// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using Microsoft.AspNetCore.Shared;
 
namespace Microsoft.Extensions.FileProviders.Embedded.Manifest;
 
internal sealed class ManifestDirectoryInfo : IFileInfo, IDirectoryContents
{
    private IFileInfo[]? _entries;
 
    public ManifestDirectoryInfo(Assembly assembly, ManifestDirectory directory, DateTimeOffset lastModified)
    {
        ArgumentNullThrowHelper.ThrowIfNull(assembly);
        ArgumentNullThrowHelper.ThrowIfNull(directory);
 
        Assembly = assembly;
        Directory = directory;
        LastModified = lastModified;
    }
 
    public Assembly Assembly { get; }
 
    public bool Exists => true;
 
    public long Length => -1;
 
    public string? PhysicalPath => null;
 
    public string Name => Directory.Name;
 
    public DateTimeOffset LastModified { get; }
 
    public bool IsDirectory => true;
 
    public ManifestDirectory Directory { get; }
 
    public Stream CreateReadStream() =>
        throw new InvalidOperationException("Cannot create a stream for a directory.");
 
    public IEnumerator<IFileInfo> GetEnumerator()
    {
        return EnsureEntries().GetEnumerator();
 
        IEnumerable<IFileInfo> EnsureEntries() => _entries ??= ResolveEntries().ToArray();
 
        IEnumerable<IFileInfo> ResolveEntries()
        {
            if (Directory == ManifestEntry.UnknownPath)
            {
                return Array.Empty<IFileInfo>();
            }
 
            var entries = new List<IFileInfo>();
 
            foreach (var entry in Directory.Children)
            {
                IFileInfo fileInfo = entry switch
                {
                    ManifestFile file => new ManifestFileInfo(Assembly, file, LastModified),
                    ManifestDirectory directory => new ManifestDirectoryInfo(Assembly, directory, LastModified),
                    _ => throw new InvalidOperationException("Unknown entry type")
                };
 
                entries.Add(fileInfo);
            }
 
            return entries;
        }
    }
 
    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
}