Refactor: remove deep nest

lib/models/external-account.js

@@ -68,42 +68,38 @@ class ExternalAccount {
    * @returns {Promise<ExternalAccount>}
    * @memberof ExternalAccount
    */
-  static findOrRegister(providerType, accountId, usernameToBeRegistered) {
+  static async findOrRegister(providerType, accountId, usernameToBeRegistered) {
 
-    return this.findOne({ providerType, accountId })
-      .then((account) => {
-        // found
-        if (account != null) {
-          debug(`ExternalAccount '${accountId}' is found `, account);
-          return account;
-        }
-        // not found
-        else {
-          const User = ExternalAccount.crowi.model('User');
-
-          return User.find({username: usernameToBeRegistered})
-            .then(users => {
-              // throw Exception when count is not zero
-              if (users.length > 1) {
-                throw new DuplicatedUsernameException(`username '${usernameToBeRegistered}' has already been existed`);
-              }
-              else if (users.length === 0) {
-                debug(`ExternalAccount '${accountId}' is not found, it is going to be registered.`);
-                // create user with STATUS_ACTIVE
-                return User.createUser('', usernameToBeRegistered, undefined, undefined, undefined, User.STATUS_ACTIVE);
-              }
-              else {
-                debug(`ExternalAccount '${accountId}' will be linked to an exisiting account`);
-                return users[0];
-              }
-
-            })
-            .then((user) => {
-              return this.create({ providerType: 'ldap', accountId, user: user._id });
-            });
-        }
-      });
+    const account = await this.findOne({ providerType, accountId })
+    // found
+    if (account != null) {
+      debug(`ExternalAccount '${accountId}' is found `, account);
+      return account;
+    }
+
+    const User = ExternalAccount.crowi.model('User');
+    const treatExternalUserAsLocalUser = false; // TODO: fetch from config model
+
+    const users = await User.find({username: usernameToBeRegistered})
+
+    // throw Exception when count is not zero
+    const maxDuplicateUserCount = treatExternalUserAsLocalUser ? 1 : 0;
+    if (users.length > maxDuplicateUserCount) {
+      throw new DuplicatedUsernameException(`username '${usernameToBeRegistered}' has already been existed`);
+    }
+
+    let newUser;
+    if (users.length === 0) {
+      debug(`ExternalAccount '${accountId}' is not found, it is going to be registered.`);
+      // create user with STATUS_ACTIVE
+      newUser = await User.createUser('', usernameToBeRegistered, undefined, undefined, undefined, User.STATUS_ACTIVE);
+    }
+    else {
+      debug(`ExternalAccount '${accountId}' will be linked to an exisiting account`);
+      newUser = users[0];
+    }
 
+    return this.create({ providerType: 'ldap', accountId, user: newUser._id });
   }
 
   /**