Check the structure of the input data.

src/check-structure.js

+var assert = require('assert');
+function checkType(obj, propName, typeName) {
+	var prop = obj[propName];
+	var actualTypeName = Array.isArray(prop) ? 'array' : typeof prop;
+	var msg = `"${propName}" must be of type: ${typeName}, but it is: ${actualTypeName} "${prop}".`;
+	assert(actualTypeName === typeName, msg);
+}
+module.exports = function (data) {
+	checkType(data, 'header', 'string');
+	checkType(data, 'footer', 'string');
+	checkType(data, 'blockHeader', 'string');
+	checkType(data, 'blockFooter', 'string');
+	checkType(data, 'hosts', 'array');
+	data.hosts.forEach(function (block) {
+		checkType(block, 'name', 'string');
+		checkType(block, 'items', 'array');
+		block.items.forEach(function (item) {
+			if (item.comment !== undefined) checkType(item, 'comment', 'string');
+			else {
+				checkType(item, 'ip', 'string');
+				if (item.domain !== undefined) checkType(item, 'domain', 'string');
+				else {
+					checkType(item, 'domains', 'array');
+					item.domains.forEach(function (domain) {
+						checkType({ domains: domain }, 'domains', 'string');
+					});
+				}
+			}
+		});
+	});
+};

src/generate.js

@@ -12,6 +12,7 @@ glob.sync(path.join(process.argv[2], '*.yml')).forEach(function(specFile) {
 		data.hosts = specData.hosts.concat(data.hosts);
 		specSuffix = `-${specName}`;
 	}
+	require('./check-structure')(data);
 	glob.sync(path.join(__dirname, 'generators/*.js')).forEach(function (genFile) {
 		var generator = require(genFile);
 		var outputPath = path.parse(path.join(process.argv[4], generator.fileName));