defmodule Polymarket.Schemas.LastTradePriceEvent do
  @moduledoc """
  Last trade price event. Reports the price, size and side of the most recent
  trade executed against an asset.
  """

  use TypedEctoSchema

  alias Polymarket.Schemas.Coerce
  alias Polymarket.Schemas.LastTradePriceEvent

  @primary_key false

  @derive Jason.Encoder
  typed_embedded_schema do
    field(:market, :string)
    field(:asset_id, :string)
    field(:price, :float)
    field(:size, :float)
    # Maker fee in basis points, delivered as a string (e.g. "0").
    field(:fee_rate_bps, :integer)
    field(:side, :string)
    field(:transaction_hash, :string)
    # Unix epoch in milliseconds, delivered as a string (e.g. "1782553200051").
    field(:timestamp, :integer)
    field(:event_type, :string)
  end

  @required [:market, :asset_id, :price, :size, :side, :transaction_hash, :timestamp, :event_type]

  @doc """
  Builds a `LastTradePriceEvent` from a decoded (atom-keyed) websocket message.

  Constructs the struct directly — no `Ecto.Changeset` — for the websocket hot
  path. Numeric fields (delivered as JSON strings) are coerced via
  `Polymarket.Schemas.Coerce`. Returns `{:error, {:missing_fields, fields}}` when
  a required field is absent.
  """
  @spec from_attrs(map()) :: {:ok, t()} | {:error, {:missing_fields, [atom()]}}
  def from_attrs(attrs) do
    %LastTradePriceEvent{
      market: attrs[:market],
      asset_id: attrs[:asset_id],
      price: Coerce.to_float(attrs[:price]),
      size: Coerce.to_float(attrs[:size]),
      fee_rate_bps: Coerce.to_int(attrs[:fee_rate_bps]),
      side: attrs[:side],
      transaction_hash: attrs[:transaction_hash],
      timestamp: Coerce.to_int(attrs[:timestamp]),
      event_type: attrs[:event_type]
    }
    |> Coerce.require_fields(@required)
  end
end