// More STL examples this time including maps.
//
// Basic operations on maps:
//     function/operator
//     -----------------
//     insert(pair)
//     x[index] (reference to the value associated with this key)
//     size()
//     empty()
//     clear()
//     count(key) (returns a count of the # of keys equal to key, always 0 or 1
// 
// Use of iterators on maps:
//     function/operator
//     ----------------------
//     begin()
//     end()
//     *iterator (const)
//     erase(iterator)
//     insert(iterator, value)
//
// pair<type1, type2>
//     first--returns first element in the pair
//     second--returns second element in the pair
//
// use type unordered_set for a set of objects that do not overload operator <
// use type unordered_map for a map whose keys do not overload operator <

#include <iostream>
#include <set>
#include <string>
#include <map>
#include <fstream>
#include <sstream>

using namespace std;

// This is the overloaded << operator to allow us to put a set<string> onto an
// output stream as a bracketed, comma-separted sequence
ostream & operator<<(ostream & out, const set<string> & s) {
    out << "[";
    if (s.size() > 0) {
        auto itr = s.begin();
        out << *itr;
        itr++;
        while (itr != s.end()) {
            out << ", " << *itr;
            itr++;
        }
    }
    out << "]";
    return out;
}

// This example involves reading all of the words in a file and counting how
// many times each word occurs.  We ask the user for a minimum number of words
// for printing and show those entries.
void example1() {
    ifstream input("moby.txt");
    map<string, int> count;
    string word;
    while (input >> word) {
        count[word]++;
    }
    cout << "minimum count to use? ";
    int min;
    cin >> min;
    for (auto p : count) {
        if (p.second >= min) {
            cout << p.first << ": " << p.second << endl;
        }
    }
    cout << endl;
}

// This function reads a short data file with pairs of lines that have a name
// on the first line and a sequence of course abbreviations on the second line.
// It figures out who is taking each class, building up a string of student
// names with periods to keep them separate.
void example2() {
    ifstream input("stl2.txt");
    string name;
    map<string, string> data;
    while (getline(input, name)) {
        string courses;
        getline(input, courses);
        istringstream input2(courses);
        string course;
        while (input2 >> course) {
            data[course] += name + ".";
        }
    }
    for (auto itr = data.begin(); itr != data.end(); itr++) {
        cout << itr->first << " maps to " << itr->second << endl;
    }
    cout << endl;
}

// This is a variation of example2 where the map keeps a set of names for each
// course.
void example3() {
    ifstream input("stl2.txt");
    string name;
    map<string, set<string>> data;
    while (getline(input, name)) {
        string courses;
        getline(input, courses);
        istringstream input2(courses);
        string course;
        while (input2 >> course) {
            data[course].insert(name);
        }
    }
    for (auto itr = data.begin(); itr != data.end(); itr++) {
        cout << itr->first << " maps to " << itr->second << endl;
    }
    cout << endl;

    // the following code was an example of deleting all map entries where the
    // key starts with the letter 'c'
    auto itr = data.begin();
    while (itr != data.end()) {
        if (itr->first[0] == 'c') {
            itr = data.erase(itr);
        } else {
            itr++;
        }
    }
    for (auto itr = data.begin(); itr != data.end(); itr++) {
        cout << itr->first << " maps to " << itr->second << endl;
    }
    cout << endl;
}

int main() {
    example1();
    example2();
    example3();

    return 0;
}