#include <unordered_map>
#include <list>
#include "2Q_cache.h"

class TwoCache {
private:
    //2 LRU caches

    size_t cpct_q1;
    std::unordered_map<int, std::list<int>::iterator> umap1;
    std::list <int> q1;                                                 //fast queue - the most popular pages

    size_t cpct_q2;
    std::unordered_map<int, std::list<int>::iterator> umap2;
    std::list <int> q2;                                                 //slow queue - if page asked at the first time put it to q2, if itasked from q2 it put it to q1,

public:
    TwoCache(size_t q1sz, size_t q2sz): cpct_q1(q1sz), cpct_q2(q2sz) {}    //ctor

    int get_page(int id) {                                              //get_page(<int id>) - returns <int id> if page is found, and -1 if not 
        if(umap1.find(id) != umap1.end()) {
            q1.splice(q1.begin(), q1, umap1[id]);                       //if page did not find in the end of fast(q1) queue - put it in the begin

            return id;
        }

        if (umap2.find(id) != umap2.end()) {                            //if page was not found in the end of slow queue - put is from slow(q2) to begin fast(q1)
            auto it = umap2[id];

            q2.splice(q2.begin(), q2, it);                              //put this page from queue to the slow
            umap2.erase(id);                                            //delete it from slow queue

            if (q1.size() == cpct_q1) {                                 //if q1 is overflowed delete oldest element from fast(q1)
                umap1.erase(q1.back());
                q1.pop_back();
            }
            q1.push_front(id);                                          //if it is not overflowed put it at the begin
            umap2[id] = q1.begin();

            return id;
        } else return -1;                                               //page was not found - return PAGE_DID_NOT_FOUND = -1
    }

    void put_page(int id) {                                             //puts page in cache
        if (umap1.find(id) != umap1.end()) {                            //if page is q1
            return;
        }

        if (umap2.find(id) != umap2.end()) {                            //I know that in this case there will be 2 loops in get_page() i will think about it...
            get_page(id);
            return;
        }

        if (q1.size() == cpct_q1) {                                     //if overflow                    
            umap1.erase(q1.back());
            q1.pop_back();
        }

        if (q2.size() == cpct_q2) {
            umap2.erase(q2.back());
            q2.pop_back();
        }

        q1.push_front(id);                                              //in the end push page in cache
        umap1[id] = q1.begin();
    }





    void info() {
        std::cout << "q1 (the most usable): ";
        for (auto i = q1.begin(); i != q1.end(); i++) {
            std::cout << *i << " ";
        }
        std::cout << "\nq2(Less usable): ";
        for (auto i = q2.begin(); i != q2.end(); i++) {
            std::cout << *i << " ";
        }
        std::cout << "\ncapacity q1: " << cpct_q1 
        << "\ncapacity q2: " << cpct_q2 << std::endl;
    }
};