1 files changed, 35 insertions, 1 deletions
diff --git a/lib/utils/fs.js b/lib/utils/fs.js
index 42fd3c6..3f97096 100644
--- a/lib/utils/fs.js
+++ b/lib/utils/fs.js
@@ -97,12 +97,46 @@ function rmDir(base) {
     });
 }
 
+/**
+    Assert a file, if it doesn't exist, call "generator"
+
+    @param {String} filePath
+    @param {Function} generator
+    @return {Promise}
+*/
+function assertFile(filePath, generator) {
+    return fileExists(filePath)
+    .then(function(exists) {
+        if (exists) return;
+
+        return generator();
+    });
+}
+
+/**
+    Pick a file, returns the absolute path if exists, undefined otherwise
+
+    @param {String} rootFolder
+    @param {String} fileName
+    @return {String}
+*/
+function pickFile(rootFolder, fileName) {
+    var result = path.join(rootFolder, fileName);
+    if (fs.existsSync(result)) {
+        return result;
+    }
+
+    return undefined;
+}
+
 module.exports = {
     exists: fileExists,
     existsSync: fs.existsSync,
     mkdirp: Promise.nfbind(mkdirp),
     readFile: Promise.nfbind(fs.readFile),
     writeFile: Promise.nfbind(fs.writeFile),
+    assertFile: assertFile,
+    pickFile: pickFile,
     stat: Promise.nfbind(fs.stat),
     statSync: fs.statSync,
     readdir: Promise.nfbind(fs.readdir),
@@ -113,6 +147,6 @@ module.exports = {
     tmpDir: genTmpDir,
     download: download,
     uniqueFilename: uniqueFilename,
-    ensure: ensureFile,
+    ensureFile: ensureFile,
     rmDir: rmDir
 };