import fetch from 'cross-fetch'
import { logger } from '~/server/utils/logger'

export class SlackAPIError extends Error {
  constructor(message: string) {
    super(message)
  }
}

export type SlackChannel = {
  id: string
  name: string
  is_member: boolean
}

export async function getChannelsFromSlackIntegration(
  accessToken: string,
  orgSlug: string
): Promise<SlackChannel[]> {
  let nextCursor: string | null = 'first'
  const channels: SlackChannel[] = []
  let types = 'public_channel,private_channel'

  while (nextCursor) {
    const body = {
      exclude_archived: 'true',
      types,
    }

    if (nextCursor !== 'first') {
      body['cursor'] = nextCursor
    }

    try {
      const channelsResponse = await slackAPICall(
        'GET',
        'conversations.list',
        accessToken,
        body
      )

      channels.push(
        ...channelsResponse.channels
          .filter(c => c.is_member)
          .map(c => ({ id: c.id, name: c.name, is_member: c.is_member }))
      )

      if (
        channelsResponse['response_metadata'] &&
        channelsResponse['response_metadata']['next_cursor'] &&
        channelsResponse['response_metadata']['next_cursor'] !== ''
      ) {
        nextCursor = channelsResponse['response_metadata']['next_cursor']
      } else {
        nextCursor = null
      }
    } catch (error) {
      if (
        error instanceof SlackAPIError &&
        error.message === 'Error communicating with Slack: missing_scope'
      ) {
        logger.error(
          'Organization needs to re-oauth Slack for private channel access',
          {
            orgSlug,
          }
        )
        // retry with just public channels
        types = 'public_channel'
      } else {
        logger.error('Error sending slack message', error)
        nextCursor = null
      }
    }
  }

  return channels
}

export async function slackAPICall(
  method: string,
  apiMethod: string,
  accessToken: string,
  params: Record<string, string> | null = null
) {
  const urlParams =
    params && method === 'GET' ? `?` + new URLSearchParams(params) : ''
  const url = `https://slack.com/api/${apiMethod}${urlParams}`
  const headers = {
    Authorization: `Bearer ${accessToken}`,
  }

  let body
  if (method === 'POST') {
    headers['Content-Type'] = 'application/json; charset=utf-8'
    body = JSON.stringify(params)
  }

  const response = await fetch(url, {
    method,
    headers,
    body,
  }).then(res => {
    if (!res.ok) {
      throw new SlackAPIError(`Error communicating to Slack: ${res.statusText}`)
    }

    return res.json()
  })

  if (response['error']) {
    if (response['error'] === 'account_inactive') {
      throw new SlackAPIError(
        `The Interval app has been uninstalled from your Slack workspace. You'll need to reconnect to send Slack notifications.`
      )
    } else {
      throw new SlackAPIError(
        `Error communicating with Slack: ${response['error']}`
      )
    }
  }

  return response
}