Finished writing and doing basic testing of highlight-matching.xsl. The purpose of this file is to create supplement then normal way eXist tags search hits. When single items are searched for using the normal eXist &= and |= operators, each hit is tagged with an <exist:match> tag, This tag can then be used in the output to highlight the hits. However, when we search for an "exact phrase", we have to use the XPath contains() function in the XQuery. In this situation, the hits are not highlighted, because eXist isn't using its tokenized index. Therefore we need to keep track of the phrases which the user has searched on (only those searched using the + or AND operators), and then process each text node in the output to see if any of those phrases appear in the node. If they do, we need to highlight them.

This is achieved by first harvesting the search phrases from the <teiHeader> of the search results document, and putting them into a sequence called $phrasesToTag. Then we match on each text() node, and (assuming there are any phrases to highlight), we pass that node to a recursive template called tagMatches. This checks each of the elements in $phrasesToHighlight against the text node, using the contains() function; if it finds the phrase within the text node, it passes the text node and the phrase to another recursive function called tagMatch, which highlights all instances of that phrase.

The only limitation at the moment is that if there are multiple phrases, and more than one of them shows up in the same text node, only the first will be tagged. This is annoying, but it's not really a big deal; it's unlikely that multiple matches of phrases will show up often in the same text node, and in any case, the text node itself (or its ancestor node) will be returned as part of the hit report due to the first phrase being tagged in it, so we won't worry so much about this.

There's also probably room for some optimization in this code, but that will come later.