migrate_enhancements.rake

# typed: false
require "English"

namespace :db do
  task :prevent_disparate_pg_dump_versions => :environment do
    allowed_pg_dump_version = "x.x.x".freeze

    `pg_dump --version`
    pg_dump_exit_status = $CHILD_STATUS.exitstatus

    locally_installed_version = begin
                                  `pg_dump --version`.chomp[/(\d.*)/, 1]
                                rescue StandardError
                                  nil
                                end

    if locally_installed_version != allowed_pg_dump_version
      puts(<<~OUTPUT_BLOCK)
        Required pg_dump version: #{allowed_pg_dump_version}
        Your version: #{locally_installed_version}
      OUTPUT_BLOCK
      if Gem::Version.new(locally_installed_version) > Gem::Version.new(allowed_pg_dump_version)
        puts(<<~OUTPUT_BLOCK)
          ---
          Your local version of postgresql is ahead of the pinned version in:
            `lib/tasks/migrate_enhancements.rake`.

          Please update `allowed_pg_dump_version` in `lib/tasks/migrate_enhancements.rake`
          to match your version (as listed above).
          ---
        OUTPUT_BLOCK
        raise("You must update `lib/tasks/migrate_enhancements.rake` if you wish to proceed with migrating")
      else
        puts(<<~OUTPUT_BLOCK)
          ---
          Linux upgrade command: `sudo apt-get update && sudo apt-get upgrade`
          OS X upgrade command: `brew upgrade postgresql@9.6`

          You may also need to tell OS X how to use your Homebrew version of postgres.

          To do this, run `brew info postgresql@9.6`. There will be a command output that tells you
          how to add it to your path. Follow those instructions.
          ---
        OUTPUT_BLOCK
        raise("You must update your postgresql-client if you wish to proceed with migrating")
      end
    elsif pg_dump_exit_status == 127
      puts(<<~OUTPUT_BLOCK)
        System postgres client not installed - it is needed for the db:migrate task.
        ---
        Linux install command:
          `sudo add-apt-repository "deb http://apt.postgresql.org/pub/repos/apt/ $(lsb_release -sc)-pgdg main"`
          `wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -`
          `sudo apt-get update && sudo apt-get install postgresql-9.6`
        OS X install command: `brew install postgresql@9.6`
        ---
      OUTPUT_BLOCK
      raise("You must install postgresql-client if you wish to proceed with migrating")
    end
  end

  # keep structure.sql in sync with the actual files in the db/migrate folder
  # this minimises the chance of merge conflicts if different branches add migrations
  # since, ideally, migrations will not make it to master in this file unless the corresponding
  # migration actaully exists
  # also removes duplicates!
  task :make_structure_sql_match_db_migrate_folder do
    path = Rails.root.join("db", "structure.sql")
    structure_sql_lines = File.read(path).lines
    migration_insert_index = structure_sql_lines.index { |l| l == "INSERT INTO \"schema_migrations\" (version) VALUES\n" }
    migration_lines = structure_sql_lines[migration_insert_index + 1..-1]

    migrations_in_repo = Set.new(Dir.glob("db/migrate/*.rb").map { |p| p.match(/[0-9]+/).try { |m| m[0] } })
    seen_migration_lines = Set.new

    correct_structure_sql_lines = migration_lines.select do |line|
      match = line.match(/\('(\d+)'\)/)
      should_include = !match || (migrations_in_repo.include?(match[1]) && !seen_migration_lines.include?(match[1]))
      seen_migration_lines << match[1] if should_include && match
      should_include
    end.flatten

    index_of_last_populated_line = -correct_structure_sql_lines.reverse.index(&:present?) - 1
    if correct_structure_sql_lines[index_of_last_populated_line].end_with?(",\n")
      correct_structure_sql_lines[index_of_last_populated_line] = "#{correct_structure_sql_lines[index_of_last_populated_line][0...-2]};"
    end

    File.write(path, (structure_sql_lines[0..migration_insert_index] + correct_structure_sql_lines).join)
  end
end

if Rails.env.development?
  # see http://edgar.tumblr.com/post/52300664342/how-to-extend-an-existing-rake-task
  # if you call #enhance with an array it sets it as a prereq (runs before)
  # if you give #enhance a block it adds a behaviour (runs after)
  # see https://github.com/ruby/rake/blob/v10.5.0/lib/rake/task.rb#L100 if you don't believe an API this odd could exist
  Rake::Task["db:migrate"].enhance(["db:prevent_disparate_pg_dump_versions"])
  Rake::Task["db:migrate"].enhance do
    Rake::Task["db:make_structure_sql_match_db_migrate_folder"].invoke
  end
end