economy: add class Economy

economy/economy.gd

@@ -0,0 +1,79 @@
+# Economy is a game entity that tracks money.
+
+# How money is minted, how money changes hands, and which
+# money is valid is all controlled by Economy. When an
+# in-game item is purchased, the money does not disappear
+# but rather goes to the Market, an economic entity which
+# can give back to players through investments or other means.
+
+# Economy also tracks GDP, which is the total amount of
+# money that has changed hands so far during the game.
+class_name Economy extends Node
+
+# Participant in the game economy
+@abstract class Participant:
+	var participant_name = "Unnamed participant"
+	var _tokens = PackedInt32Array()
+
+	func balance():
+		return _tokens.size()
+
+	func hold_tokens(tokens):
+		_tokens.append_array(tokens)
+		on_balance_update(balance())
+
+	func pop_tokens(amount):
+		if balance() < amount:
+			return []
+
+		var dropped = []
+		for i in range(amount):
+			dropped.append(_tokens[_tokens.size() - 1])
+			_tokens.remove_at(_tokens.size() - 1)
+		on_balance_update(balance())
+		return dropped
+
+	@abstract func message(string)
+	@abstract func on_balance_update(bal)
+
+class Market extends Participant:
+	func _init():
+		participant_name = "Market"
+	func message(_s):
+		pass
+	func on_balance_update(_bal):
+		pass
+
+const max_money_supply = 1_000_000
+
+var _gdp = 0
+var _market = Market.new()
+var _participants = []
+var _token_ptr = 0
+
+# register a Participant to receive benefits
+func register(p: Participant):
+	_participants.append(p)
+
+func transfer(amount, sender: Participant, recipient: Participant):
+	if sender.balance() < amount:
+		return false
+	recipient.hold_tokens(sender.pop_tokens(amount))
+	_gdp += amount
+
+func mint(amount):
+	var tokens = PackedInt32Array()
+	if _token_ptr + amount > max_money_supply:
+		return false
+	for i in range(amount):
+		tokens.append(_token_ptr)
+		_token_ptr += 1
+	_market.hold_tokens(tokens)
+	return true
+
+func _ready():
+	while true:
+		if len(_participants) > 0:
+			mint(1000)
+			transfer(1000, _market, _participants[0])
+			break

economy/economy.tscn

@@ -0,0 +1,6 @@
+[gd_scene load_steps=2 format=3 uid="uid://cenj3dcweigwt"]
+
+[ext_resource type="Script" uid="uid://dl1jbgt83gocy" path="res://economy/economy.gd" id="1_n84lp"]
+
+[node name="Economy" type="Node"]
+script = ExtResource("1_n84lp")