Extract a list of all the reactions to messages from a Slack data export

slack_reactions_from_export.rb

# Put this script in the root directory of a Slack data export
# Run `bundle install` and then `bundle exec ruby slack_reactions_from_export.rb`
# This will create a file called `reactions.txt` with rows like this:
#
# 2017-04-09  9:56 in #general: 😀
# 2017-04-10  9:45 in #tech-discussions: ⚽️
# 2017-04-19 15:45 in #general: 💖
# 2017-04-20 11:59 in #general: :hugging_face:
# 2017-04-20 22:35 in #general: 🤕
# 2017-04-30 21:38 in #most17: ❤️❤️
# 2017-05-01 20:33 in #general: 💯
# 2017-05-02 14:52 in #library: :thinking_face:
# 2017-05-03  8:49 in #general: 👋:skin-tone-2:
# 2017-05-03 16:34 in #general: 👋:skin-tone-2:👋:skin-tone-2:
#
# Not all the emoji's show up, because the library in use doesn't recognise all
# the emoji's from Slack. ¯\_(ツ)_/¯
# 

require 'json'
require 'gemoji'

def convert_slack_time(ts_value)
  Time.at ts_value.to_f
end

def formatted_time(ts_value)
  convert_slack_time(ts_value).strftime("%F %k:%M")
end

def extract_user_name(id)
  "@#{ @users.find { |u| u["id"].eql? id }["name"] }"
end

def convert_emojis(string)
  string.gsub(/:([\w+-]+):/) do |match|
    if emoji = Emoji.find_by_alias($1)
      emoji.raw
    else
      match
    end
  end
end

def process_text(message)
  text = message['text'].gsub(/<@\S+>/) do |match|
    extract_user_name(match.delete("@<>"))
  end
  convert_emojis(text)
end

def write_message(message)
  text = "#{formatted_time(message["ts"])} in ##{message["channel"]}: "
  message["reactions"].each do |reaction|
    reaction["count"].times.each do
      # text += ":#{reaction["name"]}:"
      text += convert_emojis(":#{reaction["name"]}:")
    end
  end

  text
end

def selected_messages(channel_names)
  chosen_ones = []
  channel_names.each do |channel|
    message_files = Dir.open(channel).entries.drop(2)
    channel_message_json = []

    message_files.each do |file_name|
      file = File.open [channel, file_name].join("/")
      channel_message_json.concat JSON.parse(file.read)
    end

    messages_with_reactions = channel_message_json.select do |message|
      message["reactions"].any? if message.has_key? "reactions"
    end

    messages_with_reactions.each do |m|
      chosen_ones <<  m.merge({ "channel" => channel })
    end
  end

  chosen_ones.sort_by {|msg| msg["ts"].to_f}
end

@users = JSON.parse(File.open("users.json").read)

channel_names = JSON.parse(File.open('channels.json').read).map do |c|
  c["name"]
end

File.open("reactions.txt", "w+") do |file|
  selected_messages(channel_names).each do
    |message| file << write_message(message) + "\n"
  end
end