18F/identity-idp

#!/usr/bin/env ruby
# frozen_string_literal: true

require 'json'
require 'net/http'
require 'optparse'

# Posts a message to Slack via webhook
class NotifySlack
  def run(argv:, stdin:, stdout:)
    channel = nil
    username = nil
    text = nil
    webhook = nil
    icon = ':login-gov:'
    raise_on_failure = false

    program_name = File.basename($PROGRAM_NAME)

    parser = OptionParser.new do |opts|
      opts.banner = <<~STR
        #{program_name} [options]

        Usage:

        * Using arguments

          #{program_name} --text "my *message*" \\
           --channel "#some-channel" \\
           --webhook https://example.com/webhook

        * Passing text over STDIN

          echo "my *message*" | #{program_name} --text - \\
            --channel "#some-channel" \\
            --webhook https://example.com/webhook

        Options:
      STR

      opts.on('--channel CHANNEL', 'which channel to notify') do |channel_v|
        channel = channel_v
      end

      opts.on('--webhook WEBHOOK', 'Slack webhook URL') do |webhook_v|
        webhook = webhook_v
      end

      opts.on('--username USERNAME', 'which username to notify as') do |username_v|
        username = username_v
      end

      opts.on('--text TEXT', 'text of notification, pass - to read from STDIN') do |text_v|
        if text_v == '-'
          if stdin.tty?
            stdout.print 'please enter text of message: '
            text = stdin.gets
          else
            text = stdin.read
          end
        else
          text = text_v
        end
      end

      opts.on('--icon ICON', 'slack emoji to use as icon (optional)') do |icon_v|
        icon = icon_v
      end

      opts.on('--[no-]raise', <<~EOS) do |raise_v|
        raise errors/exit uncleanly if the webhook fails. defaults to not raising
      EOS
        raise_on_failure = raise_v
      end

      opts.on('--help') do
        puts opts
        exit 0
      end
    end

    parser.parse!(argv)

    if !channel || !username || !text || !webhook
      stdout.puts parser
      exit 1
    end

    notify(
      webhook: webhook,
      channel: channel,
      username: username,
      text: text,
      icon: format_icon(icon),
    )
    stdout.puts 'OK'
  rescue Net::HTTPClientException => err
    stdout.puts "#{program_name} HTTP ERROR: #{err.response.code}"
    raise err if raise_on_failure
  rescue => err
    stdout.puts "#{program_name} ERROR: #{err.message}"
    raise err if raise_on_failure
  end

  # @raise [Net::HTTPClientException] throws an error for non-successful response
  # @return [Net::HTTPResponse]
  def notify(webhook:, channel:, username:, text:, icon:)
    url = URI(webhook)

    req = Net::HTTP::Post.new(url)
    req.form_data = {
      'payload' => {
        channel: channel,
        username: username,
        text: text,
        icon_emoji: icon,
      }.to_json,
    }

    Net::HTTP.start(
      url.hostname,
      url.port,
      use_ssl: url.scheme == 'https',
      open_timeout: 1,
      read_timeout: 1,
      write_timeout: 1,
      ssl_timeout: 1,
    ) do |http|
      http.request(req)
    end.value
  end

  def format_icon(icon)
    if icon.start_with?(':') && icon.end_with?(':')
      icon
    else
      ":#{icon}:"
    end
  end
end

if $PROGRAM_NAME == __FILE__
  NotifySlack.new.run(argv: ARGV, stdin: STDIN, stdout: STDOUT)
end