require 'http'
require 'json'

class DataPipeline
  #
  # Slack.new(channel: '#etl').send_message('posting export done')
  #
  # options
  #   token:   bot token, default ENV['SLACK_TOKEN']
  #   channel: default '#general'
  #
  class Slack
    API_URL = 'https://slack.com/api/chat.postMessage'.freeze

    DEFAULTS = {
      token: nil,
      channel: '#general'
    }.freeze

    def initialize options = {}
      @options = DEFAULTS.merge(token: ENV['SLACK_TOKEN']).merge(options)
      raise ArgumentError, 'Slack: token missing (option token: or ENV SLACK_TOKEN)' unless @options[:token]
    end

    # returns the parsed slack response, raises when slack reports an error
    def send_message(content, verbose: false)
      response = HTTP.auth("Bearer #{@options[:token]}")
                     .post(API_URL, json: { channel: @options[:channel], text: content })
      body = JSON.parse(response.body.to_s)
      puts JSON.pretty_generate(body) if verbose
      raise "Slack#send_message failed: #{body['error']}" unless body['ok']

      body
    end
  end
end