From 8772ab410f191bd35d7d7d3df5cd0cfd00ab524e Mon Sep 17 00:00:00 2001
From: Ryan Smith <0ryansmith1994@gmail.com>
Date: Sat, 20 Jun 2020 19:23:32 +0100
Subject: [PATCH] feat: Exposes isMongoId guard

---
 src/constrainedStrings/mongoId/mongoId.ts | 23 +++++++++++------------
 src/constrainedStrings/mongoId/readme.md  |  2 +-
 src/lib.ts                                |  7 ++++++-
 3 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/src/constrainedStrings/mongoId/mongoId.ts b/src/constrainedStrings/mongoId/mongoId.ts
index ab5cbfc2d..d5141834b 100644
--- a/src/constrainedStrings/mongoId/mongoId.ts
+++ b/src/constrainedStrings/mongoId/mongoId.ts
@@ -1,7 +1,7 @@
 import { BaseError } from 'make-error'
 import validator from 'validator'
-import { string } from '../../valueRules/string/string'
-import { constrain, Static } from '../../core'
+import { isString } from '../../valueRules/string/string'
+import { Constrained } from '../../core'
 
 export class InvalidMongoIdError extends BaseError {
 	constructor() {
@@ -11,16 +11,15 @@ export class InvalidMongoIdError extends BaseError {
 
 export const mongoIdSymbol = Symbol()
 
+export type MongoId = Constrained<typeof mongoIdSymbol, string>
+
+export function isMongoId(input: unknown): input is MongoId {
+	return isString(input) && validator.isMongoId(input)
+}
+
 export function mongoId(input: unknown) {
-	try {
-		const stringInput = string(input)
-		if (validator.isMongoId(stringInput)) {
-			return constrain(mongoIdSymbol, stringInput)
-		}
-		throw new Error()
-	} catch (err) {
-		throw new InvalidMongoIdError()
+	if (isMongoId(input)) {
+		return input
 	}
+	throw new InvalidMongoIdError()
 }
-
-export type MongoId = Static<typeof mongoId>
diff --git a/src/constrainedStrings/mongoId/readme.md b/src/constrainedStrings/mongoId/readme.md
index 047c4fe7a..0c3ec9f5b 100644
--- a/src/constrainedStrings/mongoId/readme.md
+++ b/src/constrainedStrings/mongoId/readme.md
@@ -2,7 +2,7 @@
 
 [Back to root readme.md](../../../readme.md)
 
-This function can be used to check the type of the input is a valid mongoId as shown in the example below. It should only throw `rulr.InvalidMongoIdError`. This function uses [the much loved validator package](https://github.com/validatorjs/validator.js).
+This function uses `rulr.isMongoId` to check the input is a valid mongoId as shown in the example below. It should only throw `rulr.InvalidMongoIdError`. This function uses [the much loved validator package](https://github.com/validatorjs/validator.js).
 
 ```ts
 import * as rulr from 'rulr'
diff --git a/src/lib.ts b/src/lib.ts
index 15bdecfbc..a505030a7 100644
--- a/src/lib.ts
+++ b/src/lib.ts
@@ -38,7 +38,12 @@ export {
 	MimeType,
 	InvalidMimeTypeError,
 } from './constrainedStrings/mimeType/mimeType'
-export { mongoId, MongoId, InvalidMongoIdError } from './constrainedStrings/mongoId/mongoId'
+export {
+	mongoId,
+	isMongoId,
+	MongoId,
+	InvalidMongoIdError,
+} from './constrainedStrings/mongoId/mongoId'
 export {
 	scormInteractionType,
 	ScormInteractionType,