TextQuery.h

#ifndef TEXT_QUERY_H
#define TEXT_QUERY_H

#include <fstream>
#include <map>
#include <memory>
#include <set>
#include <sstream>
#include <vector>

class QueryResult;
class TextQuery {
	public:
		using line_no = std::vector<std::string>::size_type;
		TextQuery(std::ifstream &);
		QueryResult query (const std::string &) const;
	private:
		std::shared_ptr<std::vector<std::string>> text;
		std::map<std::string, std::shared_ptr<std::set<line_no>>> words_map;
};

class QueryResult {
	friend std::ostream& print(std::ostream &, const QueryResult &);
	public:
		QueryResult(std::shared_ptr<std::vector<std::string>> p,
				    std::shared_ptr<std::set<TextQuery::line_no>> ln,
					std::string w, unsigned n) :
			text(p), lines(ln), sought(w), count(n) {}
	private:
		std::shared_ptr<std::vector<std::string>> text;
		std::shared_ptr<std::set<TextQuery::line_no>> lines;
		std::string sought;
		unsigned count = 0;
};

// constructors
TextQuery::TextQuery(std::ifstream &infile) :
	text(std::make_shared<std::vector<std::string>>())
{
	std::string line, word;
	for (size_t lineNumber = 1; getline(infile, line); ++lineNumber) {
		text->push_back(line);
		std::istringstream iss(line);
		while (iss >> word) {
			auto &lines = words_map[word];
			if (!lines)
				lines = std::make_shared<std::set<line_no>>();
			lines->insert(lineNumber);
		}
	}
}

// members
QueryResult
TextQuery::query(const std::string &s) const
{
	static auto notFound = std::make_shared<std::set<line_no>>();
	auto pos = words_map.find(s);
	if (pos == words_map.end())
		return {text, notFound, s, 0};
	unsigned count = 0;
	std::string word;
	for (auto const &line : *text) {
		std::istringstream iss(line);
		while (iss >> word)
			if (word == s)
				++count;
	}
	return {text, pos->second, s, count}; 
}

// non-members
std::ostream&
print(std::ostream &os, const QueryResult &result)
{
	os << result.sought << " occurs " << result.count
	   << ((result.count > 1) ? " times" : " time") << std::endl;
	for (auto const &n : *result.lines)
		os << "\t(line " << n << ") " << result.text->at(n - 1) << '\n';
	return os;
}
#endif