supporting multiple stripPrefix & replacePrefix entries via stripPref…

…ixMulti (#138)

* treat stripPrefix as an array to support environments that rewrite paths to another directory (i.e. server sends foo/file.txt for requests to bar/file.txt, as well as caching bar/other-file.txt)

* switching from array to map prefix/replace pairs, with documentation

* seems to be working as expected now, removing the conditional check

* satisfying eslint

README.md

@@ -442,6 +442,20 @@ URL.
 
 _Default_: `''`
 
+#### stripPrefixMulti [Object]
+Maps mutliple strings to be stripped & replaced from the beginning of path URL's at runtime.
+Use this option when you have multiple discrepancies between relative paths at build time and
+the same path at run time.
+If stripPrefix and replacePrefix are not equal to `''`, they are automatically added to this option.
+```js
+stripPrefixMulti: {
+  'www-root/public-precached/': 'public/',
+  'www-root/public/': 'public/'
+}
+```
+
+_Default_: `{}`
+
 #### templateFilePath [String]
 
 The path to the  ([lo-dash](https://lodash.com/docs#template)) template used to

lib/sw-precache.js

@@ -89,6 +89,7 @@ function generate(params, callback) {
       navigateFallback: '',
       navigateFallbackWhitelist: [],
       stripPrefix: '',
+      stripPrefixMulti: {},
       replacePrefix: '',
       staticFileGlobs: [],
       templateFilePath: path.join(
@@ -102,6 +103,7 @@ function generate(params, callback) {
 
     var relativeUrlToHash = {};
     var cumulativeSize = 0;
+    params.stripPrefixMulti[params.stripPrefix] = params.replacePrefix;
 
     params.staticFileGlobs.forEach(function(globPattern) {
       var filesAndSizesAndHashes = getFilesAndSizesAndHashesForGlobPattern(
@@ -113,8 +115,10 @@ function generate(params, callback) {
           // Strip the prefix to turn this into a relative URL.
           var relativeUrl = fileAndSizeAndHash.file
             .replace(
-              new RegExp('^' + escapeRegExp(params.stripPrefix)),
-              params.replacePrefix)
+              new RegExp('^(' + Object.keys(params.stripPrefixMulti).map(escapeRegExp).join('|') + ')'),
+              function(match) {
+                return params.stripPrefixMulti[match];
+              })
             .replace(path.sep, '/');
           relativeUrlToHash[relativeUrl] = fileAndSizeAndHash.hash;