%% @doc Generic bridge from Erlang neuroevolution_evaluator to Elixir evaluators.
%%
%% This module implements the neuroevolution_evaluator behaviour and
%% delegates to any Elixir module that implements an `evaluate/2` function.
%%
%% == Usage ==
%%
%% Configure the neuroevolution_server with this module as the evaluator:
%%
%% ```
%% Config = #neuro_config{
%%     evaluator_module = elixir_evaluator_bridge,
%%     evaluator_options = #{
%%         elixir_module => 'Elixir.MyApp.Evaluator',
%%         elixir_options => #{timeout => 5000}
%%     }
%% }.
%% '''
%%
%% The Elixir module must export `evaluate/2`:
%%
%% ```elixir
%% defmodule MyApp.Evaluator do
%%   def evaluate(individual, options) do
%%     # individual is a map: %{id: _, network: _, fitness: _, metrics: _, generation_born: _}
%%     # Return {:ok, metrics} or {:error, reason}
%%     {:ok, %{fitness: 100.0, score: 50}}
%%   end
%% end
%% '''
%%
%% @author Macula.io
%% @copyright 2025 Macula.io
-module(elixir_evaluator_bridge).
-behaviour(neuroevolution_evaluator).

-include("neuroevolution.hrl").

-export([evaluate/2, calculate_fitness/1]).

%% @doc Evaluate an individual using an Elixir evaluator module.
%%
%% Options must contain:
%% - `elixir_module': The Elixir module atom (e.g., 'Elixir.MyApp.Evaluator')
%% - `elixir_options': Optional map passed to the Elixir evaluator (default: #{})
%%
%% The Elixir module must export `evaluate(individual_map, options) -> {:ok, metrics} | {:error, reason}'
-spec evaluate(Individual, Options) -> Result when
    Individual :: individual(),
    Options :: map(),
    Result :: {ok, individual()} | {error, term()}.
evaluate(Individual, Options) ->
    ElixirModule = maps:get(elixir_module, Options),
    ElixirOptions = maps:get(elixir_options, Options, #{}),

    %% Convert Erlang individual record to Elixir-friendly map
    IndividualMap = individual_to_map(Individual),

    %% Call the Elixir evaluator
    try ElixirModule:evaluate(IndividualMap, ElixirOptions) of
        {ok, Metrics} when is_map(Metrics) ->
            %% Update individual with metrics
            UpdatedIndividual = Individual#individual{
                metrics = Metrics
            },
            {ok, UpdatedIndividual};
        {error, Reason} ->
            {error, Reason};
        Other ->
            {error, {unexpected_return, Other}}
    catch
        Class:Reason:Stacktrace ->
            error_logger:error_msg(
                "[elixir_evaluator_bridge] Elixir evaluator ~p failed: ~p:~p~n~p~n",
                [ElixirModule, Class, Reason, Stacktrace]
            ),
            {error, {elixir_exception, Class, Reason}}
    end.

%% @doc Calculate fitness from metrics.
%%
%% Uses the fitness value directly from metrics if present,
%% otherwise falls back to default calculation.
-spec calculate_fitness(Metrics) -> Fitness when
    Metrics :: map(),
    Fitness :: float().
calculate_fitness(Metrics) ->
    case maps:get(fitness, Metrics, undefined) of
        undefined ->
            %% Fallback to default fitness calculation
            neuroevolution_evaluator:default_fitness(Metrics);
        Fitness when is_float(Fitness) ->
            Fitness;
        Fitness when is_integer(Fitness) ->
            float(Fitness)
    end.

%%% ============================================================================
%%% Internal Functions
%%% ============================================================================

%% @private
%% @doc Convert individual record to Elixir-friendly map.
individual_to_map(#individual{id = Id, network = Network, fitness = Fitness,
                               metrics = Metrics, generation_born = GenBorn}) ->
    #{
        id => Id,
        network => Network,
        fitness => Fitness,
        metrics => Metrics,
        generation_born => GenBorn
    }.