# frozen_string_literal: true

##
# Used to generate BBCode [chat] tags for the message IDs provided.
#
# If there is > 1 message then the channel name will be shown at
# the top of the first message, and subsequent messages will have
# the chained attribute, which will affect how they are displayed
# in the UI.
#
# Subsequent messages from the same user will be put into the same
# tag. Each new user in the chain of messages will have a new [chat]
# tag created.
#
# A single message will have the channel name displayed to the right
# of the username and datetime of the message.
class ChatTranscriptService
  CHAINED_ATTR = "chained=\"true\""
  MULTIQUOTE_ATTR = "multiQuote=\"true\""
  NO_LINK_ATTR = "noLink=\"true\""

  class ChatTranscriptBBCode
    attr_reader :channel, :multiquote, :chained, :no_link, :include_reactions

    def initialize(
      channel: nil,
      acting_user: nil,
      multiquote: false,
      chained: false,
      no_link: false,
      include_reactions: false
    )
      @channel = channel
      @acting_user = acting_user
      @multiquote = multiquote
      @chained = chained
      @no_link = no_link
      @include_reactions = include_reactions
      @message_data = []
    end

    def add(message:, reactions: nil)
      @message_data << { message: message, reactions: reactions }
    end

    def render
      attrs = [quote_attr(@message_data.first[:message])]

      if channel
        attrs << channel_attr
        attrs << channel_id_attr
      end

      attrs << MULTIQUOTE_ATTR if multiquote
      attrs << CHAINED_ATTR if chained
      attrs << NO_LINK_ATTR if no_link
      attrs << reactions_attr if include_reactions

      <<~MARKDOWN
      [chat #{attrs.compact.join(" ")}]
      #{@message_data.map { |msg| msg[:message].to_markdown }.join("\n\n")}
      [/chat]
      MARKDOWN
    end

    private

    def reactions_attr
      reaction_data =
        @message_data.reduce([]) do |array, msg_data|
          if msg_data[:reactions].any?
            array << msg_data[:reactions].map { |react| "#{react.emoji}:#{react.usernames}" }
          end
          array
        end
      return if reaction_data.empty?
      "reactions=\"#{reaction_data.join(";")}\""
    end

    def quote_attr(message)
      "quote=\"#{message.user.username};#{message.id};#{message.created_at.iso8601}\""
    end

    def channel_attr
      "channel=\"#{channel.title(@acting_user)}\""
    end

    def channel_id_attr
      "channelId=\"#{channel.id}\""
    end
  end

  def initialize(channel, acting_user, messages_or_ids: [], opts: {})
    @channel = channel
    @acting_user = acting_user

    if messages_or_ids.all? { |m| m.is_a?(Numeric) }
      @message_ids = messages_or_ids
    else
      @messages = messages_or_ids
    end
    @opts = opts
  end

  def generate_markdown
    previous_message = nil
    rendered_markdown = []
    all_messages_same_user = messages.count(:user_id) == 1
    open_bbcode_tag =
      ChatTranscriptBBCode.new(
        channel: @channel,
        acting_user: @acting_user,
        multiquote: messages.length > 1,
        chained: !all_messages_same_user,
        no_link: @opts[:no_link],
        include_reactions: @opts[:include_reactions],
      )

    messages.each.with_index do |message, idx|
      if previous_message.present? && previous_message.user_id != message.user_id
        rendered_markdown << open_bbcode_tag.render

        open_bbcode_tag =
          ChatTranscriptBBCode.new(
            acting_user: @acting_user,
            chained: !all_messages_same_user,
            no_link: @opts[:no_link],
            include_reactions: @opts[:include_reactions],
          )
      end

      if @opts[:include_reactions]
        open_bbcode_tag.add(message: message, reactions: reactions_for_message(message))
      else
        open_bbcode_tag.add(message: message)
      end
      previous_message = message
    end

    # tie off the last open bbcode + render
    rendered_markdown << open_bbcode_tag.render
    rendered_markdown.join("\n")
  end

  private

  def messages
    @messages ||=
      ChatMessage
        .includes(:user, upload_references: :upload)
        .where(id: @message_ids, chat_channel_id: @channel.id)
        .order(:created_at)
  end

  ##
  # Queries reactions and returns them in this format
  #
  # emoji   |  usernames  |  chat_message_id
  # ----------------------------------------
  # +1      | foo,bar,baz | 102
  # heart   | foo         | 102
  # sob     | bar,baz     | 103
  def reactions
    @reactions ||= DB.query(<<~SQL, @messages.map(&:id))
    SELECT emoji, STRING_AGG(DISTINCT users.username, ',') AS usernames, chat_message_id
    FROM chat_message_reactions
    INNER JOIN users on users.id = chat_message_reactions.user_id
    WHERE chat_message_id IN (?)
    GROUP BY emoji, chat_message_id
    ORDER BY chat_message_id, emoji
    SQL
  end

  def reactions_for_message(message)
    reactions.select { |react| react.chat_message_id == message.id }
  end
end