using System;
using System.Collections.Concurrent;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions.Internal;
using Microsoft.Extensions.Logging.Console;
using Microsoft.Extensions.Logging.Console.Internal;

namespace BTCPayServer.Logging
{
    public class CustomConsoleLogProvider : ILoggerProvider
    {
        ConsoleLoggerProcessor _Processor;
        public CustomConsoleLogProvider(ConsoleLoggerProcessor processor)
        {
            _Processor = processor;
        }
        public ILogger CreateLogger(string categoryName)
        {
            return new CustomerConsoleLogger(categoryName, (a, b) => true, null, _Processor);
        }

        public void Dispose()
        {
        }
    }

    /// <summary>
    /// A variant of ASP.NET Core ConsoleLogger which does not make new line for the category
    /// </summary>
    public class CustomerConsoleLogger : ILogger
    {
        private static readonly string _loglevelPadding = ": ";
        private static readonly string _messagePadding;
        private static readonly string _newLineWithMessagePadding;

        // ConsoleColor does not have a value to specify the 'Default' color
        private readonly ConsoleColor? DefaultConsoleColor = null;

        private readonly ConsoleLoggerProcessor _queueProcessor;
        private Func<string, LogLevel, bool> _filter;

        [ThreadStatic]
        private static StringBuilder _logBuilder;

        static CustomerConsoleLogger()
        {
            var logLevelString = GetLogLevelString(LogLevel.Information);
            _messagePadding = new string(' ', logLevelString.Length + _loglevelPadding.Length);
            _newLineWithMessagePadding = Environment.NewLine + _messagePadding;
        }

        public CustomerConsoleLogger(string name, Func<string, LogLevel, bool> filter, bool includeScopes)
            : this(name, filter, includeScopes ? new LoggerExternalScopeProvider() : null, new ConsoleLoggerProcessor())
        {
        }

        internal CustomerConsoleLogger(string name, Func<string, LogLevel, bool> filter, IExternalScopeProvider scopeProvider)
            : this(name, filter, scopeProvider, new ConsoleLoggerProcessor())
        {
        }

        internal CustomerConsoleLogger(string name, Func<string, LogLevel, bool> filter, IExternalScopeProvider scopeProvider, ConsoleLoggerProcessor loggerProcessor)
        {
            if (name == null)
            {
                throw new ArgumentNullException(nameof(name));
            }

            Name = name;
            Filter = filter ?? ((category, logLevel) => true);
            ScopeProvider = scopeProvider;
            _queueProcessor = loggerProcessor;

            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
            {
                Console = new WindowsLogConsole();
            }
            else
            {
                Console = new AnsiLogConsole(new AnsiSystemConsole());
            }
        }

        public IConsole Console
        {
            get
            {
                return _queueProcessor.Console;
            }
            set
            {
                if (value == null)
                {
                    throw new ArgumentNullException(nameof(value));
                }

                _queueProcessor.Console = value;
            }
        }

        public Func<string, LogLevel, bool> Filter
        {
            get
            {
                return _filter;
            }
            set
            {
                if (value == null)
                {
                    throw new ArgumentNullException(nameof(value));
                }

                _filter = value;
            }
        }

        public string Name
        {
            get;
        }

        internal IExternalScopeProvider ScopeProvider
        {
            get; set;
        }

        public bool DisableColors
        {
            get; set;
        }

        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
        {
            if (!IsEnabled(logLevel))
            {
                return;
            }

            if (formatter == null)
            {
                throw new ArgumentNullException(nameof(formatter));
            }

            var message = formatter(state, exception);

            if (!string.IsNullOrEmpty(message) || exception != null)
            {
                WriteMessage(logLevel, Name, eventId.Id, message, exception);
            }
        }

        public virtual void WriteMessage(LogLevel logLevel, string logName, int eventId, string message, Exception exception)
        {
            var logBuilder = _logBuilder;
            _logBuilder = null;

            if (logBuilder == null)
            {
                logBuilder = new StringBuilder();
            }

            var logLevelColors = default(ConsoleColors);
            var logLevelString = string.Empty;

            // Example:
            // INFO: ConsoleApp.Program[10]
            //       Request received

            logLevelColors = GetLogLevelConsoleColors(logLevel);
            logLevelString = GetLogLevelString(logLevel);
            // category and event id
            var lenBefore = logBuilder.ToString().Length;
            logBuilder.Append(_loglevelPadding);
            logBuilder.Append(logName);
            logBuilder.Append(": ");
            var lenAfter = logBuilder.ToString().Length;
            while (lenAfter++ < 18)
                logBuilder.Append(" ");
            // scope information
            GetScopeInformation(logBuilder);

            if (!string.IsNullOrEmpty(message))
            {
                // message
                //logBuilder.Append(_messagePadding);

                var len = logBuilder.Length;
                logBuilder.AppendLine(message);
                logBuilder.Replace(Environment.NewLine, _newLineWithMessagePadding, len, message.Length);
            }

            // Example:
            // System.InvalidOperationException
            //    at Namespace.Class.Function() in File:line X
            if (exception != null)
            {
                // exception message
                logBuilder.AppendLine(exception.ToString());
            }

            if (logBuilder.Length > 0)
            {
                var hasLevel = !string.IsNullOrEmpty(logLevelString);
                // Queue log message
                _queueProcessor.EnqueueMessage(new LogMessageEntry()
                {
                    Message = logBuilder.ToString(),
                    MessageColor = DefaultConsoleColor,
                    LevelString = hasLevel ? logLevelString : null,
                    LevelBackground = hasLevel ? logLevelColors.Background : null,
                    LevelForeground = hasLevel ? logLevelColors.Foreground : null
                });
            }

            logBuilder.Clear();
            if (logBuilder.Capacity > 1024)
            {
                logBuilder.Capacity = 1024;
            }
            _logBuilder = logBuilder;
        }

        public bool IsEnabled(LogLevel logLevel)
        {
            if (logLevel == LogLevel.None)
            {
                return false;
            }

            return Filter(Name, logLevel);
        }

        public IDisposable BeginScope<TState>(TState state) => ScopeProvider?.Push(state) ?? NullScope.Instance;

        private static string GetLogLevelString(LogLevel logLevel)
        {
            switch (logLevel)
            {
                case LogLevel.Trace:
                    return "trce";
                case LogLevel.Debug:
                    return "dbug";
                case LogLevel.Information:
                    return "info";
                case LogLevel.Warning:
                    return "warn";
                case LogLevel.Error:
                    return "fail";
                case LogLevel.Critical:
                    return "crit";
                default:
                    throw new ArgumentOutOfRangeException(nameof(logLevel));
            }
        }

        private ConsoleColors GetLogLevelConsoleColors(LogLevel logLevel)
        {
            if (DisableColors)
            {
                return new ConsoleColors(null, null);
            }

            // We must explicitly set the background color if we are setting the foreground color,
            // since just setting one can look bad on the users console.
            switch (logLevel)
            {
                case LogLevel.Critical:
                    return new ConsoleColors(ConsoleColor.White, ConsoleColor.Red);
                case LogLevel.Error:
                    return new ConsoleColors(ConsoleColor.Black, ConsoleColor.Red);
                case LogLevel.Warning:
                    return new ConsoleColors(ConsoleColor.Yellow, ConsoleColor.Black);
                case LogLevel.Information:
                    return new ConsoleColors(ConsoleColor.DarkGreen, ConsoleColor.Black);
                case LogLevel.Debug:
                    return new ConsoleColors(ConsoleColor.Gray, ConsoleColor.Black);
                case LogLevel.Trace:
                    return new ConsoleColors(ConsoleColor.Gray, ConsoleColor.Black);
                default:
                    return new ConsoleColors(DefaultConsoleColor, DefaultConsoleColor);
            }
        }

        private void GetScopeInformation(StringBuilder stringBuilder)
        {
            var scopeProvider = ScopeProvider;
            if (scopeProvider != null)
            {
                var initialLength = stringBuilder.Length;

                scopeProvider.ForEachScope((scope, state) =>
                {
                    var (builder, length) = state;
                    var first = length == builder.Length;
                    builder.Append(first ? "=> " : " => ").Append(scope);
                }, (stringBuilder, initialLength));

                if (stringBuilder.Length > initialLength)
                {
                    stringBuilder.Insert(initialLength, _messagePadding);
                    stringBuilder.AppendLine();
                }
            }
        }

        private struct ConsoleColors
        {
            public ConsoleColors(ConsoleColor? foreground, ConsoleColor? background)
            {
                Foreground = foreground;
                Background = background;
            }

            public ConsoleColor? Foreground
            {
                get;
            }

            public ConsoleColor? Background
            {
                get;
            }
        }

        private class AnsiSystemConsole : IAnsiSystemConsole
        {
            public void Write(string message)
            {
                System.Console.Write(message);
            }

            public void WriteLine(string message)
            {
                System.Console.WriteLine(message);
            }
        }
    }

    public class ConsoleLoggerProcessor : IDisposable
    {
        private const int _maxQueuedMessages = 1024;

        private readonly BlockingCollection<LogMessageEntry> _messageQueue = new BlockingCollection<LogMessageEntry>(_maxQueuedMessages);
        private readonly Task _outputTask;

        public IConsole Console;

        public ConsoleLoggerProcessor()
        {
            // Start Console message queue processor
            _outputTask = Task.Factory.StartNew(
                ProcessLogQueue,
                state: this,
                cancellationToken: default(CancellationToken),
                creationOptions: TaskCreationOptions.LongRunning, scheduler: TaskScheduler.Default);
        }

        public virtual void EnqueueMessage(LogMessageEntry message)
        {
            if (!_messageQueue.IsAddingCompleted)
            {
                try
                {
                    _messageQueue.Add(message);
                    return;
                }
                catch (InvalidOperationException) { }
            }

            // Adding is completed so just log the message
            WriteMessage(message);
        }

        // for testing
        internal virtual void WriteMessage(LogMessageEntry message)
        {
            if (message.LevelString != null)
            {
                Console.Write(message.LevelString, message.LevelBackground, message.LevelForeground);
            }

            Console.Write(message.Message, message.MessageColor, message.MessageColor);
            Console.Flush();
        }

        private void ProcessLogQueue()
        {
            foreach (var message in _messageQueue.GetConsumingEnumerable())
            {
                WriteMessage(message);
            }
        }

        private static void ProcessLogQueue(object state)
        {
            var consoleLogger = (ConsoleLoggerProcessor)state;

            consoleLogger.ProcessLogQueue();
        }

        public void Dispose()
        {
            _messageQueue.CompleteAdding();

            try
            {
                _outputTask.Wait(1500); // with timeout in-case Console is locked by user input
            }
            catch (TaskCanceledException) { }
            catch (AggregateException ex) when (ex.InnerExceptions.Count == 1 && ex.InnerExceptions[0] is TaskCanceledException) { }
        }
    }

    public struct LogMessageEntry
    {
        public string LevelString;
        public ConsoleColor? LevelBackground;
        public ConsoleColor? LevelForeground;
        public ConsoleColor? MessageColor;
        public string Message;
    }

}