// Single Date Formatting
// -------------------------------------------------------------------------------------------------


// call this if you want Moment's original format method to be used
function momentFormat(mom, formatStr) {
	return moment.fn.format.call(mom, formatStr);
}


// Formats `date` with a Moment formatting string, but allow our non-zero areas and
// additional token.
function formatDate(date, formatStr) {
	return formatDateWithChunks(date, getFormatStringChunks(formatStr));
}


function formatDateWithChunks(date, chunks) {
	var s = '';
	var i;

	for (i=0; i<chunks.length; i++) {
		s += formatDateWithChunk(date, chunks[i]);
	}

	return s;
}


// addition formatting tokens we want recognized
var tokenOverrides = {
	t: function(date) { // "a" or "p"
		return momentFormat(date, 'a').charAt(0);
	},
	T: function(date) { // "A" or "P"
		return momentFormat(date, 'A').charAt(0);
	}
};


function formatDateWithChunk(date, chunk) {
	var token;
	var maybeStr;

	if (typeof chunk === 'string') { // a literal string
		return chunk;
	}
	else if ((token = chunk.token)) { // a token, like "YYYY"
		if (tokenOverrides[token]) {
			return tokenOverrides[token](date); // use our custom token
		}
		return momentFormat(date, token);
	}
	else if (chunk.maybe) { // a grouping of other chunks that must be non-zero
		maybeStr = formatDateWithChunks(date, chunk.maybe);
		if (maybeStr.match(/[1-9]/)) {
			return maybeStr;
		}
	}

	return '';
}


// Date Range Formatting
// -------------------------------------------------------------------------------------------------
// TODO: make it work with timezone offset

// Using a formatting string meant for a single date, generate a range string, like
// "Sep 2 - 9 2013", that intelligently inserts a separator where the dates differ.
// If the dates are the same as far as the format string is concerned, just return a single
// rendering of one date, without any separator.
function formatRange(date1, date2, formatStr, separator, isRTL) {

	// Expand localized format strings, like "LL" -> "MMMM D YYYY"
	formatStr = date1.lang().longDateFormat(formatStr) || formatStr;
	// BTW, this is not important for `formatDate` because it is impossible to put custom tokens
	// or non-zero areas in Moment's localized format strings.

	separator = separator || ' - ';

	return formatRangeWithChunks(
		date1,
		date2,
		getFormatStringChunks(formatStr),
		separator,
		isRTL
	);
}
fc.formatRange = formatRange; // expose


function formatRangeWithChunks(date1, date2, chunks, separator, isRTL) {
	var chunkStr; // the rendering of the chunk
	var leftI;
	var leftStr = '';
	var rightI;
	var rightStr = '';
	var middleI;
	var middleStr1 = '';
	var middleStr2 = '';
	var middleStr = '';

	// Start at the leftmost side of the formatting string and continue until you hit a token
	// that is not the same between dates.
	for (leftI=0; leftI<chunks.length; leftI++) {
		chunkStr = formatSimilarChunk(date1, date2, chunks[leftI]);
		if (chunkStr === false) {
			break;
		}
		leftStr += chunkStr;
	}

	// Similarly, start at the rightmost side of the formatting string and move left
	for (rightI=chunks.length-1; rightI>leftI; rightI--) {
		chunkStr = formatSimilarChunk(date1, date2, chunks[rightI]);
		if (chunkStr === false) {
			break;
		}
		rightStr = chunkStr + rightStr;
	}

	// The area in the middle is different for both of the dates.
	// Collect them distinctly so we can jam them together later.
	for (middleI=leftI; middleI<=rightI; middleI++) {
		middleStr1 += formatDateWithChunk(date1, chunks[middleI]);
		middleStr2 += formatDateWithChunk(date2, chunks[middleI]);
	}

	if (middleStr1 || middleStr2) {
		if (isRTL) {
			middleStr = middleStr2 + separator + middleStr1;
		}
		else {
			middleStr = middleStr1 + separator + middleStr2;
		}
	}

	return leftStr + middleStr + rightStr;
}


var similarUnitMap = {
	Y: 'year',
	M: 'month',
	D: 'day', // day of month
	d: 'day' // day of week
};
// don't go any further than day, because we don't want to break apart times like "12:30:00"
// TODO: week maybe?


// Given a formatting chunk, and given that both dates are similar in the regard the
// formatting chunk is concerned, format date1 against `chunk`. Otherwise, return `false`.
function formatSimilarChunk(date1, date2, chunk) {
	var token;
	var unit;

	if (typeof chunk === 'string') { // a literal string
		return chunk;
	}
	else if ((token = chunk.token)) {
		unit = similarUnitMap[token.charAt(0)];
		// are the dates the same for this unit of measurement?
		if (unit && date1.isSame(date2, unit)) {
			return momentFormat(date1, token); // would be the same if we used `date2`
			// BTW, don't support custom tokens
		}
	}

	return false; // the chunk is NOT the same for the two dates
	// BTW, don't support splitting on non-zero areas
}


// Chunking Utils
// -------------------------------------------------------------------------------------------------


var formatStringChunkCache = {};


function getFormatStringChunks(formatStr) {
	if (formatStr in formatStringChunkCache) {
		return formatStringChunkCache[formatStr];
	}
	return (formatStringChunkCache[formatStr] = chunkFormatString(formatStr));
}


// Break the formatting string into an array of chunks
function chunkFormatString(formatStr) {
	var chunks = [];
	var chunker = /\[([^\]]*)\]|\(([^\)]*)\)|((\w)\4*o?T?)|([^\w\[\(]+)/g; // TODO: more descrimination
	var match;

	while ((match = chunker.exec(formatStr))) {
		if (match[1]) { // a literal string inside [ ... ]
			chunks.push(match[1]);
		}
		else if (match[2]) { // non-zero formatting inside ( ... )
			chunks.push({ maybe: chunkFormatString(match[2]) });
		}
		else if (match[3]) { // a formatting token
			chunks.push({ token: match[3] });
		}
		else if (match[5]) { // an unenclosed literal string
			chunks.push(match[5]);
		}
	}

	return chunks;
}