September Morn Update

Task/Caesar-cipher/Swift/caesar-cipher.swift

@@ -1,65 +1,82 @@
-var arr:[Character]=["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"]
-
-func res(st:String,ar:[Character],x:Int,ro:String)->String{
-
-    var str2:[Character]=[]
-
-    for i in st.characters
-    {
-
-        for j in 0...25
-        {
-
-
-            if i==ar[j]
-            {
-
-                switch ro
-                {
-                    case "right":
-
-                    if(j+x<=25)
-                    {
-
-                        str2.append(ar[j+x])
-                        break
-
-                    }
-                    else
-                    {
-
-                        str2.append(ar[j+x-26])
-                        break
-                    }
-
-                    case "left":
-
-                     if(j-x>=0)
-                    {
-
-                        str2.append(ar[j-x])
-                        break
-                    }
-                    else
-                    {
-
-                        str2.append(ar[j-x+26])
-                        break
-                    }
-                   default:
-                   print("incorrect input for rotation direction")
-                }
-
-
-            }
-        }
-    }
-
-    return String(str2)
+func usage(_ e:String) {
+  print("error: \(e)")
+  print("./caeser -e 19 a-secret-string")
+  print("./caeser -d 19 tskxvjxlskljafz")
 }
 
-var mssg:String="hi"
-var x1:Int=5
-var rot:String="right"
-var rotstr:String=res(st:mssg,ar:arr,x:x1,ro:rot)
-print(rotstr)
+func charIsValid(_ c:Character) -> Bool {
+  return c.isASCII && ( c.isLowercase || 45 == c.asciiValue ) // '-' = 45
+}
+
+func charRotate(_ c:Character, _ by:Int) -> Character {
+  var cv:UInt8! = c.asciiValue
+  if 45 == cv { cv = 96 }  // if '-', set it to 'a'-1
+  cv += UInt8(by)
+  if 122 < cv { cv -= 27 } // if larget than 'z', reduce by 27
+  if 96 == cv { cv = 45 }  // restore '-'
+  return Character(UnicodeScalar(cv))
+}
+
+func caesar(_ enc:Bool, _ key:Int, _ word:String) -> String {
+  let r = enc ? key : 27 - key
+  func charRotateWithKey(_ c:Character) -> Character {
+    return charRotate(c,r)
+  }
+  return String(word.map(charRotateWithKey))
+}
+
+func main() {
+  var encrypt = true
+
+  if 4 != CommandLine.arguments.count {
+    return usage("caesar expects exactly three arguments")
+  }
+
+  switch ( CommandLine.arguments[1] ) {
+  case "-e":
+    encrypt = true
+  case "-d":
+    encrypt = false
+  default:
+    return usage("first argument must be -e (encrypt) or -d (decrypt)")
+  }
+
+  guard let key = Int(CommandLine.arguments[2]) else {
+    return usage("second argument not a number (must be in range 0-26)")
+  }
+
+  if key < 0 || 26 < key {
+    return usage("second argument not in range 0-26")
+  }
+
+  if !CommandLine.arguments[3].allSatisfy(charIsValid) {
+    return usage("third argument must only be lowercase ascii characters, or -")
+  }
+
+  let ans = caesar(encrypt,key,CommandLine.arguments[3])
+  print("\(ans)")
+}
+
+func test() {
+  if ( Character("a") != charRotate(Character("a"),0) ) {
+    print("Test Fail 1")
+  }
+  if ( Character("-") != charRotate(Character("-"),0) ) {
+    print("Test Fail 2")
+  }
+  if ( Character("-") != charRotate(Character("z"),1) ) {
+    print("Test Fail 3")
+  }
+  if ( Character("z") != charRotate(Character("-"),26)) {
+    print("Test Fail 4")
+  }
+  if ( "ihgmkzma" != caesar(true,8,"a-zecret") ) {
+    print("Test Fail 5")
+  }
+  if ( "a-zecret" != caesar(false,8,"ihgmkzma") ) {
+    print("Test Fail 6")
+  }
+}
+
+test()
+main()