From c3a56c96bd8e4c92298d50f6a2b4e76ff06ed9b6 Mon Sep 17 00:00:00 2001
From: Jarry Xiao <jarry.xiao@gmail.com>
Date: Wed, 1 Mar 2023 16:43:20 -0500
Subject: [PATCH] Add PoC python script simulating the tower bft lockout
 algorithm

---
 core/tower_bft.py | 129 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 129 insertions(+)
 create mode 100644 core/tower_bft.py

diff --git a/core/tower_bft.py b/core/tower_bft.py
new file mode 100644
index 0000000..8207ebd
--- /dev/null
+++ b/core/tower_bft.py
@@ -0,0 +1,129 @@
+from collections import deque
+import pandas as pd
+
+
+class TowerEntry:
+    def __init__(self, slot, lockout, expired):
+        self.slot = slot
+        self.lockout = lockout
+        self.expired = expired
+
+    def __repr__(self) -> str:
+        return f"{self.slot} {self.lockout}"
+
+
+class Tower:
+    def __init__(self) -> None:
+        self.root = None
+        self.stack = deque()
+
+    def update(self, slot):
+        # On Tower update, remove all expired entries
+        n = len(self.stack)
+        expired_slots = []
+        for i, entry in enumerate(self.stack):
+            expiration_slot = entry.slot + 2**entry.lockout
+            if slot > expiration_slot:
+                entry.expired = True  # Mark the entry to be removed
+                expired_slots.append(i)
+
+        # Remove all expired towers
+        for i in expired_slots:
+            curr_lockout = self.stack[i].lockout
+            for j in range(i + 1, n):
+                lockout = self.stack[j].lockout
+                if curr_lockout - lockout == 1:
+                    self.stack[j].expired = True
+                curr_lockout = lockout
+        self.stack = deque([entry for entry in self.stack if not entry.expired])
+
+        # Add the new slot to the tower
+        n = len(self.stack)
+        self.stack.append(TowerEntry(slot, 1, False))
+        # Double the lockout period of the longest contiguous sequence
+        for i in range(n, 0, -1):
+            curr_exp = self.stack[i].lockout
+            prev_exp = self.stack[i - 1].lockout
+            expiration_slot = self.stack[i - 1].slot + 2 ** self.stack[i - 1].lockout
+            if curr_exp == prev_exp and slot < expiration_slot:
+                self.stack[i - 1].lockout += 1
+            else:
+                break
+
+        if len(self.stack) == 32:
+            entry = self.stack.popleft()
+            self.root = entry.slot
+
+    def print(self):
+        df = pd.DataFrame(
+            [
+                (e.slot, e.lockout, 2**e.lockout, e.slot + (2**e.lockout))
+                for e in self.stack
+            ],
+            columns=["slot", "level", "lockout", "expiration_slot"],
+        ).sort_index(ascending=False)
+        print(df.to_string(index=False))
+
+
+if __name__ == "__main__":
+    t = Tower()
+    t.update(1)
+    t.update(2)
+    t.update(3)
+    t.update(4)
+    t.print()
+    """
+    ╔══════╤═══════╤═════════╤═════════════════╗
+    ║ slot │ level │ lockout │ expiration_slot ║
+    ╠══════╪═══════╪═════════╪═════════════════╣
+    ║ 4    │ 1     │ 2       │ 6               ║
+    ╟──────┼───────┼─────────┼─────────────────╢
+    ║ 3    │ 2     │ 4       │ 7               ║
+    ╟──────┼───────┼─────────┼─────────────────╢
+    ║ 2    │ 3     │ 8       │ 10              ║
+    ╟──────┼───────┼─────────┼─────────────────╢
+    ║ 1    │ 4     │ 16      │ 17              ║
+    ╚══════╧═══════╧═════════╧═════════════════╝
+    """
+
+    t.update(9)
+    t.print()
+    """
+    ╔══════╤═══════╤═════════╤═════════════════╗
+    ║ slot │ level │ lockout │ expiration_slot ║
+    ╠══════╪═══════╪═════════╪═════════════════╣
+    ║ 9    │ 1     │ 2       │ 11              ║
+    ╟──────┼───────┼─────────┼─────────────────╢
+    ║ 2    │ 3     │ 8       │ 10              ║
+    ╟──────┼───────┼─────────┼─────────────────╢
+    ║ 1    │ 4     │ 16      │ 17              ║
+    ╚══════╧═══════╧═════════╧═════════════════╝
+    """
+
+    t.update(10)
+    t.print()
+    """
+    ╔══════╤═══════╤═════════╤═════════════════╗
+    ║ slot │ level │ lockout │ expiration_slot ║
+    ╠══════╪═══════╪═════════╪═════════════════╣
+    ║ 10   │ 1     │ 2       │ 12              ║
+    ╟──────┼───────┼─────────┼─────────────────╢
+    ║ 9    │ 2     │ 4       │ 13              ║
+    ╟──────┼───────┼─────────┼─────────────────╢
+    ║ 2    │ 3     │ 8       │ 10              ║
+    ╟──────┼───────┼─────────┼─────────────────╢
+    ║ 1    │ 4     │ 16      │ 17              ║
+    ╚══════╧═══════╧═════════╧═════════════════╝
+    """
+
+    t.update(11)
+    t.print()
+    """
+    ╔══════╤═══════╤═════════╤═════════════════╗
+    ║ slot │ level │ lockout │ expiration_slot ║
+    ╠══════╪═══════╪═════════╪═════════════════╣
+    ║ 11   │ 1     │ 2       │ 13              ║
+    ╟──────┼───────┼─────────┼─────────────────╢
+    ║ 1    │ 4     │ 16      │ 17              ║
+    ╚══════╧═══════╧═════════╧═════════════════╝
+    """