/**
 _____    _    _   _____    ______                                           _
 |  __ \  | |  | | |  __ \  |  ____|                                         | |
 | |__) | | |__| | | |__) | | |__ _ __ __ _ _ __ ___   _____      _____  _ __| | __
 |  ___/  |  __  | |  ___/  |  __| '__/ _` | '_ ` _ \ / _ \ \ /\ / / _ \| '__| |/ /
 | |      | |  | | | |  _   | |  | | | (_| | | | | | |  __/\ V  V / (_) | |  |   <
 |_|      |_|  |_| |_| (_)  |_|  |_|  \__,_|_| |_| |_|\___| \_/\_/ \___/|_|  |_|\_\


 Copyright (c) 2016 Wesley de Groot (http://www.wesleydegroot.nl), WDGWV (http://www.wdgwv.com)


 Variable prefixes:
 PFS = PHP.Framework Shared
 PFT = PHP.Framework Tests (internal)
 PFI = PHP.Framework Internal
 PFU = PHP.Framework Unspecified

 usage:
 php.the_php_function(and, parameters, ofcourse)

 documentation:
 http://wdg.github.io/php.framework/

 wiki:
 https://github.com/wdg/php.framework/wiki

 questions/bugs:
 https://github.com/wdg/php.framework/issues

 ---------------------------------------------------
 File:    crc32.swift
 Created: 15-JAN-2016
 Creator: Wesley de Groot | g: @wdg | t: @wesdegroot
 Issue:   #1 (String Functions)
 Prefix:  N/A
 ---------------------------------------------------
 Thanks:
 compute the CRC-32 of a data stream
 Copyright (C) 1995-1998 Mark Adler
 */

import Foundation

extension String {
	public var crc32: String {
		get {
			return String(generateCRC32(s: self))
		}
	}
}

/**
 Table of CRC-32's of all single-byte values
 */
private let crcTable: [UInt32] = [
	0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
	0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
	0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
	0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
	0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
	0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
	0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
	0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
	0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
	0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
	0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
	0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
	0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
	0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
	0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
	0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
	0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
	0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
	0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
	0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
	0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
	0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
	0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
	0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
	0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
	0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
	0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
	0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
	0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
	0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
	0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
	0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
	0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
	0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
	0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
	0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
	0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
	0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
	0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
	0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
	0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
	0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
	0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
	0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
	0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
	0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
	0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
	0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
	0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
	0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
	0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
	0x2d02ef8d]

func generateCRC32(s: String) -> String {
	return (NSString(format: "%2X", MYcrc32(xmessage: s)) as String).lowercased()
}

func MYcrc32(xmessage: String, seed: UInt32? = nil) -> UInt32 {
	let message: [UInt8] = Array(xmessage.utf8)
	
	var crc: UInt32 = seed != nil ? seed! : 0xffffffff
	
	for chunk in BytesSequence(chunkSize: 256, data: message) {
		for b in chunk {
			let idx = Int((crc ^ UInt32(b)) & 0xff)
			crc = (crc >> 8) ^ crcTable[idx]
		}
	}
	return crc ^ 0xffffffff
}

private func CRC_AnyGenerator<Element>(body: @escaping () -> Element?) -> AnyIterator<Element> {
	return AnyIterator(body)
}

struct BytesSequence: Sequence {
	let chunkSize: Int
	let data: [UInt8]
	
	func makeIterator() -> AnyIterator<ArraySlice<UInt8>> {
		
		var offset: Int = 0
		
		return CRC_AnyGenerator {
//          Swift 3 kills it
//			let end = min(isOrderedBefore: Int(self.chunkSize-(self.data.count-offset)))
//          let end = min(self.chunkSize, self.data.count - offset)
            
            let calc = self.data.count - offset
            let end = (self.chunkSize > calc) ? calc : self.chunkSize
            
            
                let result = self.data[offset..<(offset + end)]
                offset += result.count
                return result.count > 0 ? result : nil

		}
	}
}
