order.expires_at < timezone.now():
            cls.cancel_order(order,user)
            return False, {'bad_request':'Invoice expired. You did not send the escrow in time.'}

        # Do not gen if an escrow invoice exist. Do not return if it is already locked. Return the old one if still waiting.
        if order.trade_escrow:
            # Check if status is INVGEN and still not expired
            if cls.is_trade_escrow_locked(order):
                return False, None
            elif order.trade_escrow.status == LNPayment.Status.INVGEN:
                return True, {'escrow_invoice':order.trade_escrow.invoice, 'escrow_satoshis':order.trade_escrow.num_satoshis}

        # If there was no taker_bond object yet, generates one
        escrow_satoshis = order.last_satoshis # Amount was fixed when taker bond was locked
        description = f"RoboSats - Escrow amount for '{str(order)}' - The escrow will be released to the buyer once you confirm you received the fiat. It will automatically return if buyer does not confirm the payment."

        # Gen hold Invoice
        hold_payment = 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 = hold_payment['invoice'],
            preimage = hold_payment['preimage'],
            status = LNPayment.Status.INVGEN,
            num_satoshis = escrow_satoshis,
            description =  description,
            payment_hash = hold_payment['payment_hash'],
            created_at = hold_payment['created_at'],
            expires_at = hold_payment['expires_at'])

        order.save()
        return True, {'escrow_invoice':hold_payment['invoice'],'escrow_satoshis': escrow_satoshis}
    
    def settle_escrow(order):
        ''' Settles the trade escrow hold invoice'''
        # TODO ERROR HANDLING
        if LNNode.settle_hold_invoice(order.trade_escrow.preimage):
            order.trade_escrow.status = LNPayment.Status.SETLED
            order.trade_escrow.save()
            return True

    def settle_maker_bond(order):
        ''' Settles the maker bond hold invoice'''
        # TODO ERROR HANDLING
        if LNNode.settle_hold_invoice(order.maker_bond.preimage):
            order.maker_bond.status = LNPayment.Status.SETLED
            order.maker_bond.save()
            return True

    def settle_taker_bond(order):
        ''' Settles the taker bond hold invoice'''
        # TODO ERROR HANDLING
        if LNNode.settle_hold_invoice(order.taker_bond.preimage):
            order.taker_bond.status = LNPayment.Status.SETLED
            order.taker_bond.save()
            return True
    
    def return_bond(bond):
        '''returns a bond'''
        if LNNode.cancel_return_hold_invoice(bond.payment_hash):
            bond.status = LNPayment.Status.RETNED
            return True

    def pay_buyer_invoice(order):
        ''' Pay buyer invoice'''
        # TODO ERROR HANDLING
        if LNNode.pay_invoice(order.buyer_invoice.invoice, order.buyer_invoice.num_satoshis):
            return True

    @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): 
                    is_payed, context = cls.pay_buyer_invoice(order) ##### !!! KEY LINE - PAYS THE BUYER INVOICE !!!
                    if is_payed:
                        order.status = Order.Status.SUC
                        order.buyer_invoice.status = LNPayment.Status.SUCCED
                        order.expires_at = timezone.now() + timedelta(days=1) # One day to rate / see this order.
                        order.save()

                        # RETURN THE BONDS
                        cls.return_bond(order.taker_bond)
                        cls.return_bond(order.maker_bond)
                    else:
                        # error handling here
                        pass
        else:
            return False, {'bad_request':'You cannot confirm the fiat payment at this stage'}

        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:
                cls.add_profile_rating(order.taker.profile, rating)
            # if taker, rates maker
            if order.taker == user:
                cls.add_profile_rating(order.maker.profile, rating)
        else:
            return False, {'bad_request':'You cannot rate your counterparty yet.'}

        return True, None