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// Copyright (C) 2025 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
namespace QtVsTools
{
public class PriorityQueue<T, TPriority> : BasePriorityQueue<T, TPriority>
where TPriority : IComparable<TPriority>
{
public PriorityQueue()
{ }
public PriorityQueue(Func<T, object> getItemKey) : base(getItemKey)
{ }
public new void Enqueue(T item, TPriority priority)
{
base.Enqueue(item, priority);
}
}
public abstract class BasePriorityQueue<T, TPriority> : Concurrent, IEnumerable<T>
where TPriority : IComparable<TPriority>
{
SortedDictionary<TPriority, T> ItemsByPriority { get; }
Dictionary<object, TPriority> ItemPriority { get; }
T Head { get; set; }
public int Count { get; private set; }
public bool IsEmpty => Count == 0;
IEnumerable<T> Items => ThreadSafe(() => ItemsByPriority.Values.ToList());
IEnumerator<T> IEnumerable<T>.GetEnumerator() => Items.GetEnumerator();
IEnumerator IEnumerable.GetEnumerator() => Items.GetEnumerator();
Func<T, object> GetItemKey { get; }
public BasePriorityQueue() : this(x => x)
{ }
public BasePriorityQueue(Func<T, object> getItemKey)
{
ItemsByPriority = new SortedDictionary<TPriority, T>();
ItemPriority = new Dictionary<object, TPriority>();
Head = default;
Count = 0;
GetItemKey = getItemKey;
}
public void Clear()
{
lock (CriticalSection) {
if (Count == 0)
return;
ItemsByPriority.Clear();
ItemPriority.Clear();
Head = default;
Count = 0;
}
}
public bool Contains(T item)
{
lock (CriticalSection) {
return ItemPriority.ContainsKey(GetItemKey(item));
}
}
// Base Enqueue() is protected to allow specialized implementations to
// hide the concept of priority (e.g. PunisherQueue).
//
protected void Enqueue(T item, TPriority priority)
{
if (item == null)
throw new InvalidOperationException("Item cannot be null.");
lock (CriticalSection) {
if (ItemsByPriority.TryGetValue(priority, out T oldItem) && !item.Equals(oldItem))
throw new InvalidOperationException("An item with the same priority exists.");
if (ItemPriority.TryGetValue(GetItemKey(item), out TPriority oldPriority)) {
ItemsByPriority.Remove(oldPriority);
--Count;
}
ItemPriority[GetItemKey(item)] = priority;
ItemsByPriority[priority] = item;
Head = ItemsByPriority.First().Value;
++Count;
}
}
public bool TryPeek(out T result)
{
lock (CriticalSection) {
result = Head;
return Count > 0;
}
}
public T Peek()
{
lock (CriticalSection) {
if (!TryPeek(out T result))
throw new InvalidOperationException("Queue is empty.");
return result;
}
}
public void Remove(T item)
{
lock (CriticalSection) {
object key = GetItemKey(item);
if (key == null)
return;
ItemsByPriority.Remove(ItemPriority[key]);
ItemPriority.Remove(key);
--Count;
if (key == GetItemKey(Head))
Head = IsEmpty ? default : ItemsByPriority.First().Value;
}
}
public bool TryDequeue(out T result)
{
lock (CriticalSection) {
result = Head;
if (IsEmpty)
return false;
Remove(Head);
return true;
}
}
public T Dequeue()
{
lock (CriticalSection) {
if (!TryDequeue(out T result))
throw new InvalidOperationException("Queue is empty.");
return result;
}
}
}
}
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