/**
 * Copyright 2013 (c) Anna Schumaker.
 */
#ifndef OCARINA_CORE_FILTER_H
#define OCARINA_CORE_FILTER_H

#include <set>
#include <string>

/**
 * The filter layer is used to find a subset of songs based on an input
 * string.  Since this layer does text processing, it also provides a
 * functions for converting strings to lowercase.
 *
 * The text processing is mostly interested in alphanumeric characters, so
 * any special characters included in the input text will be stripped out.
 * Tabs, spaces and the following characters are used to delimit words:
 *
 * 	\/,;()_-~+"
 */
namespace filter {

	/**
	 * Convert the key to lowercase and break into individual words.
	 * Generate substrings for each word and add each (substring, index)
	 * pair to the Index.
	 *
	 * To generate substrings: iterate over the word starting from the
	 * first character, and append a character for every iteration.  For
	 * example, the word "goron" would contain the substrings:
	 * 	{ g, go, gor, goro, goron }.
	 *
	 * @param  text   The text to parse.
	 * @param  index  The track index to pair with the text.
	 * @return The lowercase form of the input text.
	 */
	const std::string add(const std::string &, unsigned int);

	/**
	 * Break the input text into lowercase words and search the Index
	 * for matches.  The results set should be filled out with the
	 * intersection of the IndexEntry for each word.  If any word does
	 * not appear in the index, then the result set should be empty.
	 *
	 * @param  text  The text to search for.
	 * @param  res   The results set to fill in with matching indexes.
	 */
	void search(const std::string &, std::set<unsigned int> &);

	/**
	 * Converts the input text to lowercase and returns the result.
	 *
	 * @param  text  The text to be converted.
	 * @return The lowercase form of the input text.
	 */
	std::string lowercase(const std::string &);

};

#endif /* OCARINA_CORE_FILTER_H */