import fs from 'node:fs'

const todosPath = './mcp-todos.json'

// In-memory todos storage
const todos = fs.existsSync(todosPath)
  ? JSON.parse(fs.readFileSync(todosPath, 'utf8'))
  : [
      {
        id: 1,
        title: 'Buy groceries',
      },
    ]

// Subscription callbacks per userID
let subscribers: ((todos: Todo[]) => void)[] = []

export type Todo = {
  id: number
  title: string
}

// Get the todos for a user
export function getTodos(): Todo[] {
  return todos
}

// Add an item to the todos
export function addTodo(title: string) {
  todos.push({ id: todos.length + 1, title })
  fs.writeFileSync(todosPath, JSON.stringify(todos, null, 2))
  notifySubscribers()
}

// Subscribe to cart changes for a user
export function subscribeToTodos(callback: (todos: Todo[]) => void) {
  subscribers.push(callback)
  callback(todos)
  return () => {
    subscribers = subscribers.filter((cb) => cb !== callback)
  }
}

// Notify all subscribers of a user's cart
function notifySubscribers() {
  for (const cb of subscribers) {
    try {
      cb(todos)
    } catch {}
  }
}