erlang_python

%% Copyright 2026 Benoit Chesneau
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%%     http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.

%%% @doc Initializes the context router during application startup.
%%%
%%% This module provides a supervisor-compatible start function that
%%% initializes the context pools and returns `ignore' (since no
%%% process needs to stay running after initialization).
%%%
%%% == Pools ==
%%%
%%% Two pools are started by default:
%%% - `default' - For quick CPU-bound operations, sized to number of schedulers
%%% - `io' - For I/O-bound operations, larger pool (default: 10) for concurrency
%%%
%%% Pool sizes can be configured via application env:
%%% ```
%%% {erlang_python, [
%%%     {default_pool_size, 4},        % Number of contexts (default: schedulers)
%%%     {io_pool_size, 10},            % I/O pool size (default: 10)
%%%     {io_pool_mode, worker}         % Mode for io pool (default: auto)
%%% ]}.
%%% '''
%%% @private
-module(py_context_init).

-export([start_link/1]).

%% @doc Start the context pools.
%%
%% This function is called by the supervisor to initialize the
%% py_context_router pools. After starting the contexts, it returns
%% `ignore' since no process needs to remain running.
%%
%% @param Opts Options for the default pool
%% @returns {ok, pid()} | ignore | {error, Reason}
-spec start_link(map()) -> {ok, pid()} | ignore | {error, term()}.
start_link(Opts) ->
    %% Start default pool
    DefaultSize = maps:get(contexts, Opts, erlang:system_info(schedulers)),
    DefaultMode = maps:get(mode, Opts, auto),

    case py_context_router:start_pool(default, DefaultSize, DefaultMode) of
        {ok, _DefaultContexts} ->
            %% Start I/O pool if configured
            IoSize = application:get_env(erlang_python, io_pool_size, 10),
            IoMode = application:get_env(erlang_python, io_pool_mode, auto),
            case py_context_router:start_pool(io, IoSize, IoMode) of
                {ok, _IoContexts} ->
                    %% The contexts are supervised by py_context_sup
                    %% We don't need a process here, just return ignore
                    ignore;
                {error, IoReason} ->
                    {error, {io_pool_start_failed, IoReason}}
            end;
        {error, Reason} ->
            {error, {default_pool_start_failed, Reason}}
    end.