exercises(secret-handshake): overhaul to use enum (#537)

This exercise has always [1] required the user to return seq[string],
but the scenario is better modelled with an enum.

This commit is similar to previous overhauls for the allergies [2] and
space-age [3] exercises.

Closes: #536

[1] 8015636, 2019-02-24, "Adds secret-handshake exercise"
[2] a8ab9c8, 2023-01-11, "exercises(allergies): overhaul to use enum"
[3] b770d96, 2023-01-11, "exercises(space-age): overhaul to use enum"

config.json

@@ -853,6 +853,7 @@
         "topics": [
           "bitwise_operations",
           "conditionals",
+          "enumerations",
           "integers",
           "lists",
           "logic",

exercises/practice/secret-handshake/.meta/example.nim

@@ -1,22 +1,16 @@
-import std/algorithm
+import std/[algorithm, bitops]
 
-const
-  signals = [
-    "wink",
-    "double blink",
-    "close your eyes",
-    "jump"
-  ]
-  reverseBit = 4
+type
+  Action* = enum
+    Wink, DoubleBlink, CloseEyes, Jump, Reverse
 
+func commands*(n: Natural): seq[Action] =
+  result = newSeqOfCap[Action](Action.high.ord)
 
-func bitset(input: Natural, position: Natural): bool =
-  (input and 1 shl position) != 0
-
-func commands*(input: Natural): seq[string] =
-  for index, item in signals:
-    if input.bitset(index):
-      result.add(item)
-
-  if input.bitset(reverseBit):
-    result.reverse
+  for action in Action:
+    if n.testBit(action.ord):
+      case action
+      of Wink..Jump:
+        result.add action
+      of Reverse:
+        result.reverse()

exercises/practice/secret-handshake/secret_handshake.nim

@@ -1,2 +1,6 @@
-proc commands*(n: int): seq[string] =
+type
+  Action* = enum
+    Wink, DoubleBlink, CloseEyes, Jump
+
+proc commands*(n: int): seq[Action] =
   discard

exercises/practice/secret-handshake/test_secret_handshake.nim

@@ -3,34 +3,34 @@ import secret_handshake
 
 suite "Secret Handshake":
   test "wink for 1":
-    check commands(1) == @["wink"]
+    check commands(1) == @[Wink]
 
   test "double blink for 10":
-    check commands(2) == @["double blink"]
+    check commands(2) == @[DoubleBlink]
 
   test "close your eyes for 100":
-    check commands(4) == @["close your eyes"]
+    check commands(4) == @[CloseEyes]
 
   test "jump for 1000":
-    check commands(8) == @["jump"]
+    check commands(8) == @[Jump]
 
   test "combine two actions":
-    check commands(3) == @["wink", "double blink"]
+    check commands(3) == @[Wink, DoubleBlink]
 
   test "reverse two actions":
-    check commands(19) == @["double blink", "wink"]
+    check commands(19) == @[DoubleBlink, Wink]
 
   test "reversing one action gives the same action":
-    check commands(24) == @["jump"]
+    check commands(24) == @[Jump]
 
   test "reversing no actions still gives no actions":
     check commands(16).len == 0
 
   test "all possible actions":
-    check commands(15) == @["wink", "double blink", "close your eyes", "jump"]
+    check commands(15) == @[Wink, DoubleBlink, CloseEyes, Jump]
 
   test "reverse all possible actions":
-    check commands(31) == @["jump", "close your eyes", "double blink", "wink"]
+    check commands(31) == @[Jump, CloseEyes, DoubleBlink, Wink]
 
   test "do nothing for zero":
     check commands(0).len == 0