Move to separate file and add id check

lib/node_modules/@stdlib/_tools/links/validate/README.md

@@ -18,7 +18,7 @@ limitations under the License.
 
 -->
 
-# validate
+# validateLinks
 
 > Validate an array of link objects.
 

lib/node_modules/@stdlib/_tools/links/validate/lib/async.js

@@ -28,6 +28,7 @@ var format = require( '@stdlib/string/format' );
 var cwd = require( '@stdlib/process/cwd' );
 var config = require( './defaults.js' );
 var validate = require( './validate.js' );
+var check = require( './check.js' );
 
 
 // MAIN //
@@ -98,35 +99,11 @@ function validateLinks( links, options, clbk ) {
 	* @returns {void}
 	*/
 	function onRead( error, db ) {
-		var link;
 		var out;
-		var url;
-		var id;
-		var i;
 		if ( error ) {
 			return cb( error );
 		}
-		out = [];
-		for ( i = 0; i < links.length; i++ ) {
-			link = links[ i ];
-			url = link.url;
-			id = link.id;
-			if ( !db[ url ] ) {
-				out.push({
-					'error': 'Entry not found in database',
-					'id': id,
-					'url': url
-				});
-			}
-			else if ( db[ url ].id !== id ) {
-				out.push({
-					'error': 'Mismatched link identifier',
-					'id': id,
-					'url': url,
-					'expected': db[ url ].id
-				});
-			}
-		}
+		out = check( links, db );
 		cb( null, out );
 	}
 }

lib/node_modules/@stdlib/_tools/links/validate/lib/check.js

@@ -0,0 +1,103 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2022 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MODULES //
+
+var objectEntries = require( '@stdlib/utils/entries' );
+
+
+// VARIABLES //
+
+var idToUrl = null;
+
+
+// FUNCTIONS //
+
+/**
+* Creates a mapping from link identifiers to link URLs and stores the mapping in  variable `idToUrl`.
+*
+* @private
+* @param {Object} db - link database mapping link URLs to metadata
+*/
+function createIdToUrl( db ) {
+	var entries;
+	var i;
+
+	idToUrl = {};
+	entries = objectEntries( db );
+	for ( i = 0; i < entries.length; i++ ) {
+		idToUrl[ entries[ i ][ 1 ].id ] = entries[ i ][ 0 ];
+	}
+}
+
+
+// MAIN //
+
+/**
+* Validates an array of link objects against a link database.
+*
+* @private
+* @param {ObjectArray} links - array of link objects to validate
+* @param {Object} db - link database mapping link URLs to metadata
+* @returns {ObjectArray} array of validation errors
+*/
+function check( links, db ) {
+	var link;
+	var out;
+	var msg;
+	var url;
+	var id;
+	var i;
+
+	out = [];
+	for ( i = 0; i < links.length; i++ ) {
+		link = links[ i ];
+		url = link.url;
+		id = link.id;
+		if ( !db[ url ] ) {
+			if ( !idToUrl ) {
+				createIdToUrl( db );
+			}
+			msg = 'Entry not found in database';
+			if ( idToUrl[ id ] ) {
+				msg += '. Did you mean to use URL `'+idToUrl[ id ]+'`?';
+			}
+			out.push({
+				'error': msg,
+				'id': id,
+				'url': url
+			});
+		}
+		else if ( db[ url ].id !== id ) {
+			out.push({
+				'error': 'Mismatched link identifier',
+				'id': id,
+				'url': url,
+				'expected': db[ url ].id
+			});
+		}
+	}
+	return out;
+}
+
+
+// EXPORTS //
+
+module.exports = check;

lib/node_modules/@stdlib/_tools/links/validate/lib/sync.js

@@ -28,6 +28,7 @@ var format = require( '@stdlib/string/format' );
 var cwd = require( '@stdlib/process/cwd' );
 var config = require( './defaults.js' );
 var validate = require( './validate.js' );
+var check = require( './check.js' );
 
 
 // MAIN //
@@ -55,13 +56,9 @@ var validate = require( './validate.js' );
 function validateLinks( links, options ) {
 	var fopts;
 	var opts;
-	var link;
-	var url;
 	var err;
 	var out;
 	var db;
-	var id;
-	var i;
 	if ( !isObjectArray( links ) ) {
 		throw new TypeError( format( 'invalid argument. First argument must be an array of objects. Value: `%s`.', links ) );
 	}
@@ -82,27 +79,7 @@ function validateLinks( links, options ) {
 	if ( instanceOf( db, Error ) ) {
 		return db;
 	}
-	out = [];
-	for ( i = 0; i < links.length; i++ ) {
-		link = links[ i ];
-		url = link.url;
-		id = link.id;
-		if ( !db[ url ] ) {
-			out.push({
-				'message': 'Entry not found in database',
-				'id': id,
-				'url': url
-			});
-		}
-		else if ( db[ url ].id !== id ) {
-			out.push({
-				'message': 'Mismatched link identifier',
-				'id': id,
-				'url': url,
-				'expected': db[ url ].id
-			});
-		}
-	}
+	out = check( links, db );
 	return out;
 }