defmodule Cairnloop.Repo.Migrations.AddToolApprovals do
  use Ecto.Migration

  def change do
    create table(:cairnloop_tool_approvals) do
      add(:tool_proposal_id,
          references(:cairnloop_tool_proposals, on_delete: :delete_all),
          null: false)

      # Enum stored as :string — mirrors review_tasks migration pattern
      add(:status, :string, null: false, default: "pending")
      add(:decided_by, :string)
      add(:last_decision, :string)
      add(:decided_at, :utc_datetime_usec)
      add(:reason, :text)
      add(:expires_at, :utc_datetime_usec)

      timestamps(type: :utc_datetime_usec)
    end

    # Compound index for status-filtered proposal lookups
    create(index(:cairnloop_tool_approvals, [:tool_proposal_id, :status]))

    # Expiry-sweep predicate index
    create(index(:cairnloop_tool_approvals, [:status, :expires_at]))

    # One-active-lane constraint (APRV-04):
    # Only one `:pending` approval may exist per tool_proposal_id at any time.
    # Mirrors cairnloop_review_tasks_one_active_task_per_suggestion_index pattern.
    create(
      unique_index(
        :cairnloop_tool_approvals,
        [:tool_proposal_id],
        name: :cairnloop_tool_approvals_one_active_lane_index,
        where: "status = 'pending'"
      )
    )
  end
end