import { EventEmitter } from 'events'
import { IpcMainInvokeEvent } from 'electron'

class IpcMain extends EventEmitter {
  private _invokeHandlers: Map<string, (e: IpcMainInvokeEvent, ...args: any[]) => void> = new Map();

  handle: Electron.IpcMain['handle'] = (method, fn) => {
    if (this._invokeHandlers.has(method)) {
      throw new Error(`Attempted to register a second handler for '${method}'`)
    }
    if (typeof fn !== 'function') {
      throw new Error(`Expected handler to be a function, but found type '${typeof fn}'`)
    }
    this._invokeHandlers.set(method, async (e, ...args) => {
      try {
        (e as any)._reply(await Promise.resolve(fn(e, ...args)))
      } catch (err) {
        (e as any)._throw(err)
      }
    })
  }

  handleOnce: Electron.IpcMain['handleOnce'] = (method, fn) => {
    this.handle(method, (e, ...args) => {
      this.removeHandler(method)
      return fn(e, ...args)
    })
  }

  removeHandler (method: string) {
    this._invokeHandlers.delete(method)
  }
}

const ipcMain = new IpcMain()

// Do not throw exception when channel name is "error".
ipcMain.on('error', () => {})

export default ipcMain
