feat(*): issue console warning/error if a single patterns expands beyond limits

applies to compose patterns and therefore to learn custom entities

Author: sanjayaksaxena

src/compose-patterns.js

@@ -110,13 +110,18 @@ var product = function ( a ) {
  * (if any) must be separated by a `|` character. The patterns are composed by
  * computing the cartesian product of all the phrases.
  *
+ * If a single patterns expands to a large size then it issues console
+ * warning/error at 512/65536 level.
+ *
  * @param {string} str the input string.
  * @return {string[]} of all possible patterns.
  * @private
 */
 var composePatterns = function ( str ) {
   if ( !str || ( typeof str !== 'string' ) ) return [];
 
+  const LIMIT1 = 512;
+  const LIMIT2 = 65536;
   var quotedTextElems = extractEnclosedText( str );
   var patterns = [];
   var finalPatterns = [];
@@ -126,6 +131,20 @@ var composePatterns = function ( str ) {
     patterns.push( e.split( '|' ) );
   } );
 
+  // Compute the size of the array that will be produced as a result of processing
+  // the pattern.
+  const size = patterns.reduce( ( ( prev, curr ) => prev * curr.length ), 1 );
+
+  // Issue warning/error if the size is prohibitively large from the end-user
+  // prespective. Note: while winkNLP can handle even larger sizes, it can
+  // still break down in the event of explosion!
+  if ( size > LIMIT1 && size < LIMIT2 ) {
+    console.warn( 'winkNLP: complex pattern detected, consider simplifying it!' );
+  } else if ( size > LIMIT2 ) console.error(
+                              'winkNLP: very complex pattern detected, please review and simplify.\n' +
+                              '         === It may slow down further execution! ===\n\n'
+                             );
+
   product( patterns ).forEach( function ( e ) {
     finalPatterns.push( e.join( ' ' ).trim().split( /\s+/ ) );
   } );

test/compose-patterns.specs.js

@@ -65,4 +65,14 @@ describe( 'composePatterns()', function () {
   it( 'should return [ [ \'text\' ] ] for input "text"', function () {
     expect( composePatterns( 'text' ) ).to.deep.equal( [ [ 'text' ] ] );
   } );
+
+  it( 'should issue warning when patterns > 512', function () {
+    const text = '[a|b|c|d] [a|b|c|d] [a|b|c|d] [a|b|c|d] [a|b|c|d]';
+    expect( composePatterns( text ).length ).to.equal( 1024 );
+  } );
+
+  it( 'should issue error when patterns > 65536', function () {
+    const text = '[a|b|c|d] [a|b|c|d] [a|b|c|d] [a|b|c|d] [a|b|c|d] [a|b|c|d] [a|b|c|d] [a|b|c|d] [a|b]';
+    expect( composePatterns( text ).length ).to.equal( 131072 );
+  } );
 } );