// APS101, Winter 2009: Assignment 2 (Spy class)
// Examples of using some of the methods and their expected outputs

> Spy.getAllCodeNumbers()
""

> Spy.removeCodeNumber(1234)
false

> Spy spy1 = new Spy(1234)

> spy1.getCodeNumber()
1234

> Spy.getAllCodeNumbers()
"1234"

> Spy spy2 = new Spy(9999)

> Spy.getAllCodeNumbers()
"9999:1234"

> Spy spy3 = new Spy(1235)

> Spy.getAllCodeNumbers()
"9999:1235:1234"

> Spy.removeCodeNumber(9999)
true

> Spy.getAllCodeNumbers()
"1235:1234"

> Spy.removeCodeNumber(9999)
false

> Spy spy4 = new Spy(1234)
This code number already exists in the record!


> Spy.charToBinary('a')
"01100001"

> Spy.charToBinary('~')
"01111110"

> Spy.charToBinary(a)
Static Error: Undefined name 'a'

> Spy.charToBinary(97)
Static Error: No method in Spy with name 'charToBinary' accepts arguments (int)

// these are the ONLY 4 inputs & outputs for exclusiveOr
> Spy.exclusiveOr(1, 1)
0

> Spy.exclusiveOr(0, 1)
1

> Spy.exclusiveOr(1, 0)
1

> Spy.exclusiveOr(0, 0)
0


> Spy.stretch("1001", 3)
"1001"

> Spy.stretch("1001", 4)
"1001"

> Spy.stretch("1001", 5)
"100111"

> Spy.stretch("1001", 8)
"100111011" // what's the problem here? (an ODD number of bits was produced)

// so, if you wanted to do: Spy.stretch("1001", 10), this would be a problem,
// because the method would try to split a 9-bit String into two EVEN halves.

// This is a flaw of the method, but it's OK, because for our purposes this
// sort of situation won't happen. Why? Because in the encrypt method, you'll
// be stretching 128-bit keys. Let's see how that happens...

// 1st iteration: 128 / 2 = 64. Then 128 + 64 = 192 <- even number of bits!
// 2nd iteration: 192 / 2 = 96. Then 192 + 96 = 288 <- even number of bits!
// 3rd iteration: 288 / 2 = 144. Then 288 + 144 = 432 <- even number of bits!
// 4th iteration: 432 / 2 = 216. Then 432 + 216 = 648 <- even number of bits!
// 5th iteration: 648 / 2 = 324. Then 648 + 324 = 972 <- even number of bits!
// 6th iteration: 972 / 2 = 486. Then 972 + 486 = 1458 <- even number of bits!

// 7th iteration: 1458 / 2 = 729. Then 1458 + 729 = 2187. <- odd number of bits! (finally)

// What this means for you is the following:
// Since each character is represented by an 8-bit String, you must only test method encrypt
// on messages with 273 characters or less (because 8 * 273 would give us a 2184-bit String, which is OK).
// If the message is 274 characters or more (i.e., 8 * 274 = 2192 bits long), then we'd have to run 
// method stretch one more time, for an 8th iteration, which would give us problems. 

// In other words...

> String msg = "This message has 273 characters. This is the maximum length of the messages you're allowed to test. If you test your encrypt method on longer messages, there will be a problem with the stretch method. I ran out of things to say so I'm just writing useless things.... :)))))";

> msg.length()
273


> Spy.encrypt("", 1234)
""

> Spy.encrypt("lol.", 1234)
"01101000101111010110100011111100"

> Spy.encrypt("lol.", spy1.getCodeNumber())
"01101000101111010110100011111100"

> String msg = "This is a secret message!";

> String encrypted = Spy.encrypt(msg, spy1.getCodeNumber())

> encrypted
"01010000101110100110110110100001001001001011101101110111111100100110010111110010011101111011011101100111101000000110000110100110001000000110110101100101011100110111001101100001011001110110010100100001"

> encrypted.length() == 8 * msg.length()
true

> String decrypted = Spy.decrypt(encrypted, 1234)

> decrypted
"This is a secret message!"

> Spy spy2 = new Spy(1234)
This code number already exists in the record!

> spy2.getCodeNumber()
1234

> spy2.decrypt(encrypted, spy2.getCodeNumber())
"This is a secret message!"

> spy2.decrypt(encrypted, 1235)
"Tiir hs!a!sdcseu message!"

> spy2.decrypt(encrypted, 1230)
"Ttio us<a<sycneh message!"