%% Translate Elixir quoted expressions to Erlang Abstract Format.
%% Expects the tree to be expanded.
-module(elixir_translator).
-export([translate/2, translate_arg/3, translate_args/2, translate_block/3]).
-import(elixir_scope, [mergev/2, mergec/2]).
-import(elixir_errors, [compile_error/3, compile_error/4]).
-include("elixir.hrl").

%% =

translate({'=', Meta, [Left, Right]}, S) ->
  Return = case Left of
    {'_', _, Atom} when is_atom(Atom) -> S#elixir_scope.return;
    _ -> true
  end,

  {TRight, SR} = translate_block(Right, Return, S),
  {TLeft, SL} = elixir_clauses:match(fun translate/2, Left, SR),
  {{match, ?line(Meta), TLeft, TRight}, SL};

%% Containers

translate({'{}', Meta, Args}, S) when is_list(Args) ->
  {TArgs, SE} = translate_args(Args, S),
  {{tuple, ?line(Meta), TArgs}, SE};

translate({'%{}', Meta, Args}, S) when is_list(Args) ->
  elixir_map:translate_map(Meta, Args, S);

translate({'%', Meta, [Left, Right]}, S) ->
  elixir_map:translate_struct(Meta, Left, Right, S);

translate({'<<>>', Meta, Args}, S) when is_list(Args) ->
  elixir_bitstring:translate(Meta, Args, S);

%% Blocks

translate({'__block__', Meta, Args}, #elixir_scope{return=Return} = S) when is_list(Args) ->
  {TArgs, SA} = translate_block(Args, [], Return, S#elixir_scope{return=true}),
  {{block, ?line(Meta), TArgs}, SA};

%% Erlang op

translate({'__op__', Meta, [Op, Expr]}, S) when is_atom(Op) ->
  {TExpr, NS} = translate(Expr, S),
  {{op, ?line(Meta), Op, TExpr}, NS};

translate({'__op__', Meta, [Op, Left, Right]}, S) when is_atom(Op) ->
  {[TLeft, TRight], NS}  = translate_args([Left, Right], S),
  {{op, ?line(Meta), Op, TLeft, TRight}, NS};

%% Lexical

translate({Lexical, _, [_, _]}, S) when Lexical == import; Lexical == alias; Lexical == require ->
  {{atom, 0, nil}, S};

%% Pseudo variables

translate({'__CALLER__', Meta, Atom}, S) when is_atom(Atom) ->
  {{var, ?line(Meta), '__CALLER__'}, S#elixir_scope{caller=true}};

%% Functions

translate({'&', Meta, [{'/', [], [{Fun, [], Atom}, Arity]}]}, S)
    when is_atom(Fun), is_atom(Atom), is_integer(Arity) ->
  {{'fun', ?line(Meta), {function, Fun, Arity}}, S};
translate({'&', Meta, [Arg]}, S) when is_integer(Arg) ->
  compile_error(Meta, S#elixir_scope.file, "unhandled &~B outside of a capture", [Arg]);

translate({fn, Meta, Clauses}, S) ->
  elixir_fn:translate(Meta, Clauses, S);

%% Cond

translate({'cond', CondMeta, [[{do, Pairs}]]}, S) ->
  [{'->', Meta, [[Condition], Body]}|T] = lists:reverse(Pairs),
  Case =
    case Condition of
      {'_', _, Atom} when is_atom(Atom) ->
        compile_error(Meta, S#elixir_scope.file, "unbound variable _ inside cond. "
          "If you want the last clause to always match, you probably meant to use: true ->");
      X when is_atom(X) and (X /= false) and (X /= nil) ->
        build_cond_clauses(T, Body, Meta);
      _ ->
        {Truthy, Other} = build_truthy_clause(Meta, Condition, Body),
        Error = {{'.', Meta, [erlang, error]}, [], [cond_clause]},
        Falsy = {'->', Meta, [[Other], Error]},
        Acc = {'case', Meta, [Condition, [{do, [Truthy, Falsy]}]]},
        build_cond_clauses(T, Acc, Meta)
    end,
  translate(replace_case_meta(CondMeta, Case), S);

%% Case

translate({'case', Meta, [Expr, KV]}, #elixir_scope{return=Return} = RS) ->
  S = RS#elixir_scope{return=true},
  Clauses = elixir_clauses:get_pairs(do, KV, match),
  {TExpr, NS} = translate(Expr, S),
  {TClauses, TS} = elixir_clauses:clauses(Meta, Clauses, Return, NS),
  {{'case', ?line(Meta), TExpr, TClauses}, TS};

%% Try

translate({'try', Meta, [Clauses]}, #elixir_scope{return=Return} = RS) ->
  S  = RS#elixir_scope{noname=true, return=true},
  Do = proplists:get_value('do', Clauses, nil),
  {TDo, SB} = elixir_translator:translate(Do, S),

  Catch = [Tuple || {X, _} = Tuple <- Clauses, X == 'rescue' orelse X == 'catch'],
  {TCatch, SC} = elixir_try:clauses(Meta, Catch, Return, mergec(S, SB)),

  case lists:keyfind('after', 1, Clauses) of
    {'after', After} ->
      {TBlock, SA} = translate(After, mergec(S, SC)),
      TAfter = unblock(TBlock);
    false ->
      {TAfter, SA} = {[], mergec(S, SC)}
  end,

  Else = elixir_clauses:get_pairs(else, Clauses, match),
  {TElse, SE} = elixir_clauses:clauses(Meta, Else, Return, mergec(S, SA)),

  SF = (mergec(S, SE))#elixir_scope{noname=RS#elixir_scope.noname},
  {{'try', ?line(Meta), unblock(TDo), TElse, TCatch, TAfter}, SF};

%% Receive

translate({'receive', Meta, [KV]}, #elixir_scope{return=Return} = RS) ->
  S  = RS#elixir_scope{return=true},
  Do = elixir_clauses:get_pairs(do, KV, match, true),

  case lists:keyfind('after', 1, KV) of
    false ->
      {TClauses, SC} = elixir_clauses:clauses(Meta, Do, Return, S),
      {{'receive', ?line(Meta), TClauses}, SC};
    _ ->
      After = elixir_clauses:get_pairs('after', KV, expr),
      {TClauses, SC} = elixir_clauses:clauses(Meta, Do ++ After, Return, S),
      {FClauses, TAfter} = elixir_utils:split_last(TClauses),
      {_, _, [FExpr], _, FAfter} = TAfter,
      {{'receive', ?line(Meta), FClauses, FExpr, FAfter}, SC}
  end;

%% Comprehensions

translate({for, Meta, [_|_] = Args}, S) ->
  elixir_for:translate(Meta, Args, S);

%% Super

translate({super, Meta, Args}, S) when is_list(Args) ->
  Module = assert_module_scope(Meta, super, S),
  Function = assert_function_scope(Meta, super, S),
  elixir_def_overridable:ensure_defined(Meta, Module, Function, S),

  {_, Arity} = Function,

  {TArgs, TS} = if
    length(Args) == Arity ->
      translate_args(Args, S);
    true ->
      compile_error(Meta, S#elixir_scope.file, "super must be called with the same number of "
                    "arguments as the current function")
  end,

  Super = elixir_def_overridable:name(Module, Function),
  {{call, ?line(Meta), {atom, ?line(Meta), Super}, TArgs}, TS#elixir_scope{super=true}};

%% Variables

translate({'^', Meta, [{Name, VarMeta, Kind}]}, #elixir_scope{context=match} = S) when is_atom(Name), is_atom(Kind) ->
  Tuple = {Name, var_kind(VarMeta, Kind)},
  case orddict:find(Tuple, S#elixir_scope.backup_vars) of
    {ok, {Value, _Counter}} ->
      {{var, ?line(Meta), Value}, S};
    error ->
      compile_error(Meta, S#elixir_scope.file, "unbound variable ^~ts", [Name])
  end;

translate({'_', Meta, Kind}, #elixir_scope{context=match} = S) when is_atom(Kind) ->
  {{var, ?line(Meta), '_'}, S};

translate({'_', Meta, Kind}, S) when is_atom(Kind) ->
  compile_error(Meta, S#elixir_scope.file, "unbound variable _");

translate({Name, Meta, Kind}, #elixir_scope{extra=map_key} = S) when is_atom(Name), is_atom(Kind) ->
  compile_error(Meta, S#elixir_scope.file, "illegal use of variable ~ts in map key", [Name]);

translate({Name, Meta, Kind}, S) when is_atom(Name), is_atom(Kind) ->
  elixir_scope:translate_var(Meta, Name, var_kind(Meta, Kind), S);

%% Local calls

translate({Name, Meta, Args}, S) when is_atom(Name), is_list(Meta), is_list(Args) ->
  if
    S#elixir_scope.context == match ->
      compile_error(Meta, S#elixir_scope.file,
                    "cannot invoke local ~ts/~B inside match", [Name, length(Args)]);
    S#elixir_scope.context == guard ->
      Arity = length(Args),
      File  = S#elixir_scope.file,
      case Arity of
        0 -> compile_error(Meta, File, "unknown variable ~ts or cannot invoke "
                           "local ~ts/~B inside guard", [Name, Name, Arity]);
        _ -> compile_error(Meta, File, "cannot invoke local ~ts/~B inside guard",
                           [Name, Arity])
      end;
    true ->
      Line = ?line(Meta),
      {TArgs, NS} = translate_args(Args, S),
      {{call, Line, {atom, Line, Name}, TArgs}, NS}
  end;

%% Remote calls

translate({{'.', _, [Left, Right]}, Meta, Args}, S)
    when (is_tuple(Left) orelse is_atom(Left)), is_atom(Right), is_list(Meta), is_list(Args) ->
  {TLeft, SL} = translate(Left, S),
  {TArgs, SA} = translate_args(Args, mergec(S, SL)),

  Line   = ?line(Meta),
  Arity  = length(Args),
  TRight = {atom, Line, Right},

  %% We need to rewrite erlang function calls as operators
  %% because erl_eval chokes on them. We can remove this
  %% once a fix is merged into Erlang, keeping only the
  %% list operators one (since it is required for inlining
  %% [1, 2, 3] ++ Right in matches).
  case (Left == erlang) andalso erl_op(Right, Arity) of
    true ->
      {list_to_tuple([op, Line, Right] ++ TArgs), mergev(SL, SA)};
    false ->
      assert_allowed_in_context(Meta, Left, Right, Arity, S),
      SC = mergev(SL, SA),

      case not is_atom(Left) andalso (Arity == 0) of
        true ->
          {Var, _, SV} = elixir_scope:build_var('_', SC),
          TVar = {var, Line, Var},
          TMap = {map, Line, [
            {map_field_assoc, Line,
              {atom, Line, '__struct__'},
              {atom, Line, 'Elixir.KeyError'}},
            {map_field_assoc, Line,
              {atom, Line, '__exception__'},
              {atom, Line, 'true'}},
            {map_field_assoc, Line,
              {atom, Line, key},
              TRight},
            {map_field_assoc, Line,
              {atom, Line, term},
              TVar}]},

          %% TODO There is a bug in dialyzer that makes it fail on
          %% empty maps. We work around the bug below by using
          %% the is_map/1 guard instead of matching on map. Hopefully
          %% we can use a match on 17.1.
          %%
          %% In the future, we could also use maps:get/2 instead
          %% of pattern match, reducing the AST footprint.
          %%
          %% http://erlang.org/pipermail/erlang-bugs/2014-April/004338.html
          {{'case', -1, TLeft, [
            {clause, -1,
              [{map, Line, [{map_field_exact, Line, TRight, TVar}]}],
              [],
              [TVar]},
            {clause, -1,
              [TVar],
              [[elixir_utils:erl_call(Line, erlang, is_map, [TVar])]],
              [elixir_utils:erl_call(Line, erlang, error, [TMap])]},
            {clause, -1,
              [TVar],
              [],
              [{call, Line, {remote, Line, TVar, TRight}, []}]}
          ]}, SV};
        false ->
          {{call, Line, {remote, Line, TLeft, TRight}, TArgs}, SC}
      end
  end;

%% Anonymous function calls

translate({{'.', _, [Expr]}, Meta, Args}, S) when is_list(Args) ->
  {TExpr, SE} = translate(Expr, S),
  {TArgs, SA} = translate_args(Args, mergec(S, SE)),
  {{call, ?line(Meta), TExpr, TArgs}, mergev(SE, SA)};

%% Literals

translate(List, S) when is_list(List) ->
  Fun = case S#elixir_scope.context of
    match -> fun translate/2;
    _     -> fun(X, Acc) -> translate_arg(X, Acc, S) end
  end,
  translate_list(List, Fun, S, []);

translate({Left, Right}, S) ->
  {TArgs, SE} = translate_args([Left, Right], S),
  {{tuple, 0, TArgs}, SE};

translate(Other, S) ->
  {elixir_utils:elixir_to_erl(Other), S}.

%% Helpers

erl_op(Op, Arity) ->
  erl_internal:list_op(Op, Arity) orelse
    erl_internal:comp_op(Op, Arity) orelse
    erl_internal:bool_op(Op, Arity) orelse
    erl_internal:arith_op(Op, Arity).

translate_list([{'|', _, [_, _]=Args}], Fun, Acc, List) ->
  {[TLeft, TRight], TAcc} = lists:mapfoldl(Fun, Acc, Args),
  {build_list([TLeft|List], TRight), TAcc};
translate_list([H|T], Fun, Acc, List) ->
  {TH, TAcc} = Fun(H, Acc),
  translate_list(T, Fun, TAcc, [TH|List]);
translate_list([], _Fun, Acc, List) ->
  {build_list(List, {nil, 0}), Acc}.

build_list([H|T], Acc) ->
  build_list(T, {cons, 0, H, Acc});
build_list([], Acc) ->
  Acc.

var_kind(Meta, Kind) ->
  case lists:keyfind(counter, 1, Meta) of
    {counter, Counter} -> Counter;
    false -> Kind
  end.

%% Pack a list of expressions from a block.
unblock({'block', _, Exprs}) -> Exprs;
unblock(Expr)                -> [Expr].

%% Translate args

translate_arg(Arg, Acc, S) when is_number(Arg); is_atom(Arg); is_binary(Arg); is_pid(Arg); is_function(Arg) ->
  {TArg, _} = translate(Arg, S),
  {TArg, Acc};
translate_arg(Arg, Acc, S) ->
  {TArg, TAcc} = translate(Arg, mergec(S, Acc)),
  {TArg, mergev(Acc, TAcc)}.

translate_args(Args, #elixir_scope{context=match} = S) ->
  lists:mapfoldl(fun translate/2, S, Args);

translate_args(Args, S) ->
  lists:mapfoldl(fun(X, Acc) -> translate_arg(X, Acc, S) end, S, Args).

%% Translate blocks

translate_block([], Acc, _Return, S) ->
  {lists:reverse(Acc), S};
translate_block([H], Acc, Return, S) ->
  {TH, TS} = translate_block(H, Return, S),
  translate_block([], [TH|Acc], Return, TS);
translate_block([H|T], Acc, Return, S) ->
  {TH, TS} = translate_block(H, false, S),
  translate_block(T, [TH|Acc], Return, TS).

translate_block(Expr, Return, S) ->
  case (Return == false) andalso handles_no_return(Expr) of
    true  -> translate(Expr, S#elixir_scope{return=Return});
    false -> translate(Expr, S)
  end.

%% return is typically true, except when we find one
%% of the expressions below, which may handle return=false
%% but must always return return=true.
handles_no_return({'try', _, [_]}) -> true;
handles_no_return({'cond', _, [_]}) -> true;
handles_no_return({'for', _, [_|_]}) -> true;
handles_no_return({'case', _, [_, _]}) -> true;
handles_no_return({'receive', _, [_]}) -> true;
handles_no_return({'__block__', _, [_|_]}) -> true;
handles_no_return(_) -> false.

%% Cond

build_cond_clauses([{'->', NewMeta, [[Condition], Body]}|T], Acc, OldMeta) ->
  {Truthy, Other} = build_truthy_clause(NewMeta, Condition, Body),
  Falsy = {'->', OldMeta, [[Other], Acc]},
  Case = {'case', NewMeta, [Condition, [{do, [Truthy, Falsy]}]]},
  build_cond_clauses(T, Case, NewMeta);
build_cond_clauses([], Acc, _) ->
  Acc.

replace_case_meta(Meta, {'case', _, Args}) ->
  {'case', Meta, Args};
replace_case_meta(_Meta, Other) ->
  Other.

build_truthy_clause(Meta, Condition, Body) ->
  case elixir_utils:returns_boolean(Condition) of
    true ->
      {{'->', Meta, [[true], Body]}, false};
    false ->
      Var  = {'cond', [], 'Elixir'},
      Head = {'when', [], [Var,
        {'__op__', [], [
          'andalso',
          {{'.', [], [erlang, '/=']}, [], [Var, nil]},
          {{'.', [], [erlang, '/=']}, [], [Var, false]}
        ]}
      ]},
      {{'->', Meta, [[Head], Body]}, {'_', [], nil}}
  end.

%% Assertions

assert_module_scope(Meta, Kind, #elixir_scope{module=nil, file=File}) ->
  compile_error(Meta, File, "cannot invoke ~ts outside module", [Kind]);
assert_module_scope(_Meta, _Kind, #elixir_scope{module=Module}) -> Module.

assert_function_scope(Meta, Kind, #elixir_scope{function=nil, file=File}) ->
  compile_error(Meta, File, "cannot invoke ~ts outside function", [Kind]);
assert_function_scope(_Meta, _Kind, #elixir_scope{function=Function}) -> Function.

assert_allowed_in_context(Meta, Left, Right, Arity, #elixir_scope{context=Context} = S)
    when (Context == match) orelse (Context == guard) ->
  case (Left == erlang) andalso erl_internal:guard_bif(Right, Arity) of
    true  -> ok;
    false ->
      compile_error(Meta, S#elixir_scope.file, "cannot invoke remote function ~ts.~ts/~B inside ~ts",
        ['Elixir.Macro':to_string(Left), Right, Arity, Context])
  end;
assert_allowed_in_context(_, _, _, _, _) ->
  ok.
