# Gemfile
gem 'tricle', '~> 0.1.0'

# Rakefile
require 'tricle/tasks'

# your/config/file.rb
# unless you already have ActionMailer set up
ActionMailer::Base.raise_delivery_errors = true
ActionMailer::Base.smtp_settings = {
  # ...
}

class MyMetric < Tricle::Metric

  # Retrieve the value of this metric for the provided time period. Generally
  # this will be the count/value added/removed. Not necessary if #items_for_range
  # is defined.
  #
  # @param start_at [Time]
  # @param end_at [Time] non-inclusive
  # @return [Fixnum]
  def size_for_range(start_at, end_at)
    # ...
  end

  # Retrieve the cumulative value for this metric.
  #
  # @return [Fixnum] the grand total
  def total
    # ...
  end

  # Optional: only necessary if using `list` for this Metric within your Mailer.
  #
  # @param start_at [Time]
  # @param end_at [Time] non-inclusive
  # @return [Enumerator]
  def items_for_range(start_at, end_at)
    # ...
  end

end

# metrics/new_users.rb
class NewUsers < Tricle::Metric

  def size_for_range(start_at, end_at)
    self.items_for_range(start_at, end_at).count
  end

  def total
    self.users.count
  end

  def items_for_range(start_at, end_at)
    self.users.where('created_at >= ? AND created_at < ?', start_at, end_at)
  end


  private

  # You can add whatever helper methods in that class that you need.
  def users
    # non-deleted Users
    User.where(deleted_at: nil)
  end

end

class MyMailer < Tricle::Mailer

  # accepts the same options as ActionMailer... see "Default Hash" at
  # http://rubydoc.info/gems/actionmailer/ActionMailer/Base
  default(
    # ...
  )

  metric MyMetric1
  metric MyMetric2
  # ...

  # optional: metrics can be grouped
  group "Group 1 Name" do
    metric MyMetric3
    # ...
  end
  group "Group 2 Name" do
    metric MyMetric4
    # ...
  end

  # optional: list the items for the specified Metric
  list MyMetric2 do |item|
    # return the HTML string for each particular item
  end
  # ...

end

# mailers/weekly_insights.rb
class WeeklyInsights < Tricle::Mailer

  default(
    to: ['[email protected]', '[email protected]'],
    from: '[email protected]'
  )

  metric NewUsers

  list NewUsers do |user|
    <<-MARKUP
      <h3>#{user.name}</h3>
      <div>#{user.location}</div>
      <a href="mailto:#{user.email}>#{user.email}</a>
    MARKUP
  end

end

# config/initializers/tricle.rb
require 'tricle/mail_preview'

# config/routes.rb
if Rails.env.development?
  mount MailPreview => 'mail_view'
end