# frozen_string_literal: true

require 'spec_helper'

RSpec.describe InternalId do
  let(:project) { create(:project) }
  let(:usage) { :issues }
  let(:issue) { build(:issue, project: project) }
  let(:id_subject) { issue }
  let(:scope) { { project: project } }
  let(:init) { ->(issue, scope) { issue&.project&.issues&.size || Issue.where(**scope).count } }

  it_behaves_like 'having unique enum values'

  context 'validations' do
    it { is_expected.to validate_presence_of(:usage) }
  end

  describe '.flush_records!' do
    subject { described_class.flush_records!(project: project) }

    let(:another_project) { create(:project) }

    before do
      create_list(:issue, 2, project: project)
      create_list(:issue, 2, project: another_project)
    end

    it 'deletes all records for the given project' do
      expect { subject }.to change { described_class.where(project: project).count }.from(1).to(0)
    end

    it 'retains records for other projects' do
      expect { subject }.not_to change { described_class.where(project: another_project).count }
    end

    it 'does not allow an empty filter' do
      expect { described_class.flush_records!({}) }.to raise_error(/filter cannot be empty/)
    end
  end

  shared_examples_for 'a monotonically increasing id generator' do
    describe '.generate_next' do
      subject { described_class.generate_next(id_subject, scope, usage, init) }

      context 'in the absence of a record' do
        it 'creates a record if not yet present' do
          expect { subject }.to change { described_class.count }.from(0).to(1)
        end

        it 'stores record attributes' do
          subject

          described_class.first.tap do |record|
            expect(record.project).to eq(project)
            expect(record.usage).to eq(usage.to_s)
          end
        end

        context 'with existing issues' do
          before do
            create_list(:issue, 2, project: project)
            described_class.delete_all
          end

          it 'calculates last_value values automatically' do
            expect(subject).to eq(project.issues.size + 1)
          end
        end
      end

      it 'generates a strictly monotone, gapless sequence' do
        seq = Array.new(10).map do
          described_class.generate_next(issue, scope, usage, init)
        end
        normalized = seq.map { |i| i - seq.min }

        expect(normalized).to eq((0..seq.size - 1).to_a)
      end

      context 'there are no instances to pass in' do
        let(:id_subject) { Issue }

        it 'accepts classes instead' do
          expect(subject).to eq(1)
        end
      end

      context 'when executed outside of transaction' do
        it 'increments counter with in_transaction: "false"' do
          allow(ActiveRecord::Base.connection).to receive(:transaction_open?) { false } # rubocop: disable Database/MultipleDatabases

          expect(InternalId.internal_id_transactions_total).to receive(:increment)
            .with(operation: :generate, usage: 'issues', in_transaction: 'false').and_call_original

          subject
        end
      end

      context 'when executed within transaction' do
        it 'increments counter with in_transaction: "true"' do
          expect(InternalId.internal_id_transactions_total).to receive(:increment)
            .with(operation: :generate, usage: 'issues', in_transaction: 'true').and_call_original

          InternalId.transaction { subject }
        end
      end
    end

    describe '.reset' do
      subject { described_class.reset(issue, scope, usage, value) }

      context 'in the absence of a record' do
        let(:value) { 2 }

        it 'does not revert back the value' do
          expect { subject }.not_to change { described_class.count }
          expect(subject).to be_falsey
        end
      end

      context 'when valid iid is used to reset' do
        let!(:value) { generate_next }

        context 'and iid is a latest one' do
          it 'does rewind and next generated value is the same' do
            expect(subject).to be_truthy
            expect(generate_next).to eq(value)
          end
        end

        context 'and iid is not a latest one' do
          it 'does not rewind' do
            generate_next

            expect(subject).to be_falsey
            expect(generate_next).to be > value
          end
        end

        def generate_next
          described_class.generate_next(issue, scope, usage, init)
        end
      end

      context 'when executed outside of transaction' do
        let(:value) { 2 }

        it 'increments counter with in_transaction: "false"' do
          allow(ActiveRecord::Base.connection).to receive(:transaction_open?) { false } # rubocop: disable Database/MultipleDatabases

          expect(InternalId.internal_id_transactions_total).to receive(:increment)
            .with(operation: :reset, usage: 'issues', in_transaction: 'false').and_call_original

          subject
        end
      end

      context 'when executed within transaction' do
        let(:value) { 2 }

        it 'increments counter with in_transaction: "true"' do
          expect(InternalId.internal_id_transactions_total).to receive(:increment)
            .with(operation: :reset, usage: 'issues', in_transaction: 'true').and_call_original

          InternalId.transaction { subject }
        end
      end
    end

    describe '.track_greatest' do
      let(:value) { 9001 }

      subject { described_class.track_greatest(id_subject, scope, usage, value, init) }

      context 'in the absence of a record' do
        it 'creates a record if not yet present' do
          expect { subject }.to change { described_class.count }.from(0).to(1)
        end
      end

      it 'stores record attributes' do
        subject

        described_class.first.tap do |record|
          expect(record.project).to eq(project)
          expect(record.usage).to eq(usage.to_s)
          expect(record.last_value).to eq(value)
        end
      end

      context 'with existing issues' do
        before do
          create(:issue, project: project)
          described_class.delete_all
        end

        it 'still returns the last value to that of the given value' do
          expect(subject).to eq(value)
        end
      end

      context 'when value is less than the current last_value' do
        it 'returns the current last_value' do
          described_class.create!(**scope, usage: usage, last_value: 10_001)

          expect(subject).to eq 10_001
        end
      end

      context 'there are no instances to pass in' do
        let(:id_subject) { Issue }

        it 'accepts classes instead' do
          expect(subject).to eq(value)
        end
      end

      context 'when executed outside of transaction' do
        it 'increments counter with in_transaction: "false"' do
          allow(ActiveRecord::Base.connection).to receive(:transaction_open?) { false } # rubocop: disable Database/MultipleDatabases

          expect(InternalId.internal_id_transactions_total).to receive(:increment)
            .with(operation: :track_greatest, usage: 'issues', in_transaction: 'false').and_call_original

          subject
        end
      end

      context 'when executed within transaction' do
        it 'increments counter with in_transaction: "true"' do
          expect(InternalId.internal_id_transactions_total).to receive(:increment)
            .with(operation: :track_greatest, usage: 'issues', in_transaction: 'true').and_call_original

          InternalId.transaction { subject }
        end
      end
    end
  end

  context 'when the feature flag is disabled' do
    stub_feature_flags(generate_iids_without_explicit_locking: false)

    it_behaves_like 'a monotonically increasing id generator'
  end

  context 'when the feature flag is enabled' do
    stub_feature_flags(generate_iids_without_explicit_locking: true)

    it_behaves_like 'a monotonically increasing id generator'
  end

  describe '#increment_and_save!' do
    let(:id) { create(:internal_id) }

    subject { id.increment_and_save! }

    it 'returns incremented iid' do
      value = id.last_value

      expect(subject).to eq(value + 1)
    end

    it 'saves the record' do
      subject

      expect(id.changed?).to be_falsey
    end

    context 'with last_value=nil' do
      let(:id) { build(:internal_id, last_value: nil) }

      it 'returns 1' do
        expect(subject).to eq(1)
      end
    end
  end

  describe '#track_greatest_and_save!' do
    let(:id) { create(:internal_id) }
    let(:new_last_value) { 9001 }

    subject { id.track_greatest_and_save!(new_last_value) }

    it 'returns new last value' do
      expect(subject).to eq new_last_value
    end

    it 'saves the record' do
      subject

      expect(id.changed?).to be_falsey
    end

    context 'when new last value is lower than the max' do
      it 'does not update the last value' do
        id.update!(last_value: 10_001)

        subject

        expect(id.reload.last_value).to eq 10_001
      end
    end
  end
end
