import {type ChannelInput, type ChannelInstance} from '@sanity/comlink'
import {isEqual} from 'lodash-es'

import {type StoreContext} from '../../../store/defineStore'
import {type FrameMessage, type WindowMessage} from '../../types'
import {type ComlinkControllerState} from '../comlinkControllerStore'

/**
 * Retrieve or create a channel to be used for communication between
 * an application and the controller.
 * @public
 */
export const getOrCreateChannel = (
  {state}: StoreContext<ComlinkControllerState>,
  options: ChannelInput,
): ChannelInstance<FrameMessage, WindowMessage> => {
  const controller = state.get().controller

  if (!controller) {
    throw new Error('Controller must be initialized before using or creating channels')
  }

  const channels = state.get().channels
  const existing = channels.get(options.name)

  // limit channels to one per name
  if (existing) {
    if (!isEqual(existing.options, options)) {
      throw new Error(`Channel "${options.name}" already exists with different options`)
    }

    state.set('incrementChannelRefCount', {
      channels: new Map(channels).set(options.name, {
        ...existing,
        refCount: existing.refCount + 1,
      }),
    })
    existing.channel.start()
    return existing.channel
  }

  const channel = controller.createChannel(options)
  channel.start()
  state.set('createChannel', {
    channels: new Map(channels).set(options.name, {
      channel,
      options,
      refCount: 1,
    }),
  })

  return channel
}