using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using LinqToDB;
using Microsoft.Extensions.DependencyInjection;
using Pf2e.Scrapper.Processors.Attributes;
using Pf2e.Scrapper.Processors.Definitions;
using Pf2e.Scrapper.Processors.Factory;

namespace Pf2e.Scrapper.Processors.Collection;

/// <summary>
/// Класс с коллекцией обработчиков.
/// </summary>
internal class ProcessorCollection
{
    public IServiceProvider ServiceProvider { get; }

    /// <summary>
    /// Коллекция всех доступных обработчиков.
    /// </summary>
    public ICollection<ProcessorRecord> AllItems { get; } = [];

    /// <summary>
    /// Коллекция обработчиков, которые будут обрабатываться.
    /// Для изменения необходимо использовать <see cref="FilterProcessors"/>.
    /// </summary>
    public List<ProcessorRecord> Items { get; private set; } = [];

    /// <summary>
    /// Обеспечение доступа к элементам обработчиков.
    /// </summary>
    /// <param name="name"></param>
    /// <returns></returns>
    public ProcessorRecord this[string name] => AllItems.First(item => item.Name == name);

    /// <summary>
    /// Конструктор класса <see cref="ProcessorCollection"/>.
    /// </summary>
    public ProcessorCollection(IServiceProvider serviceProvider)
    {
        ServiceProvider = serviceProvider;
        Assembly assembly = Assembly.GetExecutingAssembly();

        foreach (Type type in assembly.GetTypes())
        {
            ProcessType(type, type.GetCustomAttribute<AbstractProcessorAttribute>());
        }

        CheckDependencies();
        FilterProcessors([]);
    }

    private void ProcessType(Type type, AbstractProcessorAttribute? attribute)
    {
        switch (attribute)
        {
            case null:
                break;

            case ProcessorAttribute processorAttribute:
                ProcessType(type, processorAttribute);
                break;

            case ProcessorCollectionAttribute processorCollectionAttribute:
                ProcessType(type, processorCollectionAttribute);
                break;

            case ProcessorFactoryAttribute processorFactoryAttribute:
                ProcessType(type, processorFactoryAttribute);
                break;

            default:
                throw new(
                    $"Неизвестная реализация класса {typeof(AbstractProcessorAttribute)} - {attribute.GetType()}"
                );
        }
    }

    private void ProcessType(Type type, ProcessorAttribute? attribute)
    {
        if (attribute is null)
        {
            return;
        }

        if (!type.IsAssignableTo(typeof(IProcessor)))
        {
            throw new(
                $"Процессор {type}, которому установлен аттрибут {attribute.GetType()}, не представляет интерфейс {typeof(IProcessor)}"
            );
        }

        ProcessorDependenciesAttribute? dependenciesAttribute =
            type.GetCustomAttribute<ProcessorDependenciesAttribute>();

        ProcessorRecord item = new()
        {
            Name = attribute.Name,
            Type = type,
            Description = attribute.Description,
            Group = attribute.Group,
            Dependencies = dependenciesAttribute?.Dependencies ?? [],
            Active = attribute.Active,
            Parallel = attribute.Parallel,
        };

        item.Factory = ActivatorUtilities.CreateInstance<SimpleProcessorFactory>(
            ServiceProvider,
            item
        );

        AllItems.Add(item);
    }

    private void ProcessType(Type type, ProcessorCollectionAttribute? attribute)
    {
        if (attribute is null)
        {
            return;
        }

        if (!type.IsAssignableTo(typeof(AbstractInputProcessor)))
        {
            throw new(
                $"Процессор {type}, которому установлен аттрибут {attribute.GetType()}, не реализует класс {typeof(AbstractInputProcessor)}."
            );
        }

        ProcessorDependenciesAttribute? dependenciesAttribute =
            type.GetCustomAttribute<ProcessorDependenciesAttribute>();

        ProcessorRecord item = new()
        {
            Name = attribute.Name,
            Type = type,
            Description = attribute.Description,
            Group = attribute.Group,
            Dependencies = dependenciesAttribute?.Dependencies ?? [],
            Active = attribute.Active,
            Parallel = attribute.Parallel,
        };

        CompendiumProcessorFactory factory =
            ActivatorUtilities.CreateInstance<CompendiumProcessorFactory>(ServiceProvider, item);

        factory.CompendiumType = attribute.CompendiumType;
        factory.InnerType = attribute.InnerType;

        item.Factory = factory;

        AllItems.Add(item);
    }

    private void ProcessType(Type type, ProcessorFactoryAttribute? attribute)
    {
        if (attribute is null)
        {
            return;
        }

        if (!type.IsAssignableTo(typeof(AbstractProcessorFactory)))
        {
            throw new(
                $"Процессор {type}, которому установлен аттрибут {attribute.GetType()}, не реализует класс {typeof(AbstractProcessorFactory)}."
            );
        }

        ProcessorDependenciesAttribute? dependenciesAttribute =
            type.GetCustomAttribute<ProcessorDependenciesAttribute>();

        ProcessorRecord item = new()
        {
            Name = attribute.Name,
            Type = attribute.ProcessorType,
            Description = attribute.Description,
            Group = attribute.Group,
            Dependencies = dependenciesAttribute?.Dependencies ?? [],
            Active = attribute.Active,
            Parallel = attribute.Parallel,
            Factory = (AbstractProcessorFactory)
                ActivatorUtilities.CreateInstance(ServiceProvider, type),
        };

        AllItems.Add(item);
    }

    /// <summary>
    /// Проверка, что все зависимости всех обработчиков могут быть удовлетворены.
    /// </summary>
    private void CheckDependencies()
    {
        foreach (ProcessorRecord item in Items)
        {
            foreach (string dependency in item.Dependencies)
            {
                if (Items.All(i => i.Name != dependency))
                {
                    throw new($"Dependency '{dependency}' for processor '{item.Name}' not found.");
                }
            }
        }
    }

    /// <summary>
    /// Сортировать обработчики в соответсвии со всеми зависимостями.
    /// </summary>
    public void SortItems()
    {
        Items.ForEach(item => item.Priority = -1);

        Dictionary<string, int> priorities = [];

        while (priorities.Count < Items.Count)
        {
            foreach (ProcessorRecord item in Items)
            {
                if (item.Priority >= 0)
                {
                    continue;
                }

                IEnumerable<int> dependencyPriorities = item.Dependencies.Select(d =>
                    priorities.GetValueOrDefault(d, -1)
                );

                if (dependencyPriorities.Any(p => p == -1))
                {
                    continue;
                }

                item.Priority = Math.Max(
                    dependencyPriorities.Any() ? dependencyPriorities.Max() + 1 : 1,
                    (int)item.Group * 100
                );
                priorities.Add(item.Name, item.Priority);
            }
        }

        Items.Sort((a, b) => a.Priority - b.Priority);
    }

    /// <summary>
    /// Ограничить список используемых обработчиков по названию.
    /// Автоматически включает все обработчики, от которых зависят указанные в аргументе обработчики.
    /// </summary>
    /// <param name="processorNames">Коллекция названиий требуемых обработчиков.</param>
    public void FilterProcessors(ICollection<string> processorNames)
    {
        if (processorNames.Count == 0)
        {
            Items = [.. AllItems];
            SortItems();
            return;
        }

        Dictionary<string, bool> nameFlags = processorNames.ToDictionary(name => name, _ => false);

        while (nameFlags.Values.Any(v => !v))
        {
            foreach (
                KeyValuePair<string, bool> pair in nameFlags.Where(pair => !pair.Value).ToList()
            )
            {
                ProcessorRecord item = AllItems.First(item => item.Name == pair.Key);

                foreach (string dependency in item.Dependencies)
                {
                    nameFlags.TryAdd(dependency, false);
                }

                nameFlags[pair.Key] = true;
            }
        }

        Items = AllItems.Where(item => nameFlags.ContainsKey(item.Name)).ToList();
    }

    /// <summary>
    /// Получить список типов, которые обрабатываются в компендиуме.
    /// </summary>
    /// <param name="compendium">Тип компендиума.</param>
    /// <returns>Набор типов.</returns>
    public ICollection<string> GetTypesOfCompendium(ProcessorCompendiumEnum compendium) =>
        Items
            .Where(item =>
                item.Factory.GetType().IsAssignableTo(typeof(CompendiumProcessorFactory))
            )
            .Where(item =>
                (item.Factory as CompendiumProcessorFactory)!.CompendiumType == compendium
            )
            .Select(item => (item.Factory as CompendiumProcessorFactory)!.InnerType)
            .OfType<string>()
            .ToList();
}