(*
 * Copyright (c) 2015 - present Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *)

open! Utils

open CFrontend_utils

(* To create a new checker you should: *)
(* 1. Define a checker function, say my_checker, in this module. *)
(* my_checker should define: *)
(*   -a) a condition that determine if the checker fires *)
(*   -b) a warning_desc that describes the warning (see warning_desc definition) *)
(* 2. Add your checker to the CFrontend_checkers interface *)
(* 3. Decide in which element of the AST my_checker should be evaluated. *)
(*    - If it is a statement then you need to invoke my_checker from *)
(*    run_frontend_checkers_on_stmt in CFrontend_error module.*)
(*    - If it is a declaration invoke it from run_frontend_checkers_on_decl *)

type warning_desc = {
  name : string; (* name for the checker, this will be a kind of bug *)
  description : string; (* Description in the error message *)
  suggestion : string; (* an optional suggestion or correction *)
  loc : Location.t; (* location in the code *)
}

(* Helper functions *)

let name_contains_word pname word =
  let rexp = Str.regexp_string_case_fold word in
  try
    Str.search_forward rexp pname.Clang_ast_t.ni_name 0 >= 0
  with Not_found -> false

let location_from_sinfo info =
  CLocation.get_sil_location_from_range info.Clang_ast_t.si_source_range true

let location_from_dinfo info =
  CLocation.get_sil_location_from_range info.Clang_ast_t.di_source_range true

let proc_name_from_context context =
  Cfg.Procdesc.get_proc_name (CContext.get_procdesc context)

let rec is_self s =
  let open Clang_ast_t in
  match s with
  | ImplicitCastExpr(_, [s], _, _) -> is_self s
  | DeclRefExpr(_, _, _, dr) ->
      (match dr.drti_decl_ref with
       | Some decl_ref ->
           (match decl_ref.dr_name with
            | Some n -> n.ni_name = CFrontend_config.self
            | _ -> false)
       | _ -> false)
  | _ -> false

(* Call method m and on the pn parameter pred holds *)
(* st |= call_method(m(p1,...,pn,...pk)) /\ pred(pn) *)
let call_method_on_nth pred pn m st =
  match st with
  | Clang_ast_t.ObjCMessageExpr (_, params, _, omei) when omei.omei_selector = m ->
      (try
         let p = IList.nth params pn in
         pred p
       with _ -> false)
  | _ -> false

(* st |= EF (atomic_pred param) *)
let rec exists_eventually_st atomic_pred param  st =
  if atomic_pred param st then true
  else
    let _, st_list = Clang_ast_proj.get_stmt_tuple st in
    IList.exists (exists_eventually_st atomic_pred param) st_list

let dec_body_eventually atomic_pred param dec =
  match dec with
  | Clang_ast_t.ObjCMethodDecl (_, _, omdi) ->
      (match omdi.Clang_ast_t.omdi_body with
       | Some body -> exists_eventually_st atomic_pred param body
       | _ -> false)
  | _ -> false

(* === Warnings on properties === *)

(* Assing Pointer Warning: a property with a pointer type should not be declared `assign` *)
let assign_pointer_warning decl_info pname obj_c_property_decl_info =
  let open Clang_ast_t in
  let condition =
    let has_assign_property () = ObjcProperty_decl.is_assign_property obj_c_property_decl_info in
    let is_pointer_type () =
      let type_ptr = obj_c_property_decl_info.opdi_type_ptr in
      let raw_ptr = Clang_ast_types.type_ptr_to_clang_pointer type_ptr in
      match Clang_ast_main.PointerMap.find raw_ptr !CFrontend_config.pointer_type_index with
      | MemberPointerType _ | ObjCObjectPointerType _ | BlockPointerType _ -> true
      | TypedefType (type_info, _) -> type_info.ti_raw = "id"
      | exception Not_found -> false
      | _ -> false in
    has_assign_property() && is_pointer_type () in
  if condition then
    Some
      { name = "ASSIGN_POINTER_WARNING";
        description =
          Printf.sprintf
            "Property `%s` is a pointer type marked with the `assign` attribute"
            pname.ni_name;
        suggestion = "Use a different attribute like `strong` or `weak`.";
        loc = location_from_dinfo decl_info;
      }
  else None

(* Strong Delegate Warning: a property with name delegate should not be declared strong *)
let strong_delegate_warning decl_info pname obj_c_property_decl_info =
  let condition = (name_contains_word pname "delegate")
                  && not (name_contains_word pname "queue")
                  && ObjcProperty_decl.is_strong_property obj_c_property_decl_info in
  if condition then
    Some { name = "STRONG_DELEGATE_WARNING";
           description = "Property or ivar "^pname.Clang_ast_t.ni_name^" declared strong";
           suggestion = "In general delegates should be declared weak or assign";
           loc = location_from_dinfo decl_info; }
  else None

(* Direct Atomic Property access:
   a property declared atomic should not be accessed directly via its ivar *)
let direct_atomic_property_access_warning context stmt_info ivar_name =
  let tenv = CContext.get_tenv context in
  let mname = proc_name_from_context context in
  let ivar, cname = match ivar_name with
    | Some n ->
        General_utils.mk_class_field_name n,
        Ast_utils.get_class_name_from_member n
    | _ -> Ident.create_fieldname (Mangled.from_string "") 0, "" in
  let tname = Typename.TN_csu (Csu.Class Csu.Objc, Mangled.from_string cname) in
  let condition = match Tenv.lookup tenv tname with
    | Some { Sil.instance_fields; static_fields } ->
        (* We give the warning when:
             (1) the property has the atomic attribute and
               (2) the access of the ivar is not in a getter or setter method.
                 (3) the access of the ivar is not in the init method
                   Last two conditions avoids false positives *)
        (CField_decl.is_ivar_atomic ivar (instance_fields @ static_fields))
        && not (CContext.is_curr_proc_objc_getter context ivar)
        && not (CContext.is_curr_proc_objc_setter context ivar)
        && not (Procname.is_constructor mname)
        && not (Procname.is_objc_dealloc mname)
    | _ -> false in
  if condition then
    Some {
      name = "DIRECT_ATOMIC_PROPERTY_ACCESS";
      description = "Direct access to ivar " ^ (Ident.fieldname_to_string ivar) ^
                    " of an atomic property";
      suggestion = "Accessing an ivar of an atomic property makes the property nonatomic";
      loc = location_from_sinfo stmt_info; }
  else None


(* CXX_REFERENCE_CAPTURED_IN_OBJC_BLOCK: C++ references
   should not be captured in blocks.  *)
let captured_cxx_ref_in_objc_block_warning stmt_info captured_vars =
  let is_cxx_ref (_, typ) =
    match typ with
    | Sil.Tptr(_, Sil.Pk_reference) -> true
    | _ -> false in
  let capt_refs = IList.filter is_cxx_ref captured_vars in
  let pvar_descs =
    IList.fold_left (fun s (v, _)  -> s ^ " '" ^ (Pvar.to_string v) ^ "' ") "" capt_refs in
  (* Fire if the list of captured references is not empty *)
  let condition = IList.length capt_refs > 0 in
  if condition then
    Some {
      name = "CXX_REFERENCE_CAPTURED_IN_OBJC_BLOCK";
      description = "C++ Reference variable(s) " ^ pvar_descs ^
                    " captured by Objective-C block";
      suggestion = "C++ References are unmanaged and may be invalid " ^
                   "by the time the block executes.";
      loc = location_from_sinfo stmt_info; }
  else None


(* exist m1:  m1.body|- EF call_method(addObserver:) => exists m2 : m2.body |- EF call_method(removeObserver:) *)
let checker_NSNotificationCenter decl_info decls =
  let exists_method_calling_addObserver =
    IList.exists (dec_body_eventually (call_method_on_nth is_self 1) "addObserver:selector:name:object:") decls in
  let exists_method_calling_addObserverForName =
    IList.exists (dec_body_eventually (call_method_on_nth is_self 1) "addObserverForName:object:queue:usingBlock:") decls in
  let eventually_addObserver = exists_method_calling_addObserver
                               || exists_method_calling_addObserverForName in
  let exists_method_calling_removeObserver =
    IList.exists (dec_body_eventually (call_method_on_nth is_self 1) "removeObserver:") decls in
  let exists_method_calling_removeObserverName =
    IList.exists (dec_body_eventually (call_method_on_nth is_self 1) "removeObserver:name:object:") decls in
  let eventually_removeObserver = exists_method_calling_removeObserver
                                  || exists_method_calling_removeObserverName in
  let condition = eventually_addObserver && (not eventually_removeObserver) in
  if condition then
    Some {
      name = Localise.to_string (Localise.registered_observer_being_deallocated);
      description = Localise.registered_observer_being_deallocated_str CFrontend_config.self;
      suggestion =  "Consider removing the object from the notification center before its deallocation.";
      loc = location_from_dinfo decl_info; }
  else None