import { createContext, useContext, useState } from 'react';

const LoanContext = createContext(null);

export function LoanProvider({ children }) {
  const [loans, setLoans] = useState(() => {
    const saved = localStorage.getItem('loans');
    return saved ? JSON.parse(saved) : [];
  });

  function addLoan(book, borrowerUsername, dueDate) {
    const loan = {
      loanId: crypto.randomUUID(),
      bookId: book.isbn,
      bookTitle: book.title,
      bookAuthor: book.author,
      borrowerUsername,
      dueDate,
      status: 'ACTIVE',
      loanedAt: new Date().toISOString(),
    };
    const updated = [...loans, loan];
    setLoans(updated);
    localStorage.setItem('loans', JSON.stringify(updated));
    return loan;
  }

  function returnLoan(loanId) {
    const updated = loans.map(l =>
      l.loanId === loanId ? { ...l, status: 'RETURNED' } : l
    );
    setLoans(updated);
    localStorage.setItem('loans', JSON.stringify(updated));
  }

  return (
    <LoanContext.Provider value={{ loans, addLoan, returnLoan }}>
      {children}
    </LoanContext.Provider>
  );
}

export function useLoans() {
  return useContext(LoanContext);
}