defmodule ApiBrasil.Core.HTTP do
  @moduledoc """
  Pipeline HTTP interno da SDK.

  Injeta os headers de autenticação da plataforma (`Authorization: Bearer`,
  `DeviceToken`, `SecretKey`), aplica retry com backoff, dispara os hooks de
  observabilidade e converte falhas em `ApiBrasil.Core.Error`.

  ## Opções por requisição

  Todas as funções de serviço aceitam uma keyword list final com:

  - `:query` — query string, um mapa ou keyword (valores `nil` são ignorados);
  - `:headers` — headers extras desta requisição;
  - `:bearer_token` — Bearer Token só desta requisição;
  - `:device_token` — DeviceToken só desta requisição;
  - `:secret_key` — SecretKey desta requisição (header `SecretKey`);
  - `:timeout` — tempo limite desta requisição, em ms;
  - `:response_type` — `:json` (padrão) ou `:binary` para baixar bytes crus.
  """

  alias ApiBrasil.Client
  alias ApiBrasil.Core.{Error, Hooks, JSON, Retry, Transport, Utils}
  alias ApiBrasil.Core.Transport.Request

  @user_agent "APIBRASIL/SDK-ELIXIR"

  @doc "Identificação da SDK enviada em `User-Agent`."
  @spec user_agent() :: String.t()
  def user_agent, do: @user_agent

  @doc "Monta a URL completa de um caminho."
  @spec url(Client.t(), String.t()) :: String.t()
  def url(%Client{base_url: base_url}, path), do: Utils.join_url(base_url, path)

  @doc """
  Executa uma requisição e devolve o corpo já decodificado, sem normalizar
  em objeto JSON.
  """
  @spec execute(Client.t(), Transport.method(), String.t(), term(), keyword()) ::
          {:ok, term()} | {:error, Error.t()}
  def execute(%Client{} = client, method, path, body \\ nil, opts \\ []) do
    opts = merge_options(client.options, opts)
    body = Utils.to_body(body)

    with {:ok, payload} <- encode_body(body) do
      request = %Request{
        method: method,
        url: url(client, path) <> Utils.build_query_string(opts[:query]),
        headers: build_headers(client, opts),
        body: payload,
        timeout: opts[:timeout] || client.timeout,
        response_type: opts[:response_type] || :json
      }

      run(client, request, body, 0)
    end
  end

  @doc "Executa a requisição e devolve o corpo normalizado em um mapa JSON."
  @spec request_json(Client.t(), Transport.method(), String.t(), term(), keyword()) ::
          {:ok, map()} | {:error, Error.t()}
  def request_json(%Client{} = client, method, path, body \\ nil, opts \\ []) do
    with {:ok, data} <- execute(client, method, path, body, opts) do
      {:ok, Utils.to_json_object(data)}
    end
  end

  @doc "`GET path`."
  @spec get(Client.t(), String.t(), keyword()) :: {:ok, map()} | {:error, Error.t()}
  def get(client, path, opts \\ []), do: request_json(client, :get, path, nil, opts)

  @doc "`POST path`."
  @spec post(Client.t(), String.t(), term(), keyword()) :: {:ok, map()} | {:error, Error.t()}
  def post(client, path, body \\ nil, opts \\ []),
    do: request_json(client, :post, path, body, opts)

  @doc "`PUT path`."
  @spec put(Client.t(), String.t(), term(), keyword()) :: {:ok, map()} | {:error, Error.t()}
  def put(client, path, body \\ nil, opts \\ []), do: request_json(client, :put, path, body, opts)

  @doc "`PATCH path`."
  @spec patch(Client.t(), String.t(), term(), keyword()) :: {:ok, map()} | {:error, Error.t()}
  def patch(client, path, body \\ nil, opts \\ []),
    do: request_json(client, :patch, path, body, opts)

  @doc "`DELETE path`."
  @spec delete(Client.t(), String.t(), term(), keyword()) :: {:ok, map()} | {:error, Error.t()}
  def delete(client, path, body \\ nil, opts \\ []),
    do: request_json(client, :delete, path, body, opts)

  @doc "Baixa o corpo cru de uma rota (PDF de boleto, imagens...)."
  @spec bytes(Client.t(), Transport.method(), String.t(), term(), keyword()) ::
          {:ok, binary()} | {:error, Error.t()}
  def bytes(client, method, path, body \\ nil, opts \\ []) do
    with {:ok, data} <-
           execute(client, method, path, body, Keyword.put(opts, :response_type, :binary)) do
      {:ok, to_binary(data)}
    end
  end

  @doc """
  Mescla as opções padrão do cliente com as da chamada — headers e query são
  mesclados, os demais campos são sobrescritos.
  """
  @spec merge_options(keyword(), keyword()) :: keyword()
  def merge_options(defaults, opts) do
    defaults = defaults || []
    opts = opts || []

    headers =
      Utils.merge_headers(
        Utils.normalize_headers(defaults[:headers]),
        Utils.normalize_headers(opts[:headers])
      )

    query = merge_query(defaults[:query], opts[:query])

    defaults
    |> Keyword.merge(opts)
    |> Keyword.put(:headers, headers)
    |> put_query(query)
  end

  defp put_query(opts, nil), do: Keyword.delete(opts, :query)
  defp put_query(opts, query), do: Keyword.put(opts, :query, query)

  defp merge_query(nil, nil), do: nil
  defp merge_query(nil, query), do: normalize_query(query)
  defp merge_query(query, nil), do: normalize_query(query)

  defp merge_query(base, override) do
    Map.merge(normalize_query(base), normalize_query(override))
  end

  defp normalize_query(query) when is_map(query), do: Utils.stringify_keys(query)

  defp normalize_query(query) when is_list(query),
    do: query |> Map.new() |> Utils.stringify_keys()

  defp normalize_query(query), do: query

  defp run(%Client{} = client, %Request{} = request, body, attempt) do
    Hooks.notify(client.hooks, :request, %{
      method: request.method,
      url: request.url,
      headers: request.headers,
      body: body,
      attempt: attempt
    })

    started_at = System.monotonic_time(:millisecond)

    case Transport.call(client.transport, request) do
      {:ok, response} ->
        Hooks.notify(client.hooks, :response, %{
          method: request.method,
          url: request.url,
          status: response.status,
          duration: System.monotonic_time(:millisecond) - started_at,
          attempt: attempt
        })

        handle_response(client, request, body, attempt, response)

      {:error, %Error{} = error} ->
        # Timeouts nunca são refeitos: a requisição pode ter sido processada
        # e o retry duplicaria cobranças/envios.
        if Error.network?(error) and not Error.timeout?(error) and retry?(client, attempt) do
          retry(
            client,
            request,
            body,
            attempt,
            Retry.backoff_delay(client.retry, attempt),
            error.message
          )
        else
          {:error, error}
        end
    end
  end

  defp handle_response(client, request, body, attempt, response) do
    if response.status >= 400 do
      error =
        Error.from_api(
          response.status,
          Transport.decode_body(response.body, :json),
          response.headers
        )

      if Retry.retries_status?(client.retry, response.status) and retry?(client, attempt) do
        delay = error.retry_after || Retry.backoff_delay(client.retry, attempt)
        retry(client, request, body, attempt, delay, "HTTP #{response.status}")
      else
        {:error, error}
      end
    else
      {:ok, response.data}
    end
  end

  defp retry?(%Client{retry: retry}, attempt), do: attempt + 1 < Retry.max_attempts(retry)

  defp retry(client, request, body, attempt, delay, reason) do
    next = attempt + 1

    Hooks.notify(client.hooks, :retry, %{
      method: request.method,
      url: request.url,
      attempt: next,
      delay: delay,
      reason: reason
    })

    Retry.sleep(delay)
    run(client, request, body, next)
  end

  defp build_headers(%Client{} = client, opts) do
    base = %{
      "Content-Type" => "application/json",
      "Accept" => "application/json",
      "User-Agent" => @user_agent
    }

    auth =
      %{}
      |> maybe_put("Authorization", bearer(opts[:bearer_token] || client.bearer_token))
      |> maybe_put("DeviceToken", opts[:device_token] || client.device_token)
      |> maybe_put("SecretKey", opts[:secret_key])

    base
    |> Utils.merge_headers(client.headers)
    |> Utils.merge_headers(auth)
    |> Utils.merge_headers(Utils.normalize_headers(opts[:headers]))
  end

  defp bearer(nil), do: nil
  defp bearer(""), do: nil
  defp bearer(token), do: "Bearer " <> token

  defp maybe_put(map, _key, nil), do: map
  defp maybe_put(map, _key, ""), do: map
  defp maybe_put(map, key, value), do: Map.put(map, key, value)

  defp encode_body(nil), do: {:ok, nil}

  defp encode_body(body) do
    {:ok, JSON.encode!(body)}
  rescue
    error ->
      {:error,
       Error.validation(
         "Não foi possível serializar o corpo da requisição: #{Exception.message(error)}",
         reason: error
       )}
  end

  defp to_binary(nil), do: ""
  defp to_binary(data) when is_binary(data), do: data
  defp to_binary(data), do: JSON.encode!(data)
end