-module(pig@agent@update).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/pig/agent/update.gleam").
-export([update/2]).

-if(?OTP_RELEASE >= 27).
-define(MODULEDOC(Str), -moduledoc(Str)).
-define(DOC(Str), -doc(Str)).
-else.
-define(MODULEDOC(Str), -compile([])).
-define(DOC(Str), -compile([])).
-endif.

?MODULEDOC(
    " Pure agent state machine — the sans-IO update function.\n"
    "\n"
    " `update(state, msg) -> StepResult(msg)` is a pure function:\n"
    " no provider calls, no tool execution, no telemetry, no hooks.\n"
    "\n"
    " The runtime calls this function, interprets the returned effects,\n"
    " and feeds results back as new messages.\n"
).

-file("src/pig/agent/update.gleam", 89).
-spec handle_tool_results(
    pig@agent@state:agent_state(),
    list({pig_protocol@message:tool_call(),
        {ok, gleam@json:json()} | {error, pig@tool:tool_error()}})
) -> pig@agent@step_result:step_result(pig@agent@msg:agent_msg()).
handle_tool_results(St, Results) ->
    Tool_messages = gleam@list:map(
        Results,
        fun(Pair) ->
            {Call, Result} = Pair,
            Content = case Result of
                {ok, Json_val} ->
                    gleam@json:to_string(Json_val);

                {error, Tool_err} ->
                    <<"Tool error: "/utf8,
                        (pig@tool:error_message(Tool_err))/binary>>
            end,
            {tool, erlang:element(2, Call), Content}
        end
    ),
    New_st = begin
        _pipe = Tool_messages,
        _pipe@1 = gleam@list:fold(_pipe, St, fun pig@agent@state:add_message/2),
        pig@agent@state:increment_iterations(_pipe@1)
    end,
    case pig@agent@state:exceeded_max_iterations(New_st) of
        true ->
            {failed, New_st, pig@agent@state:max_iterations_error(New_st)};

        false ->
            Msgs = pig@agent@state:messages_for_provider(New_st),
            Tools = pig@agent@state:tool_definitions(New_st),
            {continue, New_st, [{call_provider, Msgs, Tools, fun(R) -> case R of
                                {ok, Ir} ->
                                    {provider_responded,
                                        {ok, erlang:element(2, Ir)}};

                                {error, E} ->
                                    {provider_responded, {error, E}}
                            end end}]}
    end.

-file("src/pig/agent/update.gleam", 49).
-spec handle_provider_responded(
    pig@agent@state:agent_state(),
    {ok, pig_protocol@message:message()} |
        {error, pig_protocol@error:ai_error()}
) -> pig@agent@step_result:step_result(pig@agent@msg:agent_msg()).
handle_provider_responded(St, Result) ->
    case Result of
        {ok, {assistant, _, Calls, _, _} = Assistant_msg} ->
            case Calls of
                [] ->
                    New_st = pig@agent@state:add_message(St, Assistant_msg),
                    {done, New_st, Assistant_msg};

                _ ->
                    New_st@1 = pig@agent@state:add_message(St, Assistant_msg),
                    {continue,
                        New_st@1,
                        [{execute_tools,
                                Calls,
                                fun(Results) -> {tool_results, Results} end}]}
            end;

        {ok, Other} ->
            New_st@2 = pig@agent@state:add_message(St, Other),
            {done, New_st@2, Other};

        {error, E} ->
            {failed, St, E}
    end.

-file("src/pig/agent/update.gleam", 33).
-spec handle_user_prompt(pig@agent@state:agent_state(), binary()) -> pig@agent@step_result:step_result(pig@agent@msg:agent_msg()).
handle_user_prompt(St, Prompt) ->
    New_st = pig@agent@state:add_message(St, {user, Prompt}),
    Msgs = pig@agent@state:messages_for_provider(New_st),
    Tools = pig@agent@state:tool_definitions(New_st),
    {continue, New_st, [{call_provider, Msgs, Tools, fun(R) -> case R of
                        {ok, Ir} ->
                            {provider_responded, {ok, erlang:element(2, Ir)}};

                        {error, E} ->
                            {provider_responded, {error, E}}
                    end end}]}.

-file("src/pig/agent/update.gleam", 23).
?DOC(
    " Pure state transition: given current state and a message, return\n"
    " the next state and any effects the runtime should execute.\n"
    "\n"
    " This is the entire agent loop logic, sans IO.\n"
).
-spec update(pig@agent@state:agent_state(), pig@agent@msg:agent_msg()) -> pig@agent@step_result:step_result(pig@agent@msg:agent_msg()).
update(St, M) ->
    case M of
        {user_prompt, Prompt} ->
            handle_user_prompt(St, Prompt);

        {provider_responded, Result} ->
            handle_provider_responded(St, Result);

        {tool_results, Results} ->
            handle_tool_results(St, Results)
    end.