using System;
using System.Collections.Generic;
using System.IO;
using Robust.Shared.Utility;

namespace Robust.Shared.ContentPack
{
    /// <summary>
    ///     Utility functions
    /// </summary>
    internal static class PathHelpers
    {
        /// <summary>
        ///     Get the full directory path that the executable is located in.
        /// </summary>
        internal static string GetExecutableDirectory()
        {
            // Fallback in case the above doesn't work ig?
            var assembly = typeof(PathHelpers).Assembly;
            var location = assembly.Location;
            if (location == string.Empty)
            {
                // See https://docs.microsoft.com/en-us/dotnet/api/system.reflection.assembly.location?view=net-5.0#remarks
                // This doesn't apply to us really because we don't do that kind of publishing, but whatever.
                throw new InvalidOperationException("Cannot find path of executable.");
            }
            return Path.GetDirectoryName(location)!;
        }

        /// <summary>
        ///     Turns a relative path from the executable directory into a full path.
        /// </summary>
        public static string ExecutableRelativeFile(string file)
        {
            return Path.GetFullPath(Path.Combine(GetExecutableDirectory(), file));
        }

        /// <summary>
        ///     Recursively gets all files in a directory and all sub directories.
        /// </summary>
        /// <param name="path">Directory to start in.</param>
        /// <returns>Enumerable of all file paths in that directory and sub directories.</returns>
        public static IEnumerable<string> GetFiles(string path)
        {
            return Directory.EnumerateFiles(path, "*", SearchOption.AllDirectories);
        }

        public static bool IsFileInUse(IOException exception)
        {
            var errorCode = exception.HResult & 0xFFFF;
            return errorCode switch
            {
                // TODO: verify works on non-win systems
                32 => /* sharing not allowed */ true,
                33 => /* file is locked */ true,
                _ => false
            };
        }

        // TODO: gaf
        public static bool IsFileSystemCaseSensitive() =>
            !OperatingSystem.IsWindows()
            && !OperatingSystem.IsMacOS();


        internal static string SafeGetResourcePath(string baseDir, ResPath path)
        {
            var relSysPath = path.ToRelativeSystemPath();

            // This also blocks files like "..foo.yml". But whatever, I CBF fixing that.
            if (relSysPath.Contains("\\..")
                || relSysPath.Contains("/..")
                || relSysPath.StartsWith(".."))
            {
                // Hard cap on any exploit smuggling a .. in there.
                // Since that could allow leaving sandbox.
                throw new InvalidOperationException($"This branch should never be reached. Path: {path}");
            }

            var retPath = Path.GetFullPath(Path.Join(baseDir, relSysPath));
            // better safe than sorry check
            if (!retPath.StartsWith(baseDir))
            {
                // Allow path to match if it's just missing the directory separator at the end.
                if (retPath != baseDir.TrimEnd(Path.DirectorySeparatorChar))
                    throw new InvalidOperationException($"This branch should never be reached. Path: {path}");
            }

            return retPath;
        }
    }
}