Data commit

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

@@ -0,0 +1,82 @@
+func usage(_ e:String) {
+  print("error: \(e)")
+  print("./caeser -e 19 a-secret-string")
+  print("./caeser -d 19 tskxvjxlskljafz")
+}
+
+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()