Implemented a better way of choosing the encryption algorithm

source/chacha20.d

@@ -67,13 +67,6 @@ auto chacha20Cipher(R)(R range, ubyte[32] key, ubyte[8] nonce)
                 return copy;
             }
         }
-
-        // We need this, so choose works with, if hasElaborateCopyConstructor!R
-        static if (hasElaborateCopyConstructor!R)
-        this(this)
-        {
-
-        }
     }
     return rangeResult(range, key, nonce);
 }

source/cipher.d

@@ -1,9 +1,8 @@
 module cipher;
 
-private import std.range : isInputRange, ElementType, chooseAmong;
+private import std.range : isInputRange, ElementType, InputRange, ForwardRange, inputRangeObject;
 private import salsa20;
 private import chacha20;
-import std.stdio;
 
 public:
 
@@ -13,10 +12,36 @@ enum Cipher
     chacha20
 }
 
-auto cipherFunction(R)(R range, ubyte[32] key, ubyte[8] nonce, Cipher cipher)
-    if(isInputRange!R && is(ElementType!R : ubyte))
+mixin(cipherFunctionString.format(q{InputRange}, q{isInputRange!R && !(isForwardRange!R)}));
+mixin(cipherFunctionString.format(q{ForwardRange}, q{isForwardRange!R}));
+
+unittest
 {
-    return chooseAmong(cipher,
-                  range.salsa20Cipher(key, nonce),
-                  range.chacha20Cipher(key, nonce));
+    import std.array;
+    
+    ubyte[32] key;
+    ubyte[8] nonce;
+    ubyte[] a = [1, 2, 3];
+    auto b = a.cipherFunction(key, nonce, Cipher.salsa20);
+    InputRange!ubyte c = a.inputRangeObject;
+    auto d = c.cipherFunction(key, nonce, Cipher.salsa20);
+
+    static assert(isForwardRange!(typeof(b)));
+    static assert(isInputRange!(typeof(d)) && !(isForwardRange!(typeof(d))));
 }
+
+private:
+
+enum cipherFunctionString = q{
+    %s!(ElementType!R) cipherFunction(R)(R range, ubyte[32] key, ubyte[8] nonce, Cipher cipher)
+        if(is(ElementType!R : ubyte) && %s)
+    {
+        final switch(cipher)
+        {
+            case Cipher.salsa20:
+                return range.salsa20Cipher(key, nonce).inputRangeObject;
+            case Cipher.chacha20:
+                return range.chacha20Cipher(key, nonce).inputRangeObject;
+        }
+    }
+};

source/salsa20.d

@@ -65,14 +65,6 @@ auto salsa20Cipher(R)(R range, ubyte[32] key, ubyte[8] nonce)
                 return copy;
             }
         }
-
-        // We need this, so choose works with, if hasElaborateCopyConstructor!R
-        static if (hasElaborateCopyConstructor!R)
-        this(this)
-        {
-
-        }
-
     }
 
     return rangeResult(range, key, nonce);