defmodule SyntropyWeb.Api.TaskRequest do
  @moduledoc false

  @type parsed_request :: %{prompt: String.t(), opts: keyword()}

  @strategies ~w(single parallel all auto)

  @spec parse(map()) :: {:ok, parsed_request()} | {:error, [map()]}
  def parse(params) do
    with {:ok, prompt} <- parse_prompt(Map.get(params, "prompt")),
         {:ok, strategy} <- parse_strategy(Map.get(params, "strategy")),
         {:ok, agent_ids} <- parse_agent_ids(Map.get(params, "agent_ids")),
         {:ok, agent_count} <-
           parse_positive_integer(Map.get(params, "agent_count"), 3, "agent_count"),
         {:ok, synthesize} <- parse_boolean(Map.get(params, "synthesize"), true, "synthesize") do
      {:ok,
       %{
         prompt: prompt,
         opts:
           []
           |> Keyword.put(:strategy, strategy)
           |> maybe_put(:agent_ids, agent_ids)
           |> Keyword.put(:agent_count, agent_count)
           |> Keyword.put(:synthesize, synthesize)
       }}
    else
      {:error, errors} -> {:error, errors}
    end
  end

  defp maybe_put(opts, _key, nil), do: opts
  defp maybe_put(opts, key, value), do: Keyword.put(opts, key, value)

  defp parse_prompt(prompt) when is_binary(prompt) do
    trimmed = String.trim(prompt)

    if trimmed == "" do
      {:error, [error("prompt", "must be a non-empty string")]}
    else
      {:ok, trimmed}
    end
  end

  defp parse_prompt(_prompt), do: {:error, [error("prompt", "is required")]}

  defp parse_strategy(nil), do: {:ok, :parallel}

  defp parse_strategy(strategy) when is_binary(strategy) do
    if strategy in @strategies do
      {:ok, String.to_atom(strategy)}
    else
      {:error, [error("strategy", "must be one of single, parallel, all, auto")]}
    end
  end

  defp parse_strategy(_strategy),
    do: {:error, [error("strategy", "must be one of single, parallel, all, auto")]}

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

  defp parse_agent_ids(agent_ids) when is_list(agent_ids) do
    if Enum.all?(agent_ids, &is_binary/1) do
      {:ok, agent_ids}
    else
      {:error, [error("agent_ids", "must be an array of strings")]}
    end
  end

  defp parse_agent_ids(_agent_ids),
    do: {:error, [error("agent_ids", "must be an array of strings")]}

  defp parse_positive_integer(nil, default, _field), do: {:ok, default}

  defp parse_positive_integer(value, _default, _field) when is_integer(value) and value > 0,
    do: {:ok, value}

  defp parse_positive_integer(value, _default, field) when is_binary(value) do
    case Integer.parse(value) do
      {parsed, ""} when parsed > 0 -> {:ok, parsed}
      _other -> {:error, [error(field, "must be a positive integer")]}
    end
  end

  defp parse_positive_integer(_value, _default, field),
    do: {:error, [error(field, "must be a positive integer")]}

  defp parse_boolean(nil, default, _field), do: {:ok, default}
  defp parse_boolean(value, _default, _field) when is_boolean(value), do: {:ok, value}
  defp parse_boolean(_value, _default, field), do: {:error, [error(field, "must be a boolean")]}

  defp error(field, message), do: %{field: field, message: message}
end