#include "qutexAcquisitionHistoryTracker.h"
#include "serializedAsynchronousContinuation.h"
#include "qutex.h"
#include <memory>
#include <forward_list>
#include <functional>

namespace smo {

/**	EXPLANATION - GRIDLOCK DETECTION ALGORITHM:
 * This file implements gridlock detection algorithms that use a central
 * acquisition history to track all lockvokers suspected of being gridlocked.
 *
 *	ALGORITHM OVERVIEW:
 * 1. When a lockvoker finds that DEADLOCK_TIMEOUT_MS has elapsed and it
 *    still can't acquire a particular lock (firstFailedQutex), it creates
 *    a new entry in a global acquisition history.
 *
 * 2. The acquisition history is an unordered_map with:
 *    - Key: std::shared_ptr<AsynchronousContinuationChainLink>
 *		(the timed-out lockvoker's continuation)
 *    - Value: std::pair<
 *					std::reference_wrapper<Qutex>,
 *					std::unique_ptr<std::forward_list<std::reference_wrapper<Qutex>>>>
 *      * pair.first: The firstFailedQutex that this lockvoker WANTS but
 *			can't acquire. This metadata is essential for later-arriving
 *			entrants to analyze what their predecessor timed-out sequences
 *			want.
 *      * pair.second: A unique_ptr to a list of all acquired Qutexes in this
 *			lockvoker's continuation history.
 *
 * 3. Each timed-out lockvoker:
 *    a) Adds itself to the acquisition history map with its wanted lock and
 *		acquired locks
 *    b) Iterates through all OTHER entries in the map (excluding itself)
 *    c) For each other entry, checks if that entry's acquired locks
 *		(pair.second) contains the lock that this lockvoker wants
 *		(aka: firstFailedQutex/pair.first)
 *    d) If found, we have detected a gridlock: two sequences where at least
 *		one wants a lock held by the other, and the other wants a lock that
 *		it can't acquire.
 *
 *	GRIDLOCK CONDITION:
 * A gridlock exists when we find a circular chain of dependencies:
 * - Lockvoker A wants LockX but can't acquire it (held by Lockvoker B)
 * - Lockvoker B wants LockY but can't acquire it (held by Lockvoker C, D, etc.)
 * - The chain must be circular (eventually leading back to Lockvoker A or another
 *   lockvoker in the chain) to ensure it's a true gridlock, not just a delay
 *
 *	TIMED DELAY, I/O DELAY, or LONG-RUNNING OPERATION FALSE-POSITIVE:
 * Without circularity detection, we could incorrectly flag a simple delay, I/O
 * delay, or long-running operation as a gridlock. For example: Lockvoker A
 * wants LockX (held by Lockvoker B), and Lockvoker B is currently in a 10-second
 * sleep/delay. When B wakes up, it will release LockX, allowing A to proceed.
 * This is not a gridlock - it's just A waiting longer than DEADLOCK_TIMEOUT_MS
 * for B to finish its work. True gridlocks require circular dependencies where
 * no sequence can make progress because they're all waiting for each other in
 * a cycle.
 *
 * The central history metadata enables us to detect complex gridlocks involving
 * multiple lockvokers (2, 3, 4, 5+ sequences) by building up the acquisition
 * history over time as different lockvokers timeout and add their information.
 */

bool QutexAcquisitionHistoryTracker
::heuristicallyTraceContinuationHistoryForGridlockOn(Qutex &firstFailedQutex)
const
{
	/**	HEURISTIC APPROACH:
	 * Due to the computational complexity of full circularity detection,
	 * we implement a heuristically adequate check: when we find 2 sequences
	 * where one depends on the other, and the other has reached timeout,
	 * we assume this is a likely gridlock. This approach is not
	 * algorithmically complete (it may miss some complex circular
	 * dependencies or flag false positives), but it is heuristically useful
	 * for debugging and identifying potential concurrency issues in
	 * practice.
	 *
	 * See the file-local comment above for the complete algorithm
	 * explanation.
	 */

	return false;
}

bool QutexAcquisitionHistoryTracker
::completelyTraceContinuationHistoryForGridlockOn(Qutex &firstFailedQutex)
const
{
	/** ALGORITHMICALLY COMPLETE VERSION:
	 * This function is intended to implement the algorithmically complete
	 * version of gridlock detection that performs full circularity detection.
	 * This would involve building a dependency graph from the acquisition
	 * history and using graph traversal algorithms (such as DFS with cycle
	 * detection) to identify true circular dependencies.
	 *
	 * See the file-local comment above for the complete algorithm
	 * explanation.
	 */

	return false;
}

} // namespace smo