/**
* Calculates the SHA1 checksum.
* @authors Mika Palmu
* @version 2.0
*
* Original Javascript implementation:
* Secure Hash Algorithm, SHA-1, as defined in FIPS PUB 180-1
* Version 2.1 Copyright Paul Johnston 2000 - 2002
* Other contributors: Greg Holt, Andrew Kepert, Ydnar, Lostinet
* See http://pajhome.org.uk/crypt/md5 for more info.
*/

class com.meychi.ascrypt.SHA1 {

	/**
	* Calculates the SHA1 checksum.
	*/
	public static function calculate(src:String):String {
		return hex_sha1(src);
	}

	/**
	* Private methods.
	*/
	private static function hex_sha1(src:String):String {
		return binb2hex(core_sha1(str2binb(src), src.length*8));
	}
	private static function core_sha1(x:Array, len:Number):Array {
		x[len >> 5] |= 0x80 << (24-len%32);
		x[((len+64 >> 9) << 4)+15] = len;
		var w:Array = new Array(80), a:Number = 1732584193;
		var b:Number = -271733879, c:Number = -1732584194;
		var d:Number = 271733878, e:Number = -1009589776;
		for (var i:Number = 0; i<x.length; i += 16) {
			var olda:Number = a, oldb:Number = b;
			var oldc:Number = c, oldd:Number = d, olde:Number = e;
			for (var j:Number = 0; j<80; j++) {
				if (j<16) w[j] = x[i+j];
				else w[j] = rol(w[j-3] ^ w[j-8] ^ w[j-14] ^ w[j-16], 1);
				var t:Number = safe_add(safe_add(rol(a, 5), sha1_ft(j, b, c, d)), safe_add(safe_add(e, w[j]), sha1_kt(j)));
				e = d; d = c;
				c = rol(b, 30);
				b = a; a = t;
			}
			a = safe_add(a, olda);
			b = safe_add(b, oldb);
			c = safe_add(c, oldc);
			d = safe_add(d, oldd);
			e = safe_add(e, olde);
		}
		return new Array(a, b, c, d, e);
	}
	private static function sha1_ft(t:Number, b:Number, c:Number, d:Number):Number {
		if (t<20) return (b & c) | ((~b) & d);
		if (t<40) return b ^ c ^ d;
		if (t<60) return (b & c) | (b & d) | (c & d);
		return b ^ c ^ d;
	}
	private static function sha1_kt(t:Number):Number {
		return (t<20) ? 1518500249 : (t<40) ? 1859775393 : (t<60) ? -1894007588 : -899497514;
	}
	private static function safe_add(x:Number, y:Number):Number {
		var lsw:Number = (x & 0xFFFF)+(y & 0xFFFF);
		var msw:Number = (x >> 16)+(y >> 16)+(lsw >> 16);
		return (msw << 16) | (lsw & 0xFFFF);
	}
	private static function rol(num:Number, cnt:Number):Number {
		return (num << cnt) | (num >>> (32-cnt));
	}
	private static function str2binb(str:String):Array {
		var bin:Array = new Array();
		var mask:Number = (1 << 8)-1;
		for (var i:Number = 0; i<str.length*8; i += 8) {
			bin[i >> 5] |= (str.charCodeAt(i/8) & mask) << (24-i%32);
		}
		return bin;
	}
	private static function binb2hex(binarray:Array):String {
		var str:String = new String("");
		var tab:String = new String("0123456789abcdef");
		for (var i:Number = 0; i<binarray.length*4; i++) {
			str += tab.charAt((binarray[i >> 2] >> ((3-i%4)*8+4)) & 0xF) + tab.charAt((binarray[i >> 2] >> ((3-i%4)*8)) & 0xF);
		}
		return str;
	}

}