From 13c76a06559450a0183f9f8ec188f8e54e3cd3d1 Mon Sep 17 00:00:00 2001
From: Dr Jess Bromley <jess.bromley@googlemail.com>
Date: Fri, 13 May 2022 19:24:45 +0100
Subject: [PATCH] Fixes #10

---
 src/Crypto/Strings/Crypt.elm | 99 +++++++++++++++++++++++++++++++++++-
 1 file changed, 97 insertions(+), 2 deletions(-)

diff --git a/src/Crypto/Strings/Crypt.elm b/src/Crypto/Strings/Crypt.elm
index cad86dd..9986a11 100644
--- a/src/Crypto/Strings/Crypt.elm
+++ b/src/Crypto/Strings/Crypt.elm
@@ -57,7 +57,6 @@ import Crypto.Strings.Types
         , Plaintext
         , RandomGenerator
         )
-import List.Extra as LE
 import Random
 
 
@@ -334,11 +333,107 @@ padding is added.
 -}
 listToBlocks : Int -> List Int -> List Block
 listToBlocks blockSize list =
-    LE.greedyGroupsOf blockSize list
+    greedyGroupsOfTailRec blockSize list
         |> List.map (extendArray blockSize 0 << Array.fromList)
         |> padLastBlock blockSize
 
 
+
+{- Fully tail recursive version of greedyGroupsOf.  Modified from the source of
+   elm-community/list-extra which carries the following copywrite notice:
+
+   The MIT License (MIT)
+
+   Copyright (c) 2016 CircuitHub Inc., Elm Community members
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in all
+   copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+   SOFTWARE.
+
+-}
+
+
+greedyGroupsOfTailRec : Int -> List a -> List (List a)
+greedyGroupsOfTailRec size xs =
+    greedyGroupsOfWithStepTailRec size size xs
+
+
+greedyGroupsOfWithStepTailRec : Int -> Int -> List a -> List (List a)
+greedyGroupsOfWithStepTailRec size step list =
+    if size <= 0 || step <= 0 then
+        []
+
+    else
+        let
+            go : List a -> List (List a) -> List (List a)
+            go xs acc =
+                if List.isEmpty xs then
+                    List.reverse acc
+
+                else
+                    go
+                        (List.drop step xs)
+                        (takeTailRec size xs :: acc)
+        in
+        go list []
+
+
+
+{- List.take starts out non-tail-recursive and switches to a tail-recursive
+   implementation after the first 1000 iterations.  For functions which are themselves
+   recursive and use List.take on each call (e.g. List.Extra.groupsOf), this can result
+   in potential call stack overflow from the successive accumulation of 1000-long
+   non-recursive List.take calls.  Here we provide an always tail recursive version of
+   List.take to avoid this problem.  The code is taken directly from the implementation
+   of elm/core and carries the following copywrite:
+
+   Copyright 2014-present Evan Czaplicki
+
+   Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
+
+   1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
+
+   2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
+
+   3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
+
+   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+-}
+
+
+takeTailRec : Int -> List a -> List a
+takeTailRec n list =
+    List.reverse (takeReverse n list [])
+
+
+takeReverse : Int -> List a -> List a -> List a
+takeReverse n list kept =
+    if n <= 0 then
+        kept
+
+    else
+        case list of
+            [] ->
+                kept
+
+            x :: xs ->
+                takeReverse (n - 1) xs (x :: kept)
+
+
 {-| Convert a list of blocks into a list of integers.
 -}
 blocksToList : List Block -> List Int