83 lines
2.0 KiB
Swift
83 lines
2.0 KiB
Swift
func usage(_ e:String) {
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print("error: \(e)")
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print("./caeser -e 19 a-secret-string")
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print("./caeser -d 19 tskxvjxlskljafz")
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}
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func charIsValid(_ c:Character) -> Bool {
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return c.isASCII && ( c.isLowercase || 45 == c.asciiValue ) // '-' = 45
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}
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func charRotate(_ c:Character, _ by:Int) -> Character {
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var cv:UInt8! = c.asciiValue
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if 45 == cv { cv = 96 } // if '-', set it to 'a'-1
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cv += UInt8(by)
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if 122 < cv { cv -= 27 } // if larget than 'z', reduce by 27
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if 96 == cv { cv = 45 } // restore '-'
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return Character(UnicodeScalar(cv))
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}
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func caesar(_ enc:Bool, _ key:Int, _ word:String) -> String {
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let r = enc ? key : 27 - key
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func charRotateWithKey(_ c:Character) -> Character {
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return charRotate(c,r)
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}
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return String(word.map(charRotateWithKey))
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}
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func main() {
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var encrypt = true
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if 4 != CommandLine.arguments.count {
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return usage("caesar expects exactly three arguments")
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}
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switch ( CommandLine.arguments[1] ) {
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case "-e":
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encrypt = true
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case "-d":
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encrypt = false
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default:
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return usage("first argument must be -e (encrypt) or -d (decrypt)")
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}
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guard let key = Int(CommandLine.arguments[2]) else {
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return usage("second argument not a number (must be in range 0-26)")
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}
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if key < 0 || 26 < key {
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return usage("second argument not in range 0-26")
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}
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if !CommandLine.arguments[3].allSatisfy(charIsValid) {
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return usage("third argument must only be lowercase ascii characters, or -")
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}
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let ans = caesar(encrypt,key,CommandLine.arguments[3])
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print("\(ans)")
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}
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func test() {
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if ( Character("a") != charRotate(Character("a"),0) ) {
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print("Test Fail 1")
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}
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if ( Character("-") != charRotate(Character("-"),0) ) {
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print("Test Fail 2")
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}
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if ( Character("-") != charRotate(Character("z"),1) ) {
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print("Test Fail 3")
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}
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if ( Character("z") != charRotate(Character("-"),26)) {
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print("Test Fail 4")
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}
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if ( "ihgmkzma" != caesar(true,8,"a-zecret") ) {
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print("Test Fail 5")
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}
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if ( "a-zecret" != caesar(false,8,"ihgmkzma") ) {
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print("Test Fail 6")
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}
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}
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test()
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main()
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