Added an internal algorithm for fuzzy string matching

* This works similar to a regex matching "abc" as /a.*b.*c/ (ie. all characters of $needle need to be contained in $haystack in the correct order but not neccesarily consecutive). Additionaly some unicode equivalencies are handled.
* Changed a tiny helper function from ObjC to plain C

4 files changed, 179 insertions, 11 deletions

diff --git a/Source/SPStringAdditions.h b/Source/SPStringAdditions.h
index 3296326f..c6871e2a 100644
--- a/Source/SPStringAdditions.h
+++ b/Source/SPStringAdditions.h
@@ -81,4 +81,23 @@ static inline id NSMutableAttributedStringAttributeAtIndex(NSMutableAttributedSt
 
 - (CGFloat)levenshteinDistanceWithWord:(NSString *)stringB;
 
+/**
+ * Checks if the string other is contained in self on a per-character basis.
+ * In regex-speak that would mean "abc" is matched as /a.*b.*c/ (not anchored).
+ * This is a SEARCH function, NOT a MATCHING function! 
+ * Namely the following options will be applied when matching: 
+ *   NSCaseInsensitiveSearch|NSDiacriticInsensitiveSearch|NSDiacriticInsensitiveSearch
+ * Additionaly this method might match even when it should not.
+ *
+ * @param other      String to match against self
+ * @param submatches Pass the pointer to a variable that will be set to an NSArray *
+ *                   of NSNumber *s of NSRanges. This will only be the case if
+ *                   the method also returns YES. The variable will not be modified
+ *                   otherwise.
+ *                   Pass NULL if you don't care for the ranges.
+ *                   The object will be set to autorelase.
+ * @return YES if self contains all characters from other in the order given in other
+ * @warning This method is NOT thread-safe (probably), NOT constant-time and DOES NOT check binary equivalence
+ */
+- (BOOL)nonConsecutivelySearchString:(NSString *)other matchingRanges:(NSArray **)submatches;
 @end
diff --git a/Source/SPStringAdditions.m b/Source/SPStringAdditions.m
index 29b4144d..0c623af7 100644
--- a/Source/SPStringAdditions.m
+++ b/Source/SPStringAdditions.m
@@ -31,11 +31,7 @@
 #import "SPStringAdditions.h"
 #import "RegexKitLite.h"
 
-@interface NSString (PrivateAPI)
-
-- (NSInteger)_smallestOf:(NSInteger)a andOf:(NSInteger)b andOf:(NSInteger)c;
-
-@end
+static NSInteger _smallestOf(NSInteger a, NSInteger b, NSInteger c);
 
 @implementation NSString (SPStringAdditions)
 
@@ -426,9 +422,9 @@
 			cost = ([stringA characterAtIndex:i - 1] == [stringB characterAtIndex:j - 1]) ? 0 : 1;
 
 			d[j * n + i] = 
-			[self _smallestOf:d[(j - 1) * n + i] + 1 
-						andOf:d[j * n + i - 1] +  1
-						andOf:d[(j - 1) * n + i -1] + cost];
+			_smallestOf(d[(j - 1) * n + i] + 1,
+			            d[j * n + i - 1] +  1,
+			            d[(j - 1) * n + i -1] + cost);
 		}
 
 		distance = d[n * m - 1];
@@ -468,10 +464,95 @@
 	}
 }
 
+- (BOOL)nonConsecutivelySearchString:(NSString *)other matchingRanges:(NSArray **)submatches
+{
+	NSStringCompareOptions opts = NSCaseInsensitiveSearch|NSDiacriticInsensitiveSearch|NSWidthInsensitiveSearch;
+	BOOL recordMatches = (submatches != NULL); //for readability
+	NSRange selfRange = NSMakeRange(0, [self length]);
+	
+	//shortcut: * a longer string can never be contained in a shorter one.
+	//          * nil can never match in a string.
+	//          * an empty other can never match if self is non-empty
+	if(([other length] > [self length]) || (!other) || ([self length] && ![other length]))
+		return NO;
+	
+	//handle the simple case via the default algorithm
+	if ([self compare:other options:opts] == NSOrderedSame) {
+		if(recordMatches) {
+			*submatches = [NSArray arrayWithObject:[NSValue valueWithRange:selfRange]];
+		}
+		return YES;
+	}
+	
+	// for now let's save the overhead of NSArray and NSValues
+	NSRange *tmpMatchStore = recordMatches? calloc([other length], sizeof(NSRange)) : NULL;
+	__block NSUInteger matchCount = 0;
+	__block NSRange searchRange = selfRange;
+	
+	//this looks a bit silly but is basically Apples approach to handling multibyte charsets
+	void (^it)(NSString *,NSRange,NSRange,BOOL *) = ^(NSString *substring,NSRange substringRange,NSRange enclosingRange,BOOL *stop) {
+		//look for the current character of other in the remaining part of self
+		NSRange found = [self rangeOfString:substring options:opts range:searchRange];
+		if(found.location == NSNotFound) {
+			matchCount = 0; //reset match count to "no match"
+			*stop = YES;
+			return;
+		}
+		if(recordMatches)
+			tmpMatchStore[matchCount] = found;
+		matchCount++;
+		//move the next search past the current match
+		searchRange.location = found.location + found.length;
+		searchRange.length   = [self length] - searchRange.location;
+	};
+	
+	[other enumerateSubstringsInRange:NSMakeRange(0, [other length])
+							  options:NSStringEnumerationByComposedCharacterSequences
+						   usingBlock:it];
+	
+	if(matchCount && recordMatches) {
+		//we want to re-combine sub-matches that are actually consecutive
+		
+		//This algorithm uses a simple look-behind for merges:
+		//  Object 1 checks if it continues object 0. If so, 1 and 0 will merge
+		//  and be placed in the slot of 0 (slot 1 is now invalid).
+		//  Then object 2 checks if it continues object 0. If it does not, it is
+		//  placed in slot 1.
+		//  Object 3 then checks if it continues object 1 and so on...
+		NSUInteger mergeTarget = 0;
+		for (NSUInteger i = 1; i < matchCount; i++ ) {
+			NSRange prev = tmpMatchStore[mergeTarget];
+			NSRange this = tmpMatchStore[i];
+			//if the previous match ends right before this match begins we can merge them
+			if(prev.location + prev.length == this.location) {
+				NSRange mergedRange = NSMakeRange(prev.location, prev.length+this.length);
+				tmpMatchStore[mergeTarget] = mergedRange;
+			}
+			//otherwise we have to move on to the next and make ourselves the new base
+			else {
+				if(++mergeTarget != i)
+					tmpMatchStore[mergeTarget] = this;
+			}
+		}
+		
+		NSMutableArray *combinedArray = [NSMutableArray arrayWithCapacity:mergeTarget+1];
+		for (NSUInteger j = 0; j <= mergeTarget; j++) {
+			[combinedArray addObject:[NSValue valueWithRange:tmpMatchStore[j]]];
+		}
+		
+		*submatches = combinedArray;
+	}
+	
+	free(tmpMatchStore); // free(NULL) is safe as per OS X man page
+	return (matchCount > 0);
+}
+
+@end
+
 /**
  * Returns the minimum of a, b and c.
  */
-- (NSInteger)_smallestOf:(NSInteger)a andOf:(NSInteger)b andOf:(NSInteger)c
+static NSInteger _smallestOf(NSInteger a, NSInteger b, NSInteger c)
 {
 	NSInteger min = a;
 	
@@ -481,5 +562,3 @@
 
 	return min;
 }
-
-@end
diff --git a/UnitTests/SPStringAdditionsTests.h b/UnitTests/SPStringAdditionsTests.h
index d6854dbe..56b5c6f9 100644
--- a/UnitTests/SPStringAdditionsTests.h
+++ b/UnitTests/SPStringAdditionsTests.h
@@ -35,5 +35,6 @@
 - (void)testStringByRemovingCharactersInSet;
 - (void)testStringWithNewUUID;
 - (void)testCreateViewSyntaxPrettifier;
+- (void)testNonConsecutivelySearchStringMatchingRanges;
 
 @end
diff --git a/UnitTests/SPStringAdditionsTests.m b/UnitTests/SPStringAdditionsTests.m
index af22df77..f455066f 100644
--- a/UnitTests/SPStringAdditionsTests.m
+++ b/UnitTests/SPStringAdditionsTests.m
@@ -86,4 +86,73 @@
 	STAssertEqualObjects([actualSyntax description], [expectedSyntax description], @"Actual view syntax '%@' does not equal expected syntax '%@'", actualSyntax, expectedSyntax);
 }
 
+- (void)testNonConsecutivelySearchStringMatchingRanges
+{
+	//basic tests
+	{
+		NSArray *matches = nil;
+		STAssertTrue([@"" nonConsecutivelySearchString:@"" matchingRanges:&matches], @"Equality of empty strings");
+		STAssertTrue(([matches count] == 1) && NSEqualRanges(NSMakeRange(0, 0), [(NSValue *)[matches objectAtIndex:0] rangeValue]), @"Returned matches in empty string");
+	}
+	
+	{
+		NSArray *matches = (void *)0xdeadbeef;
+		STAssertFalse([@"" nonConsecutivelySearchString:@"R" matchingRanges:&matches], @"Inequality with empty left side");
+		STAssertTrue((matches == (void *)0xdeadbeef), @"out variable not touched by mismatch");
+	}
+	
+	STAssertFalse([@"L" nonConsecutivelySearchString:@"" matchingRanges:NULL], @"Inequality with empty right side");
+	
+	{
+		NSArray *matches = nil;
+		STAssertTrue([@"left" nonConsecutivelySearchString:@"le" matchingRanges:&matches], @"Anchored match left");
+		STAssertTrue(([matches count] == 1) && NSEqualRanges(NSMakeRange(0, 2), [(NSValue *)[matches objectAtIndex:0] rangeValue]), @"Returned matches in anchored left match");
+	}
+	
+	{
+		NSArray *matches = nil;
+		STAssertTrue([@"right" nonConsecutivelySearchString:@"ht" matchingRanges:&matches], @"Anchored match right");
+		STAssertTrue(([matches count] == 1) && NSEqualRanges(NSMakeRange(3, 2), [(NSValue *)[matches objectAtIndex:0] rangeValue]), @"Returned matches in anchroed right match");
+	}
+	
+	STAssertFalse([@"ht" nonConsecutivelySearchString:@"right" matchingRanges:NULL], @"Left and Right are not commutative");
+	
+	//real tests
+	{
+		NSArray *matches = nil;
+		STAssertTrue([@"... is not secure anymore!" nonConsecutivelySearchString:@"NSA"  matchingRanges:&matches], @"Non-consecutive match, ignoring case");
+		STAssertTrue(([matches count] == 3) &&
+					 (NSEqualRanges(NSMakeRange(7, 1), [(NSValue *)[matches objectAtIndex:0] rangeValue])) &&
+					 (NSEqualRanges(NSMakeRange(11, 1), [(NSValue *)[matches objectAtIndex:1] rangeValue])) &&
+					 (NSEqualRanges(NSMakeRange(18, 1), [(NSValue *)[matches objectAtIndex:2] rangeValue])), @"Returned matches in non-consecutive string");
+	}
+	
+	STAssertFalse([@"Deoxyribonucleic Acid" nonConsecutivelySearchString:@"DNS"  matchingRanges:NULL], @"Non-consecutive mismatch");
+	
+	{
+		NSArray *matches = nil;
+		STAssertTrue([@"Turn left, then right at the corner" nonConsecutivelySearchString:@"left right" matchingRanges:&matches], @"Partly consecutive match");
+		STAssertTrue(([matches count] == 3) &&
+					 (NSEqualRanges(NSMakeRange(5, 4), [(NSValue *)[matches objectAtIndex:0] rangeValue])) &&
+					 (NSEqualRanges(NSMakeRange(10, 1), [(NSValue *)[matches objectAtIndex:1] rangeValue])) &&
+					 (NSEqualRanges(NSMakeRange(16, 5), [(NSValue *)[matches objectAtIndex:2] rangeValue])), @"Returned matches in partly-consecutive string");
+	}
+	
+	//advanced tests
+	
+	// LATIN CAPITAL LETTER A              == LATIN SMALL LETTER A
+	// LATIN SMALL LETTER O WITH DIAERESIS == LATIN SMALL LETTER O
+	// FULLWIDTH LATIN SMALL LETTER b      == LATIN SMALL LETTER B
+	STAssertTrue([@"A:\xC3\xB6:\xEF\xBD\x82" nonConsecutivelySearchString:@"aob" matchingRanges:NULL], @"Fuzzy matching of defined characters");
+	
+	//all bytes on the right are contained on the left, but on a character level "ä" is not contained in "Hütte Ф"
+	STAssertFalse([@"H\xC3\xBCtte \xD0\xA4" nonConsecutivelySearchString:@"\xC3\xA4" matchingRanges:NULL], @"Mismatch of composed characters with same prefix");
+	
+	// ":😥:𠘄:" vs "😄" (according to wikipedia "𠘄" is the arachic variant of "印")
+	// TECHNICALLY THIS SHOULD NOT MATCH!
+	// However Apple doesn't correctly handle characters in the 4-Byte UTF range, so let's use this test to check for changes in Apples behaviour :)
+	STAssertTrue([@":\xF0\x9F\x98\x84:\xF0\xA0\x98\x84:" nonConsecutivelySearchString:@"\xF0\x9F\x98\x84" matchingRanges:NULL], @"Mismatch of composed characters (4-byte) with same prefix");
+	
+}
+
 @end