# frozen_string_literal: true
require 'spec_helper'

RSpec.describe Gitlab::Database::Migrations::Runner do
  let(:result_dir) { Pathname.new(Dir.mktmpdir) }

  let(:migration_runs) { [] } # This list gets populated as the runner tries to run migrations

  # Tests depend on all of these lists being sorted in the order migrations would be applied
  let(:applied_migrations_other_branches) { [double(ActiveRecord::Migration, version: 1, name: 'migration_complete_other_branch')] }

  let(:applied_migrations_this_branch) do
    [
      double(ActiveRecord::Migration, version: 2, name: 'older_migration_complete_this_branch'),
      double(ActiveRecord::Migration, version: 3, name: 'newer_migration_complete_this_branch')
    ].sort_by(&:version)
  end

  let(:pending_migrations) do
    [
      double(ActiveRecord::Migration, version: 4, name: 'older_migration_pending'),
      double(ActiveRecord::Migration, version: 5, name: 'newer_migration_pending')
    ].sort_by(&:version)
  end

  before do
    stub_const('Gitlab::Database::Migrations::Runner::BASE_RESULT_DIR', result_dir)
    allow(ActiveRecord::Migrator).to receive(:new) do |dir, _all_migrations, _schema_migration_class, version_to_migrate|
      migrator = double(ActiveRecord::Migrator)
      expect(migrator).to receive(:run) do
        migration_runs << OpenStruct.new(dir: dir, version_to_migrate: version_to_migrate)
      end
      migrator
    end

    all_versions = (applied_migrations_other_branches + applied_migrations_this_branch).map(&:version)
    migrations = applied_migrations_other_branches + applied_migrations_this_branch + pending_migrations
    ctx = double(ActiveRecord::MigrationContext, get_all_versions: all_versions, migrations: migrations, schema_migration: ActiveRecord::SchemaMigration)

    allow(described_class).to receive(:migration_context).and_return(ctx)

    names_this_branch = (applied_migrations_this_branch + pending_migrations).map { |m| "db/migrate/#{m.version}_#{m.name}.rb"}
    allow(described_class).to receive(:migration_file_names_this_branch).and_return(names_this_branch)
  end

  after do
    FileUtils.rm_rf(result_dir)
  end

  it 'creates the results dir when one does not exist' do
    FileUtils.rm_rf(result_dir)

    expect do
      described_class.new(direction: :up, migrations: [], result_dir: result_dir).run
    end.to change { Dir.exist?(result_dir) }.from(false).to(true)
  end

  describe '.up' do
    context 'result directory' do
      it 'uses the /up subdirectory' do
        expect(described_class.up.result_dir).to eq(result_dir.join('up'))
      end
    end

    context 'migrations to run' do
      subject(:up) { described_class.up }

      it 'is the list of pending migrations' do
        expect(up.migrations).to eq(pending_migrations)
      end
    end

    context 'running migrations' do
      subject(:up) { described_class.up }

      it 'runs the unapplied migrations in version order', :aggregate_failures do
        up.run

        expect(migration_runs.map(&:dir)).to eq([:up, :up])
        expect(migration_runs.map(&:version_to_migrate)).to eq(pending_migrations.map(&:version))
      end
    end
  end

  describe '.down' do
    subject(:down) { described_class.down }

    context 'result directory' do
      it 'is the /down subdirectory' do
        expect(down.result_dir).to eq(result_dir.join('down'))
      end
    end

    context 'migrations to run' do
      it 'is the list of migrations that are up and on this branch' do
        expect(down.migrations).to eq(applied_migrations_this_branch)
      end
    end

    context 'running migrations' do
      it 'runs the applied migrations for the current branch in reverse order', :aggregate_failures do
        down.run

        expect(migration_runs.map(&:dir)).to eq([:down, :down])
        expect(migration_runs.map(&:version_to_migrate)).to eq(applied_migrations_this_branch.reverse.map(&:version))
      end
    end
  end
end