-module(scamper@testing).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/scamper/testing.gleam").
-export([assert_transition/3, assert_final/1, reachable_states/2, run_events/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(
    " Test helpers for scamper FSMs.\n"
    "\n"
    " Provides convenience functions for testing state machine behavior.\n"
    " These functions use `let assert` which panics on failure — they are\n"
    " designed for test code only, not for library or application code.\n"
).

-file("src/scamper/testing.gleam", 16).
?DOC(
    " Attempt a transition and assert the machine reaches the expected state.\n"
    " Panics if the transition fails or the machine is not in the expected state.\n"
    " Returns the new machine for chaining.\n"
).
-spec assert_transition(scamper:machine(IYE, IYF, IYG), IYG, IYE) -> scamper:machine(IYE, IYF, IYG).
assert_transition(Machine, Event, Expected_state) ->
    New_machine@1 = case scamper:transition(Machine, Event) of
        {ok, New_machine} -> New_machine;
        _assert_fail ->
            erlang:error(#{gleam_error => let_assert,
                        message => <<"Pattern match failed, no pattern matched the value."/utf8>>,
                        file => <<?FILEPATH/utf8>>,
                        module => <<"scamper/testing"/utf8>>,
                        function => <<"assert_transition"/utf8>>,
                        line => 21,
                        value => _assert_fail,
                        start => 763,
                        'end' => 826,
                        pattern_start => 774,
                        pattern_end => 789})
    end,
    case scamper:current_state(New_machine@1) =:= Expected_state of
        true -> nil;
        _assert_fail@1 ->
            erlang:error(#{gleam_error => let_assert,
                        message => <<"Pattern match failed, no pattern matched the value."/utf8>>,
                        file => <<?FILEPATH/utf8>>,
                        module => <<"scamper/testing"/utf8>>,
                        function => <<"assert_transition"/utf8>>,
                        line => 22,
                        value => _assert_fail@1,
                        start => 829,
                        'end' => 899,
                        pattern_start => 840,
                        pattern_end => 844})
    end,
    New_machine@1.

-file("src/scamper/testing.gleam", 29).
?DOC(
    " Assert that the machine is in a final state.\n"
    " Panics if the machine is not in a final state.\n"
    " Returns the machine for chaining.\n"
).
-spec assert_final(scamper:machine(IYN, IYO, IYP)) -> scamper:machine(IYN, IYO, IYP).
assert_final(Machine) ->
    case scamper:is_final(Machine) of
        true -> nil;
        _assert_fail ->
            erlang:error(#{gleam_error => let_assert,
                        message => <<"Pattern match failed, no pattern matched the value."/utf8>>,
                        file => <<?FILEPATH/utf8>>,
                        module => <<"scamper/testing"/utf8>>,
                        function => <<"assert_final"/utf8>>,
                        line => 32,
                        value => _assert_fail,
                        start => 1159,
                        'end' => 1202,
                        pattern_start => 1170,
                        pattern_end => 1174})
    end,
    Machine.

-file("src/scamper/testing.gleam", 38).
?DOC(
    " Find all states reachable from the initial state via transition rules.\n"
    " Delegates to validation.reachable_states.\n"
).
-spec reachable_states(scamper@config:config(IYW, any(), any()), IYW) -> list(IYW).
reachable_states(Config, Initial_state) ->
    scamper@validation:reachable_states(Config, Initial_state).

-file("src/scamper/testing.gleam", 48).
?DOC(
    " Run a sequence of events against the machine.\n"
    " Returns the final machine if all transitions succeed,\n"
    " or the first TransitionError encountered.\n"
).
-spec run_events(scamper:machine(IZD, IZE, IZF), list(IZF)) -> {ok,
        scamper:machine(IZD, IZE, IZF)} |
    {error, scamper@error:transition_error(IZD, IZF)}.
run_events(Machine, Events) ->
    gleam@list:try_fold(
        Events,
        Machine,
        fun(M, Evt) -> scamper:transition(M, Evt) end
    ).