using System.Collections.Concurrent;
using System.Data;
using InServiceQue.Core.Models;
using InServiceQue.Core.Repositories;

namespace InServiceQue.InMemory;

public class TaskRepositoryInMemory: ITaskRepository
{
    //todo: concurrent access here
    private static int _currentShard;
    private static ConcurrentDictionary<string, ConcurrentQueue<QueueTask>> _quesByType = new();
    public void Dispose()
    {
        // TODO release managed resources here
    }

    public void Insert(QueueTask task)
    {
        if (_quesByType.ContainsKey(task.TaskType))
        {
            _quesByType.AddOrUpdate(task.TaskType, 
                (t) => new ConcurrentQueue<QueueTask>(new[] { task }), 
                (t, queue) =>
                {
                    queue.Enqueue(task);
                    return queue;
                }
            );
        }
    }

    public async Task InsertAsync(QueueTask task)
    {
        
        Insert(task);
        await Task.CompletedTask;
    }

    public IDbTransaction StartTransaction()
    {
        return null;
    }

    public async Task<IDbTransaction> StartTransactionAsync()
    {
        return await Task.FromResult<IDbTransaction>(null);
    }

    public void CommitTransaction(IDbTransaction tx)
    {
       
    }

    public async Task CommitTransactionAsync(IDbTransaction tx)
    {
        await Task.CompletedTask;
    }

    public void RollbackTransaction(IDbTransaction tx)
    {
        
    }

    public async Task RollbackTransactionAsync(IDbTransaction tx)
    {
        await Task.CompletedTask;
    }

    public QueueTask? GetNextTask(IDbTransaction tx, string? taskType = null)
    {
        if (taskType == null)
            return GetNextTaskRolling();
        
        QueueTask? task = null;
        if (_quesByType.TryGetValue(taskType, out var que))
        {
            que.TryDequeue(out task);
        }

        return task;
    }

    public QueueTask? GetNextTaskRolling()
    {
        QueueTask? task = null;
        var topicsCount = _quesByType.Count;
        for (int i = 0; i < topicsCount; i++)
        {
            //todo: concurrent access
            if (i == _currentShard)
            {
                var keyValuePair = _quesByType.ToArray()[i];
                var que = keyValuePair.Value;
                que.TryDequeue(out task);

                if (que.IsEmpty)
                {
                    _quesByType.TryRemove(keyValuePair);
                }

                break;
            }
        }
        //todo: concurrent access
        _currentShard = _currentShard == topicsCount - 1 ? 0 : _currentShard + 1;
        
        return task;
    }
    
    

    public async Task<QueueTask?> GetNextTaskAsync(IDbTransaction tx, string? taskType = null)
    {
        if (taskType == null)
            return await Task.FromResult(GetNextTaskRolling());
        
        QueueTask? task = null;
        if (_quesByType.TryGetValue(taskType, out var que))
        {
            que.TryDequeue(out task);
        }
        
        return await Task.FromResult(task);
    }

    public void SaveTask(QueueTask task, IDbTransaction tx)
    {
        
    }

    public async Task SaveTaskAsync(QueueTask task, IDbTransaction tx)
    {
        await Task.CompletedTask;
    }
}