tremor-script 0.9.0

%% Copyright 2020, The Tremor Team
%%
%% 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.
%%

-module(model).

-include_lib("pbt.hrl").

-export([eval/1, eval/2]).


resolve(#state{locals = L}, {local, _} = K) ->
    maps:get(K, L).


-spec ast_eval(#vars{}, {}) -> {#vars{}, integer() | float() | boolean() | binary()}.
ast_eval(#vars{}=S, {'+', A, B}) when is_binary(A) andalso is_binary(B) -> {S, <<A/binary, B/binary>>};
ast_eval(#vars{}=S, {'+', A, B}) ->
    {S1, A1} = ast_eval(S, A),
    {S2, B1} = ast_eval(S1, B),
    case {A1, B1} of 
        {A1, B1} when is_binary(A1) andalso is_binary(B1) ->
            {S, <<A1/binary, B1/binary>>};
        {A1, B1} ->
            {S2, A1 + B1}
    end;
ast_eval(#vars{}=S, {'-', A, B}) ->
    {S1, A1} = ast_eval(S, A),
    {S2, B1} = ast_eval(S1, B),
    {S2, A1 - B1};
ast_eval(#vars{}=S, {'/', A, B}) ->
    {S1, A1} = ast_eval(S, A),
    {S2, B1} = ast_eval(S1, B),
    {S2, A1 / B1};

ast_eval(#vars{}=S, {'*', A, B}) ->
    {S1, A1} = ast_eval(S, A),
    {S2, B1} = ast_eval(S1, B),
    {S2, A1 * B1};

ast_eval(#vars{}=S, {'%', A, B}) ->
    {S1, A1} = ast_eval(S, A),
    {S2, B1} = ast_eval(S1, B),
    {S2, util:mod(A1 ,B1)};

ast_eval(#vars{}=S, {'==', A, B}) ->
    {S1, A1} = ast_eval(S, A),
    {S2, B1} = ast_eval(S1, B),
    {S2, A1 == B1};
ast_eval(#vars{}=S, {'!=', A, B}) ->
    {S1, A1} = ast_eval(S, A),
    {S2, B1} = ast_eval(S1, B),
    {S2, A1 /= B1};
ast_eval(#vars{}=S, {'>=', A, B}) ->
    {S1, A1} = ast_eval(S, A),
    {S2, B1} = ast_eval(S1, B),
    {S2, A1 >= B1};
ast_eval(#vars{}=S, {'>', A, B}) ->
    {S1, A1} = ast_eval(S, A),
    {S2, B1} = ast_eval(S1, B),
    {S2, A1 > B1};
ast_eval(#vars{}=S, {'<', A, B}) ->
    {S1, A1} = ast_eval(S, A),
    {S2, B1} = ast_eval(S1, B),
    {S2, A1 < B1};
ast_eval(#vars{}=S, {'<=', A, B}) ->
    {S1, A1} = ast_eval(S, A),
    {S2, B1} = ast_eval(S1, B),
    {S2, A1 =< B1};
ast_eval(#vars{}=S, {'and', A, B}) ->
    {S1, A1} = ast_eval(S, A),
    {S2, B1} = ast_eval(S1, B),
    {S2, A1 andalso B1};
ast_eval(#vars{}=S, {'or', A, B}) ->
    {S1, A1} = ast_eval(S, A),
    {S2, B1} = ast_eval(S1, B),
    {S2, A1 orelse B1};
ast_eval(#vars{}=S, {'not', A}) ->
    {S1, A1} = ast_eval(S, A),
    {S1, not A1};
ast_eval(#vars{}=S, {'+', A})  ->
    {S1, A1} = ast_eval(S, A),
    {S1, A1};
ast_eval(#vars{}=S, {'-', A})  ->
    {S1, A1} = ast_eval(S, A),
    {S1,-A1};
ast_eval(#vars{locals=L}=S, {'let', Path, Expr}) ->
    {S1, R} = ast_eval(S,Expr),
    LL = maps:put(Path, R, L),
    {S1#vars{locals=LL}, R};
ast_eval(S, true) -> {S, true};
ast_eval(S, false) -> {S, false};
ast_eval(S, null) -> {S, null};
ast_eval(S, N) when is_number(N) -> {S, N};
ast_eval(S, B) when is_binary(B) -> {S, B};
ast_eval(S, {local, _} = L) -> {S, resolve(S, L)};


ast_eval(#vars{}=S, {emit, A}) -> {S1, R} = ast_eval(S, A), {S1, {emit, R}};
ast_eval(#vars{}=S, drop) -> {S, drop}.

%% We run the model specification through a simple implementation of
%% tremor-script implemented in Erlang natively.
eval(Spec) ->
    eval(#vars{}, Spec).

eval(#vars{}=SNOT, Spec) ->
    case ast_eval(SNOT, Spec) of
        {S, {emit, X}} -> {S, [{<<"emit">>, util:clamp(X,13)}]};
        {S, drop} -> {S, [{<<"drop">>, null}]};
        {S, X} -> {S, [{<<"emit">>, util:clamp(X,13)}]}
    end.