chore: staking python script

scripts/staking.py

@@ -0,0 +1,72 @@
+# Simplified staking model that only has a single vault
+
+class Staking:
+    def __init__(self):
+        self.total_stake = 0
+        self.total_current_stake = 0
+        self.reward_per_token = 0
+        self.reward_tally = {'alice': 0, 'bob': 0}
+        self.stake = {'alice': 0, 'bob': 0}
+        self.slash_tally = {'alice': 0, 'bob': 0}
+        self.slash_per_token = 0
+
+    def apply_slash(self, nominator):
+        self.total_stake -= self.stake[nominator] * self.slash_per_token - self.slash_tally[nominator];
+        self.stake[nominator] -= self.stake[nominator] * self.slash_per_token - self.slash_tally[nominator];
+        self.slash_tally[nominator] = self.stake[nominator] * self.slash_per_token;
+
+    def distribute_reward(self, nominator, x):
+        self.reward_per_token += x / self.total_current_stake;
+
+    def withdraw_reward(self, nominator):
+        self.apply_slash(nominator);
+        withdrawal_reward = self.stake[nominator] * self.reward_per_token - self.reward_tally[nominator];
+        self.reward_tally[nominator] = self.stake[nominator] * self.reward_per_token;
+        return withdrawal_reward
+
+    def deposit_stake(self, nominator, x):
+        self.apply_slash(nominator);
+        self.stake[nominator] += x;
+        self.total_stake += x;
+        self.total_current_stake += x;
+        self.slash_tally[nominator] += self.slash_per_token * x;
+        self.reward_tally[nominator] += self.reward_per_token * x;
+
+        self.reward_per_token += x / self.total_current_stake;
+
+    def withdraw_stake(self, nominator, x):
+        self.deposit_stake(nominator, -x)
+
+    def slash_stake(self, x):
+        self.slash_per_token += x / self.total_stake;
+        self.total_current_stake -= x;
+        self.reward_per_token += (self.reward_per_token * x) / self.total_current_stake;
+
+    def compute_stake(self, nominator):
+        return self.stake[nominator] - (self.stake[nominator] * self.slash_per_token - self.slash_tally[nominator])
+
+staking = Staking()
+alice = "alice"
+bob = "bob"
+
+# step 1: initial setup
+staking.deposit_stake(alice, 50);
+assert(staking.compute_stake(alice) == 50);
+
+# step 2: slash
+staking.slash_stake(30);
+assert(staking.compute_stake(alice) == 20);
+
+# step 3: add nominator. Both should have equal stake
+staking.deposit_stake(bob, 20);
+assert(staking.compute_stake(alice) == 20);
+assert(staking.compute_stake(bob) == 20);
+
+# step 4: slash stake. Both should lose equal amount of stake
+staking.slash_stake(10);
+# for Alice, SlashPerToken should be set to 0.7,  s.t. toSlash = 50*0.7 - 0 = 35
+# for Bob,   SlashPerToken should be set to 0.85, s.t. toSlash = 20*0.85 - 12 = 5
+
+print('actual stake', staking.compute_stake(alice)) # prints 12.857142857142854
+assert(staking.compute_stake(alice) == 15); # fail!
+assert(staking.compute_stake(bob) == 15);