fix(converter): add support of the server's URL template

closes #37

src/converter.js

@@ -38,6 +38,8 @@ const {
 } = require('./utils')
 const { BOUNDARY, BASE64_PATTERN } = require('./common')
 
+const REGEX_EXTRACT_VARS = /{([^{}]*?)}/g
+
 /**
  * Create HAR Request object for path and method pair described in given swagger.
  *
@@ -154,15 +156,45 @@ const getPayload = (swagger, path, method) => {
  * @returns {string[]}
  */
 const parseUrls = (swagger) => {
-  if (!Array.isArray(swagger.servers)) {
+  if (Array.isArray(swagger.servers) && swagger.servers.length) {
+    return swagger.servers.map((server) => {
+      const variables = server.variables || {}
+
+      let urlString = removeTrailingSlash(server.url)
+      let substitutions = 0
+      let replacements = 0
+
+      do {
+        urlString = urlString.replace(REGEX_EXTRACT_VARS, (match, token) => {
+          replacements += 1
+
+          const variable = variables[token]
+
+          if (!variable || !variable.default) {
+            return match
+          }
+
+          return variable.default
+        })
+
+        if (replacements) {
+          substitutions += 1
+        }
+      } while (replacements && substitutions < 30)
+
+      return urlString
+    })
+  }
+
+  if (swagger.host) {
     const basePath =
       typeof swagger.basePath !== 'undefined' ? removeLeadingSlash(swagger.basePath) : ''
     const host = removeTrailingSlash(swagger.host)
     const schemes = typeof swagger.schemes !== 'undefined' ? swagger.schemes : ['https']
     return schemes.map((x) => x + '://' + removeTrailingSlash(host + '/' + basePath))
   }
 
-  return swagger.servers.map((server) => removeTrailingSlash(server.url))
+  return []
 }
 
 /**
@@ -174,6 +206,10 @@ const parseUrls = (swagger) => {
 const getBaseUrl = (swagger) => {
   const urls = parseUrls(swagger)
 
+  if (!Array.isArray(urls) || !urls.length) {
+    throw new Error('None server or host is defined.')
+  }
+
   let preferredUrls = urls.filter((x) => x.startsWith('https') || x.startsWith('wss'))
 
   if (!preferredUrls.length) {