// Copyright © 2021 rsiddharth <s@ricketyspace.net>
// SPDX-License-Identifier: ISC

package challenge

import (
	"fmt"

	"ricketyspace.net/cryptopals/lib"
)

func C20() {
	texts := []string{
		"SSdtIHJhdGVkICJSIi4uLnRoaXMgaXMgYSB3YXJuaW5nLCB5YSBiZXR0ZXIgdm9pZCAvIFBvZXRzIGFyZSBwYXJhbm9pZCwgREoncyBELXN0cm95ZWQ=",
		"Q3V6IEkgY2FtZSBiYWNrIHRvIGF0dGFjayBvdGhlcnMgaW4gc3BpdGUtIC8gU3RyaWtlIGxpa2UgbGlnaHRuaW4nLCBJdCdzIHF1aXRlIGZyaWdodGVuaW4nIQ==",
		"QnV0IGRvbid0IGJlIGFmcmFpZCBpbiB0aGUgZGFyaywgaW4gYSBwYXJrIC8gTm90IGEgc2NyZWFtIG9yIGEgY3J5LCBvciBhIGJhcmssIG1vcmUgbGlrZSBhIHNwYXJrOw==",
		"WWEgdHJlbWJsZSBsaWtlIGEgYWxjb2hvbGljLCBtdXNjbGVzIHRpZ2h0ZW4gdXAgLyBXaGF0J3MgdGhhdCwgbGlnaHRlbiB1cCEgWW91IHNlZSBhIHNpZ2h0IGJ1dA==",
		"U3VkZGVubHkgeW91IGZlZWwgbGlrZSB5b3VyIGluIGEgaG9ycm9yIGZsaWNrIC8gWW91IGdyYWIgeW91ciBoZWFydCB0aGVuIHdpc2ggZm9yIHRvbW9ycm93IHF1aWNrIQ==",
		"TXVzaWMncyB0aGUgY2x1ZSwgd2hlbiBJIGNvbWUgeW91ciB3YXJuZWQgLyBBcG9jYWx5cHNlIE5vdywgd2hlbiBJJ20gZG9uZSwgeWEgZ29uZSE=",
		"SGF2ZW4ndCB5b3UgZXZlciBoZWFyZCBvZiBhIE1DLW11cmRlcmVyPyAvIFRoaXMgaXMgdGhlIGRlYXRoIHBlbmFsdHksYW5kIEknbSBzZXJ2aW4nIGE=",
		"RGVhdGggd2lzaCwgc28gY29tZSBvbiwgc3RlcCB0byB0aGlzIC8gSHlzdGVyaWNhbCBpZGVhIGZvciBhIGx5cmljYWwgcHJvZmVzc2lvbmlzdCE=",
		"RnJpZGF5IHRoZSB0aGlydGVlbnRoLCB3YWxraW5nIGRvd24gRWxtIFN0cmVldCAvIFlvdSBjb21lIGluIG15IHJlYWxtIHlhIGdldCBiZWF0IQ==",
		"VGhpcyBpcyBvZmYgbGltaXRzLCBzbyB5b3VyIHZpc2lvbnMgYXJlIGJsdXJyeSAvIEFsbCB5YSBzZWUgaXMgdGhlIG1ldGVycyBhdCBhIHZvbHVtZQ==",
		"VGVycm9yIGluIHRoZSBzdHlsZXMsIG5ldmVyIGVycm9yLWZpbGVzIC8gSW5kZWVkIEknbSBrbm93bi15b3VyIGV4aWxlZCE=",
		"Rm9yIHRob3NlIHRoYXQgb3Bwb3NlIHRvIGJlIGxldmVsIG9yIG5leHQgdG8gdGhpcyAvIEkgYWluJ3QgYSBkZXZpbCBhbmQgdGhpcyBhaW4ndCB0aGUgRXhvcmNpc3Qh",
		"V29yc2UgdGhhbiBhIG5pZ2h0bWFyZSwgeW91IGRvbid0IGhhdmUgdG8gc2xlZXAgYSB3aW5rIC8gVGhlIHBhaW4ncyBhIG1pZ3JhaW5lIGV2ZXJ5IHRpbWUgeWEgdGhpbms=",
		"Rmxhc2hiYWNrcyBpbnRlcmZlcmUsIHlhIHN0YXJ0IHRvIGhlYXI6IC8gVGhlIFItQS1LLUktTSBpbiB5b3VyIGVhcjs=",
		"VGhlbiB0aGUgYmVhdCBpcyBoeXN0ZXJpY2FsIC8gVGhhdCBtYWtlcyBFcmljIGdvIGdldCBhIGF4IGFuZCBjaG9wcyB0aGUgd2Fjaw==",
		"U29vbiB0aGUgbHlyaWNhbCBmb3JtYXQgaXMgc3VwZXJpb3IgLyBGYWNlcyBvZiBkZWF0aCByZW1haW4=",
		"TUMncyBkZWNheWluZywgY3V6IHRoZXkgbmV2ZXIgc3RheWVkIC8gVGhlIHNjZW5lIG9mIGEgY3JpbWUgZXZlcnkgbmlnaHQgYXQgdGhlIHNob3c=",
		"VGhlIGZpZW5kIG9mIGEgcmh5bWUgb24gdGhlIG1pYyB0aGF0IHlvdSBrbm93IC8gSXQncyBvbmx5IG9uZSBjYXBhYmxlLCBicmVha3MtdGhlIHVuYnJlYWthYmxl",
		"TWVsb2RpZXMtdW5tYWthYmxlLCBwYXR0ZXJuLXVuZXNjYXBhYmxlIC8gQSBob3JuIGlmIHdhbnQgdGhlIHN0eWxlIEkgcG9zc2Vz",
		"SSBibGVzcyB0aGUgY2hpbGQsIHRoZSBlYXJ0aCwgdGhlIGdvZHMgYW5kIGJvbWIgdGhlIHJlc3QgLyBGb3IgdGhvc2UgdGhhdCBlbnZ5IGEgTUMgaXQgY2FuIGJl",
		"SGF6YXJkb3VzIHRvIHlvdXIgaGVhbHRoIHNvIGJlIGZyaWVuZGx5IC8gQSBtYXR0ZXIgb2YgbGlmZSBhbmQgZGVhdGgsIGp1c3QgbGlrZSBhIGV0Y2gtYS1za2V0Y2g=",
		"U2hha2UgJ3RpbGwgeW91ciBjbGVhciwgbWFrZSBpdCBkaXNhcHBlYXIsIG1ha2UgdGhlIG5leHQgLyBBZnRlciB0aGUgY2VyZW1vbnksIGxldCB0aGUgcmh5bWUgcmVzdCBpbiBwZWFjZQ==",
		"SWYgbm90LCBteSBzb3VsJ2xsIHJlbGVhc2UhIC8gVGhlIHNjZW5lIGlzIHJlY3JlYXRlZCwgcmVpbmNhcm5hdGVkLCB1cGRhdGVkLCBJJ20gZ2xhZCB5b3UgbWFkZSBpdA==",
		"Q3V6IHlvdXIgYWJvdXQgdG8gc2VlIGEgZGlzYXN0cm91cyBzaWdodCAvIEEgcGVyZm9ybWFuY2UgbmV2ZXIgYWdhaW4gcGVyZm9ybWVkIG9uIGEgbWljOg==",
		"THlyaWNzIG9mIGZ1cnkhIEEgZmVhcmlmaWVkIGZyZWVzdHlsZSEgLyBUaGUgIlIiIGlzIGluIHRoZSBob3VzZS10b28gbXVjaCB0ZW5zaW9uIQ==",
		"TWFrZSBzdXJlIHRoZSBzeXN0ZW0ncyBsb3VkIHdoZW4gSSBtZW50aW9uIC8gUGhyYXNlcyB0aGF0J3MgZmVhcnNvbWU=",
		"WW91IHdhbnQgdG8gaGVhciBzb21lIHNvdW5kcyB0aGF0IG5vdCBvbmx5IHBvdW5kcyBidXQgcGxlYXNlIHlvdXIgZWFyZHJ1bXM7IC8gSSBzaXQgYmFjayBhbmQgb2JzZXJ2ZSB0aGUgd2hvbGUgc2NlbmVyeQ==",
		"VGhlbiBub25jaGFsYW50bHkgdGVsbCB5b3Ugd2hhdCBpdCBtZWFuIHRvIG1lIC8gU3RyaWN0bHkgYnVzaW5lc3MgSSdtIHF1aWNrbHkgaW4gdGhpcyBtb29k",
		"QW5kIEkgZG9uJ3QgY2FyZSBpZiB0aGUgd2hvbGUgY3Jvd2QncyBhIHdpdG5lc3MhIC8gSSdtIGEgdGVhciB5b3UgYXBhcnQgYnV0IEknbSBhIHNwYXJlIHlvdSBhIGhlYXJ0",
		"UHJvZ3JhbSBpbnRvIHRoZSBzcGVlZCBvZiB0aGUgcmh5bWUsIHByZXBhcmUgdG8gc3RhcnQgLyBSaHl0aG0ncyBvdXQgb2YgdGhlIHJhZGl1cywgaW5zYW5lIGFzIHRoZSBjcmF6aWVzdA==",
		"TXVzaWNhbCBtYWRuZXNzIE1DIGV2ZXIgbWFkZSwgc2VlIGl0J3MgLyBOb3cgYW4gZW1lcmdlbmN5LCBvcGVuLWhlYXJ0IHN1cmdlcnk=",
		"T3BlbiB5b3VyIG1pbmQsIHlvdSB3aWxsIGZpbmQgZXZlcnkgd29yZCdsbCBiZSAvIEZ1cmllciB0aGFuIGV2ZXIsIEkgcmVtYWluIHRoZSBmdXJ0dXJl",
		"QmF0dGxlJ3MgdGVtcHRpbmcuLi53aGF0ZXZlciBzdWl0cyB5YSEgLyBGb3Igd29yZHMgdGhlIHNlbnRlbmNlLCB0aGVyZSdzIG5vIHJlc2VtYmxhbmNl",
		"WW91IHRoaW5rIHlvdSdyZSBydWZmZXIsIHRoZW4gc3VmZmVyIHRoZSBjb25zZXF1ZW5jZXMhIC8gSSdtIG5ldmVyIGR5aW5nLXRlcnJpZnlpbmcgcmVzdWx0cw==",
		"SSB3YWtlIHlhIHdpdGggaHVuZHJlZHMgb2YgdGhvdXNhbmRzIG9mIHZvbHRzIC8gTWljLXRvLW1vdXRoIHJlc3VzY2l0YXRpb24sIHJoeXRobSB3aXRoIHJhZGlhdGlvbg==",
		"Tm92b2NhaW4gZWFzZSB0aGUgcGFpbiBpdCBtaWdodCBzYXZlIGhpbSAvIElmIG5vdCwgRXJpYyBCLidzIHRoZSBqdWRnZSwgdGhlIGNyb3dkJ3MgdGhlIGp1cnk=",
		"WW8gUmFraW0sIHdoYXQncyB1cD8gLyBZbywgSSdtIGRvaW5nIHRoZSBrbm93bGVkZ2UsIEUuLCBtYW4gSSdtIHRyeWluZyB0byBnZXQgcGFpZCBpbiBmdWxs",
		"V2VsbCwgY2hlY2sgdGhpcyBvdXQsIHNpbmNlIE5vcmJ5IFdhbHRlcnMgaXMgb3VyIGFnZW5jeSwgcmlnaHQ/IC8gVHJ1ZQ==",
		"S2FyYSBMZXdpcyBpcyBvdXIgYWdlbnQsIHdvcmQgdXAgLyBaYWtpYSBhbmQgNHRoIGFuZCBCcm9hZHdheSBpcyBvdXIgcmVjb3JkIGNvbXBhbnksIGluZGVlZA==",
		"T2theSwgc28gd2hvIHdlIHJvbGxpbicgd2l0aCB0aGVuPyBXZSByb2xsaW4nIHdpdGggUnVzaCAvIE9mIFJ1c2h0b3duIE1hbmFnZW1lbnQ=",
		"Q2hlY2sgdGhpcyBvdXQsIHNpbmNlIHdlIHRhbGtpbmcgb3ZlciAvIFRoaXMgZGVmIGJlYXQgcmlnaHQgaGVyZSB0aGF0IEkgcHV0IHRvZ2V0aGVy",
		"SSB3YW5uYSBoZWFyIHNvbWUgb2YgdGhlbSBkZWYgcmh5bWVzLCB5b3Uga25vdyB3aGF0IEknbSBzYXlpbic/IC8gQW5kIHRvZ2V0aGVyLCB3ZSBjYW4gZ2V0IHBhaWQgaW4gZnVsbA==",
		"VGhpbmtpbicgb2YgYSBtYXN0ZXIgcGxhbiAvICdDdXogYWluJ3QgbnV0aGluJyBidXQgc3dlYXQgaW5zaWRlIG15IGhhbmQ=",
		"U28gSSBkaWcgaW50byBteSBwb2NrZXQsIGFsbCBteSBtb25leSBpcyBzcGVudCAvIFNvIEkgZGlnIGRlZXBlciBidXQgc3RpbGwgY29taW4nIHVwIHdpdGggbGludA==",
		"U28gSSBzdGFydCBteSBtaXNzaW9uLCBsZWF2ZSBteSByZXNpZGVuY2UgLyBUaGlua2luJyBob3cgY291bGQgSSBnZXQgc29tZSBkZWFkIHByZXNpZGVudHM=",
		"SSBuZWVkIG1vbmV5LCBJIHVzZWQgdG8gYmUgYSBzdGljay11cCBraWQgLyBTbyBJIHRoaW5rIG9mIGFsbCB0aGUgZGV2aW91cyB0aGluZ3MgSSBkaWQ=",
		"SSB1c2VkIHRvIHJvbGwgdXAsIHRoaXMgaXMgYSBob2xkIHVwLCBhaW4ndCBudXRoaW4nIGZ1bm55IC8gU3RvcCBzbWlsaW5nLCBiZSBzdGlsbCwgZG9uJ3QgbnV0aGluJyBtb3ZlIGJ1dCB0aGUgbW9uZXk=",
		"QnV0IG5vdyBJIGxlYXJuZWQgdG8gZWFybiAnY3V6IEknbSByaWdodGVvdXMgLyBJIGZlZWwgZ3JlYXQsIHNvIG1heWJlIEkgbWlnaHQganVzdA==",
		"U2VhcmNoIGZvciBhIG5pbmUgdG8gZml2ZSwgaWYgSSBzdHJpdmUgLyBUaGVuIG1heWJlIEknbGwgc3RheSBhbGl2ZQ==",
		"U28gSSB3YWxrIHVwIHRoZSBzdHJlZXQgd2hpc3RsaW4nIHRoaXMgLyBGZWVsaW4nIG91dCBvZiBwbGFjZSAnY3V6LCBtYW4sIGRvIEkgbWlzcw==",
		"QSBwZW4gYW5kIGEgcGFwZXIsIGEgc3RlcmVvLCBhIHRhcGUgb2YgLyBNZSBhbmQgRXJpYyBCLCBhbmQgYSBuaWNlIGJpZyBwbGF0ZSBvZg==",
		"RmlzaCwgd2hpY2ggaXMgbXkgZmF2b3JpdGUgZGlzaCAvIEJ1dCB3aXRob3V0IG5vIG1vbmV5IGl0J3Mgc3RpbGwgYSB3aXNo",
		"J0N1eiBJIGRvbid0IGxpa2UgdG8gZHJlYW0gYWJvdXQgZ2V0dGluJyBwYWlkIC8gU28gSSBkaWcgaW50byB0aGUgYm9va3Mgb2YgdGhlIHJoeW1lcyB0aGF0IEkgbWFkZQ==",
		"U28gbm93IHRvIHRlc3QgdG8gc2VlIGlmIEkgZ290IHB1bGwgLyBIaXQgdGhlIHN0dWRpbywgJ2N1eiBJJ20gcGFpZCBpbiBmdWxs",
		"UmFraW0sIGNoZWNrIHRoaXMgb3V0LCB5byAvIFlvdSBnbyB0byB5b3VyIGdpcmwgaG91c2UgYW5kIEknbGwgZ28gdG8gbWluZQ==",
		"J0NhdXNlIG15IGdpcmwgaXMgZGVmaW5pdGVseSBtYWQgLyAnQ2F1c2UgaXQgdG9vayB1cyB0b28gbG9uZyB0byBkbyB0aGlzIGFsYnVt",
		"WW8sIEkgaGVhciB3aGF0IHlvdSdyZSBzYXlpbmcgLyBTbyBsZXQncyBqdXN0IHB1bXAgdGhlIG11c2ljIHVw",
		"QW5kIGNvdW50IG91ciBtb25leSAvIFlvLCB3ZWxsIGNoZWNrIHRoaXMgb3V0LCB5byBFbGk=",
		"VHVybiBkb3duIHRoZSBiYXNzIGRvd24gLyBBbmQgbGV0IHRoZSBiZWF0IGp1c3Qga2VlcCBvbiByb2NraW4n",
		"QW5kIHdlIG91dHRhIGhlcmUgLyBZbywgd2hhdCBoYXBwZW5lZCB0byBwZWFjZT8gLyBQZWFjZQ==",
	}
	findKey := func(block []byte) byte {
		var k byte
		var s int

		s = 0
		for i := byte(0); i < 255; i++ {
			ks := lib.FillBytes(i, len(block))
			xs := lib.FixedXORBytes(block, ks)

			score := lib.AlphaPunchScore(xs)
			if score > s {
				s = score
				k = i
			}
		}
		return k
	}
	// 'bs' is the data to decrypt.
	// 'ks' is the key size.
	crack := func(bs []byte, ks int) ([]byte, []byte) {
		blocks := lib.BreakIntoBlocks(bs, ks)
		blocks = lib.TransposeBlocks(blocks, ks)

		key := make([]byte, 0)
		for i := 0; i < len(blocks); i++ {
			k := findKey(blocks[i])

			key = append(key, k)
		}
		return key, lib.RepeatingXOR(bs, key)
	}

	// Make ciphers from plain text data.
	ciphers := make([][]byte, len(texts))
	key, err := lib.RandomBytes(16)
	if err != nil {
		fmt.Printf("Error generating key %v", err)
		return
	}
	nonce := uint64(lib.RandomInt(0, 10))
	for i, b64 := range texts {
		text := lib.Base64ToBytes(b64)
		ciphers[i], err = lib.AESEncryptCTR(text, key, lib.AESGenCTRFunc(nonce))
		if err != nil {
			fmt.Printf("Error encrypting text:%d: %v", i, err)
			return
		}
	}
	// Find the shortest cipher. This cipher's length will
	// become the keys size for the repeating XOR.
	keySize := 2000
	for _, cipher := range ciphers {
		if len(cipher) < keySize {
			keySize = len(cipher)
		}
	}
	// Make a cipher stream.
	cipherStream := make([]byte, 0)
	for _, cipher := range ciphers {
		cipherStream = append(cipherStream, cipher[0:keySize]...)
	}
	// Crack and barf text stream.
	_, textStream := crack(cipherStream, keySize)
	for i, b := range textStream {
		if i > 0 && i%keySize == 0 {
			fmt.Printf("\n")
		}
		fmt.Printf("%s", string(b))
	}
	fmt.Printf("\n")
}

// Output:
// I'm rated "R"...this is a warning, ya better void / P
// Cuz I came back to attack others in spite- / Strike l
// But don't be afraid in the dark, in a park / Not a sc
// Ya tremble like a alcoholic, muscles tighten up / Wha
// Suddenly you feel like your in a horror flick / You g
// Music's the clue, when I come your warned / Apocalyps
// Haven't you ever heard of a MC-murderer? / This is th
// Death wish, so come on, step to this / Hysterical ide
// Friday the thirteenth, walking down Elm Street / You
// This is off limits, so your visions are blurry / All
// Terror in the styles, never error-files / Indeed I'm
// For those that oppose to be level or next to this / I
// Worse than a nightmare, you don't have to sleep a win
// Flashbacks interfere, ya start to hear: / The R-A-K-I
// Then the beat is hysterical / That makes Eric go get
// Soon the lyrical format is superior / Faces of death
// MC's decaying, cuz they never stayed / The scene of a
// The fiend of a rhyme on the mic that you know / It's
// Melodies-unmakable, pattern-unescapable / A horn if w
// I bless the child, the earth, the gods and bomb the r
// Hazardous to your health so be friendly / A matter of
// Shake 'till your clear, make it disappear, make the n
// If not, my soul'll release! / The scene is recreated,
// Cuz your about to see a disastrous sight / A performa
// Lyrics of fury! A fearified freestyle! / The "R" is i
// Make sure the system's loud when I mention / Phrases
// You want to hear some sounds that not only pounds but
// Then nonchalantly tell you what it mean to me / Stric
// And I don't care if the whole crowd's a witness! / I'
// Program into the speed of the rhyme, prepare to start
// Musical madness MC ever made, see it's / Now an emerg
// Open your mind, you will find every word'll be / Furi
// Battle's tempting...whatever suits ya! / For words th
// You think you're ruffer, then suffer the consequences
// I wake ya with hundreds of thousands of volts / Mic-t
// Novocain ease the pain it might save him / If not, Er
// Yo Rakim, what's up? / Yo, I'm doing the knowledge, E
// Well, check this out, since Norby Walters is our agen
// Kara Lewis is our agent, word up / Zakia and 4th and
// Okay, so who we rollin' with then? We rollin' with Ru
// Check this out, since we talking over / This def beat
// I wanna hear some of them def rhymes, you know what I
// Thinkin' of a master plan / 'Cuz ain't nuthin' but sw
// So I dig into my pocket, all my money is spent / So I
// So I start my mission, leave my residence / Thinkin'
// I need money, I used to be a stick-up kid / So I thin
// I used to roll up, this is a hold up, ain't nuthin' f
// But now I learned to earn 'cuz I'm righteous / I feel
// Search for a nine to five, if I strive / Then maybe I
// So I walk up the street whistlin' this / Feelin' out
// A pen and a paper, a stereo, a tape of / Me and Eric
// Fish, which is my favorite dish / But without no mone
// 'Cuz I don't like to dream about gettin' paid / So I
// So now to test to see if I got pull / Hit the studio,
// Rakim, check this out, yo / You go to your girl house
// 'Cause my girl is definitely mad / 'Cause it took us
// Yo, I hear what you're saying / So let's just pump th
// And count our money / Yo, well check this out, yo Eli
// Turn down the bass down / And let the beat just keep
// And we outta here / Yo, what happened to peace? / Pea