#include <functional>
#include <iostream>
#include <map>
#include <string>
#include <vector>
using namespace std;

const int HOLD = 5;  // minutes a seat hold lasts before it lapses
struct ShowSeat {  // one seat for one show: the row two buyers race for
    string status = "AVAILABLE";
    int version = 0, by = 0, until = 0;
    string state(int now) const {  // a lapsed hold reads as free: no cleanup job needed
        return status == "HELD" && now >= until ? "AVAILABLE" : status;
    }
    void write(const string& s, int b = 0, int u = 0) { status = s; by = b; until = u; version++; }  // every write bumps the version
};
struct Booking { int id; string user; vector<string> seats; int amount; };
string join(const vector<string>& v) {
    string r;
    for (size_t i = 0; i < v.size(); i++) r += (i ? " " : "") + v[i];
    return r;
}
class BookingService {
public:
    map<string, ShowSeat> seats;  // ordered by seat id
    function<int(const string&)> pricing;  // a Strategy: swap in weekend or dynamic pricing
    int nextId = 1;
    BookingService(vector<string> ids, function<int(const string&)> p) : pricing(p) {
        for (auto& s : ids) seats[s] = ShowSeat();
    }
    vector<int> read(const vector<string>& ids) {
        vector<int> v;
        for (auto& s : ids) v.push_back(seats[s].version);
        return v;
    }
    Booking* hold(const string& user, const vector<string>& ids, const vector<int>& seen, int now) {  // all seats or none
        string head = "t=" + to_string(now) + " " + user + " holds " + join(ids) + ": ";
        for (size_t i = 0; i < ids.size(); i++) {
            ShowSeat& seat = seats[ids[i]];
            if (seat.version != seen[i]) {  // UPDATE ... WHERE version = seen matched 0 rows
                cout << head << "FAILED, " << ids[i] << " is at version " << seat.version << ", expected " << seen[i] << "\n";
                return nullptr;
            }
            if (seat.state(now) != "AVAILABLE") { cout << head << "FAILED, " << ids[i] << " is taken\n"; return nullptr; }
        }
        int amount = 0;
        for (auto& s : ids) amount += pricing(s);
        Booking* b = new Booking{nextId++, user, ids, amount};
        for (auto& s : ids) seats[s].write("HELD", b->id, now + HOLD);
        cout << head << "OK, booking " << b->id << " held until t=" << now + HOLD << "\n";
        return b;
    }
    void pay(Booking* b, bool paid, int now) {
        vector<string> mine;
        for (auto& s : b->seats) if (seats[s].by == b->id && seats[s].state(now) == "HELD") mine.push_back(s);
        cout << "t=" << now << " " << b->user << " pays " << b->amount << ": ";
        if (paid && mine.size() == b->seats.size()) {
            for (auto& s : mine) seats[s].write("BOOKED", b->id);
            cout << "CONFIRMED booking " << b->id << "\n";
        } else {
            for (auto& s : mine) seats[s].write("AVAILABLE");
            cout << "FAILED, released " << join(mine) << "\n";
        }
    }
};
int main() {
    BookingService svc({"A1", "A2", "B1"}, [](const string& s) { return s[0] == 'A' ? 250 : 180; });  // front row A costs more
    vector<int> seenA = svc.read({"A1", "A2"}), seenB = svc.read({"A2", "B1"});  // both read before either writes
    cout << "alice and bob both read A2 at version " << seenA[1] << "\n";
    Booking* alice = svc.hold("alice", {"A1", "A2"}, seenA, 0);
    svc.hold("bob", {"A2", "B1"}, seenB, 0);
    svc.pay(alice, false, 2);  // the card is declined
    Booking* bob = svc.hold("bob", {"A2", "B1"}, svc.read({"A2", "B1"}), 3);
    svc.pay(bob, true, 4);
    svc.hold("carol", {"A1"}, svc.read({"A1"}), 6);  // carol never pays
    svc.hold("dave", {"A1"}, svc.read({"A1"}), 20);  // her hold lapsed at t=11
    cout << "t=20 seats:";
    for (auto& [id, s] : svc.seats) cout << " " << id << "=" << s.state(20);
    cout << "\n";
}