using AngleSharp;
using AngleSharp.Dom;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading;
using System.Threading.Channels;
using System.Threading.Tasks;
using System.Linq;
using System.Runtime.Serialization;
using System.IO;

using Tools;
using System.Text.RegularExpressions;
using Tools.Crypto;

namespace napdump
{
    public readonly struct DumperConfig
    {
        public readonly int MaxThreads;
        public readonly Dumper ShareContextWith;
        public readonly (string Url, string Value)[] Cookies;
        public readonly AESKey? EncryptDeleted;

        public DumperConfig(int maxThreads, Dumper ShareContext=null, (string,string)[] Cookies=null, AESKey? EncryptDeleted=null)
        {
            MaxThreads = maxThreads;
            ShareContextWith = ShareContext;
            this.Cookies = Cookies;
            this.EncryptDeleted = EncryptDeleted;
        }

        public bool Equals(in DumperConfig other)
        {
            return other.MaxThreads == this.MaxThreads &&
                ReferenceEquals(this.ShareContextWith, other.ShareContextWith) &&
                (ReferenceEquals(Cookies, other.Cookies) || (Cookies?.SequenceEqual(other.Cookies) ?? false)) &&
                (ReferenceEquals(EncryptDeleted, other.EncryptDeleted) || (EncryptDeleted?.Equals(other.EncryptDeleted ?? default) ?? false));
        }

        public override bool Equals(object obj)
        {
            return obj is DumperConfig conf && this.Equals(conf);
        }

        public override int GetHashCode()
        {
            return MaxThreads.GetHashCode() ^
                (ShareContextWith?.GetHashCode() ?? 0) ^
                (Cookies?.Select(x => x.GetHashCode())?.Aggregate((x, y) => x ^ y) ?? 0) ^
                (EncryptDeleted?.GetHashCode() ?? 0);
        }

        public static bool operator ==(DumperConfig left, DumperConfig right)
        {
            return left.Equals(right);
        }

        public static bool operator !=(DumperConfig left, DumperConfig right)
        {
            return !(left == right);
        }
    }
    public sealed class AsyncMutex : IDisposable
    {
        private readonly SemaphoreSlim sem;

        public AsyncMutex()
        {
            sem = new SemaphoreSlim(1, 1);
        }
        private AsyncMutex(SemaphoreSlim from)
        {
            sem = from;
        }

        private class Lock : IDisposable
        {
            public AsyncMutex Parent { get; }
            public Lock(AsyncMutex held)
            {
                Parent = held;
            }

            public void Dispose()
            {
                Parent.sem.Release();
            }
        }

        public IDisposable Aquire(int msTimeout, CancellationToken token = default)
        {
            sem.Wait(msTimeout, token);
            return new Lock(this);
        }

        public IDisposable Aquire(CancellationToken token)
        {
            sem.Wait(token);
            return new Lock(this);
        }

        public IDisposable Aquire()
        {
            sem.Wait();
            return new Lock(this);
        }

        public async ValueTask<IDisposable> AquireAsync(int msTimeout, CancellationToken token = default)
        {
            await sem.WaitAsync(msTimeout, token);
            return new Lock(this);
        }

        public async ValueTask<IDisposable> AquireAsync(CancellationToken token = default)
        {
            await sem.WaitAsync(token);
            return new Lock(this);
        }

        public void Dispose()
        {
            sem.Dispose();
        }

        public static AsyncMutex Semaphore(int count, int max)
        {
            SemaphoreSlim sem = new SemaphoreSlim(count, max);
            return new AsyncMutex(sem);
        }
        public static AsyncMutex Semaphore(int count)
         => Semaphore(count, count);
    }


    public abstract class Dumper : IDisposable
    {
        public DumperConfig Config { get; }

        protected readonly AsyncMutex Pool;
        protected readonly CancellationTokenSource globalCancel = new CancellationTokenSource();

        protected Dumper(DumperConfig config)
        {
            Config = config;

            Pool = config.ShareContextWith?.Pool ?? AsyncMutex.Semaphore(config.MaxThreads);
        }

        public void CancelAllOperations()
        {
            globalCancel.Cancel();
        }

        public async IAsyncEnumerable<ThreadInfo> Parse(string boardUrl, Hooks hooks = default, [EnumeratorCancellation] CancellationToken token=default)
        {
            using var cancel = CancellationTokenSource.CreateLinkedTokenSource(globalCancel.Token, token);

            //var cataloguePage = await GetCataloguePage(boardUrl, cancel.Token);
            var boardInfo = NewBoardInfo();
            boardInfo.BoardURL = boardUrl;

            if (hooks.PrintDebug)
                Console.WriteLine($"({boardUrl}) gen PostInfo");

            Channel<Task> threadGetters = Channel.CreateUnbounded<Task>();
            Channel<ThreadInfo> completedThreads = Channel.CreateUnbounded<ThreadInfo>();

            Task completer = Task.Run(async () =>
            {
                List<Task> getters = new List<Task>();
                if (hooks.PrintDebug)
                    Console.WriteLine($"({boardUrl}) gen getter");
                int gi = 0;
                await foreach (var getter in threadGetters.Reader.ReadAllAsync(cancel.Token))
                {
                    getters.Add(getter);
                    if (hooks.PrintDebug)
                        Console.WriteLine($"({boardUrl}) add getter {gi++}");
                }
                if (hooks.PrintDebug)
                    Console.WriteLine($"({boardUrl}) add getters {getters.Count}");
                await Task.WhenAll(getters);
                if (hooks.PrintDebug)
                    Console.WriteLine($"({boardUrl}) getters complete");
                completedThreads.Writer.Complete();
            });

            if (hooks.PrintDebug)
                Console.WriteLine($"({boardUrl}) start completer");
            int ti = 0;
            await foreach (var thread in GetThreads(boardInfo).WithCancellation(cancel.Token))
            {
                //Thread got.
                thread.BoardInfo = boardInfo;

                hooks.OnThreadRetrieved?.Invoke(thread);
                ThreadRetrievedHook(thread);
                await threadGetters.Writer.WriteAsync(Task.Run(async () =>
                {
                    try
                    {
                        await InternalGetPosts(thread, hooks, cancel.Token);
                        if (hooks.PrintDebug) Console.WriteLine($"({boardUrl}) writing to complete");
                        await completedThreads.Writer.WriteAsync(thread, cancel.Token);
                        if (hooks.PrintDebug) Console.WriteLine($"({thread.BoardInfo.BoardURL}) written");
                    }catch(Exception ex)
                    {
                        if (hooks.PrintDebug)
                            Console.WriteLine($"Whoops {thread.PostNumber} failed: {ex.Message}\n{ex.StackTrace}");
                        hooks.OnThreadReadFailed?.Invoke(thread, ex);
                        ThreadReadFailedHook(thread, ex);
                    }
                }), cancel.Token);
                if (hooks.PrintDebug)
                    Console.WriteLine($"({boardUrl}) thread write ({ti++}) {thread.PostNumber}");
            }
            threadGetters.Writer.Complete();

            if (hooks.PrintDebug)
                Console.WriteLine($"({boardUrl}) stop getter");

            await foreach (var completedThread in completedThreads.Reader.ReadAllAsync(cancel.Token))
            {
                boardInfo.AddChildThread(completedThread);
                yield return completedThread;
            }
            if (hooks.PrintDebug)
                Console.WriteLine($"({boardUrl}) completer complete");

            await completer;
            boardInfo.DumpTimestamp = DateTime.Now;
            hooks.OnBoardRetrieved?.Invoke(boardInfo);
            BoardRetrievedHook(boardInfo);
            if (hooks.PrintDebug)
                Console.WriteLine($"({boardUrl}) end");
        }

        public struct Hooks
        {
            public Action<BoardInfo> OnBoardRetrieved;
            public Action<ThreadInfo> OnThreadRetrieved;
            public Action<PostInfo> OnPostRetrieved;
            public Action<ThreadInfo, Exception> OnThreadReadFailed;

#if DEBUG
            public
#else
            internal
#endif
                bool PrintDebug;
        }

        public event Action<BoardInfo> OnBoardRetrieved;
        public event Action<ThreadInfo> OnThreadRetrieved;
        public event Action<PostInfo> OnPostRetrieved;
        public event Action<ThreadInfo, Exception> OnThreadReadFailed;

        protected virtual void PostRetrievedHook(PostInfo post) => OnPostRetrieved?.Invoke(post);
        protected virtual void ThreadRetrievedHook(ThreadInfo thread) => OnThreadRetrieved?.Invoke(thread);
        protected virtual void BoardRetrievedHook(BoardInfo board) => OnBoardRetrieved?.Invoke(board);
        protected virtual void ThreadReadFailedHook(ThreadInfo thread, Exception ex) => OnThreadReadFailed?.Invoke(thread, ex);

        private async Task InternalGetPosts(ThreadInfo thread, Hooks hooks, CancellationToken token = default)
        {
            using var cancel = CancellationTokenSource.CreateLinkedTokenSource(globalCancel.Token, token);
            List<PostInfo> posts = new List<PostInfo>();
            if (hooks.PrintDebug) Console.WriteLine($"({thread.BoardInfo.BoardURL}) entering context");
            using (await Pool.AquireAsync(cancel.Token))
            {
                //var threadPage = await GetThreadPage(thread, token);
                if (hooks.PrintDebug) Console.WriteLine($" ctx_aqu ({thread.BoardInfo.BoardURL}) getting posts");
                await foreach (var post in GetPosts(thread).WithCancellation(cancel.Token))
                {
                    //Post got.
                    post.Parent = thread;
                    post.BoardInfo = thread.BoardInfo;

                    cancel.Token.ThrowIfCancellationRequested();
                    hooks.OnPostRetrieved?.Invoke(post);
                    PostRetrievedHook(post);
                    posts.Add(post);
                }
                if (hooks.PrintDebug) Console.WriteLine($" ctx_aqu ({thread.BoardInfo.BoardURL}) posts got");
            }
            if (hooks.PrintDebug) Console.WriteLine($"({thread.BoardInfo.BoardURL}) adding children");
            thread.AddChildPosts(posts);
        }

        /// <summary>
        /// Run a block on this Dumper's thread pool.
        /// </summary>
        public async Task<IDisposable> EnterContextAsync(CancellationToken token = default)
        {
            return await Pool.AquireAsync(token);
        }
        /// <summary>
        /// Run a block on this Dumper's thread pool.
        /// </summary>
        public IDisposable EnterContext(CancellationToken token = default)
        {
            return Pool.Aquire(token);
        }

        protected virtual BoardInfo NewBoardInfo() => new BoardInfo();
        protected abstract IAsyncEnumerable<PostInfo> GetPosts(ThreadInfo thread, [EnumeratorCancellation] CancellationToken token = default);
        protected abstract IAsyncEnumerable<ThreadInfo> GetThreads(BoardInfo boardInfo, [EnumeratorCancellation] CancellationToken token = default);

#region IDisposable Support
        private bool disposedValue = false;

        protected virtual void Dispose(bool disposing)
        {
            if (!disposedValue)
            {
                if (disposing)
                {
                    if (!globalCancel.IsCancellationRequested) globalCancel.Cancel();

                    if (Config.ShareContextWith == null)
                        Pool.Dispose();
                    globalCancel.Dispose();
                }

                disposedValue = true;
            }
        }

        ~Dumper()
        {
            Dispose(false);
        }

        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }
#endregion
    }
}