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/******************************************************

Find and retrieve the encryption key automatically

Note: This is a draft version, please help to modify, Thanks!

******************************************************/

function keyFinder (str) { // str is used to get the input of encrypted string

const wordBank = [

'I ',

'You ',

'We ',

'They ',

'He ',

'She ',

'It ',

' the ',

'The ',

' of ',

' is ',

'Is ',

' am ',

'Am ',

' are ',

'Are ',

' have ',

'Have ',

' has ',

'Has ',

' may ',

'May ',

' be ',

'Be ']

// let wordbankelementCounter = 0;

// let key = 0; // return zero means the key can not be found

const inStr = str.toString() // convert the input to String

let outStr = '' // store the output value

let outStrElement = '' // temporary store the word inside the outStr, it is used for comparison

for (let k = 0; k < 26; k++) { // try the number of key shifted, the sum of character from a-z or A-Z is 26

outStr = caesarCipherEncodeAndDecodeEngine(inStr, k) // use the encryption engine to decrypt the input string

// loop through the whole input string

for (let s = 0; s < outStr.length; s++) {

for (let i = 0; i < wordBank.length; i++) {

// initialize the outStrElement which is a temp output string for comparison,

// use a loop to find the next digit of wordBank element and compare with outStr's digit

for (let w = 0; w < wordBank[i].length; w++) {

outStrElement += outStr[s + w]

}

// this part need to be optimize with the calculation of the number of occurrence of word's probabilities

// linked list will be used in the next stage of development to calculate the number of occurrence of the key

if (wordBank[i] === outStrElement) {

return k // return the key number if founded

}

outStrElement = '' // reset the temp word

} // end for ( let i=0; i < wordBank.length; i++)

}

}

return 0 // return 0 if found nothing

}

/* this sub-function is used to assist the keyFinder to find the key */

function caesarCipherEncodeAndDecodeEngine (inStr, numShifted) {

const shiftNum = numShifted

let charCode = 0

let outStr = ''

let shiftedCharCode = 0

let result = 0

for (let i = 0; i < inStr.length; i++) {

charCode = inStr[i].charCodeAt()

shiftedCharCode = charCode + shiftNum

result = charCode

if ((charCode >= 48 && charCode <= 57)) {

if (shiftedCharCode < 48) {

let diff = Math.abs(48 - 1 - shiftedCharCode) % 10

while (diff >= 10) {

diff = diff % 10

}

document.getElementById('diffID').innerHTML = diff

shiftedCharCode = 57 - diff

result = shiftedCharCode

} else if (shiftedCharCode >= 48 && shiftedCharCode <= 57) {

result = shiftedCharCode

} else if (shiftedCharCode > 57) {

let diff = Math.abs(57 + 1 - shiftedCharCode) % 10

while (diff >= 10) {

diff = diff % 10

}

document.getElementById('diffID').innerHTML = diff

shiftedCharCode = 48 + diff

result = shiftedCharCode

}

} else if ((charCode >= 65 && charCode <= 90)) {

if (shiftedCharCode <= 64) {

let diff = Math.abs(65 - 1 - shiftedCharCode) % 26

while ((diff % 26) >= 26) {

diff = diff % 26

}

shiftedCharCode = 90 - diff

result = shiftedCharCode

} else if (shiftedCharCode >= 65 && shiftedCharCode <= 90) {

result = shiftedCharCode

} else if (shiftedCharCode > 90) {

let diff = Math.abs(shiftedCharCode - 1 - 90) % 26

while ((diff % 26) >= 26) {

diff = diff % 26

}

shiftedCharCode = 65 + diff

result = shiftedCharCode

}

} else if ((charCode >= 97 && charCode <= 122)) {

if (shiftedCharCode <= 96) {

let diff = Math.abs(97 - 1 - shiftedCharCode) % 26

while ((diff % 26) >= 26) {

diff = diff % 26

}

shiftedCharCode = 122 - diff

result = shiftedCharCode

} else if (shiftedCharCode >= 97 && shiftedCharCode <= 122) {

result = shiftedCharCode

} else if (shiftedCharCode > 122) {

let diff = Math.abs(shiftedCharCode - 1 - 122) % 26

while ((diff % 26) >= 26) {

diff = diff % 26

}

shiftedCharCode = 97 + diff

result = shiftedCharCode

}

}

outStr = outStr + String.fromCharCode(parseInt(result))

}

return outStr

}

export { keyFinder }

// > keyFinder('test')

// 0