compile.js

'use strict';

var esniff = require('esniff')

  , i, current, literals, substitutions, sOut, sEscape, sAhead, sIn, sInEscape, template;

sOut = function (char) {
	if (char === '\\') return sEscape;
	if (char === '$') return sAhead;
	current += char;
	return sOut;
};
sEscape = function (char) {
	if ((char !== '\\') && (char !== '$')) current += '\\';
	current += char;
	return sOut;
};
sAhead = function (char) {
	if (char === '{') {
		literals.push(current);
		current = '';
		return sIn;
	}
	if (char === '$') {
		current += '$';
		return sAhead;
	}
	current += '$' + char;
	return sOut;
};
sIn = function (char) {
	var code = template.slice(i), end;
	esniff(code, '}', function (j) {
		if (esniff.nest >= 0) return esniff.next();
		end = j;
	});
	if (end != null) {
		substitutions.push(template.slice(i, i + end));
		i += end;
		current = '';
		return sOut;
	}
	end = code.length;
	i += end;
	current += code;
	return sIn;
};
sInEscape = function (char) {
	if ((char !== '\\') && (char !== '}')) current += '\\';
	current += char;
	return sIn;
};

module.exports = function (str) {
	var length, state, result;
	current = '';
	literals = [];
	substitutions = [];

	template = String(str);
	length = template.length;

	state = sOut;
	for (i = 0; i < length; ++i) state = state(template[i]);
	if (state === sOut) {
		literals.push(current);
	} else if (state === sEscape) {
		literals.push(current + '\\');
	} else if (state === sAhead) {
		literals.push(current + '$');
	} else if (state === sIn) {
		literals[literals.length - 1] += '${' + current;
	} else if (state === sInEscape) {
		literals[literals.length - 1] += '${' + current + '\\';
	}
	result = { literals: literals, substitutions: substitutions };
	literals = substitutions = null;
	return result;
};