--- /dev/null
+// try to find the most reasonable prefix to use
+
+module.exports = findPrefix
+
+var fs = require("fs")
+var path = require("path")
+
+function findPrefix (p, cb_) {
+ function cb (er, p) {
+ process.nextTick(function () {
+ cb_(er, p)
+ })
+ }
+
+ p = path.resolve(p)
+ // if there's no node_modules folder, then
+ // walk up until we hopefully find one.
+ // if none anywhere, then use cwd.
+ var walkedUp = false
+ while (path.basename(p) === "node_modules") {
+ p = path.dirname(p)
+ walkedUp = true
+ }
+ if (walkedUp) return cb(null, p)
+
+ findPrefix_(p, p, cb)
+}
+
+function findPrefix_ (p, original, cb) {
+ if (p === "/"
+ || (process.platform === "win32" && p.match(/^[a-zA-Z]:(\\|\/)?$/))) {
+ return cb(null, original)
+ }
+ fs.readdir(p, function (er, files) {
+ // an error right away is a bad sign.
+ // unless the prefix was simply a non
+ // existent directory.
+ if (er && p === original) {
+ if (er.code === "ENOENT") return cb(null, original);
+ return cb(er)
+ }
+
+ // walked up too high or something.
+ if (er) return cb(null, original)
+
+ if (files.indexOf("node_modules") !== -1
+ || files.indexOf("package.json") !== -1) {
+ return cb(null, p)
+ }
+
+ var d = path.dirname(p)
+ if (d === p) return cb(null, original)
+
+ return findPrefix_(d, original, cb)
+ })
+}