# Controller for an admin screen
# Admin wants to rapidly prototype different texts/wordings sent out to new authors
# Used to compose and send out retention emails to authors who published their first recipe within a specified timeframe
# Admin can download CSV of recipients for each email

# Model
class RetentionEmail < ActiveRecord::Base
end

class User < ActiveRecord::Base
  has_many :recipes
  scope :recent, -> { order("created_at DESC") }
  scope :first_publication_in, (from, to)-> {
    joins(:recipes).group("recipes.user_id").where(published_recipes_count: 1).
      where(published_at: from..to)
  }
end

class Recipe < ActiveRecord::Base
end

class CsvBuilder
  def initialize(attributes, data)
    @data = data
    @attributes = attributes
  end

  def generate
    CSV.generate(headers: true) do |csv|
      csv << @attributes
      @data.each do |line|
        csv << @attributes.map { |attr| line.send(attr) }
      end
    end
  end
end

class BulkEmailWorker
  def perform(recipients)
    recipients.find_each do |r|
      UserMailer.bulk_email(r).deliver_later
    end
  end
end

# Controller
class RetentionEmailsController < ApplicationController
  attr_reader :provider

  def new
    @email = RetentionEmail.new
    if params[:date_from].present? && params[:date_to].present?
      users
    end
  end

  def create
    @email = RetentionEmail.new(retention_email_params)

    recipients = []
    users.each do |user|
      recipients << user.email
    end

    if @email.save && send_mail(recipients)
      redirect_to retention_emails_path, notice: "Emails Sent Successfully!"
    end
  end

  def download_csv
    csv = CsvBuilder.new(%w{id email name}, users).generate
    send_data csv, filename: "author-retention-users-#{Time.zone.today}.csv"
  end

  private

    def send_mail(recipients)
      BulkEmailWorker.new.perform recipients
    end

    def users
      @users ||= User.recent
              .first_publication_in(Date.parse(params[:date_from], Date.parse(params[:date_to]))
              .page(params[:page])
    end

    def retention_email_params
      params.permit(:body, :date_from, :date_to)
    end
end