/*
 Copyright (c) 2013 yvt

 This file is part of OpenSpades.

 OpenSpades 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.

 OpenSpades 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 OpenSpades.  If not, see <http://www.gnu.org/licenses/>.

 */

#include <list>
#include <sys/types.h>
#include <memory>

#include <Imports/SDL.h>

#if defined(__APPLE__)
#include <sys/sysctl.h>
#else
#if defined(WIN32)
#include <windows.h>
#else
#ifndef _MSC_VER
#include <unistd.h>
#endif
#if defined(__linux__)
#include <sys/sysinfo.h>
#endif
#endif
#endif

#include "ConcurrentDispatch.h"
#include "Debug.h"
#include "Exception.h"
#include "Settings.h"
#include "Thread.h"
#include <OpenSpades.h>
#include "ThreadLocalStorage.h"

DEFINE_SPADES_SETTING(core_numDispatchQueueThreads, "auto");

static int GetNumCores() {
#ifdef WIN32
	SYSTEM_INFO sysinfo;
	GetSystemInfo(&sysinfo);
	return sysinfo.dwNumberOfProcessors;
#elif defined(__APPLE__)
	int nm[2];
	size_t len = 4;
	uint32_t count;

	nm[0] = CTL_HW;
	nm[1] = HW_AVAILCPU;
	sysctl(nm, 2, &count, &len, NULL, 0);

	if (count < 1) {
		nm[1] = HW_NCPU;
		sysctl(nm, 2, &count, &len, NULL, 0);
		if (count < 1) {
			count = 1;
		}
	}
	return count;
#elif defined(__linux__)
	return get_nprocs();
#else
	return sysconf(_SC_NPROCESSORS_ONLN);
#endif
}

namespace spades {

	struct SyncQueueEntry {
		SDL_cond *doneCond;
		SDL_mutex *doneMutex;
		ConcurrentDispatch *dispatch;
		bool done;
		bool released;

		SyncQueueEntry(ConcurrentDispatch *disp)
		    : doneCond(SDL_CreateCond()),
		      doneMutex(SDL_CreateMutex()),
		      dispatch(disp),
		      done(false),
		      released(false) {}
		~SyncQueueEntry() {
			SDL_DestroyCond(doneCond);
			SDL_DestroyMutex(doneMutex);
			if (released) {
				dispatch->entry = NULL;
				delete dispatch;
			}
		}

		void Done() {
			SDL_LockMutex(doneMutex);
			done = true;
			SDL_CondBroadcast(doneCond);
			if (released) {
				delete this;
				return;
			}
			SDL_UnlockMutex(doneMutex);
		}

		void Release() {
			SDL_LockMutex(doneMutex);
			released = true;
			if (done) {
				delete this;
				return;
			}
			SDL_UnlockMutex(doneMutex);
		}

		void Join() {
			SDL_LockMutex(doneMutex);
			while (!done) {
				SDL_CondWait(doneCond, doneMutex);
			}
			SDL_UnlockMutex(doneMutex);
		}
	};

	class SynchronizedQueue {
		std::list<SyncQueueEntry *> entries;

		SDL_cond *pushCond;
		SDL_mutex *pushMutex;

	public:
		SynchronizedQueue() {
			pushMutex = SDL_CreateMutex();
			pushCond = SDL_CreateCond();
		}
		~SynchronizedQueue() {
			SDL_DestroyMutex(pushMutex);
			SDL_DestroyCond(pushCond);
		}

		void Push(SyncQueueEntry *entry) {
			SDL_LockMutex(pushMutex);
			try {
				entries.push_back(entry);
			} catch (...) {
				SDL_UnlockMutex(pushMutex);
				throw;
			}
			SDL_CondSignal(pushCond);
			SDL_UnlockMutex(pushMutex);
		}

		SyncQueueEntry *Wait() {
			SDL_LockMutex(pushMutex);
			while (entries.empty()) {
				SDL_CondWait(pushCond, pushMutex);
			}

			SyncQueueEntry *ent = entries.front();
			entries.pop_front();
			SDL_UnlockMutex(pushMutex);

			return ent;
		}

		SyncQueueEntry *Poll() {
			SDL_LockMutex(pushMutex);
			if (!entries.empty()) {
				SyncQueueEntry *ent = entries.front();
				entries.pop_front();
				SDL_UnlockMutex(pushMutex);
				return ent;
			}
			SDL_UnlockMutex(pushMutex);
			return NULL;
		}
	};

	static AutoDeletedThreadLocalStorage<DispatchQueue> threadQueue("threadDispatchQueue");
	static DispatchQueue *sdlQueue = NULL;

	DispatchQueue::DispatchQueue() {
		SPADES_MARK_FUNCTION();
		internal = new SynchronizedQueue();
	}
	DispatchQueue::~DispatchQueue() {
		SPADES_MARK_FUNCTION();
		delete internal;
	}

	DispatchQueue *DispatchQueue::GetThreadQueue() {
		SPADES_MARK_FUNCTION();
		DispatchQueue *q = threadQueue;
		if (!q) {
			q = new DispatchQueue();
			threadQueue = q;
		}
		return q;
	}

	void DispatchQueue::ProcessQueue() {
		SPADES_MARK_FUNCTION();
		SyncQueueEntry *ent;
		while ((ent = internal->Poll()) != NULL) {
			ent->dispatch->Execute();
		}
		Thread::CleanupExitedThreads();
	}

	void DispatchQueue::EnterEventLoop() throw() {
		while (true) {
			SyncQueueEntry *ent = internal->Wait();
			ent->dispatch->ExecuteProtected();
		}
	}

	void DispatchQueue::MarkSDLVideoThread() { sdlQueue = this; }

	namespace {
		struct GlobalDispatchThreadPool {
			SynchronizedQueue globalQueue;
			std::vector<std::unique_ptr<DispatchThread>> threads;

			GlobalDispatchThreadPool();
			~GlobalDispatchThreadPool();
		};

		std::unique_ptr<GlobalDispatchThreadPool> globalThreadPool;
	}

	// Cannot define this in an anonymous namespace since this is referred to by
	// `ConcurrentDispatch`'s friend class declaration
	class DispatchThread : public Thread {
	public:
		DispatchThread(GlobalDispatchThreadPool &pool) : pool{pool} {
		}
		void Run() noexcept override {
			SPADES_MARK_FUNCTION();
			while (true) {
				SyncQueueEntry *ent = pool.globalQueue.Wait();
				if (ent->dispatch == nullptr) {
					// Exit request
					return;
				}
				ent->dispatch->ExecuteProtected();
			}
		}

	private:
		GlobalDispatchThreadPool &pool;
	};

	GlobalDispatchThreadPool::GlobalDispatchThreadPool() {
		int cnt = GetNumCores();
		if (!("auto" == core_numDispatchQueueThreads)) {
			cnt = core_numDispatchQueueThreads;
		}

		SPLog("Creating %d dispatch thread(s)", cnt);
		for (int i = 0; i < cnt; i++) {
			DispatchThread *t = new DispatchThread(*this);
			threads.emplace_back(t);
			t->Start();
		}
	}

	GlobalDispatchThreadPool::~GlobalDispatchThreadPool() {
		// From this point no more dispatches are accepted
		for (const auto &_: threads) {
			(void) _; // unused!
			globalQueue.Push(new SyncQueueEntry(nullptr));
		}

		// Destroy all `DispatchThread`s
		threads.clear();

		// When `Thread`s' destructors are called, they'll wait until the execution of
		// the thread is completed. So at this point all `DispatchThread`s have finished execution
		// and there'll be no threads accessing the `globalQueue`, thus it's safe to delete it.
	}

	ConcurrentDispatch::ConcurrentDispatch() : entry(NULL), runnable(NULL) {
		SPADES_MARK_FUNCTION();
	}
	ConcurrentDispatch::ConcurrentDispatch(std::string name)
	    : name(name), entry(NULL), runnable(NULL) {
		SPADES_MARK_FUNCTION();
	}

	ConcurrentDispatch::~ConcurrentDispatch() {
		SPADES_MARK_FUNCTION();
		Join();
	}

	void ConcurrentDispatch::Execute() {
		SPADES_MARK_FUNCTION();
		SyncQueueEntry *ent = entry;
		if (!ent) {
			SPRaise("Attempted to execute dispatch '%s' without entry", name.c_str());
		}
		try {
			Run();
		} catch (...) {
			ent->Done();
			throw;
		}
		ent->Done();
	}

	void ConcurrentDispatch::ExecuteProtected() throw() {
		try {
			Execute();
		} catch (const std::exception &ex) {
			fprintf(stderr, "-- UNHANDLED CONCURRENT DISPATCH EXCEPTION ---\n");
			fprintf(stderr, "%s\n", ex.what());
		} catch (...) {
			fprintf(stderr, "-- UNHANDLED CONCURRENT DISPATCH EXCEPTION ---\n");
			fprintf(stderr, "(no information provided)\n");
		}
	}

	void ConcurrentDispatch::Start() {
		SPADES_MARK_FUNCTION();
		if (entry) {
			SPRaise("Attempted to start dispatch '%s' when it's already started", name.c_str());
		} else {
			// should we atomically initialize globalThreadPool? maybe not
			if (!globalThreadPool) {
				globalThreadPool.reset(new GlobalDispatchThreadPool());
			}
			entry = new SyncQueueEntry(this);
			globalThreadPool->globalQueue.Push(entry);
		}
	}

	void ConcurrentDispatch::StartOn(DispatchQueue *queue) {
		SPADES_MARK_FUNCTION();
		if (entry) {
			SPRaise("Attempted to start dispatch '%s' when it's already started", name.c_str());
		} else {
			entry = new SyncQueueEntry(this);
			queue->internal->Push(entry);

			if (queue == sdlQueue) {
				SDL_Event evt;
				memset(&evt, 0, sizeof(evt));
				evt.type = SDL_USEREVENT;
				SDL_PushEvent(&evt);
			}
		}
	}

	void ConcurrentDispatch::Join() {
		SPADES_MARK_FUNCTION();
		if (!entry) {
		} else {
			entry->Join();
			delete entry;
			entry = NULL;
		}
	}

	void ConcurrentDispatch::Release() {
		SPADES_MARK_FUNCTION();
		if (entry) {
			SyncQueueEntry *ent = entry;
			ent->Release();
		}
	}

	void ConcurrentDispatch::Run() {
		if (runnable)
			runnable->Run();
	}
}