/**
*  Contains functions for formatting a SysTime object
*
*  Code taken from https://github.com/cmays90/datetimeformat
*  with minor modifications:
*     - no UTF validation
*     - refactor with statement
**/

module gfx.priv.datetimeformat;

package(gfx):

private import std.datetime : DayOfWeek, Month, SysTime;
private import std.ascii 	: toLower, isDigit, isAlpha;
private import std.utf 		: toUTF32, toUTF8, toUCSindex, toUTFindex, encode;
private import std..string : toStringz, format;
private import std.conv   : to;

/// Short (three-letter) Days of the week
immutable string[] SHORT_DAY_NAME = [
	DayOfWeek.sun: "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
];

///	Full names of the days of the week.
immutable string[] LONG_DAY_NAME = [
	DayOfWeek.sun: "Sunday", "Monday", "Tuesday", "Wednesday",
	  "Thursday", "Friday", "Saturday"
];

///	Short (three-letter) names of the months of the year.
immutable string[] SHORT_MONTH_NAME = [
	Month.jan: "Jan", "Feb", "Mar", "Apr", "May", "Jun",
	"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
];

///	Full names of the months of the year.
immutable string[Month.max + 1] LONG_MONTH_NAME = [
  Month.jan: "January", "February", "March", "April", "May", "June",
	"July", "August", "September", "October", "November", "December"
];

/**	Formats dt according to formatString.
 *
 *	Returns:
 *		the formatted date string.
 *	Throws:
 *		SysTimeFormatException  if the formatting fails, e.g. because of an error in the format
 *		                         string.
 */

string format(const SysTime dt, string formatString) {
	return format(dt, dt.dayOfWeek, formatString);
}

string format(const SysTime dt, DayOfWeek dayOfWeek, string formatString) {
	bool nonNull;
	immutable(char)* charPos = toStringz(formatString);
	scope(success) assert (*charPos == '\0');

	return format(dt, dayOfWeek, charPos, nonNull, '\0');
}


private {

	// taken from Phobos (where it is private in D2)
	const ubyte[256] UTF8stride = [
		1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
		1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
		1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
		1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
		1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
		1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
		1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
		1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
		0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
		0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
		0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
		0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
		2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
		2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
		3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
		4,4,4,4,4,4,4,4,5,5,5,5,6,6,0xFF,0xFF,
	];

	string format(const SysTime dt, DayOfWeek dayOfWeek,
		  ref immutable(char)* charPos, out bool nonNull, char portionEnd) {

		// function uses null-terminated string to make finding the end easier
		long lastNumber = int.min;
		string result;

		while (*charPos != portionEnd) {
			if (beginsElement(*charPos)) {
				bool newNonNull;
				result ~= formatElement(dt, dayOfWeek, charPos, newNonNull, lastNumber);
				if (newNonNull) nonNull = true;
			} else if (beginsLiteral(*charPos)) {
				result ~= formatLiteral(charPos);
			} else switch (*charPos) {
				case '\0':		// unclosed portion
					assert (portionEnd == '}');
					throw new SysTimeFormatException(E_UNCLOSED_COLLAPSIBLE);

				case '}':
					throw new SysTimeFormatException(E_UNOPENED_COLLAPSIBLE);

				case ']':
					throw new SysTimeFormatException(E_UNOPENED_FIELD);

				default: // self-literal character
					result ~= *(charPos++);
			}
		}

		return result;
	}


	/*	Processes a single format element.  A format element is any of the following:
	 *	- an alphabetical format specifier
	 *	- a collapsible portion
	 *	- an alignment field
	 *	Literals and alignment field widths are not included.  The purpose is
	 *	to deal with those elements that cannot be part of an alignment field
	 *	padding or width.
	 */
	string formatElement(const SysTime dt, DayOfWeek dayOfWeek,
	                     ref immutable(char)* charPos, out bool nonNull, ref long lastNumber)
	in {
		assert (beginsElement(*charPos));
	} body {
		switch (*charPos) {
			case '[': {
				charPos++;
				string portion = formatField(dt, dayOfWeek, charPos, nonNull);
				charPos++;
				return portion;
			}

			case '{': {
				charPos++;
				string portion = format(dt, dayOfWeek, charPos, nonNull, '}');
				charPos++;
				return nonNull ? portion : null;
			}

			default:
				char letter = cast(char) toLower(*charPos);
				immutable(char)* beginSpec = charPos;

				do {
					++charPos;
				} while (toLower(*charPos) == letter);

				string formatted = formatBySpec(dt, dayOfWeek,
				  beginSpec[0 .. charPos-beginSpec], lastNumber);

				if (formatted.length != 0) {
					nonNull = true;
					return formatted;
				} else {
					return null;
				}
		}
	}


	string formatLiteral(ref immutable(char)* charPos)
	in {
		assert (beginsLiteral(*charPos));
	} body {
		switch (*charPos) {
			case '`': {		// literal character
				if (*++charPos == '\0') {
					throw new SysTimeFormatException(E_MISSING_LITERAL);
				}
				uint len = UTF8stride[*charPos];
				scope(exit) charPos += len;
				return charPos[0..len];
			}

			case '\'': {	// literal portion
				immutable(char)* beginLiteral = ++charPos;
				while (*charPos != '\'') {
					if (*charPos == '\0') {
						throw new SysTimeFormatException(E_UNCLOSED_LITERAL);
					}
					charPos++;
				}
				return beginLiteral[0 .. (charPos++) - beginLiteral];
			}

			default: assert (false);
		}
	}


	struct Piece {
		dstring dtext;
		string  text;
		ubyte type;  // 0 = raw, 1 = literal; 2 = formatted

		@property uint asNumber() {
			if (dtext.length > 9) throw new SysTimeFormatException(E_OVERFLOW_WIDTH);
			uint result;
			foreach (c; dtext) {
				assert (c >= '0' && c <= '9');
				result = result * 10 + (c - '0');
			}
			return result;
		}
	}


	string formatField(const SysTime dt, DayOfWeek dayOfWeek,
	                   ref immutable(char)* charPos, out bool nonNull) {
		Piece[] pieces;

		// first parse the format string within the [...]
		{
			Piece[] tempPieces;
			long lastNumber = int.min;

			while (*charPos != ']') {
				if (beginsElement(*charPos)) {
					bool newNonNull;
					tempPieces ~= Piece(null, formatElement(dt, dayOfWeek, charPos, newNonNull, lastNumber), 2);
					if (newNonNull) nonNull = true;
				} else if (beginsLiteral(*charPos)) {
					tempPieces ~= Piece(null, formatLiteral(charPos), 1);
				} else switch (*charPos) {
					case '\0':
						throw new SysTimeFormatException(E_UNCLOSED_FIELD);

					case '}':
						throw new SysTimeFormatException(E_UNOPENED_COLLAPSIBLE);

					default: {
						immutable(char)* begin = charPos;
						do {
							charPos++;
						} while (*charPos != '\0' && *charPos != ']' && *charPos != '}'
						  && !beginsElement(*charPos) && !beginsLiteral(*charPos));

						tempPieces ~= Piece(null, begin[0 .. charPos - begin], 0);
					}
				}
			}

			/*	convert tempPieces into a form in which
			 *	- no two consecutive tempPieces have the same type
			 *	- only non-literalised numbers have type 0
			 */
			ubyte lastType = ubyte.max;

			foreach (piece; tempPieces) {
				switch (piece.type) {
				case 0:
					foreach (dchar c; piece.text) {
						if (isDigit(c)) {
							if (lastType == 0) {
								pieces[$-1].dtext ~= c;
							} else {
								pieces ~= Piece([c], null, 0);
								lastType = 0;
							}
						} else {
							if (lastType == 1) {
								pieces[$-1].dtext ~= c;
							} else {
								pieces ~= Piece([c], null, 1);
								lastType = 1;
							}
						}
					}
					break;

				case 1:
					if (lastType == 1) {
						pieces[$-1].dtext ~= toUTF32(piece.text);
					} else {
						pieces ~= Piece(toUTF32(piece.text), null, 1);
						lastType = 1;
					}
					break;

				case 2:
					if (lastType == 2) {
						pieces[$-1].text ~= piece.text;
					} else {
						pieces ~= piece;
						lastType = 2;
					}
					break;

				default:
					assert (false);
				}
			}
		}

		if (pieces.length < 2) throw new SysTimeFormatException(E_INCOMPLETE_FIELD);

		// detect the field width/padding
		dchar padLeft, padRight;
		size_t fieldWidth = 0;
		bool moreOnRight;

		if (pieces[0].type == 0) {
			// field width on left
			if (pieces[$-1].type == 0) throw new SysTimeFormatException(E_DOUBLE_WIDTH);

			fieldWidth = pieces[0].asNumber;
			if (fieldWidth == 0) throw new SysTimeFormatException(E_ZERO_FIELD);
			if (pieces[1].type != 1) throw new SysTimeFormatException(E_INCOMPLETE_FIELD);

			pieces = pieces[1..$];
			padLeft = pieces[0].dtext[0];
			pieces[0].dtext = pieces[0].dtext[1..$];
			if (pieces[$-1].type == 1) {
				padRight = pieces[$-1].dtext[$-1];
				pieces[$-1].dtext.length = pieces[$-1].dtext.length - 1;
			}

		} else if (pieces[$-1].type == 0) {
			// field width on right
			moreOnRight = true;
			fieldWidth = pieces[$-1].asNumber;
			if (fieldWidth == 0) throw new SysTimeFormatException(E_ZERO_FIELD);
			if (pieces[$-2].type != 1) throw new SysTimeFormatException(E_INCOMPLETE_FIELD);

			pieces = pieces[0..$-1];
			padRight = pieces[$-1].dtext[$-1];
			pieces[$-1].dtext.length = pieces[$-1].dtext.length - 1;
			if (pieces[0].type == 1) {
				padLeft = pieces[0].dtext[0];
				pieces[0].dtext = pieces[0].dtext[1..$];
			}

		} else {
			// field width given by number of padding characters
			if (pieces[0].type == 1) {
				padLeft = pieces[0].dtext[0];
				for (fieldWidth = 1;
				  fieldWidth < pieces[0].dtext.length && pieces[0].dtext[fieldWidth] == padLeft;
				  fieldWidth++) {}
				pieces[0].dtext = pieces[0].dtext[fieldWidth..$];
			}
			if (pieces[$-1].type == 1) {
				padRight = pieces[$-1].dtext[$-1];
				size_t pos;
				for (pos = pieces[$-1].dtext.length - 1;
				  pos > 0 && pieces[$-1].dtext[pos - 1] == padRight;
				  pos--) {}
				if (pieces[$-1].dtext.length - pos > fieldWidth) moreOnRight = true;
				fieldWidth += pieces[$-1].dtext.length - pos;
				pieces[$-1].dtext.length = pos;
			}
		}

		assert (fieldWidth != 0);

		debug (datetimeformat) {
			writefln("padding chars: %s %s.", padLeft == dchar.init ? "none" : [padLeft],
			  padRight == dchar.init ? "none" : [padRight]);
			writefln("width: %d", fieldWidth);
			writefln("%d pieces", pieces.length);
		}

		// read the field format - now use it
		// but first, concatenate and measure the content
		size_t contentLength;
		string formattedContent;
		foreach (piece; pieces) {
			assert (piece.dtext.length == 0 || piece.text.length == 0);
			if (piece.text.length == 0) {
				formattedContent ~= toUTF8(piece.dtext);
				contentLength += piece.dtext.length;
			} else {
				formattedContent ~= piece.text;
				contentLength += toUCSindex(piece.text, piece.text.length);
			}
		}
		debug (datetimeformat) writefln("content length %d: %s", contentLength, formattedContent);

		if (contentLength > fieldWidth) {
			throw new SysTimeFormatException(E_FIELD_OVERFLOW);
		}
		if (contentLength >= fieldWidth) return formattedContent;
		assert (formattedContent.length == toUTFindex(formattedContent, contentLength));

		// distribute padding
		ulong padWidth = fieldWidth - contentLength, padLeftWidth = 0, padRightWidth = 0;
		if (padLeft == dchar.init) {
			padRightWidth = padWidth;
		} else if (padRight == dchar.init) {
			padLeftWidth = padWidth;
		} else {
			padLeftWidth = padRightWidth = padWidth / 2;
			if (padWidth % 2 == 1) {
				if (moreOnRight) {
					padRightWidth++;
				} else {
					padLeftWidth++;
				}
			}
		}
		debug (datetimeformat) writefln("Padding distribution: %d %d %d = %d",
		  padLeftWidth, contentLength, padRightWidth, fieldWidth);
		assert (padLeftWidth + contentLength + padRightWidth == fieldWidth);

		// now do it!
		char[] result;

		for (int i = 0; i < padLeftWidth; i++) encode(result, padLeft);
		result ~= formattedContent;
		for (int i = 0; i < padRightWidth; i++) encode(result, padRight);
		return cast(string) result;
	}

	bool beginsElement(char c) { return isAlpha(c) || c == '[' || c == '{'; }
	bool beginsLiteral(char c) { return c == '\'' || c == '`'; }

	immutable string	DIGITS12 = "110123456789";
					/+TEN = DIGITS12[1..3],
					ELEVEN = DIGITS12[0..2],
					TWELVE = DIGITS12[3..5];+/

	/*const E_BAD_UTF
	  = "Error in date/time format string: invalid UTF-8 sequence";*/
	immutable E_MISSING_LITERAL
	  = "Error in date/time format string: missing character after '`'";
	immutable E_UNCLOSED_LITERAL
	  = "Error in date/time format string: unterminated literal portion";
	immutable E_UNCLOSED_FIELD
	  = "Error in date/time format string: '[' without matching ']'";
	immutable E_UNCLOSED_COLLAPSIBLE
	  = "Error in date/time format string: '{' without matching '}'";
	immutable E_UNOPENED_FIELD
	  = "Error in date/time format string: ']' without matching '['";
	immutable E_UNOPENED_COLLAPSIBLE
	  = "Error in date/time format string: '}' without matching '{'";
	immutable E_INCOMPLETE_FIELD
	  = "Error in date/time format string: Incomplete alignment field";
	immutable E_ZERO_FIELD
	  = "Error in date/time format string: Zero-width alignment field";
	immutable E_DOUBLE_WIDTH
	  = "Error in date/time format string: Width of alignment field doubly specified";
	immutable E_OVERFLOW_WIDTH
	  = "Error in date/time format string: Field width too large";
	immutable E_FIELD_OVERFLOW
	  = "Date/time formatting failed: Insufficient field width to hold content";
	immutable E_BC_YY
	  = "Date/time formatting failed: Format 'yy' for BC dates undefined";
	immutable E_INVALID_DATE_TIME
	  = "Date/time formatting failed: Invalid date/time";

	string formatBySpec(const SysTime dt, DayOfWeek dow,
		  string spec, ref long lastNumber) {
		switch (spec) {

			case "yy":
				lastNumber = dt.year;
				if (dt.year <= 0) {
					throw new SysTimeFormatException(E_BC_YY);
				}
				return formatTwoDigit(cast(byte) (dt.year % 100));

			case "yyy":
				lastNumber = dt.year;
				return to!string(dt.year > 0 ? dt.year : (lastNumber = 1 - dt.year));

			case "yyyy":
				lastNumber = dt.year;
				return format("%04d", dt.year > 0 ? dt.year :
				  (lastNumber = 1 - dt.year));

			case "YYY":
				lastNumber = dt.year < 0 ? -cast(int)dt.year : dt.year; // dt.year.min remains the same
				return to!string(dt.year);

			case "b":
				return (dt.year == dt.year.min || dt.year > 0) ? null : "bc";

			case "bb":
				return dt.year > 0 ? "ad" : "bc";

			case "bbb":
				return dt.year > 0 ? "ce" : "bce";

			case "bbbb":
				return (dt.year == dt.year.min || dt.year > 0) ? null : "bce";

			case "B":
				return (dt.year == dt.year.min || dt.year > 0) ? null : "BC";

			case "BB":
				return dt.year > 0 ? "AD" : "BC";

			case "BBB":
				return dt.year > 0 ? "CE" : "BCE";

			case "BBBB":
				return (dt.year == dt.year.min || dt.year > 0) ? null : "BCE";

			case "m":
				lastNumber = dt.month;
				return format12(dt.month);

			case "mm":
				lastNumber = dt.month;
				char[] fmt = new char[2];
				if (dt.month < 10) {
					fmt[0] = '0';
					fmt[1] = cast(char) ('0' + dt.month);
				} else {
					fmt[0] = '1';
					fmt[1] = cast(char) ('0' - 10 + dt.month);
				}
				return cast(string) fmt;

			case "mmm":
				return SHORT_L_MONTH_NAME[dt.month];

			case "Mmm":
				return SHORT_MONTH_NAME[dt.month];

			case "MMM":
				return SHORT_U_MONTH_NAME[dt.month];

			case "mmmm":
				return LONG_L_MONTH_NAME[dt.month];

			case "Mmmm":
				return LONG_MONTH_NAME[dt.month];

			case "MMMM":
				return LONG_U_MONTH_NAME[dt.month];

			case "d":
				lastNumber = dt.day;
				return to!string(dt.day);

			case "dd":
				lastNumber = dt.day;
				return formatTwoDigit(dt.day);

			case "t":
				return ordinalSuffix(lastNumber, false);

			case "T":
				return ordinalSuffix(lastNumber, true);

			case "www":
				return SHORT_L_DAY_NAME[dow];

			case "Www":
				debug (datetimeformat) writefln("Day of week: %d", cast(byte) dow);
				return SHORT_DAY_NAME[dow];

			case "WWW":
				return SHORT_U_DAY_NAME[dow];

			case "wwww":
				return LONG_L_DAY_NAME[dow];

			case "Wwww":
				return LONG_DAY_NAME[dow];

			case "WWWW":
				return LONG_U_DAY_NAME[dow];

			case "h":
				lastNumber = dt.hour;
				if (dt.hour == 0) {
					return DIGITS12[3..5];
				} else if (dt.hour <= 12) {
					return format12(dt.hour);
				} else {
					return format12(dt.hour - 12);
				}

			case "hh":
				lastNumber = dt.hour;
				if (dt.hour == 0) {
					return DIGITS12[3..5];
				} else if (dt.hour <= 12) {
					return formatTwoDigit(dt.hour);
				} else {
					return formatTwoDigit(dt.hour - 12);
				}

			case "H":
				lastNumber = dt.hour;
				return to!string(dt.hour);

			case "HH":
				lastNumber = dt.hour;
				return formatTwoDigit(dt.hour);

			case "a":
				return dt.hour < 12 ? "a" : "p";

			case "aa":
				return dt.hour < 12 ? "am" : "pm";

			case "A":
				return dt.hour < 12 ? "A" : "P";

			case "AA":
				return dt.hour < 12 ? "AM" : "PM";

			case "i":
				lastNumber = dt.minute;
				return to!string(dt.minute);

			case "ii":
				lastNumber = dt.minute;
				return formatTwoDigit(dt.minute);

			case "s":
				lastNumber = dt.second;
				return to!string(dt.second);

			case "ss":
				lastNumber = dt.second;
				return formatTwoDigit(dt.second);

			case "f":
				lastNumber = dt.fracSecs().total!"msecs" / 100;
				return DIGITS12[cast(size_t)(lastNumber+2) .. cast(size_t)(lastNumber+3)];

			case "ff":
				lastNumber = dt.fracSecs().total!"msecs" / 10;
				return to!string(lastNumber);

			case "FF":
				lastNumber = dt.fracSecs().total!"msecs" / 10;
				return formatTwoDigit(cast(byte) lastNumber);

			case "fff":
				lastNumber = dt.fracSecs().total!"msecs";
				return to!string(dt.fracSecs().total!"msecs");

			case "FFF":
				lastNumber = dt.fracSecs().total!"msecs";
				return format("%03d", dt.fracSecs().total!"msecs");


      /*
			case "zzzz":
				return dt.hour == dt.hour.min ? null :
				  timezone().utcOffsetAt(stdTime) >= 0 ?
				    format("+%02d%02d", timezone().utcOffsetAt(stdTime) / 60,
				      timezone().utcOffsetAt(stdTime) % 60) :
  				  format("-%02d%02d", -timezone().utcOffsetAt(stdTime) / 60,
				      -timezone().utcOffsetAt(stdTime) % 60);
      */

			default:
				throw new SysTimeFormatException(cast(string)
				  ("Error in date/time format string: Undefined format specifier '" ~ spec ~ "'"));
		}
	}

	string formatTwoDigit(int b)
	in {
		assert (b == byte.min || (b >= 0 && b <= 99));
	} body {
		if (b == byte.min) return null;
		char[] fmt = new char[2];
		fmt[0] = cast(byte) ('0' + b / 10);
		fmt[1] = cast(byte) ('0' + b % 10);
		return cast(string) fmt;
	}

	string format12(int b)
	in {
		assert (b >= 0);
		assert (b <= 12);
	} body {
		switch (b) {
			case 10: return DIGITS12[1..3];
			case 11: return DIGITS12[0..2];
			case 12: return DIGITS12[3..5];
			default: return DIGITS12[2+b .. 3+b];
		}
	}

	string ordinalSuffix(long lastNumber, bool upperCase) {
		if (lastNumber < 0) return null;
		lastNumber %= 100;
		if (lastNumber >= 4 && lastNumber <= 20) {
			return upperCase ? "TH" : "th";
		}
		switch (lastNumber % 10) {
			case 1:
				return upperCase ? "ST" : "st";

			case 2:
				return upperCase ? "ND" : "nd";

			case 3:
				return upperCase ? "RD" : "rd";

			default:
				return upperCase ? "TH" : "th";
		}
	}
}


///	Exception thrown if there was a problem in formatting a date or time.
class SysTimeFormatException : Exception {
	private this(string msg) {
		super(msg);
	}
}


///	Short (three-letter) names of the days of the week.
immutable string[7] SHORT_L_DAY_NAME = [
	DayOfWeek.sun: "sun", "mon", "tue", "wed", "thu", "fri", "sat"
];

///	Short (three-letter) names of the days of the week.
immutable string[7] SHORT_U_DAY_NAME = [
	DayOfWeek.sun: "SUN", "MON", "TUE", "WED", "THU", "FRI", "SAT"
];

///	Full names of the days of the week.
immutable string[7] LONG_L_DAY_NAME = [
	DayOfWeek.sun: "sunday", "monday", "tuesday", "wednesday",
	  "thursday", "friday", "saturday"
];

///	Full names of the days of the week.
immutable string[7] LONG_U_DAY_NAME = [
	DayOfWeek.sun: "SUNDAY", "MONDAY", "TUESDAY", "WEDNESDAY",
	  "THURSDAY", "FRIDAY", "SATURDAY"
];

///	Short (three-letter) names of the months of the year.
immutable string[13] SHORT_L_MONTH_NAME = [
	['\xFF', '\xFF', '\xFF'],
	Month.jan: "jan", "feb", "mar", "apr", "may", "jun",
	"jul", "aug", "sep", "oct", "nov", "dec"
];

///	Short (three-letter) names of the months of the year.
immutable string[13] SHORT_U_MONTH_NAME = [
	['\xFF', '\xFF', '\xFF'],
	Month.jan: "JAN", "FEB", "MAR", "APR", "MAY", "JUN",
	"JUL", "AUG", "SEP", "OCT", "NOV", "DEC"
];

///	Full names of the months of the year.
immutable string[13] LONG_L_MONTH_NAME = [
	null, Month.jan: "january", "february", "march", "april", "may", "june",
	"july", "august", "september", "october", "november", "december"
];

///	Full names of the months of the year.
immutable string[13] LONG_U_MONTH_NAME = [
	null, Month.jan: "JANUARY", "FEBRUARY", "MARCH", "APRIL", "MAY", "JUNE",
	"JULY", "AUGUST", "SEPTEMBER", "OCTOBER", "NOVEMBER", "DECEMBER"
];

unittest {
	import std.datetime;
	import std.stdio;

	writefln("Unittest commenced at %s",  Clock.currTime.toString);

	SysTime dt = SysTime(DateTime(2005, 9, 8, 16, 51, 9), dur!"msecs"(427));
	// basic formatting
	assert (dt.format("dd/mm/yy") == "08/09/05");
	assert (dt.format("Www dt Mmm yyyy BB") == "Thu 8th Sep 2005 AD");
	assert (dt.format("h:ii AA") == "4:51 PM");
	assert (dt.format("yyyy-mm-dd HH:ii:ss") == "2005-09-08 16:51:09");
	assert (dt.format("HH:ii:ss.FFF") == "16:51:09.427");
	// alignment fields
	assert (dt.format("[------Wwww.....]") == "--Thursday.");
	assert (dt.format("[11-Wwww.]") == "--Thursday.");
	assert (dt.format("[-----Wwww......]") == "-Thursday..");
	assert (dt.format("[-Wwww.11]") == "-Thursday..");
	assert (dt.format("[9`1Www]") == "111111Thu");
	assert (dt.format("[`1Wwww-10]") == "1Thursday-");
	assert (dt.format("[d/m/yyy           ]HH:ii:ss") == "8/9/2005   16:51:09");

	assert (dt.format("d Mmm yyy{ B}{ HH:ii:ss}") == "8 Sep 2005 16:51:09");
	assert (dt.format("{d }{Mmm }yyy BB") == "8 Sep 2005 AD");
	assert (dt.format("HH:ii{:ss}{.FFF}") == "16:51:09.427");

	assert (dt.format("HH:ii{:ss}{.FFF}") == "16:51:09.427");
	dt.fracSecs(dur!"msecs"(0));
	assert (dt.format("HH:ii{:ss}{.FFF}") == "16:51:09.000");
	dt.second = 0;
	assert (dt.format("HH:ii{:ss}{.FFF}") == "16:51:00.000");
	assert (dt.format("d Mmm yyy{ B}{ HH:ii:ss}") == "8 Sep 2005 16:51:00");
	dt.hour = 0;
	assert (dt.format("d Mmm yyy{ B}{ HH:ii:ss}") == "8 Sep 2005 00:51:00");
	dt.minute = 0;
	assert (dt.format("d Mmm yyy{ B}{ HH:ii:ss}") == "8 Sep 2005 00:00:00");
	assert (dt.format("{d }{Mmm }yyy BB") == "8 Sep 2005 AD");
	dt.month = Month.min;
	assert (dt.format("{d }{Mmm }yyy BB") == "8 Jan 2005 AD");
	dt.day = 1;
	assert (dt.format("{d }{Mmm }yyy BB") == "1 Jan 2005 AD");

  dt.month = Month.sep;
  dt.day = 8;

	// nesting of fields and collapsible portions
	assert (dt.format("[13 Mmmm [d..]]") == " September 8.");
	assert (dt.format("[13 Mmmm{ d}]") == "  September 8");
	dt.day = 1;
	assert (dt.format("[13 Mmmm{ d}]") == "  September 1");
	assert (dt.format("{[13 Mmmm{ d}]}") == "  September 1");
	dt.month = Month.min;
	assert (dt.format("{[13 Mmmm{ d}]}") == "    January 1");
	dt.day = 8;
	assert (dt.format("{[13 Mmmm{ d}]}") == "    January 8");
}