#include <windows.h>
#include <usp10.h>

bool calculateWordOffsets(wchar_t* text, int textLength, int offset, int* startOffset, int* endOffset) {
	if(textLength<=0) return false;
	if(offset<0) return false;
	if(offset>=textLength) {
		*startOffset=offset;
		*endOffset=offset+1;
		return true;
	}
	SCRIPT_ITEM* pItems=new SCRIPT_ITEM[textLength+1];
	int numItems=0;
	if(ScriptItemize(text,textLength,textLength,NULL,NULL,pItems,&numItems)!=S_OK||numItems==0) {
		delete[] pItems;
		return false;
	}
	SCRIPT_LOGATTR* logAttrArray=new SCRIPT_LOGATTR[textLength];
	int nextICharPos=textLength;
	for(int itemIndex=numItems-1;itemIndex>=0;--itemIndex) {
		int iCharPos=pItems[itemIndex].iCharPos;
		int iCharLength=nextICharPos-iCharPos;
		if(ScriptBreak(text+iCharPos,iCharLength,&(pItems[itemIndex].a),logAttrArray+iCharPos)!=S_OK) {
			delete[] pItems;
			delete[] logAttrArray;
			return false;
		}
	}
	delete[] pItems;
	for(int i=offset;i>=0;--i) {
		if(logAttrArray[i].fWordStop) {
			*startOffset=i;
			break;
		}
	}
	// #1656: fWordStop doesn't seem to stop on whitespace where punctuation follows the whitespace.
	bool skipWhitespace=true;
	for(int i=offset;i>=*startOffset;--i) {
		if(iswspace(text[i])) {
			if(skipWhitespace) {
				// If we start in a block of whitespace, the word must start before this,
				// as whitespace is included at the end of a word.
				// Therefore, skip the whitespace and keep searching.
				continue;
			}
			// This is whitespace. The word starts after it.
			*startOffset=i+1;
			break;
		} else
			skipWhitespace=false;
	}
	*endOffset=textLength;
	for(int i=offset+1;i<textLength;++i) {
		if(logAttrArray[i].fWordStop) {
			*endOffset=i;
			break;
		}
	}
	// #1656: fWordStop doesn't seem to stop on whitespace where punctuation follows the whitespace.
	for(int i=offset;i<*endOffset;++i) {
		if(iswspace(text[i])) {
			// This begins a block of whitespace. The word ends after it.
			// Find the end of the whitespace.
			for(;i<*endOffset;++i) {
				if(!iswspace(text[i]))
					break;
			}
			// We're now positioned on the first non-whitespace character,
			// so the word ends here.
			*endOffset=i;
			break;
		}
	}
	delete[] logAttrArray;
	return true;
}