From d799438181ecce625471a59477bd86bf17ad7654 Mon Sep 17 00:00:00 2001
From: David Sancho Moreno <dsnxmoreno@gmail.com>
Date: Tue, 15 Aug 2023 11:08:52 +0200
Subject: [PATCH] Implement Js.String2.replaceByRe

---
 packages/js/dune    |  2 +-
 packages/js/js.ml   | 34 +++++++++++++++++++++++++++++++++-
 packages/js/test.ml | 14 ++++++++------
 3 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/packages/js/dune b/packages/js/dune
index 52c8ae2fe..1c439eee2 100644
--- a/packages/js/dune
+++ b/packages/js/dune
@@ -12,4 +12,4 @@
  (modules test)
  (libraries alcotest alcotest-lwt lwt server-reason-react.js)
  (preprocess
-  (pps lwt_ppx)))
+  (pps lwt_ppx regex_ppx)))
diff --git a/packages/js/js.ml b/packages/js/js.ml
index 246d7c5a6..0117ceb92 100644
--- a/packages/js/js.ml
+++ b/packages/js/js.ml
@@ -457,6 +457,7 @@ module Re = struct
       let substrings = Pcre.exec ~rex ~pos:regexp.lastIndex str in
       let _, lastIndex = Pcre.get_substring_ofs substrings 0 in
       regexp.lastIndex <- lastIndex;
+      print_endline @@ string_of_int regexp.lastIndex;
       Some { substrings }
     with Not_found -> None
 
@@ -809,7 +810,38 @@ module String2 = struct
     repeat' str "" count
 
   let replace _ _ _ = notImplemented "Js.String2" "replace"
-  let replaceByRe _ _ _ = notImplemented "Js.String2" "replaceByRe"
+
+  let replaceByRe pattern replacement str =
+    let rec replace_all str =
+      match Re.exec_ pattern str with
+      | None -> str
+      | Some result ->
+          Re.setLastIndex pattern 0;
+          let matches = Re.matches result in
+          let matched_str = Stdlib.Array.get matches 0 in
+          let prefix = Stdlib.String.sub str 0 (Re.index result) in
+          let suffix_start = Re.index result + String.length matched_str in
+          let suffix =
+            Stdlib.String.sub str suffix_start (String.length str - suffix_start)
+          in
+          prefix ^ replacement ^ replace_all suffix
+    in
+    let replace_first str =
+      match Re.exec_ pattern str with
+      | None -> str
+      | Some result ->
+          let matches = Re.matches result in
+          let matched_str = Stdlib.Array.get matches 0 in
+          let prefix = Stdlib.String.sub str 0 (Re.index result) in
+          let suffix_start = Re.index result + String.length matched_str in
+          let suffix =
+            Stdlib.String.sub str suffix_start (String.length str - suffix_start)
+          in
+          prefix ^ replacement ^ suffix
+    in
+
+    if Re.global pattern then replace_all str else replace_first str
+
   let unsafeReplaceBy0 _ _ = notImplemented "Js.String2" "unsafeReplaceBy0"
   let unsafeReplaceBy1 _ _ = notImplemented "Js.String2" "unsafeReplaceBy1"
   let unsafeReplaceBy2 _ _ = notImplemented "Js.String2" "unsafeReplaceBy2"
diff --git a/packages/js/test.ml b/packages/js/test.ml
index 2002054b4..9469eed81 100644
--- a/packages/js/test.ml
+++ b/packages/js/test.ml
@@ -231,13 +231,15 @@ let string2_tests =
                "this cat and the dog" *)
           ());
       case "replaceByRe" (fun () ->
+          assert_string (Js.String2.replaceByRe [%re "/d/"] "x" "david") "xavid"
           (* assert_string
-               (replaceByRe [%re "/[aeiou]/g"] "x" "vowels be gone")
-               "vxwxls bx gxnx";
-             assert_string
-               (replaceByRe [%re "/(\\w+) (\\w+)/"] "$2, $1" "Juan Fulano")
-               "Fulano, Juan" *)
-          ());
+             (Js.String2.replaceByRe [%re "/(\\w+) (\\w+)/"] "$2, $1"
+                "Juan Fulano")
+             "Fulano, Juan" *));
+      case "replaceByRe with global" (fun () ->
+          assert_string
+            (Js.String2.replaceByRe [%re "/[aeiou]/g"] "x" "vowels be gone")
+            "vxwxls bx gxnx");
       case "unsafeReplaceBy0" (fun () ->
           (* let str = "beautiful vowels" in
              let re = [%re "/[aeiou]/g"] in