backend challenge solution (first 47 minutes)

coursera_syncer/Rakefile

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+require "active_record"
+require 'yaml'
+
+namespace :db do
+
+  db_config       = YAML::load(File.open('config/database.yml'))
+  db_config_admin = db_config.merge({'database' => 'postgres', 'schema_search_path' => 'public'})
+
+  desc "Create the database"
+  task :create do
+    ActiveRecord::Base.establish_connection(db_config_admin)
+    ActiveRecord::Base.connection.create_database(db_config["database"])
+    puts "Database created."
+  end
+
+  desc "Migrate the database"
+  task :migrate do
+    ActiveRecord::Base.establish_connection(db_config)
+    ActiveRecord::Migrator.migrate("db/migrate/")
+    Rake::Task["db:schema"].invoke
+    puts "Database migrated."
+  end
+
+  desc "Drop the database"
+  task :drop do
+    ActiveRecord::Base.establish_connection(db_config_admin)
+    ActiveRecord::Base.connection.drop_database(db_config["database"])
+    puts "Database deleted."
+  end
+
+  desc "Reset the database"
+  task :reset => [:drop, :create, :migrate]
+
+  desc 'Create a db/schema.rb file that is portable against any DB supported by AR'
+  task :schema do
+    ActiveRecord::Base.establish_connection(db_config)
+    require 'active_record/schema_dumper'
+    filename = "db/schema.rb"
+    File.open(filename, "w:utf-8") do |file|
+      ActiveRecord::SchemaDumper.dump(ActiveRecord::Base.connection, file)
+    end
+  end
+
+end
+
+namespace :g do
+  desc "Generate migration"
+  task :migration do
+    name = ARGV[1] || raise("Specify name: rake g:migration your_migration")
+    timestamp = Time.now.strftime("%Y%m%d%H%M%S")
+    path = File.expand_path("../db/migrate/#{timestamp}_#{name}.rb", __FILE__)
+    migration_class = name.split("_").map(&:capitalize).join
+
+    File.open(path, 'w') do |file|
+      file.write <<-EOF
+class #{migration_class} < ActiveRecord::Migration
+  def self.up
+  end
+  def self.down
+  end
+end
+      EOF
+    end
+
+    puts "Migration #{path} created"
+    abort # needed stop other tasks
+  end
+end

coursera_syncer/config/database.yml

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+# config/database.yml
+host: 'localhost'
+adapter: 'postgresql'
+encoding: utf-8
+database: 'coursera_syncer_test'

coursera_syncer/coursera_client.rb

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+module CourseraClient
+  def self.get_courses
+    courses_response_body = get_raw_courses
+    raw_courses = courses_response_body['elements']
+    raw_courses.map do |raw_course|
+      {
+        coursera_id: raw_course['id'],
+        name: raw_course['name'],
+        description: raw_course['description'],
+        coursera_url: raw_course['previewLink']
+        # : raw_course['coursera_url'],
+      }
+    end
+  end
+
+  def self.get_raw_courses
+    # Assume we can send GET request to coursera and return raw course list
+    # JSON response body.
+  end
+end

coursera_syncer/coursera_syncer.rb

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+require_relative './coursera_client'
+
+module CourseraSyncer
+  def self.sync!
+    courses_attributes = CourseraClient.get_courses
+    courses_attributes.each { |course_attrs| Course.create(course_attrs) }
+  end
+end

coursera_syncer/db/migrate/20160624144643_create_courses.rb

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+class CreateCourses < ActiveRecord::Migration
+  def change
+    create_table :courses do |t|
+      t.string :name
+      t.text :description
+      t.string :coursera_url
+      t.string :coursera_id
+      t.datetime :starts_at
+    end
+  end
+end

coursera_syncer/db/schema.rb

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+# encoding: UTF-8
+# This file is auto-generated from the current state of the database. Instead
+# of editing this file, please use the migrations feature of Active Record to
+# incrementally modify your database, and then regenerate this schema definition.
+#
+# Note that this schema.rb definition is the authoritative source for your
+# database schema. If you need to create the application database on another
+# system, you should be using db:schema:load, not running all the migrations
+# from scratch. The latter is a flawed and unsustainable approach (the more migrations
+# you'll amass, the slower it'll run and the greater likelihood for issues).
+#
+# It's strongly recommended that you check this file into your version control system.
+
+ActiveRecord::Schema.define(version: 20160624144643) do
+
+  # These are extensions that must be enabled in order to support this database
+  enable_extension "plpgsql"
+
+  create_table "courses", force: :cascade do |t|
+    t.string   "name"
+    t.text     "description"
+    t.string   "coursera_url"
+    t.string   "coursera_id"
+    t.datetime "starts_at"
+    t.datetime "created_at"
+    t.datetime "updated_at"
+  end
+
+end

coursera_syncer/models/course.rb

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+class Course < ActiveRecord::Base
+end

coursera_syncer/spec/coursera_syncer_spec.rb

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+require_relative './spec_helper'
+require_relative '../coursera_syncer'
+require_relative '../models/course'
+
+describe CourseraSyncer do
+  before do
+    Course.destroy_all
+    file =
+      File.open(File.dirname(__FILE__) + '/fixtures/courses.json', 'rb').read
+    course_data = JSON.parse(file)
+    allow(CourseraClient).to receive(:get_raw_courses).and_return(course_data)
+  end
+  describe '::sync!' do
+    it 'syncs sources from coursera api course list' do
+      CourseraSyncer.sync!
+      expect(Course.count).not_to eq 0
+      expect(Course.find_by(coursera_id: 'v1-228')).not_to be_nil
+    end
+  end
+end

coursera_syncer/spec/models/course_spec.rb

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+require_relative '../spec_helper'
+require_relative '../../models/course'
+
+describe Course do
+  before { Course.destroy_all }
+  it 'can be persisted with attributes' do
+    Course.create(name: 'other name')
+    expect(Course.count).to eq 1
+    expect(Course.first.name).to eq 'other name'
+  end
+end

coursera_syncer/spec/spec_helper.rb

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+require 'active_record'
+require_relative '../models/course'
+
+ActiveRecord::Base.establish_connection(
+  :adapter  => 'postgresql',
+  :database => 'coursera_syncer_test',
+  :host     => 'localhost'
+)