-module(scamper@validation).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/scamper/validation.gleam").
-export([detect_deadlocks/1, reachable_states/2, validate_config/2]).
-export_type([validation_warning/1]).

-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(" Configuration validation, deadlock detection, and reachability analysis.\n").

-type validation_warning(IQA) :: {unreachable_state, IQA} |
    {transition_from_final_state, IQA} |
    {missing_fallback, IQA}.

-file("src/scamper/validation.gleam", 37).
?DOC(" Find non-final states that have no outgoing transitions (deadlock states).\n").
-spec detect_deadlocks(scamper@config:config(IQL, any(), any())) -> list(IQL).
detect_deadlocks(Config) ->
    Transitions = scamper@config:get_transitions(Config),
    Final_states = scamper@config:get_final_states(Config),
    All_to_states = begin
        _pipe = Transitions,
        _pipe@1 = gleam@list:map(
            _pipe,
            fun(Rule) -> erlang:element(4, Rule) end
        ),
        gleam@list:unique(_pipe@1)
    end,
    States_with_outgoing = begin
        _pipe@2 = Transitions,
        _pipe@3 = gleam@list:map(
            _pipe@2,
            fun(Rule@1) -> erlang:element(2, Rule@1) end
        ),
        gleam@list:unique(_pipe@3)
    end,
    _pipe@4 = All_to_states,
    gleam@list:filter(
        _pipe@4,
        fun(S) ->
            not gleam@list:contains(Final_states, S) andalso not gleam@list:contains(
                States_with_outgoing,
                S
            )
        end
    ).

-file("src/scamper/validation.gleam", 70).
-spec bfs(
    list(IQZ),
    list(IQZ),
    list(scamper@config:transition_rule(IQZ, any(), any()))
) -> list(IQZ).
bfs(Queue, Visited, Transitions) ->
    case Queue of
        [] ->
            Visited;

        [Current | Rest] ->
            Neighbors = begin
                _pipe = Transitions,
                _pipe@1 = gleam@list:filter(
                    _pipe,
                    fun(Rule) -> erlang:element(2, Rule) =:= Current end
                ),
                _pipe@2 = gleam@list:map(
                    _pipe@1,
                    fun(Rule@1) -> erlang:element(4, Rule@1) end
                ),
                _pipe@3 = gleam@list:unique(_pipe@2),
                gleam@list:filter(
                    _pipe@3,
                    fun(S) -> not gleam@list:contains(Visited, S) end
                )
            end,
            New_visited = lists:append(Visited, Neighbors),
            New_queue = lists:append(Rest, Neighbors),
            bfs(New_queue, New_visited, Transitions)
    end.

-file("src/scamper/validation.gleam", 62).
?DOC(
    " Find all states reachable from the initial state via BFS.\n"
    " Ignores guards (assumes all guards could pass).\n"
).
-spec reachable_states(scamper@config:config(IQS, any(), any()), IQS) -> list(IQS).
reachable_states(Config, Initial_state) ->
    Transitions = scamper@config:get_transitions(Config),
    bfs([Initial_state], [Initial_state], Transitions).

-file("src/scamper/validation.gleam", 95).
-spec check_unreachable(scamper@config:config(IRJ, any(), any()), IRJ) -> list(validation_warning(IRJ)).
check_unreachable(Config, Initial_state) ->
    Transitions = scamper@config:get_transitions(Config),
    Reachable = reachable_states(Config, Initial_state),
    All_states = begin
        _pipe = Transitions,
        _pipe@1 = gleam@list:flat_map(
            _pipe,
            fun(Rule) -> [erlang:element(2, Rule), erlang:element(4, Rule)] end
        ),
        gleam@list:unique(_pipe@1)
    end,
    _pipe@2 = All_states,
    _pipe@3 = gleam@list:filter(
        _pipe@2,
        fun(S) -> not gleam@list:contains(Reachable, S) end
    ),
    gleam@list:map(_pipe@3, fun(S@1) -> {unreachable_state, S@1} end).

-file("src/scamper/validation.gleam", 113).
-spec check_transitions_from_final(scamper@config:config(IRR, any(), any())) -> list(validation_warning(IRR)).
check_transitions_from_final(Config) ->
    Transitions = scamper@config:get_transitions(Config),
    Final_states = scamper@config:get_final_states(Config),
    _pipe = Transitions,
    _pipe@1 = gleam@list:filter(
        _pipe,
        fun(Rule) ->
            gleam@list:contains(Final_states, erlang:element(2, Rule))
        end
    ),
    _pipe@2 = gleam@list:map(
        _pipe@1,
        fun(Rule@1) -> erlang:element(2, Rule@1) end
    ),
    _pipe@3 = gleam@list:unique(_pipe@2),
    gleam@list:map(_pipe@3, fun(S) -> {transition_from_final_state, S} end).

-file("src/scamper/validation.gleam", 126).
-spec check_missing_fallbacks(scamper@config:config(IRZ, any(), any())) -> list(validation_warning(IRZ)).
check_missing_fallbacks(Config) ->
    Transitions = scamper@config:get_transitions(Config),
    From_states = begin
        _pipe = Transitions,
        _pipe@1 = gleam@list:map(
            _pipe,
            fun(Rule) -> erlang:element(2, Rule) end
        ),
        gleam@list:unique(_pipe@1)
    end,
    _pipe@2 = From_states,
    _pipe@3 = gleam@list:filter(
        _pipe@2,
        fun(From) ->
            Rules = gleam@list:filter(
                Transitions,
                fun(Rule@1) -> erlang:element(2, Rule@1) =:= From end
            ),
            Has_guarded = gleam@list:any(
                Rules,
                fun(Rule@2) ->
                    gleam@option:is_some(erlang:element(5, Rule@2))
                end
            ),
            Has_fallback = gleam@list:any(
                Rules,
                fun(Rule@3) -> erlang:element(5, Rule@3) =:= none end
            ),
            Has_guarded andalso not Has_fallback
        end
    ),
    gleam@list:map(_pipe@3, fun(S) -> {missing_fallback, S} end).

-file("src/scamper/validation.gleam", 19).
?DOC(
    " Validate a config for common issues.\n"
    " Returns Ok(Nil) if no warnings, or Error with a list of warnings.\n"
).
-spec validate_config(scamper@config:config(IQB, any(), any()), IQB) -> {ok,
        nil} |
    {error, list(validation_warning(IQB))}.
validate_config(Config, Initial_state) ->
    Warnings = lists:append(
        [check_unreachable(Config, Initial_state),
            check_transitions_from_final(Config),
            check_missing_fallbacks(Config)]
    ),
    case Warnings of
        [] ->
            {ok, nil};

        _ ->
            {error, Warnings}
    end.