add lib

Author: azu

Diff for: .gitignore

@@ -82,7 +82,6 @@ crashlytics.properties
 crashlytics-build.properties
 
 
-/lib
 ### https://raw.github.com/github/gitignore/608690d6b9a78c2a003affc792e49a84905b3118/Node.gitignore
 
 # Logs

Diff for: lib/can-npm-publish.js

@@ -0,0 +1,58 @@
+// MIT © 2018 azu
+"use strict";
+const fetch = require("node-fetch");
+const readPkg = require("read-pkg");
+/**
+ * Return rejected promise if the package is not `private:true`
+ * @param packagePath
+ * @returns {Promise}
+ */
+const checkPrivateField = packagePath => {
+    return readPkg(packagePath).then(pkg => {
+        if (pkg["private"] === true) {
+            return Promise.reject(new Error("This package is private."));
+        }
+    });
+};
+
+const checkAlreadyPublish = packagePath => {
+    return readPkg(packagePath).then(pkg => {
+        const name = pkg["name"];
+        const version = pkg["version"];
+        if (name === undefined) {
+            return Promise.reject(new Error("This package has not `name`."));
+        }
+        if (version === undefined) {
+            return Promise.reject(new Error("This package has not `version`."));
+        }
+        // https://github.com/npm/registry/blob/master/docs/REGISTRY-API.md#getpackageversion
+        return fetch(`https://registry.npmjs.com/${encodeURIComponent(name)}`)
+            .then(response => {
+                if (response.status === 404) {
+                    // not published yet
+                    return {
+                        versions: []
+                    };
+                }
+                if (!response.ok) {
+                    return Promise.reject(new Error(response.statusText));
+                }
+                return response.json();
+            })
+            .then(json => {
+                if (json.error) {
+                    // {"error":"version not found: 18.0.0"}
+                    return Promise.reject(new Error(json.error));
+                }
+                const versions = json["versions"];
+                if (versions[version]) {
+                    return Promise.reject(new Error(`${name}@${versions} is already published`));
+                }
+                return;
+            });
+    });
+};
+const canNpmPublish = packagePath => {
+    return Promise.all([checkAlreadyPublish(packagePath), checkPrivateField(packagePath)]);
+};
+module.exports.canNpmPublish = canNpmPublish;