Source code for evennia.contrib.game_systems.barter.barter

Barter system

Evennia contribution - Griatch 2012

This implements a full barter system - a way for players to safely
trade items between each other using code rather than simple free-form
talking.  The advantage of this is increased buy/sell safety but it
also streamlines the process and makes it faster when doing many
transactions (since goods are automatically exchanged once both

This system is primarily intended for a barter economy, but can easily
be used in a monetary economy as well -- just let the "goods" on one
side be coin objects (this is more flexible than a simple "buy"
command since you can mix coins and goods in your trade).

In this module, a "barter" is generally referred to as a "trade".

- Trade example

A trade (barter) action works like this: A and B are the parties.

1) opening a trade

A: trade B: Hi, I have a nice extra sword. You wanna trade?
B sees: A says: "Hi, I have a nice extra sword. You wanna trade?"
   A wants to trade with you. Enter 'trade A <emote>' to accept.
B: trade A: Hm, I could use a good sword ...
A sees: B says: "Hm, I could use a good sword ...
   B accepts the trade. Use 'trade help' for aid.
B sees: You are now trading with A. Use 'trade help' for aid.

2) negotiating

A: offer sword: This is a nice sword. I would need some rations in trade.
B sees: A says: "This is a nice sword. I would need some rations in trade."
   [A offers Sword of might.]
B evaluate sword
B sees: <Sword's description and possibly stats>
B: offer ration: This is a prime ration.
A sees: B says: "This is a prime ration."
  [B offers iron ration]
A: say Hey, this is a nice sword, I need something more for it.
B sees: A says: "Hey this is a nice sword, I need something more for it."
B: offer sword,apple: Alright. I will also include a magic apple. That's my last offer.
A sees: B says: "Alright, I will also include a magic apple. That's my last offer."
  [B offers iron ration and magic apple]
A accept: You are killing me here, but alright.
B sees: A says: "You are killing me here, but alright."
  [A accepts your offer. You must now also accept.]
B accept: Good, nice making business with you.
  You accept the deal. Deal is made and goods changed hands.
A sees: B says: "Good, nice making business with you."
  B accepts the deal. Deal is made and goods changed hands.

At this point the trading system is exited and the negotiated items
are automatically exchanged between the parties. In this example B was
the only one changing their offer, but also A could have changed their
offer until the two parties found something they could agree on. The
emotes are optional but useful for RP-heavy worlds.

- Technical info

The trade is implemented by use of a TradeHandler. This object is a
common place for storing the current status of negotiations. It is
created on the object initiating the trade, and also stored on the
other party once that party agrees to trade. The trade request times
out after a certain time - this is handled by a Script. Once trade
starts, the CmdsetTrade cmdset is initiated on both parties along with
the commands relevant for the trading.

- Ideas for NPC bartering:

This module is primarily intended for trade between two players. But
it can also in principle be used for a player negotiating with an
AI-controlled NPC. If the NPC uses normal commands they can use it
directly -- but more efficient is to have the NPC object send its
replies directly through the tradehandler to the player. One may want
to add some functionality to the decline command, so players can
decline specific objects in the NPC offer (decline <object>) and allow
the AI to maybe offer something else and make it into a proper
barter.  Along with an AI that "needs" things or has some sort of
personality in the trading, this can make bartering with NPCs at least
moderately more interesting than just plain 'buy'.

- Installation:

Just import the CmdTrade command into (for example) the default
cmdset. This will make the trade (or barter) command available


from evennia.commands.cmdset import CmdSet
from evennia.commands.command import Command
from evennia.scripts.scripts import DefaultScript

TRADE_TIMEOUT = 60  # timeout for B to accept trade

[docs]class TradeTimeout(DefaultScript): """ This times out the trade request, in case player B did not reply in time. """
[docs] def at_script_creation(self): """ Called when script is first created """ self.key = "trade_request_timeout" self.desc = "times out trade requests" self.interval = TRADE_TIMEOUT self.start_delay = True self.repeats = 1 self.persistent = False
[docs] def at_repeat(self): """ called once """ if self.ndb.tradeevent: self.obj.ndb.tradeevent.finish(force=True) self.obj.msg("Trade request timed out.")
[docs] def is_valid(self): """ Only valid if the trade has not yet started """ return self.obj.ndb.tradeevent and not self.obj.ndb.tradeevent.trade_started
[docs]class TradeHandler(object): """ Objects of this class handles the ongoing trade, notably storing the current offers from each side and wether both have accepted or not. """
[docs] def __init__(self, part_a, part_b): """ Initializes the trade. This is called when part A tries to initiate a trade with part B. The trade will not start until part B repeats this command (B will then call the self.join() command) Args: part_a (object): The party trying to start barter. part_b (object): The party asked to barter. Notes: We also store the back-reference from the respective party to this object. """ # parties self.part_a = part_a self.part_b = part_b self.part_a.cmdset.add(CmdsetTrade()) self.trade_started = False self.part_a.ndb.tradehandler = self # trade variables self.part_a_offers = [] self.part_b_offers = [] self.part_a_accepted = False self.part_b_accepted = False
[docs] def msg_other(self, sender, string): """ Relay a message to the *other* party without needing to know which party that is. This allows the calling command to not have to worry about which party they are in the handler. Args: sender (object): One of A or B. The method will figure out the *other* party to send to. string (str): Text to send. """ if self.part_a == sender: self.part_b.msg(string) elif self.part_b == sender: self.part_a.msg(string) else: # no match, relay to oneself sender.msg(string) if sender else self.part_a.msg(string)
[docs] def get_other(self, party): """ Returns the other party of the trade Args: party (object): One of the parties of the negotiation Returns: party_other (object): The other party, not the first party. """ if self.part_a == party: return self.part_b if self.part_b == party: return self.part_a return None
[docs] def join(self, part_b): """ This is used once B decides to join the trade Args: part_b (object): The party accepting the barter. """ if self.part_b == part_b: self.part_b.ndb.tradehandler = self self.part_b.cmdset.add(CmdsetTrade()) self.trade_started = True return True return False
[docs] def unjoin(self, part_b): """ This is used if B decides not to join the trade. Args: part_b (object): The party leaving the barter. """ if self.part_b == part_b: self.finish(force=True) return True return False
[docs] def offer(self, party, *args): """ Change the current standing offer. We leave it up to the command to do the actual checks that the offer consists of real, valid, objects. Args: party (object): Who is making the offer args (objects or str): Offerings. """ if self.trade_started: # reset accept statements whenever an offer changes self.part_a_accepted = False self.part_b_accepted = False if party == self.part_a: self.part_a_offers = list(args) elif party == self.part_b: self.part_b_offers = list(args) else: raise ValueError
[docs] def list(self): """ List current offers. Returns: offers (tuple): A tuple with two lists, (A_offers, B_offers). """ return self.part_a_offers, self.part_b_offers
[docs] def search(self, offername): """ Search current offers. Args: offername (str or int): Object to search for, or its index in the list of offered items. Returns: offer (object): An object on offer, based on the search criterion. """ all_offers = self.part_a_offers + self.part_b_offers if isinstance(offername, int): # an index to return if 0 <= offername < len(all_offers): return all_offers[offername] all_keys = [offer.key for offer in all_offers] try: imatch = all_keys.index(offername) return all_offers[imatch] except ValueError: for offer in all_offers: if offer.aliases.get(offername): return offer return None
[docs] def accept(self, party): """ Accept the current offer. Args: party (object): The party accepting the deal. Returns: result (object): `True` if this closes the deal, `False` otherwise Notes: This will only close the deal if both parties have accepted independently. This is done by calling the `finish()` method. """ if self.trade_started: if party == self.part_a: self.part_a_accepted = True elif party == self.part_b: self.part_b_accepted = True else: raise ValueError return self.finish() # try to close the deal return False
[docs] def decline(self, party): """ Decline the offer (or change one's mind). Args: party (object): Party declining the deal. Returns: did_decline (bool): `True` if there was really an `accepted` status to change, `False` otherwise. Notes: If previously having used the `accept` command, this function will only work as long as the other party has not yet accepted. """ if self.trade_started: if party == self.part_a: if self.part_a_accepted: self.part_a_accepted = False return True return False elif party == self.part_b: if self.part_b_accepted: self.part_b_accepted = False return True return False else: raise ValueError return False
[docs] def finish(self, force=False): """ Conclude trade - move all offers and clean up Args: force (bool, optional): Force cleanup regardless of if the trade was accepted or not (if not, no goods will change hands but trading will stop anyway) Returns: result (bool): If the finish was successful. """ fin = False if self.trade_started and self.part_a_accepted and self.part_b_accepted: # both accepted - move objects before cleanup for obj in self.part_a_offers: obj.location = self.part_b for obj in self.part_b_offers: obj.location = self.part_a fin = True if fin or force: # cleanup self.part_a.cmdset.delete("cmdset_trade") self.part_b.cmdset.delete("cmdset_trade") self.part_a_offers = None self.part_b_offers = None self.part_a.scripts.stop("trade_request_timeout") # this will kill it also from B del self.part_a.ndb.tradehandler if self.part_b.ndb.tradehandler: del self.part_b.ndb.tradehandler return True return False
# trading commands (will go into CmdsetTrade, initialized by the # CmdTrade command further down).
[docs]class CmdTradeBase(Command): """ Base command for Trade commands to inherit from. Implements the custom parsing. """
[docs] def parse(self): """ Parse the relevant parts and make it easily available to the command """ self.args = self.args.strip() self.tradehandler = self.caller.ndb.tradehandler self.part_a = self.tradehandler.part_a self.part_b = self.tradehandler.part_b self.other = self.tradehandler.get_other(self.caller) self.msg_other = self.tradehandler.msg_other self.trade_started = self.tradehandler.trade_started self.emote = "" self.str_caller = "Your trade action: %s" self.str_other = "%s:s trade action: " % self.caller.key + "%s" if ":" in self.args: self.args, self.emote = [part.strip() for part in self.args.rsplit(":", 1)] self.str_caller = 'You say, "' + self.emote + '"\n [%s]' if self.caller.has_account: self.str_other = '|c%s|n says, "' % self.caller.key + self.emote + '"\n [%s]' else: self.str_other = '%s says, "' % self.caller.key + self.emote + '"\n [%s]'
# trade help
[docs]class CmdTradeHelp(CmdTradeBase): """ help command for the trade system. Usage: trade help Displays help for the trade commands. """ key = "trade help" locks = "cmd:all()" help_category = "Trade"
[docs] def func(self): """Show the help""" string = """ Trading commands |woffer <objects> [:emote]|n offer one or more objects for trade. The emote can be used for RP/arguments. A new offer will require both parties to re-accept it again. |waccept [:emote]|n accept the currently standing offer from both sides. Also 'agree' works. Once both have accepted, the deal is finished and goods will change hands. |wdecline [:emote]|n change your mind and remove a previous accept (until other has also accepted) |wstatus|n show the current offers on each side of the deal. Also 'offers' and 'deal' works. |wevaluate <nr> or <offer>|n examine any offer in the deal. List them with the 'status' command. |wend trade|n end the negotiations prematurely. No trade will take place. You can also use |wemote|n, |wsay|n etc to discuss without making a decision or offer. """ self.caller.msg(string)
# offer
[docs]class CmdOffer(CmdTradeBase): """ offer one or more items in trade. Usage: offer <object> [, object2, ...][:emote] Offer objects in trade. This will replace the currently standing offer. """ key = "offer" locks = "cmd:all()" help_category = "Trading"
[docs] def func(self): """implement the offer""" caller = self.caller if not self.args: caller.msg("Usage: offer <object> [, object2, ...] [:emote]") return if not self.trade_started: caller.msg("Wait until the other party has accepted to trade with you.") return # gather all offers offers = [part.strip() for part in self.args.split(",")] offerobjs = [] for offername in offers: obj = if not obj: return offerobjs.append(obj) self.tradehandler.offer(self.caller, *offerobjs) # output if len(offerobjs) > 1: objnames = ( ", ".join("|w%s|n" % obj.key for obj in offerobjs[:-1]) + " and |w%s|n" % offerobjs[-1].key ) else: objnames = "|w%s|n" % offerobjs[0].key caller.msg(self.str_caller % ("You offer %s" % objnames)) self.msg_other(caller, self.str_other % ("They offer %s" % objnames))
# accept
[docs]class CmdAccept(CmdTradeBase): """ accept the standing offer Usage: accept [:emote] agreee [:emote] This will accept the current offer. The other party must also accept for the deal to go through. You can use the 'decline' command to change your mind as long as the other party has not yet accepted. You can inspect the current offer using the 'offers' command. """ key = "accept" aliases = ["agree"] locks = "cmd:all()" help_category = "Trading"
[docs] def func(self): """accept the offer""" caller = self.caller if not self.trade_started: caller.msg("Wait until the other party has accepted to trade with you.") return if self.tradehandler.accept(self.caller): # deal finished. Trade ended and cleaned. caller.msg( self.str_caller % "You |gaccept|n the deal. |gDeal is made and goods changed hands.|n" ) self.msg_other( caller, self.str_other % "%s |gaccepts|n the deal." " |gDeal is made and goods changed hands.|n" % caller.key, ) else: # a one-sided accept. caller.msg( self.str_caller % "You |Gaccept|n the offer. %s must now also accept." % self.other.key ) self.msg_other( caller, self.str_other % "%s |Gaccepts|n the offer. You must now also accept." % caller.key, )
# decline
[docs]class CmdDecline(CmdTradeBase): """ decline the standing offer Usage: decline [:emote] This will decline a previously 'accept'ed offer (so this allows you to change your mind). You can only use this as long as the other party has not yet accepted the deal. Also, changing the offer will automatically decline the old offer. """ key = "decline" locks = "cmd:all()" help_category = "Trading"
[docs] def func(self): """decline the offer""" caller = self.caller if not self.trade_started: caller.msg("Wait until the other party has accepted to trade with you.") return offer_a, offer_b = self.tradehandler.list() if not offer_a or not offer_b: caller.msg("No offers have been made yet, so there is nothing to decline.") return if self.tradehandler.decline(self.caller): # changed a previous accept caller.msg(self.str_caller % "You change your mind, |Rdeclining|n the current offer.") self.msg_other( caller, self.str_other % "%s changes their mind, |Rdeclining|n the current offer." % caller.key, ) else: # no acceptance to change caller.msg(self.str_caller % "You |Rdecline|n the current offer.") self.msg_other(caller, self.str_other % "%s declines the current offer." % caller.key)
# evaluate # Note: This version only shows the description. If your particular game # lists other important properties of objects (such as weapon damage, weight, # magical properties, ammo requirements or whatnot), then you need to add this # here.
[docs]class CmdEvaluate(CmdTradeBase): """ evaluate objects on offer Usage: evaluate <offered object> This allows you to examine any object currently on offer, to determine if it's worth your while. """ key = "evaluate" aliases = ["eval"] locks = "cmd:all()" help_category = "Trading"
[docs] def func(self): """evaluate an object""" caller = self.caller if not self.args: caller.msg("Usage: evaluate <offered object>") return # we also accept indices try: ind = int(self.args) self.args = ind - 1 except Exception: # not a valid index - ignore pass offer = if not offer: caller.msg("No offer matching '%s' was found." % self.args) return # show the description caller.msg(offer.db.desc)
# status
[docs]class CmdStatus(CmdTradeBase): """ show a list of the current deal Usage: status deal offers Shows the currently suggested offers on each sides of the deal. To accept the current deal, use the 'accept' command. Use 'offer' to change your deal. You might also want to use 'say', 'emote' etc to try to influence the other part in the deal. """ key = "status" aliases = ["offers", "deal"] locks = "cmd:all()" help_category = "Trading"
[docs] def func(self): """Show the current deal""" caller = self.caller part_a_offers, part_b_offers = self.tradehandler.list() count = 1 part_a_offerlist = [] for offer in part_a_offers: part_a_offerlist.append("\n |w%i|n %s" % (count, offer.key)) count += 1 if not part_a_offerlist: part_a_offerlist = "\n <nothing>" part_b_offerlist = [] for offer in part_b_offers: part_b_offerlist.append("\n |w%i|n %s" % (count, offer.key)) count += 1 if not part_b_offerlist: part_b_offerlist = "\n <nothing>" string = "|gOffered by %s:|n%s\n|yOffered by %s:|n%s" % ( self.part_a.key, "".join(part_a_offerlist), self.part_b.key, "".join(part_b_offerlist), ) accept_a = self.tradehandler.part_a_accepted and "|gYes|n" or "|rNo|n" accept_b = self.tradehandler.part_b_accepted and "|gYes|n" or "|rNo|n" string += "\n\n%s agreed: %s, %s agreed: %s" % ( self.part_a.key, accept_a, self.part_b.key, accept_b, ) string += "\n Use 'offer', 'eval' and 'accept'/'decline' to trade. See also 'trade help'." caller.msg(string)
# finish
[docs]class CmdFinish(CmdTradeBase): """ end the trade prematurely Usage: end trade [:say] finish trade [:say] This ends the trade prematurely. No trade will take place. """ key = "end trade" aliases = "finish trade" locks = "cmd:all()" help_category = "Trading"
[docs] def func(self): """end trade""" caller = self.caller self.tradehandler.finish(force=True) caller.msg(self.str_caller % "You |raborted|n trade. No deal was made.") self.msg_other( caller, self.str_other % "%s |raborted|n trade. No deal was made." % caller.key )
# custom Trading cmdset
[docs]class CmdsetTrade(CmdSet): """ This cmdset is added when trade is initated. It is handled by the trade event handler. """ key = "cmdset_trade"
[docs] def at_cmdset_creation(self): """Called when cmdset is created""" self.add(CmdTradeHelp()) self.add(CmdOffer()) self.add(CmdAccept()) self.add(CmdDecline()) self.add(CmdEvaluate()) self.add(CmdStatus()) self.add(CmdFinish())
# access command - once both have given this, this will create the # trading cmdset to start trade.
[docs]class CmdTrade(Command): """ Initiate trade with another party Usage: trade <other party> [:say] trade <other party> accept [:say] trade <other party> decline [:say] Initiate trade with another party. The other party needs to repeat this command with trade accept/decline within a minute in order to properly initiate the trade action. You can use the decline option yourself if you want to retract an already suggested trade. The optional say part works like the say command and allows you to add info to your choice. """ key = "trade" aliases = ["barter"] locks = "cmd:all()" help_category = "General"
[docs] def func(self): """Initiate trade""" if not self.args: if self.caller.ndb.tradehandler and self.caller.ndb.tradeevent.trade_started: self.caller.msg("You are already in a trade. Use 'end trade' to abort it.") else: self.caller.msg("Usage: trade <other party> [accept|decline] [:emote]") return self.args = self.args.strip() # handle the emote manually here selfemote = "" theiremote = "" if ":" in self.args: self.args, emote = [part.strip() for part in self.args.rsplit(":", 1)] selfemote = 'You say, "%s"\n ' % emote if self.caller.has_account: theiremote = '|c%s|n says, "%s"\n ' % (self.caller.key, emote) else: theiremote = '%s says, "%s"\n ' % (self.caller.key, emote) # for the sake of this command, the caller is always part_a; this # might not match the actual name in tradehandler (in the case of # using this command to accept/decline a trade invitation). part_a = self.caller accept = "accept" in self.args decline = "decline" in self.args if accept: part_b = self.args.rstrip("accept").strip() elif decline: part_b = self.args.rstrip("decline").strip() else: part_b = self.args part_b = if not part_b: return if part_a == part_b: part_a.msg("You play trader with yourself.") return # messages str_init_a = "You ask to trade with %s. They need to accept within %s secs." str_init_b = "%s wants to trade with you. Use |wtrade %s accept/decline [:emote]|n to answer (within %s secs)." str_noinit_a = "%s declines the trade" str_noinit_b = "You decline trade with %s." str_start_a = "%s starts to trade with you. See |wtrade help|n for aid." str_start_b = "You start to trade with %s. See |wtrade help|n for aid." if not (accept or decline): # initialization of trade if self.caller.ndb.tradehandler: # trying to start trade without stopping a previous one if self.caller.ndb.tradehandler.trade_started: string = "You are already in trade with %s. You need to end trade first." else: string = "You are already trying to initiate trade with %s. You need to decline that trade first." self.caller.msg(string % part_b.key) elif part_b.ndb.tradehandler and part_b.ndb.tradehandler.part_b == part_a: # this is equivalent to part_a accepting a trade from part_b (so roles are reversed) part_b.ndb.tradehandler.join(part_a) part_b.msg(theiremote + str_start_a % part_a.key) part_a.msg(selfemote + str_start_b % part_b.key) else: # initiate a new trade TradeHandler(part_a, part_b) part_a.msg(selfemote + str_init_a % (part_b.key, TRADE_TIMEOUT)) part_b.msg(theiremote + str_init_b % (part_a.key, part_a.key, TRADE_TIMEOUT)) part_a.scripts.add(TradeTimeout) return elif accept: # accept a trade proposal from part_b (so roles are reversed) if part_a.ndb.tradehandler: # already in a trade part_a.msg( "You are already in trade with %s. You need to end that first." % part_b.key ) return if part_b.ndb.tradehandler.join(part_a): part_b.msg(theiremote + str_start_a % part_a.key) part_a.msg(selfemote + str_start_b % part_b.key) else: part_a.msg("No trade proposal to accept.") return else: # decline trade proposal from part_b (so roles are reversed) if part_a.ndb.tradehandler and part_a.ndb.tradehandler.part_b == part_a: # stopping an invite part_a.ndb.tradehandler.finish(force=True) part_b.msg(theiremote + "%s aborted trade attempt with you." % part_a) part_a.msg(selfemote + "You aborted the trade attempt with %s." % part_b) elif part_b.ndb.tradehandler and part_b.ndb.tradehandler.unjoin(part_a): part_b.msg(theiremote + str_noinit_a % part_a.key) part_a.msg(selfemote + str_noinit_b % part_b.key) else: part_a.msg("No trade proposal to decline.") return