distribute

-module(distribute@cluster@health).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/distribute/cluster/health.gleam").
-export([is_healthy/0, node_health/0, cluster_health/0, alive_count/0, suspect_count/0, has_quorum/1, current_leader/0]).
-export_type([cluster_health/0, node_health/0]).

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

-type cluster_health() :: healthy | {degraded, integer(), integer()} | isolated.

-type node_health() :: node_healthy | {node_unhealthy, binary()}.

-file("src/distribute/cluster/health.gleam", 28).
?DOC(
    " Check if the local node is healthy.\n"
    " A node is considered healthy if:\n"
    " - The membership service is running\n"
    " - It can see at least one other node (or is intentionally standalone)\n"
).
-spec is_healthy() -> boolean().
is_healthy() ->
    Suspects = distribute@cluster@membership:suspect(),
    Suspects =:= [].

-file("src/distribute/cluster/health.gleam", 35).
?DOC(" Get detailed health status of the local node.\n").
-spec node_health() -> node_health().
node_health() ->
    Suspects = distribute@cluster@membership:suspect(),
    case Suspects of
        [] ->
            node_healthy;

        _ ->
            {node_unhealthy, <<"Nodes in suspect state"/utf8>>}
    end.

-file("src/distribute/cluster/health.gleam", 44).
?DOC(" Get the overall cluster health status.\n").
-spec cluster_health() -> cluster_health().
cluster_health() ->
    Members = distribute@cluster@membership:members_with_status(),
    Alive_count = erlang:length(gleam@list:filter(Members, fun(M) -> case M of
                    {_, alive, _} ->
                        true;

                    _ ->
                        false
                end end)),
    Suspect_count = erlang:length(
        gleam@list:filter(Members, fun(M@1) -> case M@1 of
                    {_, suspect, _} ->
                        true;

                    _ ->
                        false
                end end)
    ),
    Dead_count = erlang:length(
        gleam@list:filter(Members, fun(M@2) -> case M@2 of
                    {_, dead, _} ->
                        true;

                    _ ->
                        false
                end end)
    ),
    case {Alive_count, Suspect_count, Dead_count} of
        {0, 0, 0} ->
            isolated;

        {_, 0, 0} ->
            healthy;

        {_, S, D} ->
            {degraded, S, D}
    end.

-file("src/distribute/cluster/health.gleam", 82).
?DOC(" Get count of alive nodes.\n").
-spec alive_count() -> integer().
alive_count() ->
    erlang:length(distribute@cluster@membership:alive()).

-file("src/distribute/cluster/health.gleam", 87).
?DOC(" Get count of suspect nodes.\n").
-spec suspect_count() -> integer().
suspect_count() ->
    erlang:length(distribute@cluster@membership:suspect()).

-file("src/distribute/cluster/health.gleam", 93).
?DOC(
    " Check if we have quorum (majority of expected nodes alive).\n"
    " `expected_nodes` is the total expected cluster size including self.\n"
).
-spec has_quorum(integer()) -> boolean().
has_quorum(Expected_nodes) ->
    Alive = alive_count() + 1,
    Alive > (Expected_nodes div 2).

-file("src/distribute/cluster/health.gleam", 100).
?DOC(" Get the current leader if available.\n").
-spec current_leader() -> {ok, binary()} | {error, nil}.
current_leader() ->
    distribute@cluster@membership:current_leader().