using System;
using System.Globalization;
using System.IO;
using System.Runtime.InteropServices;
using System.Threading;
using System.Threading.Tasks;
using Jellyfin.Api.Models.StreamingDtos;
using MediaBrowser.Controller.MediaEncoding;
using MediaBrowser.Model.IO;
using Microsoft.Extensions.Logging;

namespace Jellyfin.Api.Helpers
{
    /// <summary>
    /// The hls helpers.
    /// </summary>
    public static class HlsHelpers
    {
        /// <summary>
        /// Waits for a minimum number of segments to be available.
        /// </summary>
        /// <param name="playlist">The playlist string.</param>
        /// <param name="segmentCount">The segment count.</param>
        /// <param name="logger">Instance of the <see cref="ILogger"/> interface.</param>
        /// <param name="cancellationToken">The <see cref="CancellationToken"/>.</param>
        /// <returns>A <see cref="Task"/> indicating the waiting process.</returns>
        public static async Task WaitForMinimumSegmentCount(string playlist, int? segmentCount, ILogger logger, CancellationToken cancellationToken)
        {
            logger.LogDebug("Waiting for {0} segments in {1}", segmentCount, playlist);

            while (!cancellationToken.IsCancellationRequested)
            {
                try
                {
                    // Need to use FileShare.ReadWrite because we're reading the file at the same time it's being written
                    var fileStream = new FileStream(
                        playlist,
                        FileMode.Open,
                        FileAccess.Read,
                        FileShare.ReadWrite,
                        IODefaults.FileStreamBufferSize,
                        FileOptions.SequentialScan);
                    await using (fileStream.ConfigureAwait(false))
                    {
                        using var reader = new StreamReader(fileStream);
                        var count = 0;

                        while (!reader.EndOfStream)
                        {
                            var line = await reader.ReadLineAsync().ConfigureAwait(false);
                            if (line == null)
                            {
                                // Nothing currently in buffer.
                                break;
                            }

                            if (line.IndexOf("#EXTINF:", StringComparison.OrdinalIgnoreCase) != -1)
                            {
                                count++;
                                if (count >= segmentCount)
                                {
                                    logger.LogDebug("Finished waiting for {0} segments in {1}", segmentCount, playlist);
                                    return;
                                }
                            }
                        }
                    }

                    await Task.Delay(100, cancellationToken).ConfigureAwait(false);
                }
                catch (IOException)
                {
                    // May get an error if the file is locked
                }

                await Task.Delay(50, cancellationToken).ConfigureAwait(false);
            }
        }

        /// <summary>
        /// Gets the #EXT-X-MAP string.
        /// </summary>
        /// <param name="outputPath">The output path of the file.</param>
        /// <param name="state">The <see cref="StreamState"/>.</param>
        /// <param name="isOsDepends">Get a normal string or depends on OS.</param>
        /// <returns>The string text of #EXT-X-MAP.</returns>
        public static string GetFmp4InitFileName(string outputPath, StreamState state, bool isOsDepends)
        {
            var directory = Path.GetDirectoryName(outputPath) ?? throw new ArgumentException($"Provided path ({outputPath}) is not valid.", nameof(outputPath));
            var outputFileNameWithoutExtension = Path.GetFileNameWithoutExtension(outputPath);
            var outputPrefix = Path.Combine(directory, outputFileNameWithoutExtension);
            var outputExtension = EncodingHelper.GetSegmentFileExtension(state.Request.SegmentContainer);

            // on Linux/Unix
            // #EXT-X-MAP:URI="prefix-1.mp4"
            var fmp4InitFileName = outputFileNameWithoutExtension + "-1" + outputExtension;
            if (!isOsDepends)
            {
                return fmp4InitFileName;
            }

            var isWindows = RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
            if (isWindows)
            {
                // on Windows
                // #EXT-X-MAP:URI="X:\transcodes\prefix-1.mp4"
                fmp4InitFileName = outputPrefix + "-1" + outputExtension;
            }

            return fmp4InitFileName;
        }

        /// <summary>
        /// Gets the hls playlist text.
        /// </summary>
        /// <param name="path">The path to the playlist file.</param>
        /// <param name="state">The <see cref="StreamState"/>.</param>
        /// <returns>The playlist text as a string.</returns>
        public static string GetLivePlaylistText(string path, StreamState state)
        {
            using var stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
            using var reader = new StreamReader(stream);

            var text = reader.ReadToEnd();

            var segmentFormat = EncodingHelper.GetSegmentFileExtension(state.Request.SegmentContainer).TrimStart('.');
            if (string.Equals(segmentFormat, "mp4", StringComparison.OrdinalIgnoreCase))
            {
                var fmp4InitFileName = GetFmp4InitFileName(path, state, true);
                var baseUrlParam = string.Format(
                    CultureInfo.InvariantCulture,
                    "hls/{0}/",
                    Path.GetFileNameWithoutExtension(path));
                var newFmp4InitFileName = baseUrlParam + GetFmp4InitFileName(path, state, false);

                // Replace fMP4 init file URI.
                text = text.Replace(fmp4InitFileName, newFmp4InitFileName, StringComparison.InvariantCulture);
            }

            return text;
        }
    }
}