/////////////////////////////////////////////////////////
//TextChunker.m
//PodReader
////////////////////////////////////////////////////////

#import "TextChunker.h"

@implementation TextChunker

- (void)chunkIt:(NSString*)fileName
		  toDir:(NSString*)destDir 
  withSeparator:(NSString*)separator {
	
	unsigned PR_CHUNK = 4000;
	unsigned PR_INITIAL_CUT_POINT = PR_CHUNK-50;
	unsigned PR_CUT_DELTA = 50;
	
	NSMutableString* fileContents = [NSMutableString stringWithContentsOfFile:fileName];
	NSMutableArray* chunksArray = [[NSMutableArray alloc] init];
	unsigned endOfChunk = 0;
	
	//Create an NSArray of NSMutableStrings by segmenting fileContents with `separator.' 
	while ([fileContents length] != 0) {
		endOfChunk = [[fileContents substringFromIndex:1] 
						rangeOfString:separator].location;
		
		if (NSNotFound == endOfChunk) {
			endOfChunk = [fileContents length];
		}
		
		NSRange paragraphRange = [fileContents paragraphRangeForRange:
										NSMakeRange(0, endOfChunk)];
		
		//the lastLineInParagraph is ideally the heading such as `CHAPTER 1' that 
		//introduces the next chapter, section, act, etc.
		NSRange lastLineInParagraph = [fileContents 
			lineRangeForRange:NSMakeRange(endOfChunk, paragraphRange.location)];
	
		//if the last line in the paragraph is the entire paragraph, 
		//use it as the entire chunk
		if (lastLineInParagraph.location == 0) {
			endOfChunk = lastLineInParagraph.length;
		}
		else {
			endOfChunk = lastLineInParagraph.location;
		}
		
		NSMutableString* theSubstring = [NSMutableString stringWithString:
										[fileContents substringWithRange:
											NSMakeRange(0,endOfChunk)]];
		[chunksArray addObject:theSubstring];
				
		[fileContents setString:[fileContents substringFromIndex:endOfChunk]];
		[fileContents setString:[fileContents stringByTrimmingCharactersInSet:
								[NSCharacterSet whitespaceAndNewlineCharacterSet]]];
	}
	
	//Size chunks `intelligently' as close to PR_CHUNK as possible:
	
	//Walk through the array and segment the chunk if it's too big,
	//try and merge it with it's predecessor if it's small enough, and
	//leave it `as is' otherwise
	unsigned index=0;
	while (index < [chunksArray count]) {
		NSMutableString* currentChunk = [chunksArray  objectAtIndex:index];
		
		//segment the chunk
		if ([currentChunk length] > PR_CHUNK) {
			unsigned cutPoint = PR_INITIAL_CUT_POINT;
			BOOL done = NO;
			
			while (!done) {
				NSRange lineRange = [currentChunk lineRangeForRange:
										NSMakeRange(0, cutPoint)];
				
				if (lineRange.length < PR_CHUNK) { //segmentation at line ending
					[chunksArray insertObject:[NSMutableString stringWithString:
						[currentChunk substringFromIndex:lineRange.length]]  
									  atIndex:(index+1)];
					[chunksArray replaceObjectAtIndex:index withObject:
						[NSMutableString stringWithString:
							[currentChunk substringToIndex:lineRange.length]]];
					done = YES;
				}
				else if (cutPoint > 0) { //back up and try to segment again
					cutPoint -= PR_CUT_DELTA;
				}
				else { //arbitrary segmentation
					[chunksArray insertObject:[NSMutableString stringWithString:
						[currentChunk substringFromIndex:PR_CHUNK]]  
									  atIndex:(index+1)];
					[chunksArray replaceObjectAtIndex:index withObject:
						[NSMutableString stringWithString:
							[currentChunk substringToIndex:PR_CHUNK]]];
					done = YES;
				}
			}
			index++;
		}
		//Try to combine chunks
		else if ((index >= 1) &&
		([currentChunk length] +
		[[[chunksArray objectAtIndex:(index-1)] description] length] < PR_CHUNK)) {
			
			NSString* combinedString = [[chunksArray objectAtIndex:(index-1)] 
										   stringByAppendingString:currentChunk];
			[chunksArray replaceObjectAtIndex:index withObject:
				[NSMutableString stringWithString:combinedString]];
			[chunksArray removeObjectAtIndex:(index-1)];
			//Don't increment the counter. Index already points to the next chunk
		}
		//Leave `as is' and advance the placeholder index
		else {
			index++;
		}
	}

	//Write each element of the array to the directory specified.
	//Pad the filenames all to the same length with leading zeros
	//so that files appear in order

	unsigned numDigits = [[[NSString stringWithFormat:@"%u", [chunksArray count]] 
		description] length];
	
	NSString* filePrefix = [[fileName lastPathComponent] stringByDeletingPathExtension];
	
	NSMutableArray* finalFileNames = [[NSMutableArray alloc] init];
	 
	unsigned chunkNumber=1;
	NSEnumerator*	enumerator = [chunksArray objectEnumerator]; 
	while (nil != [enumerator nextObject]) {
		
		unsigned digitLength = [[[NSString stringWithFormat:@"%u", chunkNumber] 
			description] length];
		
		NSString* padding = [@"" stringByPaddingToLength:(numDigits-digitLength) 
											  withString:@"0"
										 startingAtIndex:0];
		
		NSString* finalFileName = [[[destDir 
	 stringByAppendingPathComponent:filePrefix]
			stringByAppendingString:padding]
			stringByAppendingFormat:@"%u", chunkNumber++];
		
		[finalFileNames addObject:finalFileName];		
	} 
	
	unsigned currentChunk = 0;
	while (currentChunk < [chunksArray count]-1) {
		NSString* linkedChunk = [[[[chunksArray objectAtIndex:currentChunk] 
			stringByAppendingString:@"<a href=\""]
			stringByAppendingString:[[finalFileNames objectAtIndex:(currentChunk+1)]
											lastPathComponent]]
			stringByAppendingString:@"\">NEXT</a>"];
		
		[linkedChunk writeToFile:[finalFileNames objectAtIndex:currentChunk]
					  atomically:YES];
		
		currentChunk++;
	}
	[[chunksArray objectAtIndex:currentChunk] 
		writeToFile:[finalFileNames objectAtIndex:currentChunk] 
		 atomically:YES];
	
	[finalFileNames release];
	[chunksArray release];
}



@end