(**
 * Copyright (c) 2013-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *)

open Parser_env
open Flow_ast
module Error = Parse_error

type pattern_errors = {
  if_expr: (Loc.t * Parse_error.t) list;
  if_patt: (Loc.t * Parse_error.t) list;
}

type pattern_cover =
  | Cover_expr of (Loc.t, Loc.t) Expression.t
  | Cover_patt of (Loc.t, Loc.t) Expression.t * pattern_errors

module type PARSER = sig
  val program : env -> (Loc.t, Loc.t) program
  val statement : env -> (Loc.t, Loc.t) Statement.t
  val statement_list_item : ?decorators:(Loc.t, Loc.t) Class.Decorator.t list -> env -> (Loc.t, Loc.t) Statement.t
  val statement_list : term_fn:(Token.t -> bool) -> env -> (Loc.t, Loc.t) Statement.t list
  val statement_list_with_directives : term_fn:(Token.t -> bool) -> env -> (Loc.t, Loc.t) Statement.t list * bool
  val module_body : term_fn:(Token.t -> bool) -> env -> (Loc.t, Loc.t) Statement.t list
  val expression : env -> (Loc.t, Loc.t) Expression.t
  val expression_or_pattern : env -> pattern_cover
  val conditional : env -> (Loc.t, Loc.t) Expression.t
  val assignment : env -> (Loc.t, Loc.t) Expression.t
  val left_hand_side : env -> (Loc.t, Loc.t) Expression.t
  val object_initializer : env -> Loc.t * (Loc.t, Loc.t) Expression.Object.t * pattern_errors
  val identifier : ?restricted_error:Error.t -> env -> Loc.t Identifier.t
  val identifier_with_type : env -> ?no_optional:bool -> Error.t -> Loc.t * (Loc.t, Loc.t) Pattern.Identifier.t
  val assert_identifier_name_is_identifier :
    ?restricted_error:Error.t -> env -> Loc.t * string -> unit
  val block_body : env -> Loc.t * (Loc.t, Loc.t) Statement.Block.t
  val function_block_body : env -> Loc.t * (Loc.t, Loc.t) Statement.Block.t * bool
  val jsx_element_or_fragment :
    env -> Loc.t * [`Element of (Loc.t, Loc.t) JSX.element | `Fragment of (Loc.t, Loc.t) JSX.fragment]
  val pattern : env -> Error.t -> (Loc.t, Loc.t) Pattern.t
  val pattern_from_expr : env -> (Loc.t, Loc.t) Expression.t -> (Loc.t, Loc.t) Pattern.t
  val object_key : ?class_body: bool -> env -> Loc.t * (Loc.t, Loc.t) Expression.Object.Property.key
  val class_declaration : env -> (Loc.t, Loc.t) Class.Decorator.t list -> (Loc.t, Loc.t) Statement.t
  val class_expression : env -> (Loc.t, Loc.t) Expression.t
  val is_assignable_lhs : (Loc.t, Loc.t) Expression.t -> bool
end

(* IdentifierName - https://tc39.github.io/ecma262/#prod-IdentifierName *)
let identifier_name env =
  let open Token in
  let loc = Peek.loc env in
  let name = match Peek.token env with
  (* obviously, Identifier is a valid IdentifierName *)
  | T_IDENTIFIER { value; _ } -> value
  (* keywords are also IdentifierNames *)
  | T_AWAIT -> "await"
  | T_BREAK -> "break"
  | T_CASE -> "case"
  | T_CATCH -> "catch"
  | T_CLASS -> "class"
  | T_CONST -> "const"
  | T_CONTINUE -> "continue"
  | T_DEBUGGER -> "debugger"
  | T_DEFAULT -> "default"
  | T_DELETE -> "delete"
  | T_DO -> "do"
  | T_ELSE -> "else"
  | T_EXPORT -> "export"
  | T_EXTENDS -> "extends"
  | T_FINALLY -> "finally"
  | T_FOR -> "for"
  | T_FUNCTION -> "function"
  | T_IF -> "if"
  | T_IMPORT -> "import"
  | T_IN -> "in"
  | T_INSTANCEOF -> "instanceof"
  | T_NEW -> "new"
  | T_RETURN -> "return"
  | T_SUPER -> "super"
  | T_SWITCH -> "switch"
  | T_THIS -> "this"
  | T_THROW -> "throw"
  | T_TRY -> "try"
  | T_TYPEOF -> "typeof"
  | T_VAR -> "var"
  | T_VOID -> "void"
  | T_WHILE -> "while"
  | T_WITH -> "with"
  | T_YIELD -> "yield"
  (* FutureReservedWord *)
  | T_ENUM -> "enum"
  | T_LET -> "let"
  | T_STATIC -> "static"
  | T_INTERFACE -> "interface"
  | T_IMPLEMENTS -> "implements"
  | T_PACKAGE -> "package"
  | T_PRIVATE -> "private"
  | T_PROTECTED -> "protected"
  | T_PUBLIC -> "public"
  (* NullLiteral *)
  | T_NULL -> "null"
  (* BooleanLiteral *)
  | T_TRUE -> "true"
  | T_FALSE -> "false"
  (* Flow-specific stuff *)
  | T_DECLARE -> "declare"
  | T_TYPE -> "type"
  | T_OPAQUE -> "opaque"
  | T_ANY_TYPE -> "any"
  | T_MIXED_TYPE -> "mixed"
  | T_EMPTY_TYPE -> "empty"
  | T_BOOLEAN_TYPE BOOL -> "bool"
  | T_BOOLEAN_TYPE BOOLEAN -> "boolean"
  | T_NUMBER_TYPE -> "number"
  | T_STRING_TYPE -> "string"
  | T_VOID_TYPE -> "void"
  (* Contextual stuff *)
  | T_OF -> "of"
  | T_ASYNC -> "async"
  (* punctuators, types, literals, etc are not identifiers *)
  | _ -> error_unexpected env; ""
  in
  Eat.token env;
  loc, name

(**
 * The abstract operation IsLabelledFunction
 *
 * https://tc39.github.io/ecma262/#sec-islabelledfunction
 *)
let rec is_labelled_function = function
  | _, Flow_ast.Statement.Labeled { Flow_ast.Statement.Labeled.body; _ } ->
    begin match body with
    | _, Flow_ast.Statement.FunctionDeclaration _ -> true
    | _ -> is_labelled_function body
    end
  | _ ->
    false

let with_loc ?start_loc fn env =
  let start_loc = match start_loc with
  | Some x -> x
  | None -> Peek.loc env
  in
  let result = fn env in
  let loc = match last_loc env with
  | Some end_loc -> Loc.btwn start_loc end_loc
  | None -> start_loc
  in
  loc, result
