defmodule <%= context.namespace %><%= name %> do
  @moduledoc false

  alias Pbuf.Decoder
  import Bitwise, only: [bsr: 2, band: 2]

  <%
    # Oneof fields are "hidden" behind their parent. We don't want to generate
    # a field/typespec for it, only for the parent. But we do want to generate
    # an encoder for it which is why it isn't filtered already
    hidden_oneofs = fields
    |> Enum.reject(fn f -> f.hidden end)

    # now merge the pseudo parent fields of the oneofs
    hidden_oneofs = context.oneofs
    |> Enum.map(fn {_idx, oneof} -> oneof end)
    |> Kernel.++(hidden_oneofs)
    |> Enum.with_index()

    last_index = Enum.count(hidden_oneofs) - 1
  %>

  <%= if Keyword.get(options, :jason) do %>@derive Jason.Encoder<% end %>
  defstruct [
  <%= for {field, i} <- hidden_oneofs do %>
    <%= field.name %>: <%= field.default %><%= if_neq(i, last_index, ",") %>
  <% end %>
  ]

  @type t :: %__MODULE__{
  <%= for {field, i} <- hidden_oneofs do %>
    <%= field.name %>: <%= field.typespec %><%= if_neq(i, last_index, ",") %>
  <% end %>
  }

  <%= for e <- enums do %>
<%= Pbuf.Protoc.Template.enumeration(e, true) %>
  <% end %>

  @spec new(Enum.t) :: t
  def new(data) do
    struct(__MODULE__, data)
  end

  <% last_index = Enum.count(fields) %>
  @spec encode_to_iodata!(t | map) :: iodata
  def encode_to_iodata!(data) do
    alias Elixir.Pbuf.Encoder
    [
    <%= for {field, i} <- Enum.with_index(fields) do %>
      <%= field.encode_fun %><%= if_neq(i, last_index, ",") %>
    <% end %>
    ]
  end

  @spec encode!(t | map) :: binary
  def encode!(data) do
    :erlang.iolist_to_binary(encode_to_iodata!(data))
  end

  @spec decode!(binary) :: t
  def decode!(data) do
    Decoder.decode!(__MODULE__, data)
  end

  @spec decode(binary) :: {:ok, t} | :error
  def decode(data) do
    Decoder.decode(__MODULE__, data)
  end

  <%= for {field, _i} <- Enum.with_index(fields) do %>
  <% prefix = String.replace(field.prefix, ">>" , "") %>
  def decode(acc, <%= prefix %>, data::binary>>) do
    <%= "    " <> field.decode_fun <> "\n" %>
  end
  <% end %>

  <% tag_list = fields
     |> Enum.map(fn f -> f.tag end)
     |> Enum.join(",")
  %>

  # failed to decode, either this is an unknown tag (which we can skip), or
  # it is a wrong type (which is an error)
  def decode(acc, data) do
    {prefix, data} = Decoder.varint(data)
    tag = bsr(prefix, 3)
    type = band(prefix, 7)

    case tag in [<%= tag_list %>] do
      false -> {acc, Decoder.skip(type, data)}
      true ->
        err = %Decoder.Error{
          tag: tag,
          module: __MODULE__,
          message: "#{__MODULE__} tag #{tag} has an incorrect type of #{type}"
        }
        {:error, err}
    end
  end

  <%= if Enum.any?(fields, fn f -> f.post_decode == :map end) do %>
  defp post_map(name, tag, {:error, %{tag: nil, message: message}}) do
    err = %Decoder.Error{
      tag: tag,
      module: __MODULE__,
      message: "#{__MODULE__}.#{name} tag #{tag} " <> message
    }
    {:error, err}
  end

  # either valid data or a complete error (which would happen if our value
  # was a struct and the error happened decoding it)
  defp post_map(_name, _prefix, data) do
    data
  end
  <% end %>

  <%
    maps = Enum.filter(fields, fn f -> f.post_decode == :map end)
    repack = Enum.filter(fields, fn f -> f.post_decode == :repack end)
  %>
  def __finalize_decode__(args) do
    struct = Elixir.Enum.reduce(args, %__MODULE__{}, fn
      <%= for field <- maps do %>
      {:<%= field.name %>, {c, v}}, acc -> Map.update(acc, :<%= field.name %>, %{c => v}, fn m -> Map.put(m, c, v) end)
      <% end %>
      <%= for field <- repack do %>
      {:<%= field.name %>, v}, acc -> Map.update(acc, :<%= field.name %>, [v], fn e -> [v | e] end)
      <% end %>
      {k, v}, acc -> Map.put(acc, k, v)
    end)

    <%= for field <- repack do %>
    struct = Map.put(struct, :<%=field.name%>, Elixir.Enum.reverse(struct.<%=field.name%>))
    <% end %>
    struct
  end
end