(**************************************************************************)
(*                                                                        *)
(*                                 OCaml                                  *)
(*                                                                        *)
(*           Damien Doligez, projet Gallium, INRIA Rocquencourt           *)
(*                                                                        *)
(*   Copyright 2014 Institut National de Recherche en Informatique et     *)
(*     en Automatique.                                                    *)
(*                                                                        *)
(*   All rights reserved.  This file is distributed under the terms of    *)
(*   the GNU Lesser General Public License version 2.1, with the          *)
(*   special exception on linking described in the file LICENSE.          *)
(*                                                                        *)
(**************************************************************************)

(* String operations, based on byte sequence operations *)

(* WARNING: Some functions in this file are duplicated in bytes.ml for
   efficiency reasons. When you modify the one in this file you need to
   modify its duplicate in bytes.ml.
   These functions have a "duplicated" comment above their definition.
*)

external length : string -> int = "%string_length"
external get : string -> int -> char = "%string_safe_get"
external set : bytes -> int -> char -> unit = "%string_safe_set"
external create : int -> bytes = "caml_create_string"
external unsafe_get : string -> int -> char = "%string_unsafe_get"
external unsafe_set : bytes -> int -> char -> unit = "%string_unsafe_set"
external unsafe_blit : string -> int ->  bytes -> int -> int -> unit
                     = "caml_blit_string" [@@noalloc]
external unsafe_fill : bytes -> int -> int -> char -> unit
                     = "caml_fill_string" [@@noalloc]

module B = Bytes

let bts = B.unsafe_to_string
let bos = B.unsafe_of_string

let make n c =
  B.make n c |> bts
let init n f =
  B.init n f |> bts
let copy s =
  B.copy (bos s) |> bts
let sub s ofs len =
  B.sub (bos s) ofs len |> bts
let fill =
  B.fill
let blit =
  B.blit_string

let ensure_ge (x:int) y = if x >= y then x else invalid_arg "String.concat"

let rec sum_lengths acc seplen = function
  | [] -> acc
  | hd :: [] -> length hd + acc
  | hd :: tl -> sum_lengths (ensure_ge (length hd + seplen + acc) acc) seplen tl

let rec unsafe_blits dst pos sep seplen = function
    [] -> dst
  | hd :: [] ->
    unsafe_blit hd 0 dst pos (length hd); dst
  | hd :: tl ->
    unsafe_blit hd 0 dst pos (length hd);
    unsafe_blit sep 0 dst (pos + length hd) seplen;
    unsafe_blits dst (pos + length hd + seplen) sep seplen tl

let concat sep = function
    [] -> ""
  | l -> let seplen = length sep in bts @@
          unsafe_blits
            (B.create (sum_lengths 0 seplen l))
            0 sep seplen l

(* duplicated in bytes.ml *)
let iter f s =
  for i = 0 to length s - 1 do f (unsafe_get s i) done

(* duplicated in bytes.ml *)
let iteri f s =
  for i = 0 to length s - 1 do f i (unsafe_get s i) done

let map f s =
  B.map f (bos s) |> bts
let mapi f s =
  B.mapi f (bos s) |> bts

(* Beware: we cannot use B.trim or B.escape because they always make a
   copy, but String.mli spells out some cases where we are not allowed
   to make a copy. *)

let is_space = function
  | ' ' | '\012' | '\n' | '\r' | '\t' -> true
  | _ -> false

let trim s =
  if s = "" then s
  else if is_space (unsafe_get s 0) || is_space (unsafe_get s (length s - 1))
    then bts (B.trim (bos s))
  else s

let escaped s =
  let rec needs_escape i =
    if i >= length s then false else
      match unsafe_get s i with
      | '\"' | '\\' | '\n' | '\t' | '\r' | '\b' -> true
      | ' ' .. '~' -> needs_escape (i+1)
      | _ -> true
  in
  if needs_escape 0 then
    bts (B.escaped (bos s))
  else
    s

(* duplicated in bytes.ml *)
let rec index_rec s lim i c =
  if i >= lim then raise Not_found else
  if unsafe_get s i = c then i else index_rec s lim (i + 1) c

(* duplicated in bytes.ml *)
let index s c = index_rec s (length s) 0 c

(* duplicated in bytes.ml *)
let rec index_rec_opt s lim i c =
  if i >= lim then None else
  if unsafe_get s i = c then Some i else index_rec_opt s lim (i + 1) c

(* duplicated in bytes.ml *)
let index_opt s c = index_rec_opt s (length s) 0 c

(* duplicated in bytes.ml *)
let index_from s i c =
  let l = length s in
  if i < 0 || i > l then invalid_arg "String.index_from / Bytes.index_from" else
    index_rec s l i c

(* duplicated in bytes.ml *)
let index_from_opt s i c =
  let l = length s in
  if i < 0 || i > l then invalid_arg "String.index_from_opt / Bytes.index_from_opt" else
  index_rec_opt s l i c

(* duplicated in bytes.ml *)
let rec rindex_rec s i c =
  if i < 0 then raise Not_found else
  if unsafe_get s i = c then i else rindex_rec s (i - 1) c

(* duplicated in bytes.ml *)
let rindex s c = rindex_rec s (length s - 1) c

(* duplicated in bytes.ml *)
let rindex_from s i c =
  if i < -1 || i >= length s then
    invalid_arg "String.rindex_from / Bytes.rindex_from"
  else
    rindex_rec s i c

(* duplicated in bytes.ml *)
let rec rindex_rec_opt s i c =
  if i < 0 then None else
  if unsafe_get s i = c then Some i else rindex_rec_opt s (i - 1) c

(* duplicated in bytes.ml *)
let rindex_opt s c = rindex_rec_opt s (length s - 1) c

(* duplicated in bytes.ml *)
let rindex_from_opt s i c =
  if i < -1 || i >= length s then
    invalid_arg "String.rindex_from_opt / Bytes.rindex_from_opt"
  else
    rindex_rec_opt s i c

(* duplicated in bytes.ml *)
let contains_from s i c =
  let l = length s in
  if i < 0 || i > l then
    invalid_arg "String.contains_from / Bytes.contains_from"
  else
    try ignore (index_rec s l i c); true with Not_found -> false

(* duplicated in bytes.ml *)
let contains s c = contains_from s 0 c

(* duplicated in bytes.ml *)
let rcontains_from s i c =
  if i < 0 || i >= length s then
    invalid_arg "String.rcontains_from / Bytes.rcontains_from"
  else
    try ignore (rindex_rec s i c); true with Not_found -> false

let uppercase_ascii s =
  B.uppercase_ascii (bos s) |> bts
let lowercase_ascii s =
  B.lowercase_ascii (bos s) |> bts
let capitalize_ascii s =
  B.capitalize_ascii (bos s) |> bts
let uncapitalize_ascii s =
  B.uncapitalize_ascii (bos s) |> bts

type t = string

let compare (x: t) (y: t) = Pervasives.compare x y
external equal : string -> string -> bool = "caml_string_equal"

let split_on_char sep s =
  let r = ref [] in
  let j = ref (length s) in
  for i = length s - 1 downto 0 do
    if unsafe_get s i = sep then begin
      r := sub s (i + 1) (!j - i - 1) :: !r;
      j := i
    end
  done;
  sub s 0 !j :: !r

(* Deprecated functions implemented via other deprecated functions *)
[@@@ocaml.warning "-3"]
let uppercase s =
  B.uppercase (bos s) |> bts
let lowercase s =
  B.lowercase (bos s) |> bts
let capitalize s =
  B.capitalize (bos s) |> bts
let uncapitalize s =
  B.uncapitalize (bos s) |> bts
