defmodule DaProductApp.Transactions.TransactionEvent do
  @moduledoc """
  Event record for transaction aggregate with hash chaining.
  """
  use Ecto.Schema
  import Ecto.Changeset

  schema "transaction_events" do
    field :seq, :integer
    field :event_type, :string
    field :payload, :map
    field :prev_hash, :binary
    field :hash, :binary
    belongs_to :transaction, DaProductApp.Transactions.Transaction
    field :inserted_at, :utc_datetime
  end

  @required ~w(seq event_type hash inserted_at transaction_id)a
  @optional ~w(payload prev_hash)a

  def changeset(struct, attrs) do
    struct
    |> cast(attrs, @required ++ @optional)
    |> validate_required(@required)
    |> unique_constraint([:transaction_id, :seq])
  end
end