chore: initialize monorepo with project scaffolding, configs, and CI setup

apps/blockchain-node/src/aitbc_chain/mempool.py

@@ -0,0 +1,47 @@
+from __future__ import annotations
+
+import hashlib
+import json
+import time
+from dataclasses import dataclass
+from threading import Lock
+from typing import Any, Dict, List
+
+from .metrics import metrics_registry
+
+
+@dataclass(frozen=True)
+class PendingTransaction:
+    tx_hash: str
+    content: Dict[str, Any]
+    received_at: float
+
+
+class InMemoryMempool:
+    def __init__(self) -> None:
+        self._lock = Lock()
+        self._transactions: Dict[str, PendingTransaction] = {}
+
+    def add(self, tx: Dict[str, Any]) -> str:
+        tx_hash = self._compute_hash(tx)
+        entry = PendingTransaction(tx_hash=tx_hash, content=tx, received_at=time.time())
+        with self._lock:
+            self._transactions[tx_hash] = entry
+            metrics_registry.set_gauge("mempool_size", float(len(self._transactions)))
+        return tx_hash
+
+    def list_transactions(self) -> List[PendingTransaction]:
+        with self._lock:
+            return list(self._transactions.values())
+
+    def _compute_hash(self, tx: Dict[str, Any]) -> str:
+        canonical = json.dumps(tx, sort_keys=True, separators=(",", ":")).encode()
+        digest = hashlib.sha256(canonical).hexdigest()
+        return f"0x{digest}"
+
+
+_MEMPOOL = InMemoryMempool()
+
+
+def get_mempool() -> InMemoryMempool:
+    return _MEMPOOL