/****************************************************************************
* OVERVIEW: Simple security to comply with legal requirements
*
* NOTE: This will need to be replaced with something server side.
*
* REF: http://www.ddj.com/dept/security/184412419
* Javascript Password Protection - Dr. Dobb's - Jan 01, 2002 - Pat Besong
*
* TODO: figure out why cookie is abandoned immediately after browser session closes
*       
****************************************************************************/

/****************************************************************************
* PERSISTENCE
****************************************************************************/

// EX: persistValue('mykey', 'myvalue');
function persistValue(key, value){
	document.cookie = key + "=" + escape(value);
}

// EX: document.write(restoreValue('mykey'));
function restoreValue(key){
	if (document.cookie.length > 0){
		var start = document.cookie.indexOf(key + "=");

		if (start != -1){
			start = start + key.length + 1;
			var end = document.cookie.indexOf(";", start);

			if (end == -1){
				end = document.cookie.length;
			}

			return unescape(document.cookie.substring(start, end));
		}
	}

	return null;
}

// EX: clearValue('mykey');
function clearValue(key){
	persistValue(key, "empty" + "; expires=Thu, 01-Jan-70 00:00:01 GMT");
}

/****************************************************************************
* SHA1 HANDLING
****************************************************************************/

/**
*
*  Secure Hash Algorithm (SHA1)
*  http://www.webtoolkit.info/
*
**/

function SHA1 (msg) {

    function rotate_left(n,s) {
        var t4 = ( n<<s ) | (n>>>(32-s));
        return t4;
    };

    function lsb_hex(val) {
        var str="";
        var i;
        var vh;
        var vl;

        for( i=0; i<=6; i+=2 ) {
            vh = (val>>>(i*4+4))&0x0f;
            vl = (val>>>(i*4))&0x0f;
            str += vh.toString(16) + vl.toString(16);
        }
        return str;
    };

    function cvt_hex(val) {
        var str="";
        var i;
        var v;

        for( i=7; i>=0; i-- ) {
            v = (val>>>(i*4))&0x0f;
            str += v.toString(16);
        }
        return str;
    };


    function Utf8Encode(string) {
        string = string.replace(/\r\n/g,"\n");
        var utftext = "";

        for (var n = 0; n < string.length; n++) {

            var c = string.charCodeAt(n);

            if (c < 128) {
                utftext += String.fromCharCode(c);
            }
            else if((c > 127) && (c < 2048)) {
                utftext += String.fromCharCode((c >> 6) | 192);
                utftext += String.fromCharCode((c & 63) | 128);
            }
            else {
                utftext += String.fromCharCode((c >> 12) | 224);
                utftext += String.fromCharCode(((c >> 6) & 63) | 128);
                utftext += String.fromCharCode((c & 63) | 128);
            }

        }

        return utftext;
    };

    var blockstart;
    var i, j;
    var W = new Array(80);
    var H0 = 0x67452301;
    var H1 = 0xEFCDAB89;
    var H2 = 0x98BADCFE;
    var H3 = 0x10325476;
    var H4 = 0xC3D2E1F0;
    var A, B, C, D, E;
    var temp;

    msg = Utf8Encode(msg);

    var msg_len = msg.length;

    var word_array = new Array();
    for( i=0; i<msg_len-3; i+=4 ) {
        j = msg.charCodeAt(i)<<24 | msg.charCodeAt(i+1)<<16 |
        msg.charCodeAt(i+2)<<8 | msg.charCodeAt(i+3);
        word_array.push( j );
    }

    switch( msg_len % 4 ) {
        case 0:
            i = 0x080000000;
        break;
        case 1:
            i = msg.charCodeAt(msg_len-1)<<24 | 0x0800000;
        break;

        case 2:
            i = msg.charCodeAt(msg_len-2)<<24 | msg.charCodeAt(msg_len-1)<<16 | 0x08000;
        break;

        case 3:
            i = msg.charCodeAt(msg_len-3)<<24 | msg.charCodeAt(msg_len-2)<<16 | msg.charCodeAt(msg_len-1)<<8    | 0x80;
        break;
    }

    word_array.push( i );

    while( (word_array.length % 16) != 14 ) word_array.push( 0 );

    word_array.push( msg_len>>>29 );
    word_array.push( (msg_len<<3)&0x0ffffffff );


    for ( blockstart=0; blockstart<word_array.length; blockstart+=16 ) {

        for( i=0; i<16; i++ ) W[i] = word_array[blockstart+i];
        for( i=16; i<=79; i++ ) W[i] = rotate_left(W[i-3] ^ W[i-8] ^ W[i-14] ^ W[i-16], 1);

        A = H0;
        B = H1;
        C = H2;
        D = H3;
        E = H4;

        for( i= 0; i<=19; i++ ) {
            temp = (rotate_left(A,5) + ((B&C) | (~B&D)) + E + W[i] + 0x5A827999) & 0x0ffffffff;
            E = D;
            D = C;
            C = rotate_left(B,30);
            B = A;
            A = temp;
        }

        for( i=20; i<=39; i++ ) {
            temp = (rotate_left(A,5) + (B ^ C ^ D) + E + W[i] + 0x6ED9EBA1) & 0x0ffffffff;
            E = D;
            D = C;
            C = rotate_left(B,30);
            B = A;
            A = temp;
        }

        for( i=40; i<=59; i++ ) {
            temp = (rotate_left(A,5) + ((B&C) | (B&D) | (C&D)) + E + W[i] + 0x8F1BBCDC) & 0x0ffffffff;
            E = D;
            D = C;
            C = rotate_left(B,30);
            B = A;
            A = temp;
        }

        for( i=60; i<=79; i++ ) {
            temp = (rotate_left(A,5) + (B ^ C ^ D) + E + W[i] + 0xCA62C1D6) & 0x0ffffffff;
            E = D;
            D = C;
            C = rotate_left(B,30);
            B = A;
            A = temp;
        }

        H0 = (H0 + A) & 0x0ffffffff;
        H1 = (H1 + B) & 0x0ffffffff;
        H2 = (H2 + C) & 0x0ffffffff;
        H3 = (H3 + D) & 0x0ffffffff;
        H4 = (H4 + E) & 0x0ffffffff;

    }

    var temp = cvt_hex(H0) + cvt_hex(H1) + cvt_hex(H2) + cvt_hex(H3) + cvt_hex(H4);

    return temp.toLowerCase();

}

/****************************************************************************
* PASSWORD HANDLING
****************************************************************************/
function check_first_visit() {
		msg = "\
Just a reminder, please use the login at the top of the page to access our content.\n\
\n\
If you do not have a password,\n\
please email us so we can determine if you meet the elgibility requirements for access.\n\
\n\
We are sorry for the inconvenience.";

		var alreadyVisited = restoreValue('alreadyVisited');

		if (!alreadyVisited) {
			alert(msg);
		}

		persistValue('alreadyVisited', true);
}

function check_access() {
	var password = restoreValue(password_key);
	if ( (password == null) || (!check_password(password)) ){
		window.location.href = login_page;
		return;
	}
	
	var login_stamp = new Date(restoreValue(login_key));	
	var expiry_stamp = new Date();

	expiry_stamp.setDate(get_expiry(login_stamp, expiry_window));
		
	if ( (login_stamp != null) || (expiry_stamp < (new Date(Date()))) ) {
		// Allow access to page, and update cookie
		persistValue(login_key, get_expiry(new Date(Date()), expiry_window));
	} else {
		window.location.href = login_page;
	}
}

function is_logged_in() {
	var password = restoreValue(password_key);
	if ( (password == null) || (!check_password(password)) ){
		return false;
	}
	
	var login_stamp = new Date(restoreValue(login_key));	
	var expiry_stamp = new Date();

	expiry_stamp.setDate(get_expiry(login_stamp, expiry_window));
		
	if ( (login_stamp != null) || (expiry_stamp < (new Date(Date()))) ) {
		// Allow access to page, and update cookie
		persistValue(login_key, get_expiry(new Date(Date()), expiry_window));
	} else {
		return false;
	}
	
	return true;
}

function check_password(password) {
	return (encrypt(password) == encrypted_password);
}

function validate_login(password) {
	if (check_password(password)) {
		persistValue(login_key, get_expiry(new Date(Date()), expiry_window));
		persistValue(password_key, password);
		
		window.location.href = "index.html";
	}
}

function get_expiry(the_date, minutes) {
	the_date.setMinutes(the_date.getMinutes() + minutes);
	return the_date;
}

function logout() {
	clearValue(login_key);
	clearValue(password_key);
	window.location.href = login_page;
	
	return true;
}

function encrypt(plain_text) {
	var encrypted_text;
	
	encrypted_text = SHA1(plain_text);
	
	return	encrypted_text;
}

/* Page Initialize Code */
check_first_visit();