[New Exercise]: Secret Handshake (#255)

* add secret handshake

* update description

config.json

@@ -105,6 +105,14 @@
           "transforming"
         ]
       },
+      {
+        "slug": "secret-handshake",
+        "name": "Secret Handshake",
+        "uuid": "d2378d74-bfb7-4f80-ad3e-dc0db0d90352",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 1
+      },
       {
         "slug": "raindrops",
         "name": "Raindrops",

exercises/practice/secret-handshake/.docs/instructions.md

@@ -0,0 +1,48 @@
+# Instructions
+
+Your task is to convert a number between 1 and 31 to a sequence of actions in the secret handshake.
+
+The sequence of actions is chosen by looking at the rightmost five digits of the number once it's been converted to binary.
+Start at the right-most digit and move left.
+
+The actions for each number place are:
+
+```plaintext
+00001 = wink
+00010 = double blink
+00100 = close your eyes
+01000 = jump
+10000 = Reverse the order of the operations in the secret handshake.
+```
+
+Let's use the number `9` as an example:
+
+- 9 in binary is `1001`.
+- The digit that is farthest to the right is 1, so the first action is `wink`.
+- Going left, the next digit is 0, so there is no double-blink.
+- Going left again, the next digit is 0, so you leave your eyes open.
+- Going left again, the next digit is 1, so you jump.
+
+That was the last digit, so the final code is:
+
+```plaintext
+wink, jump
+```
+
+Given the number 26, which is `11010` in binary, we get the following actions:
+
+- double blink
+- jump
+- reverse actions
+
+The secret handshake for 26 is therefore:
+
+```plaintext
+jump, double blink
+```
+
+~~~~exercism/note
+If you aren't sure what binary is or how it works, check out [this binary tutorial][intro-to-binary].
+
+[intro-to-binary]: https://medium.com/basecs/bits-bytes-building-with-binary-13cb4289aafa
+~~~~

exercises/practice/secret-handshake/.docs/introduction.md

@@ -0,0 +1,7 @@
+# Introduction
+
+You are starting a secret coding club with some friends and friends-of-friends.
+Not everyone knows each other, so you and your friends have decided to create a secret handshake that you can use to recognize that someone is a member.
+You don't want anyone who isn't in the know to be able to crack the code.
+
+You've designed the code so that one person says a number between 1 and 31, and the other person turns it into a series of actions.

exercises/practice/secret-handshake/.meta/SecretHandshake.example.ps1

@@ -0,0 +1,47 @@
+Function Invoke-SecretHandshake() {
+    <#
+    .SYNOPSIS
+    Convert a number between 1 and 31 to a sequence of actions in the secret handshake.
+
+    .DESCRIPTION
+    The sequence of actions is chosen by looking at the rightmost five digits of the number once it's been converted to binary.
+    Start at the right-most digit and move left.
+
+    The actions for each number place are:
+    00001 = wink
+    00010 = double blink
+    00100 = close your eyes
+    01000 = jump
+    10000 = Reverse the order of the operations in the secret handshake.
+
+    .PARAMETER Number
+    The value to be converted into a sequence of actions.
+
+    .EXAMPLE
+    Invoke-SecretHandshake -Number 2
+    Returns: @("double blink")
+     #>
+    [CmdletBinding()]
+    Param(
+        [int]$Number
+    )
+
+    if ($Number -lt 1 -or $Number -gt 31) {
+        return @()
+    }
+
+    $actions = @{
+        1   = "wink"
+        2   = "double blink"
+        4   = "close your eyes"
+        8   = "jump"
+    }
+
+    $sequence = $actions.Keys | Where-Object { $Number -band $_ } | ForEach-Object { $actions.$_ }
+
+    if (-not ($Number -band 16)) {
+        [Array]::Reverse($sequence)
+    } 
+
+    $sequence
+}

exercises/practice/secret-handshake/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "glaxxie"
+  ],
+  "files": {
+    "solution": [
+      "SecretHandshake.ps1"
+    ],
+    "test": [
+      "SecretHandshake.tests.ps1"
+    ],
+    "example": [
+      ".meta/SecretHandshake.example.ps1"
+    ]
+  },
+  "blurb": "Given a decimal number, convert it to the appropriate sequence of events for a secret handshake.",
+  "source": "Bert, in Mary Poppins",
+  "source_url": "https://www.imdb.com/title/tt0058331/quotes/?item=qt0437047"
+}

exercises/practice/secret-handshake/.meta/tests.toml

@@ -0,0 +1,43 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[b8496fbd-6778-468c-8054-648d03c4bb23]
+description = "wink for 1"
+
+[83ec6c58-81a9-4fd1-bfaf-0160514fc0e3]
+description = "double blink for 10"
+
+[0e20e466-3519-4134-8082-5639d85fef71]
+description = "close your eyes for 100"
+
+[b339ddbb-88b7-4b7d-9b19-4134030d9ac0]
+description = "jump for 1000"
+
+[40499fb4-e60c-43d7-8b98-0de3ca44e0eb]
+description = "combine two actions"
+
+[9730cdd5-ef27-494b-afd3-5c91ad6c3d9d]
+description = "reverse two actions"
+
+[0b828205-51ca-45cd-90d5-f2506013f25f]
+description = "reversing one action gives the same action"
+
+[9949e2ac-6c9c-4330-b685-2089ab28b05f]
+description = "reversing no actions still gives no actions"
+
+[23fdca98-676b-4848-970d-cfed7be39f81]
+description = "all possible actions"
+
+[ae8fe006-d910-4d6f-be00-54b7c3799e79]
+description = "reverse all possible actions"
+
+[3d36da37-b31f-4cdb-a396-d93a2ee1c4a5]
+description = "do nothing for zero"

exercises/practice/secret-handshake/SecretHandshake.ps1

@@ -0,0 +1,29 @@
+Function Invoke-SecretHandshake() {
+    <#
+    .SYNOPSIS
+    Convert a number between 1 and 31 to a sequence of actions in the secret handshake.
+
+    .DESCRIPTION
+    The sequence of actions is chosen by looking at the rightmost five digits of the number once it's been converted to binary.
+    Start at the right-most digit and move left.
+
+    The actions for each number place are:
+    00001 = wink
+    00010 = double blink
+    00100 = close your eyes
+    01000 = jump
+    10000 = Reverse the order of the operations in the secret handshake.
+    
+    .PARAMETER Number
+    The value to be converted into a sequence of actions.
+
+    .EXAMPLE
+    Invoke-SecretHandshake -Number 2
+    Returns: @("double blink")
+     #>
+    [CmdletBinding()]
+    Param(
+        [int]$Number
+    )
+    Throw "Please implement this function"
+}

exercises/practice/secret-handshake/SecretHandshake.tests.ps1

@@ -0,0 +1,83 @@
+BeforeAll {
+    . "./SecretHandshake.ps1"
+}
+
+Describe "SecretHandshake test cases" {
+    It "wink for 1" {
+        $got  =  Invoke-SecretHandshake -Number 1
+        $want =  @("wink")
+
+        $got | Should -BeExactly $want
+    }
+
+    It "double blink for 10" {
+        $got  =  Invoke-SecretHandshake -Number 2
+        $want =  @("double blink")
+
+        $got | Should -BeExactly $want
+    }
+
+    It "close your eyes for 100" {
+        $got  =  Invoke-SecretHandshake -Number 4
+        $want =  @("close your eyes")
+
+        $got | Should -BeExactly $want
+    }
+
+    It "jump for 1000" {
+        $got  =  Invoke-SecretHandshake -Number 8
+        $want =  @("jump")
+
+        $got | Should -BeExactly $want
+    }
+
+    It "combine two actions" {
+        $got  =  Invoke-SecretHandshake -Number 3
+        $want =  @("wink", "double blink")
+
+        $got | Should -BeExactly $want
+    }
+
+    It "reverse two actions" {
+        $got  =  Invoke-SecretHandshake -Number 19
+        $want =  @("double blink", "wink")
+
+        $got | Should -BeExactly $want
+    }
+
+    It "reversing one action gives the same action" {
+        $got  =  Invoke-SecretHandshake -Number 24
+        $want =  @("jump")
+
+        $got | Should -BeExactly $want
+    }
+
+    It "reversing no actions still gives no actions" {
+        $got  =  Invoke-SecretHandshake -Number 16
+        $want =  @()
+
+        $got | Should -BeExactly $want
+    }
+
+    It "all possible actions" {
+        $got  =  Invoke-SecretHandshake -Number 15
+        $want =  @("wink", "double blink", "close your eyes", "jump")
+
+        $got | Should -BeExactly $want
+    }
+
+    It "reverse all possible actions" {
+        $got  =  Invoke-SecretHandshake -Number 31
+        $want =  @("jump", "close your eyes", "double blink", "wink")
+
+        $got | Should -BeExactly $want
+    }
+
+    It "do nothing for zero" {
+        $got  =  Invoke-SecretHandshake -Number 0
+        $want =  @()
+
+        $got | Should -BeExactly $want
+    }
+
+}