DSInternals/Src/DSInternals.PowerShell/Commands/Base/PSCmdletEx.cs

namespace DSInternals.PowerShell.Commands
{
    using Microsoft.PowerShell.Commands;
    using System.IO;
    using System.Management.Automation;

    public abstract class PSCmdletEx : PSCmdlet
    {
        protected string ResolveDirectoryPath(string path)
        {
            if (path == null)
            {
                // This is probably a value passed from an optional parameter.
                return null;
            }

            string resolvedPath = this.ResolveSinglePath(path);
            bool isDirectory = File.GetAttributes(resolvedPath).HasFlag(FileAttributes.Directory);

            if (!isDirectory)
            {
                throw new DirectoryNotFoundException("The path provided does not point to a directory.");
            }

            return resolvedPath;
        }

        protected string ResolveFilePath(string path)
        {
            if (path == null)
            {
                // This is probably a value passed from an optional parameter.
                return null;
            }

            string resolvedPath = this.ResolveSinglePath(path);
            bool isDirectory = File.GetAttributes(resolvedPath).HasFlag(FileAttributes.Directory);

            if (isDirectory)
            {
                throw new FileNotFoundException("The path provided does not point to a file.");
            }

            return resolvedPath;
        }

        private string ResolveSinglePath(string path)
        {
            ProviderInfo provider;
            // This throws ItemNotFoundException if the path is not found
            var resolvedPaths = this.GetResolvedProviderPathFromPSPath(path, out provider);

            if (provider.ImplementingType != typeof(FileSystemProvider))
            {
                throw new ItemNotFoundException("The path provided does not point to a file system.");
            }

            if (resolvedPaths.Count != 1)
            {
                throw new ItemNotFoundException("Could not resolve the path provided to a single file or directory.");
            }

            return resolvedPaths[0];
        }
    }
}