defmodule SyntropyWeb.Api.AgentRequest do
  @moduledoc false

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

  @score_keys ~w(knowledge synthesis connections)

  @spec parse(map()) :: {:ok, parsed_request()} | {:error, [map()]}
  def parse(params) do
    with {:ok, name} <- parse_required_string(Map.get(params, "name"), "name"),
         {:ok, perspective} <-
           parse_required_string(Map.get(params, "perspective"), "perspective"),
         {:ok, id} <- parse_id(Map.get(params, "id")),
         {:ok, knowledge_items} <- parse_knowledge_items(Map.get(params, "knowledge_items")),
         {:ok, score_vector} <- parse_score_vector(Map.get(params, "score_vector")),
         {:ok, position} <- parse_unit_float(Map.get(params, "position"), "position") do
      {:ok,
       %{
         name: name,
         perspective: perspective,
         opts:
           [knowledge_items: knowledge_items]
           |> maybe_put(:id, id)
           |> maybe_put(:score_vector, score_vector)
           |> maybe_put(:position, position)
       }}
    end
  end

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

  defp parse_required_string(value, field) when is_binary(value) do
    trimmed = String.trim(value)

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

  defp parse_required_string(_value, field), do: {:error, [error(field, "is required")]}

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

  defp parse_id(id) when is_binary(id) do
    trimmed = String.trim(id)

    cond do
      trimmed == "" -> {:ok, nil}
      Regex.match?(~r/^[a-z0-9][a-z0-9_-]*$/, trimmed) -> {:ok, trimmed}
      true -> {:error, [error("id", "must contain only lowercase letters, digits, - or _")]}
    end
  end

  defp parse_id(_id), do: {:error, [error("id", "must be a string")]}

  defp parse_knowledge_items(nil), do: {:ok, []}

  defp parse_knowledge_items(items) when is_list(items) do
    if Enum.all?(items, &is_binary/1) do
      normalized =
        items
        |> Enum.map(&String.trim/1)
        |> Enum.reject(&(&1 == ""))
        |> Enum.uniq()

      {:ok, normalized}
    else
      {:error, [error("knowledge_items", "must be an array of strings")]}
    end
  end

  defp parse_knowledge_items(_items),
    do: {:error, [error("knowledge_items", "must be an array of strings")]}

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

  defp parse_score_vector(score_vector) when is_map(score_vector) do
    parsed =
      Enum.reduce_while(@score_keys, %{}, fn key, acc ->
        case parse_unit_float(Map.get(score_vector, key), "score_vector.#{key}") do
          {:ok, nil} -> {:cont, Map.put(acc, String.to_existing_atom(key), 0.0)}
          {:ok, value} -> {:cont, Map.put(acc, String.to_existing_atom(key), value)}
          {:error, errors} -> {:halt, {:error, errors}}
        end
      end)

    case parsed do
      {:error, errors} -> {:error, errors}
      vector -> {:ok, vector}
    end
  end

  defp parse_score_vector(_score_vector),
    do: {:error, [error("score_vector", "must be an object")]}

  defp parse_unit_float(nil, _field), do: {:ok, nil}

  defp parse_unit_float(value, field) when is_number(value) do
    if value >= 0 and value <= 1 do
      {:ok, value / 1}
    else
      {:error, [error(field, "must be a number between 0 and 1")]}
    end
  end

  defp parse_unit_float(_value, field),
    do: {:error, [error(field, "must be a number between 0 and 1")]}

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