amiramke · February 6, 2014 22:35 · Jan 12, 2014
diff --git a/active_admin_extensions.rb b/active_admin_extensions.rb
@@ -0,0 +1,26 @@
+module ActiveAdmin
+
+  module Reports    
+    module DSL
+      def enable_reports
+        action_item only: :index do
+          link_to("Download", {action: :report, params: params}, {method: :post, data: { confirm: "Are you sure you want to generate this report?"}})
+        end
+
+        collection_action :report, method: :post do
+          report = Report.create({
+            name: resource_class.to_s.pluralize.titleize,
+            model_name: resource_class.to_s,
+            admin_user: current_admin_user,
+            params: params['q']
+          })
+          Report.delay.generate(report.id)    
+          redirect_to(admin_report_path(report.id), {notice: "Report queued for processing!"})
+        end
+      end
+    end
+  end
+
+  ActiveAdmin::ResourceDSL.send :include, ActiveAdmin::Reports::DSL
+end
+
diff --git a/csv_builder.rb b/csv_builder.rb
@@ -0,0 +1,67 @@
+# CSVBuilder stores CSV configuration
+# Extracted from ActiveAdmin
+#
+# Usage example:
+#
+#   csv_builder = CSVBuilder.new
+#   csv_builder.column :id
+#   csv_builder.column("Name") { |resource| resource.full_name }
+#
+#   csv_builder = CSVBuilder.new :col_sep => ";"
+#   csv_builder.column :id
+#
+#
+class CSVBuilder
+
+  # Return a default CSVBuilder for a resource
+  # The CSVBuilder's columns would be Id followed by this
+  # resource's content columns
+  def self.default_for_resource(resource)
+    new(resource: resource).tap do |csv_builder|
+      csv_builder.column(:id)
+      resource.content_columns.each do |content_column|
+        csv_builder.column(content_column.name.to_sym)
+      end
+    end
+  end
+
+  def self.call_method_or_proc_on(receiver, *args)
+    options = { :exec => true }.merge(args.extract_options!)
+
+    symbol_or_proc = args.shift
+
+    case symbol_or_proc
+    when Symbol, String
+      receiver.send(symbol_or_proc.to_sym, *args)
+    when Proc
+      if options[:exec]
+        instance_exec(receiver, *args, &symbol_or_proc)
+      else
+        symbol_or_proc.call(receiver, *args)
+      end
+    end
+  end
+
+  attr_reader :columns, :options
+
+  def initialize(options={}, &block)
+    @resource = options.delete(:resource)
+    @columns, @options = [], options
+    instance_exec &block if block_given?
+  end
+
+  # Add a column
+  def column(name, &block)
+    @columns << Column.new(name, @resource, block)
+  end
+
+  class Column
+    attr_reader :name, :data
+
+    def initialize(name, resource = nil, block = nil)
+      @name = name.is_a?(Symbol) && resource.present? ? resource.human_attribute_name(name) : name.to_s.humanize
+      @data = block || name.to_sym
+    end
+  end
+end
+
diff --git a/report.rb b/report.rb
@@ -0,0 +1,88 @@
+class Report < ActiveRecord::Base
+  belongs_to :admin_user
+
+  # see https://github.com/thoughtbot/paperclip/wiki/Encryption-on-amazon-s3
+  has_attached_file :report, s3_permissions: :private,
+    s3_headers: { "x-amz-server-side-encryption" => "AES256" },
+    path: "private/reports/:filename"
+
+  # fog_host contains the protocol, but expiring url appends http to it so we have to remove that
+  def download_url
+    url = report.try(:expiring_url, Time.now + 60.seconds)
+    url.gsub!('http://https://', 'https://') if url
+  end
+
+  def generate
+    start!
+    path = build_csv
+    finish!
+    self.report = File.open(path)
+    uploaded!
+  end
+
+  def start!
+    self.started_at = Time.now
+    save!
+  end
+
+  def finish!
+    self.finished_at = Time.now
+    save!
+  end
+
+  def uploaded!
+    self.uploaded_at = Time.now
+    save!
+  end
+
+  def uploaded?
+    uploaded_at?
+  end
+
+  def status
+    if uploaded_at?
+      :available
+    elsif finished_at?
+      :finished
+    elsif started_at?
+      :started
+    else
+      :pending
+    end
+  end
+
+  private
+
+    def build_csv
+      model = model_name.classify.constantize
+      path = "#{Rails.root.to_s}/tmp/#{filename}"
+
+      csv_builder = model.csv_builder
+      columns = csv_builder.columns
+
+      record_count = 0
+      CSV.open(path, "wb") do |csv|
+        csv << columns.map(&:name)
+        model.report_scope.search(params).result.find_each do |resource|
+          csv << columns.map do |column|
+            CSVBuilder.call_method_or_proc_on resource, column.data
+          end
+          record_count += 1
+        end      
+      end
+
+      self.record_count = record_count
+      path
+    end
+
+    def filename
+      [model_name.try(:downcase), created_at.try(:to_i), id].join("_") + ".csv"
+    end
+
+  class << self
+    def generate(report_id)
+      find(report_id).generate
+    end
+  end
+
+end
diff --git a/reportable.rb b/reportable.rb
@@ -0,0 +1,26 @@
+# a mixin for your models to add default report behavior
+module Reportable
+  extend ActiveSupport::Concern
+
+  def to_csv
+    self.class.csv_builder.columns.map do |column|
+      CSVBuilder.call_method_or_proc_on self, column.data
+    end
+  end
+
+  module ClassMethods
+
+    def csv_builder 
+      CSVBuilder.default_for_resource(self)
+    end
+
+    def csv_columns
+      csv_builder.columns.map(&:name)
+    end
+
+    def report_scope
+      all
+    end
+
+  end
+end
diff --git a/user.rb b/user.rb
@@ -0,0 +1,26 @@
+# how to define the csv export inside of the model
+class User < ActiveRecord::Base
+  include Reportable
+
+  # override some of the reportable methods
+
+  class << self
+
+    def report_scope
+      # defaults to 'all' but you could do a custom scope like this...
+      joins(:addresses)
+    end
+
+    def csv_builder
+      csv = CSVBuilder.new({ resource: self }) do
+        column :id
+        column :user_id
+        column :first_name
+        column :last_name
+        column("Address")       { |user| user.primary_address.try(:to_str) }
+        column :created_at
+      end
+    end
+  end
+
+end
diff --git a/users.rb b/users.rb
@@ -0,0 +1,5 @@
+#admin/users.rb
+ActiveAdmin.register User do
+  enable_reports
+end
+
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