var _chr = function(c) { return String.fromCharCode(c); };

function encode_col(col) { var s=""; for(++col; col; col=Math.floor((col-1)/26)) s = _chr(((col-1)%26) + 65) + s; return s; }
function encode_row(row) { return "" + (row + 1); }
function encode_cell(cell) { return encode_col(cell.c) + encode_row(cell.r); }

function decode_col(c) { var d = 0, i = 0; for(; i !== c.length; ++i) d = 26*d + c.charCodeAt(i) - 64; return d - 1; }
function decode_row(rowstr) { return Number(rowstr) - 1; }
function split_cell(cstr) { return cstr.replace(/(\$?[A-Z]*)(\$?[0-9]*)/,"$1,$2").split(","); }
function decode_cell(cstr) { var splt = split_cell(cstr); return { c:decode_col(splt[0]), r:decode_row(splt[1]) }; }
function decode_range(range) { var x =range.split(":").map(decode_cell); return {s:x[0],e:x[x.length-1]}; }
function encode_range(range) { return encode_cell(range.s) + ":" + encode_cell(range.e); }
/**
 * Convert a sheet into an array of objects where the column headers are keys.
 **/
function sheet_to_row_object_array(sheet){
	var val, rowObject, range, columnHeaders, emptyRow, C;
	var outSheet = [];
	if (sheet["!ref"]) {
		range = decode_range(sheet["!ref"]);

		columnHeaders = {};
		for (C = range.s.c; C <= range.e.c; ++C) {
			val = sheet[encode_cell({
				c: C,
				r: range.s.r
			})];
			if(val){
				switch(val.t) {
					case 's': case 'str': columnHeaders[C] = val.v; break;
					case 'n': columnHeaders[C] = val.v; break;
				}
			}
		}

		for (var R = range.s.r + 1; R <= range.e.r; ++R) {
			emptyRow = true;
			//Row number is recorded in the prototype
			//so that it doesn't appear when stringified.
			rowObject = Object.create({ __rowNum__ : R });
			for (C = range.s.c; C <= range.e.c; ++C) {
				val = sheet[encode_cell({
					c: C,
					r: R
				})];
				if(val !== undefined) switch(val.t){
					case 's': case 'str': case 'b': case 'n':
						if(val.v !== undefined) {
							rowObject[columnHeaders[C]] = val.v;
							emptyRow = false;
						}
						break;
					case 'e': break; /* throw */
					default: throw 'unrecognized type ' + val.t;
				}
			}
			if(!emptyRow) {
				outSheet.push(rowObject);
			}
		}
	}
	return outSheet;
}

function sheet_to_csv(sheet) {
	var stringify = function stringify(val) {
		switch(val.t){
			case 'n': return String(val.v);
			case 's': case 'str': return JSON.stringify(val.v);
			case 'b': return val.v ? "TRUE" : "FALSE";
			case 'e': return ""; /* throw out value in case of error */
			default: throw 'unrecognized type ' + val.t;
		}
	};
	var out = "";
	if(sheet["!ref"]) {
		var r = utils.decode_range(sheet["!ref"]);
		for(var R = r.s.r; R <= r.e.r; ++R) {
			var row = [];
			for(var C = r.s.c; C <= r.e.c; ++C) {
				var val = sheet[utils.encode_cell({c:C,r:R})];
				row.push(val ? stringify(val).replace(/\\r\\n/g,"\n").replace(/\\t/g,"\t").replace(/\\\\/g,"\\") : "");
			}
			out += row.join(",") + "\n";
		}
	}
	return out;
}

function get_formulae(ws) {
	var cmds = [];
	for(y in ws) if(y[0] !=='!' && ws.hasOwnProperty(y)) (function(y,x) {
		var val = "";
		if(x.f) val = x.f;
		else if(typeof x.v === 'number') val = x.v;
		else val = x.v;
		cmds.push(y + "=" + val);
	})(y,ws[y]);
	return cmds;
}

var utils = {
	encode_col: encode_col,
	encode_row: encode_row,
	encode_cell: encode_cell,
	encode_range: encode_range,
	decode_col: decode_col,
	decode_row: decode_row,
	split_cell: split_cell,
	decode_cell: decode_cell,
	decode_range: decode_range,
	sheet_to_csv: sheet_to_csv,
	get_formulae: get_formulae,
	sheet_to_row_object_array: sheet_to_row_object_array
};