Composite_FileAccess.cs

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using System;
using System.IO;
 
namespace DesignPatternExamples_csharp
{
    public static class Composite_FileAccess
    {
        // The hardcoded hierarchy representing a file/directory structure.
        // Note: This is the Composite pattern in action.
        static FileDirEntry rootEntry =
            new DirEntry("root", DateTime.Now, new FileDirEntry[] {
                new FileEntry("FileA.txt", 101, DateTime.Now),
                new FileEntry("FileB.txt", 102, DateTime.Now),
                new FileEntry("FileC.txt", 103, DateTime.Now),
                new DirEntry("subdir1", DateTime.Now, new FileDirEntry[] {
                    new FileEntry("FileD.txt", 104, DateTime.Now),
                    new FileEntry("FileE.txt", 105, DateTime.Now),
                    new DirEntry("subdir2", DateTime.Now, new FileDirEntry[] {
                        new FileEntry("FileF.txt", 106, DateTime.Now),
                        new FileEntry("FileG.txt", 107, DateTime.Now)
                    }),
                }),
            });
 
 
        private static FileDirEntry? _FindEntry(string filepath)
        {
            FileDirEntry? root = rootEntry;
 
            string[] pathComponents = filepath.Split('/');
            int numComponents = pathComponents.Length;
            for (int index = 0; index < numComponents; ++index)
            {
                if (root.Name != pathComponents[index])
                {
                    // Mismatch in path to this entry, bad path
                    root = null;
                    break;
                }
                if (index + 1 >= numComponents)
                {
                    // Reached end of path so we found what was asked for.
                    break;
                }
 
                // Still haven't reached end of specified path, look at
                // the current root for children.
 
                FileDirEntry[]? children = root.Children;
                if (children == null)
                {
                    // Path included leaf in the middle, bad path
                    root = null;
                    break;
                }
 
                root = null; // Assume we won't find matching child
                // Look ahead in the path for a matching child.
                string childComponent = pathComponents[index + 1];
                foreach (FileDirEntry child in children)
                {
                    if (childComponent == child.Name)
                    {
                        root = child;
                        break;
                    }
                }
                if (root == null)
                {
                    // Couldn't find matching child, bad path
                    break;
                }
            }
 
            // Root is either a valid file/directory entry that matches the
            // requested path or it is null, indicating the entry could not be
            // found.
            return root;
        }
 
        
        public static FileDirEntry GetEntry(string filepath)
        {
            filepath = filepath.Replace('\\', '/');
            FileDirEntry? filedirEntry = _FindEntry(filepath);
 
            if (filedirEntry == null)
            {
                string msg = String.Format("Unable to find '{0}'", filepath);
                throw new FileNotFoundException(msg);
            }
 
            return filedirEntry;
        }
    }
}