-module(prometheus_boolean).
-compile({parse_transform, prometheus_pt}).
-moduledoc """
Boolean metric, to report booleans and flags.

Boolean is a non-standard metric that uses untyped metric underneath.

A Boolean is typically used as a flag i.e. enabled/disabled, online/offline.

Example:

```erlang
-module(my_fuse_instrumenter).

-export([setup/0, fuse_event/2]).

setup() ->
    prometheus_boolean:declare([{name, app_fuse_state},
                                {labels, [name]}, %% fuse name
                                {help, \"State of various app fuses.\"}]),

fuse_event(Fuse, Event) ->
    case Event of
        ok -> prometheus_boolean:set(app_fuse_state, [Fuse], true);
        blown -> prometheus_boolean:set(app_fuse_state, [Fuse], false);
        _ -> ok
    end.
```
""".

%%% metric
-export([
    new/1,
    declare/1,
    deregister/1,
    deregister/2,
    set_default/2,
    set/2,
    set/3,
    set/4,
    toggle/1,
    toggle/2,
    toggle/3,
    remove/1,
    remove/2,
    remove/3,
    reset/1,
    reset/2,
    reset/3,
    value/1,
    value/2,
    value/3,
    values/2
]).

%%% collector
-export([
    deregister_cleanup/1,
    collect_mf/2,
    collect_metrics/2
]).

-include("prometheus.hrl").

-behaviour(prometheus_metric).
-behaviour(prometheus_collector).

-define(TABLE, ?PROMETHEUS_BOOLEAN_TABLE).
-define(BOOLEAN_POS, 2).

-doc """
Creates a boolean using `Spec`.

Raises:

* `{missing_metric_spec_key, Key, Spec}` error if required `Spec` key is missing.
* `{invalid_metric_name, Name, Message}` error if metric `Name` is invalid.
* `{invalid_metric_help, Help, Message}` error if metric `Help` is invalid.
* `{invalid_metric_labels, Labels, Message}` error if `Labels` isn't a list.
* `{invalid_label_name, Name, Message}` error if `Name` isn't a valid label name.
* `{mf_already_exists, {Registry, Name}, Message}` error if a boolean with the same `Spec` already exists.
""".
-spec new(prometheus_metric:spec()) -> ok.
new(Spec) ->
    prometheus_metric:insert_new_mf(?TABLE, ?MODULE, Spec).

-doc """
Creates a boolean using `Spec`.

If a boolean with the same `Spec` exists returns `false`.

Raises:

* `{missing_metric_spec_key, Key, Spec}` error if required `Spec` key is missing.
* `{invalid_metric_name, Name, Message}` error if metric `Name` is invalid.
* `{invalid_metric_help, Help, Message}` error if metric `Help` is invalid.
* `{invalid_metric_labels, Labels, Message}` error if `Labels` isn't a list.
* `{invalid_label_name, Name, Message}` error if `Name` isn't a valid label name.
""".
-spec declare(prometheus_metric:spec()) -> boolean().
declare(Spec) ->
    prometheus_metric:insert_mf(?TABLE, ?MODULE, Spec).

-doc #{equiv => deregister(default, Name)}.
-spec deregister(prometheus_metric:name()) -> {boolean(), boolean()}.
deregister(Name) ->
    deregister(default, Name).

-doc """
Removes all boolean series with name `Name` and removes Metric Family from `Registry`.

After this call new/1 for `Name` and `Registry` will succeed.

Returns `{true, _}` if `Name` was a registered boolean. Otherwise returns `{true, _}`.
""".
-spec deregister(prometheus_registry:registry(), prometheus_metric:name()) ->
    {boolean(), boolean()}.
deregister(Registry, Name) ->
    MFR = prometheus_metric:deregister_mf(?TABLE, Registry, Name),
    NumDeleted = ets:select_delete(?TABLE, deregister_select(Registry, Name)),
    {MFR, NumDeleted > 0}.

-doc false.
-spec set_default(prometheus_registry:registry(), prometheus_metric:name()) -> ok.
set_default(Registry, Name) ->
    set(Registry, Name, [], undefined).

-doc #{equiv => set(default, Name, [], Value)}.
-spec set(prometheus_metric:name(), prometheus:prometheus_boolean()) -> ok.
set(Name, Value) ->
    set(default, Name, [], Value).

-doc #{equiv => set(default, Name, LabelValues, Value)}.
-spec set(prometheus_metric:name(), prometheus_metric:labels(), prometheus:prometheus_boolean()) ->
    ok.
set(Name, LabelValues, Value) ->
    set(default, Name, LabelValues, Value).

-doc """
Sets the boolean identified by `Registry`, `Name` and `LabelValues` to `Value`.

Valid truthy values:

* `true`;
* `false`;
* `0` -> false;
* `number > 0` -> true;
* `[]` -> false;
* `non-empty list` -> true;
* `undefined` -> undefined;

Other values will generate `invalid_value` error.

Raises:

* `{invalid_value, Value, Message}` if `Value` isn't a boolean or `undefined`.
* `{unknown_metric, Registry, Name}` error if boolean with named `Name` can't be found in `Registry`.
* `{invalid_metric_arity, Present, Expected}` error if labels count mismatch.
""".
-spec set(Registry, Name, LabelValues, Value) -> ok when
    Registry :: prometheus_registry:registry(),
    Name :: prometheus_metric:name(),
    LabelValues :: prometheus_metric:labels(),
    Value :: prometheus:prometheus_boolean().
set(Registry, Name, LabelValues, Value) ->
    Value1 = prometheus_model_helpers:boolean_value(Value),
    set_(Registry, Name, LabelValues, Value1).

-doc #{equiv => toggle(default, Name, [])}.
-spec toggle(prometheus_metric:name()) -> ok.
toggle(Name) ->
    toggle(default, Name, []).

-doc #{equiv => toggle(default, Name, LabelValues)}.
-spec toggle(prometheus_metric:name(), prometheus_metric:labels()) -> ok.
toggle(Name, LabelValues) ->
    toggle(default, Name, LabelValues).

-doc """
Toggles the boolean identified by `Registry`, `Name` and `LabelValues`.

If boolean set to undefined, it can't be toggled.

Raises:

* `{invalid_value, undefined, Message}` if boolean is undefined.
* `{unknown_metric, Registry, Name}` error if boolean with named `Name` can't be found in `Registry`.
* `{invalid_metric_arity, Present, Expected}` error if labels count mismatch.
""".
-spec toggle(prometheus_registry:registry(), prometheus_metric:name(), prometheus_metric:labels()) ->
    ok.
toggle(Registry, Name, LabelValues) ->
    Key = {Registry, Name, LabelValues},
    Spec = {?BOOLEAN_POS, 1, 1, 0},
    try
        ets:update_counter(?TABLE, Key, Spec)
    catch
        error:badarg ->
            save_toggle(Registry, Name, LabelValues)
    end,
    ok.

-doc #{equiv => remove(default, Name, [])}.
-spec remove(prometheus_metric:name()) -> boolean().
remove(Name) ->
    remove(default, Name, []).

-doc #{equiv => remove(default, Name, LabelValues)}.
-spec remove(prometheus_metric:name(), prometheus_metric:labels()) -> boolean().
remove(Name, LabelValues) ->
    remove(default, Name, LabelValues).

-doc """
Removes boolean series identified by `Registry`, `Name` and `LabelValues`.

Raises:

* `{unknown_metric, Registry, Name}` error if boolean with name `Name` can't be found in `Registry`.
* `{invalid_metric_arity, Present, Expected}` error if labels count mismatch.
""".
-spec remove(prometheus_registry:registry(), prometheus_metric:name(), prometheus_metric:labels()) ->
    boolean().
remove(Registry, Name, LabelValues) ->
    prometheus_metric:remove_labels(?TABLE, Registry, Name, LabelValues).

-doc #{equiv => reset(default, Name, [])}.
-spec reset(prometheus_metric:name()) -> boolean().
reset(Name) ->
    reset(default, Name, []).

-doc #{equiv => reset(default, Name, LabelValues)}.
-spec reset(prometheus_metric:name(), prometheus_metric:labels()) -> boolean().
reset(Name, LabelValues) ->
    reset(default, Name, LabelValues).

-doc """
Resets the value of the boolean identified by `Registry`, `Name` and `LabelValues`.

Raises:

* `{unknown_metric, Registry, Name}` error if boolean with name `Name` can't be found in `Registry`.
* `{invalid_metric_arity, Present, Expected}` error if labels count mismatch.
""".
-spec reset(prometheus_registry:registry(), prometheus_metric:name(), prometheus_metric:labels()) ->
    boolean().
reset(Registry, Name, LabelValues) ->
    prometheus_metric:check_mf_exists(?TABLE, Registry, Name, LabelValues),
    ets:update_element(?TABLE, {Registry, Name, LabelValues}, {?BOOLEAN_POS, 0}).

-doc #{equiv => value(default, Name, [])}.
-spec value(prometheus_metric:name()) -> boolean() | undefined.
value(Name) ->
    value(default, Name, []).

-doc #{equiv => value(default, Name, LabelValues)}.
-spec value(prometheus_metric:name(), prometheus_metric:labels()) -> boolean() | undefined.
value(Name, LabelValues) ->
    value(default, Name, LabelValues).

-doc """
Returns the value of the boolean identified by `Registry`, `Name` and `LabelValues`.
If there is no boolean for `LabelValues`, returns `undefined`.

Raises:

* `{unknown_metric, Registry, Name}` error if boolean named `Name` can't be found in `Registry`.
* `{invalid_metric_arity, Present, Expected}` error if labels count mismatch.
""".
-spec value(prometheus_registry:registry(), prometheus_metric:name(), prometheus_metric:labels()) ->
    boolean() | undefined.
value(Registry, Name, LabelValues) ->
    case ets:lookup(?TABLE, {Registry, Name, LabelValues}) of
        [{_Key, 0}] ->
            false;
        [{_Key, 1}] ->
            true;
        [{_Key, undefined}] ->
            undefined;
        [] ->
            prometheus_metric:check_mf_exists(?TABLE, Registry, Name, LabelValues),
            undefined
    end.

-spec values(prometheus_registry:registry(), prometheus_metric:name()) -> [{list(), boolean()}].
values(Registry, Name) ->
    case prometheus_metric:check_mf_exists(?TABLE, Registry, Name) of
        false ->
            [];
        MF ->
            Labels = prometheus_metric:mf_labels(MF),
            [
                {lists:zip(Labels, LabelValues), Value =:= 1}
             || [LabelValues, Value] <- load_all_values(Registry, Name)
            ]
    end.

%%====================================================================
%% Collector API
%%====================================================================

-doc false.
-spec deregister_cleanup(prometheus_registry:registry()) -> ok.
deregister_cleanup(Registry) ->
    prometheus_metric:deregister_mf(?TABLE, Registry),
    true = ets:match_delete(?TABLE, {{Registry, '_', '_'}, '_'}),
    ok.

-doc false.
-spec collect_mf(prometheus_registry:registry(), prometheus_collector:collect_mf_callback()) -> ok.
collect_mf(Registry, Callback) ->
    [
        Callback(create_boolean(Name, Help, {CLabels, Labels, Registry}))
     || [Name, {Labels, Help}, CLabels, _, _] <- prometheus_metric:metrics(?TABLE, Registry)
    ],
    ok.

-doc false.
-spec collect_metrics(prometheus_metric:name(), tuple()) -> [prometheus_model:'Metric'()].
collect_metrics(Name, {CLabels, Labels, Registry}) ->
    [
        prometheus_model_helpers:boolean_metric(
            CLabels ++ lists:zip(Labels, LabelValues), Value
        )
     || [LabelValues, Value] <- load_all_values(Registry, Name)
    ].

%%====================================================================
%% Private Parts
%%====================================================================

deregister_select(Registry, Name) ->
    [{{{Registry, Name, '_'}, '_'}, [], [true]}].

set_(Registry, Name, LabelValues, Value) ->
    Key = {Registry, Name, LabelValues},
    Spec = {?BOOLEAN_POS, Value},
    case ets:update_element(?TABLE, Key, Spec) of
        false ->
            insert_metric(Registry, Name, LabelValues, Value, fun set_/4);
        true ->
            ok
    end.

save_toggle(Registry, Name, LabelValues) ->
    case ets:lookup(?TABLE, {Registry, Name, LabelValues}) of
        [{_Key, undefined}] ->
            erlang:error({invalid_value, undefined, "can't toggle undefined boolean"});
        [] ->
            insert_metric(Registry, Name, LabelValues, 0, fun toggle/3)
    end.

insert_metric(Registry, Name, LabelValues, Value, ConflictCB) ->
    prometheus_metric:check_mf_exists(?TABLE, Registry, Name, LabelValues),
    case ets:insert_new(?TABLE, {{Registry, Name, LabelValues}, Value}) of
        %% some sneaky process already inserted
        false ->
            ConflictCB(Registry, Name, LabelValues, Value);
        true ->
            ok
    end.

load_all_values(Registry, Name) ->
    ets:match(?TABLE, {{Registry, Name, '$1'}, '$2'}).

create_boolean(Name, Help, Data) ->
    prometheus_model_helpers:create_mf(Name, Help, boolean, ?MODULE, Data).