Rakefile for Sequel database operations

db.rake

namespace :db do

  require 'sequel'
  Sequel.extension(:migration)
  MIGRATIONS_PATH = 'db/migrations'

  def db_conn_env
    ENV["BOOKSHELF_DATABASE_URL"]
  end

  def db_conn_url
    db = split_db_url(db_conn_env)
    db_conn = "postgres://#{db[:user]}:#{db[:pass]}@#{db[:host]}"
  end

  def split_db_url(url)
    user, pass, host, database = url.scan(/postgres:\/\/(.+?):(.+?)@(.+?)\/(.+?)$/).first
    data = {
      user:     user,
      pass:     pass,
      host:     host,
      database: database
    }
  end

  def db_migrate(version = db_migrations.last)
    puts "Migrating database to version #{version}"
    Sequel::Migrator.run(DB, MIGRATIONS_PATH, target: version.to_i)
  end

  def db_migrated?(version, schema = :sequel)
    db_versions(schema).include?(version.to_s)
  end

  def db_versions(schema = :sequel)
    if schema == :sequel
      DB[:schema_migrations].order(:filename).select_map(:filename)
    elsif schema == :rails
      DB[:schema_migrations].order(:version).select_map(:version)
    else
      []
    end
  end

  def db_migrations
    Dir[MIGRATIONS_PATH + "/*.rb"]
      .map { |f| File.basename(f) }
      .sort
  end

  def db_schema(object)
    Hash[DB.schema(object)]
  rescue Sequel::DatabaseError
    nil
  end

  desc 'Seed the database with application required data'
  task seed: :environment do
    load 'db/seeds.rb'
  end

  desc "Prints current schema version"
  task :version => :environment do
    puts "Current Schema Version: #{db_versions(:sequel).last}"
  end

  desc "Perform migration up to latest migration available"
  task :migrate, [:version] => :environment do |t, args|
    db_migrate(args[:version] || db_migrations.last)
    Rake::Task['db:version'].execute
  end

  desc "Perform rollback to specified target or previous version as default"
  task :rollback, [:version] => :environment do |t, args|
    version = args[:version] || db_versions(:sequel)[-2]
    db_migrate(version)
    Rake::Task['db:version'].execute
  end

  desc "Perform migration reset (full rollback and migration) only on local environment"
  task :reset => :environment do
    if (ENV["HANAMI_ENV"] || ENV["RACK_ENV"]) == "production"
      abort "You can't run this rake on production environment"
    end

    db_migrate(0)
    db_migrate(db_migrations.last)
    Rake::Task['db:version'].execute
  end

  desc "Creates database"
  task :create => :"settings:load" do
    db = split_db_url(db_conn_env)

    exec "psql",
      "#{db_conn_url}",
      "-c", "CREATE DATABASE #{db[:database]}"
  end

  desc "Drops database"
  task :drop => :"settings:load" do
    if (ENV["HANAMI_ENV"] || ENV["RACK_ENV"]) == "production"
      abort "You can't run this rake on production environment"
    end

    db = split_db_url(db_conn_env)

    exec "psql",
      "#{db_conn_url}",
      "-c", "DROP DATABASE IF EXISTS #{db[:database]}"
  end

  desc "Start a database console on environment"
  task :console => :'settings:load' do
    exec "psql", db_conn_env
  end

  namespace :structure do
    require 'hanami/model'
    require 'hanami/model/migrator'

    task :check_schema_migrations do
      raise "Schema_migrations not prepared! Run 'rake db:migrate'" unless db_schema(:schema_migrations)
    end
    task :check_structure_sequel do
      raise "Sequel schema_migrations not prepared! Run 'rake db:structure:to_sequel'" unless db_schema(:schema_migrations)[:filename]
    end
    task :prepare_structure_sequel do
      schema_migrations = db_schema(:schema_migrations)
      DB.run "alter table schema_migrations alter column version drop not null;" if schema_migrations[:version]
      DB.run "alter table schema_migrations add filename varchar;" unless schema_migrations[:filename]

      puts "Structure: DONE"
    end
    task :migrate_structure_sequel do
      db_migrations.each do |filename|
        version = filename.to_i
        if db_migrated?(version, :rails)
          DB.run "update schema_migrations set filename = '#{filename}' where version = '#{version}';"
        else
          DB.run "insert into schema_migrations (version, filename) values ('#{version}', '#{filename}');"
        end
        puts "> #{filename} DONE"
      end
      puts "Migration: DONE"
    end

    task :check_structure_rails do
      raise "Rails schema_migrations not prepared! Run 'rake db:structure:to_rails'" unless db_schema(:schema_migrations)[:version]
    end
    task :prepare_structure_rails do
      schema_migrations = db_schema(:schema_migrations)
      DB.run "alter table schema_migrations drop constraint schema_migrations_pkey;" if db_schema(:schema_migrations_pkey)
      DB.run "alter table schema_migrations alter column filename drop not null;" if schema_migrations[:filename]
      DB.run "alter table schema_migrations add version varchar;" unless schema_migrations[:version]
      puts "Structure: DONE"
    end
    task :migrate_structure_rails do
      db_migrations.each do |filename|
        version = filename.to_i
        if db_migrated?(filename, :sequel)
          DB.run "update schema_migrations set version = '#{version}' where filename = '#{filename}';"
        else
          DB.run "insert into schema_migrations (version, filename) values ('#{version}', '#{filename}');"
        end
        puts "> #{filename} DONE"
      end
      puts "Migration: DONE"
    end

    desc "Setup database structure from Sequel to Rails Migrations"
    task :to_rails => [
      :environment,
      :check_schema_migrations,
      :check_structure_sequel,
      :prepare_structure_rails,
      :migrate_structure_rails
    ]

    desc "Setup database structure from Rails to Sequel Migrations"
    task :to_sequel => [
      :environment,
      :check_schema_migrations,
      :check_structure_rails,
      :prepare_structure_sequel,
      :migrate_structure_sequel
    ]

    # Configure Hanami::Model for structure dump/load
    task :configure do
      Hanami::Model.configure do
        adapter type: :sql, uri: db_conn_env
        migrations 'db/migrations'
        schema     'db/schema.sql'
        mapping    {}
      end.load!
    end

    desc "Dump database structure to db/schema.sql"
    task dump: [:environment, :configure] do
      adapter = Hanami::Model::Migrator::Adapter.for(DB)
      adapter.dump
    end

    desc "Load db/schema.sql database structure"
    task load: :environment do
      adapter = Hanami::Model::Migrator::Adapter.for(DB)
      adapter.load
    end
  end
end