function write_zip_type(wb/*:Workbook*/, opts/*:?WriteOpts*/) {
	var o = opts||{};
	var z = write_zip(wb, o);
	var oopts = {};
	if(o.compression) oopts.compression = 'DEFLATE';
	switch(o.type) {
		case "base64": oopts.type = "base64"; break;
		case "binary": oopts.type = "string"; break;
		case "buffer":
		case "file": oopts.type = "nodebuffer"; break;
		default: throw new Error("Unrecognized type " + o.type);
	}
	if(o.type === "file") return _fs.writeFileSync(o.file, z.generate(oopts));
	return z.generate(oopts);
}

/* TODO: test consistency */
function write_bstr_type(out/*:string*/, opts/*:WriteOpts*/) {
	switch(opts.type) {
		case "base64": return Base64.encode(out);
		case "binary": return out;
		case "file": return _fs.writeFileSync(opts.file, out, 'binary');
		case "buffer": {
			if(has_buf) return new Buffer(out, 'binary');
			else return out.split("").map(function(c) { return c.charCodeAt(0); });
		}
	}
	throw new Error("Unrecognized type " + opts.type);
}

/* TODO: test consistency */
function write_string_type(out/*:string*/, opts/*:WriteOpts*/) {
	switch(opts.type) {
		case "base64": return Base64.encode(out);
		case "binary": return out;
		case "file": return _fs.writeFileSync(opts.file, out, 'utf8');
		case "buffer": {
			if(has_buf) return new Buffer(out, 'utf8');
			else return out.split("").map(function(c) { return c.charCodeAt(0); });
		}
	}
	throw new Error("Unrecognized type " + opts.type);
}

/* TODO: test consistency */
function write_binary_type(out, opts/*:WriteOpts*/) {
	switch(opts.type) {
		case "base64":
		case "binary":
			var bstr = "";
			for(var i = 0; i < out.length; ++i) bstr += String.fromCharCode(out[i]);
			return opts.type == 'base64' ? Base64.encode(bstr) : bstr;
		case "file": return _fs.writeFileSync(opts.file, out);
		case "buffer": return out;
		default: throw new Error("Unrecognized type " + opts.type);
	}
}

function writeSync(wb/*:Workbook*/, opts/*:?WriteOpts*/) {
	check_wb(wb);
	var o = opts||{};
	switch(o.bookType || 'xlsb') {
		case 'xml':
		case 'xlml': return write_string_type(write_xlml(wb, o), o);
		case 'slk':
		case 'sylk': return write_string_type(write_slk_str(wb, o), o);
		case 'html': return write_string_type(write_htm_str(wb, o), o);
		case 'txt': return write_bstr_type(write_txt_str(wb, o), o);
		case 'csv': return write_string_type(write_csv_str(wb, o), o);
		case 'dif': return write_string_type(write_dif_str(wb, o), o);
		case 'prn': return write_string_type(write_prn_str(wb, o), o);
		case 'fods': return write_string_type(write_ods(wb, o), o);
		case 'biff2': return write_binary_type(write_biff_buf(wb, o), o);
		case 'xlsx':
		case 'xlsm':
		case 'xlsb':
		case 'ods': return write_zip_type(wb, o);
		default: throw new Error ("Unrecognized bookType |" + o.bookType + "|");
	}
}

function resolve_book_type(o/*?WriteFileOpts*/) {
	if(!o.bookType) switch(o.file.slice(o.file.lastIndexOf(".")).toLowerCase()) {
		case '.xlsx': o.bookType = 'xlsx'; break;
		case '.xlsm': o.bookType = 'xlsm'; break;
		case '.xlsb': o.bookType = 'xlsb'; break;
		case '.fods': o.bookType = 'fods'; break;
		case '.xlml': o.bookType = 'xlml'; break;
		case '.sylk': o.bookType = 'sylk'; break;
		case '.html': o.bookType = 'html'; break;
		case '.xls': o.bookType = 'biff2'; break;
		case '.xml': o.bookType = 'xml'; break;
		case '.ods': o.bookType = 'ods'; break;
		case '.csv': o.bookType = 'csv'; break;
		case '.txt': o.bookType = 'txt'; break;
		case '.dif': o.bookType = 'dif'; break;
		case '.prn': o.bookType = 'prn'; break;
		case '.slk': o.bookType = 'sylk'; break;
		case '.htm': o.bookType = 'html'; break;
	}
}

function writeFileSync(wb/*:Workbook*/, filename/*:string*/, opts/*:?WriteFileOpts*/) {
	var o = opts||{}; o.type = 'file';
	o.file = filename;
	resolve_book_type(o);
	return writeSync(wb, o);
}

function writeFileAsync(filename/*:string*/, wb/*:Workbook*/, opts/*:?WriteFileOpts*/, cb/*:?(e?:ErrnoError)=>void*/) {
	var o = opts||{}; o.type = 'file';
	o.file = filename;
	resolve_book_type(o);
	o.type = 'buffer';
	var _cb = cb; if(!(_cb instanceof Function)) _cb = (opts/*:any*/);
	return _fs.writeFile(filename, writeSync(wb, o), _cb);
}