/* This file is part of Strawberry.
   Copyright 2011, David Sansome <me@davidsansome.com>

   Strawberry is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   Strawberry is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with Strawberry.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef CLOSURE_H
#define CLOSURE_H

#include <functional>
#include <memory>
#include <chrono>

#include <QtGlobal>
#include <QObject>
#include <QFuture>
#include <QFutureWatcher>
#include <QMetaObject>
#include <QMetaMethod>
#include <QSharedPointer>
#include <QByteArray>
#include <QString>
#include <QList>
#include <QTimer>

namespace _detail {

class ObjectHelper;

// Interface for ObjectHelper to call on signal emission.
class ClosureBase {
 public:
  virtual ~ClosureBase();
  virtual void Invoke() = 0;

  // Tests only.
  ObjectHelper *helper() const;

 protected:
  explicit ClosureBase(ObjectHelper*);
  ObjectHelper *helper_;

 private:
  Q_DISABLE_COPY(ClosureBase);
};

// QObject helper as templated QObjects do not work.
// Connects to the given signal and invokes the closure when called.
// Deletes itself and the Closure after being invoked.
class ObjectHelper : public QObject {
  Q_OBJECT
 public:
  ObjectHelper(QObject *parent, const char *signal, ClosureBase *closure);

 private slots:
  void Invoked();

 private:
  std::unique_ptr<ClosureBase> closure_;
  Q_DISABLE_COPY(ObjectHelper);
};

// Helpers for unpacking a variadic template list.

// Base case of no arguments.
void Unpack(QList<QGenericArgument>*);

template <typename Arg>
void Unpack(QList<QGenericArgument> *list, const Arg &arg) {
  list->append(Q_ARG(Arg, arg));
}

template <typename Head, typename... Tail>
void Unpack(QList<QGenericArgument> *list, const Head &head, const Tail&... tail) {
  Unpack(list, head);
  Unpack(list, tail...);
}

template <typename... Args>
class Closure : public ClosureBase {
 public:
  Closure(
      QObject *sender,
      const char *signal,
      QObject *receiver,
      const char *slot,
      const Args&... args)
      : ClosureBase(new ObjectHelper(sender, signal, this)),
        // std::bind is the easiest way to store an argument list.
        function_(std::bind(&Closure<Args...>::Call, this, args...)),
        receiver_(receiver) {
    const QMetaObject *meta_receiver = receiver->metaObject();
    QByteArray normalised_slot = QMetaObject::normalizedSignature(slot + 1);
    const int index = meta_receiver->indexOfSlot(normalised_slot.constData());
    Q_ASSERT(index != -1);
    slot_ = meta_receiver->method(index);
    QObject::connect(receiver_, SIGNAL(destroyed()), helper_, SLOT(deleteLater()));
  }

  virtual void Invoke() {
    function_();
  }

 private:
  void Call(const Args&... args) {
    QList<QGenericArgument> arg_list;
    Unpack(&arg_list, args...);

    slot_.invoke(
        receiver_,
                 arg_list.size() > 0 ? arg_list[0] : QGenericArgument(),
                 arg_list.size() > 1 ? arg_list[1] : QGenericArgument(),
                 arg_list.size() > 2 ? arg_list[2] : QGenericArgument(),
                 arg_list.size() > 3 ? arg_list[3] : QGenericArgument(),
                 arg_list.size() > 4 ? arg_list[4] : QGenericArgument(),
                 arg_list.size() > 5 ? arg_list[5] : QGenericArgument(),
                 arg_list.size() > 6 ? arg_list[6] : QGenericArgument(),
                 arg_list.size() > 7 ? arg_list[7] : QGenericArgument(),
                 arg_list.size() > 8 ? arg_list[8] : QGenericArgument(),
                 arg_list.size() > 9 ? arg_list[9] : QGenericArgument());
  }

  std::function<void()> function_;
  QObject *receiver_;
  QMetaMethod slot_;
};

template <typename T, typename... Args>
class SharedClosure : public Closure<Args...> {
 public:
  SharedClosure(
      QSharedPointer<T> sender,
      const char *signal,
      QObject *receiver,
      const char *slot,
      const Args&... args)
    : Closure<Args...>(
        sender.data(),
        signal,
        receiver,
        slot,
        args...),
      data_(sender) {
  }

 private:
  QSharedPointer<T> data_;
};

class CallbackClosure : public ClosureBase {
 public:
  CallbackClosure(QObject *sender, const char *signal, std::function<void()> callback);

  virtual void Invoke();

 private:
  std::function<void()> callback_;
};

}  // namespace _detail

template <typename... Args>
_detail::ClosureBase *NewClosure(QObject *sender, const char *signal, QObject *receiver, const char *slot, const Args&... args) {
  return new _detail::Closure<Args...>(sender, signal, receiver, slot, args...);
}

// QSharedPointer variant
template <typename T, typename... Args>
_detail::ClosureBase *NewClosure(QSharedPointer<T> sender, const char *signal, QObject *receiver, const char *slot, const Args&... args) {
  return new _detail::SharedClosure<T, Args...>(sender, signal, receiver, slot, args...);
}

_detail::ClosureBase *NewClosure(QObject *sender, const char *signal, std::function<void()> callback);

template <typename... Args>
_detail::ClosureBase *NewClosure(QObject *sender, const char *signal, std::function<void(Args...)> callback, const Args&... args) {
  return NewClosure(sender, signal, std::bind(callback, args...));
}

template <typename... Args>
_detail::ClosureBase *NewClosure(QObject *sender, const char *signal, void (*callback)(Args...), const Args&... args) {
  return NewClosure(sender, signal, std::bind(callback, args...));
}

template <typename T, typename Unused, typename... Args>
_detail::ClosureBase *NewClosure(QObject *sender, const char *signal, T *receiver, Unused (T::*callback)(Args...), const Args&... args) {
  return NewClosure(sender, signal, std::bind(callback, receiver, args...));
}

template <typename T, typename... Args>
_detail::ClosureBase *NewClosure(QFuture<T> future, QObject *receiver, const char *slot, const Args&... args) {
  QFutureWatcher<T> *watcher = new QFutureWatcher<T>;
  watcher->setFuture(future);
  QObject::connect(watcher, SIGNAL(finished()), watcher, SLOT(deleteLater()));
  return NewClosure(watcher, SIGNAL(finished()), receiver, slot, args...);
}

template <typename T, typename F, typename... Args>
_detail::ClosureBase *NewClosure(QFuture<T> future, const F &callback, const Args&... args) {
  QFutureWatcher<T> *watcher = new QFutureWatcher<T>;
  watcher->setFuture(future);
  QObject::connect(watcher, SIGNAL(finished()), watcher, SLOT(deleteLater()));
  return NewClosure(watcher, SIGNAL(finished()), callback, args...);
}

void DoAfter(QObject *receiver, const char *slot, int msec);
void DoAfter(std::function<void()> callback, std::chrono::milliseconds msec);
void DoInAMinuteOrSo(QObject *receiver, const char *slot);

template <typename R, typename P>
void DoAfter(std::function<void()> callback, std::chrono::duration<R, P> duration) {
  QTimer *timer = new QTimer;
  timer->setSingleShot(true);
  NewClosure(timer, SIGNAL(timeout()), callback);
  QObject::connect(timer, SIGNAL(timeout()), timer, SLOT(deleteLater()));
  std::chrono::milliseconds msec = std::chrono::duration_cast<std::chrono::milliseconds>(duration);
  timer->start(msec.count());
}

#endif  // CLOSURE_H