implementatiton of UTXO in typescript

UTXO.ts

type UTXO = {
    id: string;
    amount: number;
  };
  
  type Wallet = {
    address: string;
    utxos: UTXO[];
  };
  
  let state: Map<string, Wallet> = new Map();
  
  state.set("Alice", {
    address: "Alice",
    utxos: [
      { id: generateId(), amount: 100 },
      { id: generateId(), amount: 20 },
    ],
  });

  state.set("Bob", {
    address: "Bob",
    utxos: [
      { id: generateId(), amount: 17 },
      { id: generateId(), amount: 80 },
    ],
  });
  
  function generateId(): string {
    return Math.random().toString(36).substring(2, 10);
  }
  
  function getWallet(address: string): Wallet | undefined {
    return state.get(address);
  }
  
  function addUTXO(wallet: Wallet, amount: number): void {
    wallet.utxos.push({ id: generateId(), amount });
  }
  
  function removeUTXO(wallet: Wallet, utxoId: string): void {
    wallet.utxos = wallet.utxos.filter(utxo => utxo.id !== utxoId);
  }
  
  function transfer(sender: string, receiver: string, amount: number): void {
    const senderWallet = getWallet(sender);
    const receiverWallet = getWallet(receiver);
  
    if (!senderWallet || !receiverWallet) {
      throw new Error("Sender or receiver does not exist.");
    }
  
    const totalAmount = senderWallet.utxos.reduce((sum, utxo) => sum + utxo.amount, 0);
  
    if (totalAmount < amount) {
      throw new Error("Insufficient funds.");
    }
  

    let sum = 0;
    const selectedUTXOs: UTXO[] = [];
    for (const utxo of senderWallet.utxos) {
      if (sum >= amount) break;
      selectedUTXOs.push(utxo);
      sum += utxo.amount;
    }
  

    const remainingAmount = sum - amount;
    if (remainingAmount > 0) {
      addUTXO(senderWallet, remainingAmount);
    }
  
    for (const utxo of selectedUTXOs) {
      removeUTXO(senderWallet, utxo.id);
    }
  
    addUTXO(receiverWallet, amount);
  }
  
  
  transfer("Alice", "Bob", 110);
  console.log(state.get("Alice"));
  console.log(state.get("Bob"));