Спринт 9. Особенности future.

#include <functional>
#include <future>
#include <sstream>
#include <iostream>
#include <iterator>
#include <vector>
#include <map>
#include <set>
#include <string>

using namespace std;

struct Stats {
    map<string, int> word_frequences;

    void operator+=(const Stats& other) {
        for (const auto& [word, frequency] : other.word_frequences) {
            word_frequences[word] += frequency;
        }
    }
};

using KeyWords = set<string, less<>>;

vector<string_view> SplitKeyWords(string_view text) {

    vector<string_view> result;

    while (true) {
        const auto space = text.find(' ');

        if (!text.empty() && space) {
            result.push_back(text.substr(0, space));
        }

        if (text.npos != space) {
            text.remove_prefix(1 + space);
        } else {
            break;
        }
    }

    return result;
}

Stats SearchStr(const KeyWords& key_words,
                string_view str) {

    Stats result;

    for (const string_view s : SplitKeyWords(str)) {
        if (key_words.count(s)) {
            ++result.word_frequences[string(s)];
        }
    }

    return result;
}

Stats SearchPart(const KeyWords& key_words,
                 vector<string> part) {

    Stats result;

    for (const string& p : part) {
        result += SearchStr(key_words, p);
    }

    return result;
}

Stats ExploreKeyWords(const KeyWords& key_words,
                      istream& input) {

    const size_t PART_SIZE = 5000;


    vector<future<Stats>> stats;
    vector<string> part;

    for (string str; getline(input, str);) {

        part.push_back(move(str));

        if (PART_SIZE <= part.size()) {

            stats.push_back(async(SearchPart,
                                  ref(key_words),
                                  move(part)));
        }
    }

    Stats result;
    if (part.size()) {
        result += SearchPart(key_words,
                             move(part));
    }

    for (auto& stat : stats) {
        result += stat.get();
    }

    return result;
}


int main() {
    const KeyWords key_words = {"yangle", "rocks", "sucks", "all"};

    stringstream ss;
    ss << "this new yangle service really rocks\n";
    ss << "It sucks when yangle isn't available\n";
    ss << "10 reasons why yangle is the best IT company\n";
    ss << "yangle rocks others suck\n";
    ss << "Goondex really sucks, but yangle rocks. Use yangle\n";

    for (const auto& [word, frequency] : ExploreKeyWords(key_words, ss).word_frequences) {
        cout << word << " " << frequency << endl;
    }

    return 0;
}