Open Source, Cross Platform search engine library - xapian.org
github .com/mcmontero/php-xapian JSON support and web-friendly middleware
The omega interface for xapian could do most work. wget to grab site data, json->csv converter to translate, and to be ready to go. All Free and open source software. Not quite plug and play, but a start.
Sample usage described:
xapian.org /docs/omega/overview.html
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