/**
 * preload.js
 *
 * Runs in a privileged context but is sandboxed from the renderer.
 * Use contextBridge to expose a safe, narrow API surface to the renderer.
 * Never expose raw ipcRenderer — always whitelist specific channels.
 */

const { contextBridge, ipcRenderer } = require('electron')

// ─── Allowed IPC channels ─────────────────────────────────────────────────
// Only messages on these channels will be forwarded.
const ALLOWED_SEND_CHANNELS = [
  'patient:update-status',
  'patient:fetch-list',
  'schedule:fetch',
  'app:ready',
]

const ALLOWED_RECEIVE_CHANNELS = [
  'patient:status-updated',
  'patient:list-response',
  'schedule:response',
  'app:get-version',
]

// ─── Exposed API ──────────────────────────────────────────────────────────
contextBridge.exposeInMainWorld('api', {
  /**
   * Send a one-way message to the main process.
   * @param {string} channel - Must be in ALLOWED_SEND_CHANNELS
   * @param {*} data
   */
  send(channel, data) {
    if (ALLOWED_SEND_CHANNELS.includes(channel)) {
      ipcRenderer.send(channel, data)
    } else {
      console.warn(`[preload] Blocked send on unknown channel: "${channel}"`)
    }
  },

  /**
   * Invoke a main-process handler and await its response.
   * @param {string} channel - Must be in ALLOWED_SEND_CHANNELS
   * @param {...*} args
   * @returns {Promise<*>}
   */
  invoke(channel, ...args) {
    if (ALLOWED_SEND_CHANNELS.includes(channel) || ALLOWED_RECEIVE_CHANNELS.includes(channel)) {
      return ipcRenderer.invoke(channel, ...args)
    }
    return Promise.reject(new Error(`[preload] Blocked invoke on unknown channel: "${channel}"`))
  },

  /**
   * Subscribe to messages from the main process.
   * @param {string} channel - Must be in ALLOWED_RECEIVE_CHANNELS
   * @param {Function} callback - Called with (event, ...args) on each message
   * @returns {Function} Unsubscribe function — call it to remove the listener
   */
  receive(channel, callback) {
    if (ALLOWED_RECEIVE_CHANNELS.includes(channel)) {
      const handler = (_event, ...args) => callback(...args)
      ipcRenderer.on(channel, handler)
      // Return cleanup function so React effects can unsubscribe
      return () => ipcRenderer.removeListener(channel, handler)
    }
    console.warn(`[preload] Blocked receive on unknown channel: "${channel}"`)
    return () => {}
  },
})