using System.Collections.Concurrent;
using System.Text;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting.Server;
using Microsoft.AspNetCore.Hosting.Server.Features;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;

namespace WebDrop.Api.Tests;

/// <summary>只实现备份用到的 WebDAV 子集(MKCOL、PUT、DELETE、PROPFIND Depth 1),数据放在内存里,带基本认证。</summary>
public sealed class FakeWebDav : IAsyncDisposable
{
    private readonly WebApplication _app;
    public ConcurrentDictionary<string, byte[]> Files { get; } = new();
    public ConcurrentDictionary<string, bool> Dirs { get; } = new();
    public bool Down { get; set; }
    public string Url { get; private set; } = "";
    public const string User = "backup", Password = "p@ss";

    public FakeWebDav()
    {
        var builder = WebApplication.CreateSlimBuilder();
        builder.Configuration["urls"] = "http://127.0.0.1:0";
        builder.Logging.ClearProviders();
        _app = builder.Build();
        _app.Map("/dav/{**path}", async (HttpContext ctx, string? path) =>
        {
            if (Down) { ctx.Response.StatusCode = 503; return; }
            string expected = "Basic " + Convert.ToBase64String(Encoding.UTF8.GetBytes($"{User}:{Password}"));
            if (ctx.Request.Headers.Authorization != expected) { ctx.Response.StatusCode = 401; return; }
            path = Uri.UnescapeDataString(path ?? "").Trim('/');
            switch (ctx.Request.Method)
            {
                case "MKCOL":
                    ctx.Response.StatusCode = Dirs.TryAdd(path, true) ? 201 : 405;
                    break;
                case "PUT":
                    using (var ms = new MemoryStream()) { await ctx.Request.Body.CopyToAsync(ms); Files[path] = ms.ToArray(); }
                    ctx.Response.StatusCode = 201;
                    break;
                case "DELETE":
                    {
                        bool removed = Files.TryRemove(path, out _);
                        foreach (var key in Files.Keys.Where(k => k.StartsWith(path + "/", StringComparison.Ordinal)).ToList()) { Files.TryRemove(key, out _); removed = true; }
                        foreach (var key in Dirs.Keys.Where(k => k == path || k.StartsWith(path + "/", StringComparison.Ordinal)).ToList()) { Dirs.TryRemove(key, out _); removed = true; }
                        ctx.Response.StatusCode = removed ? 204 : 404;
                        break;
                    }
                case "PROPFIND":
                    {
                        if (path.Length > 0 && !Dirs.ContainsKey(path)) { ctx.Response.StatusCode = 404; return; }
                        string prefix = path.Length == 0 ? "" : path + "/";
                        var children = Files.Keys.Concat(Dirs.Keys).Where(k => k.StartsWith(prefix, StringComparison.Ordinal) && k.Length > prefix.Length && !k[prefix.Length..].Contains('/')).Distinct().Order();
                        var xml = new StringBuilder("<?xml version=\"1.0\"?><d:multistatus xmlns:d=\"DAV:\">");
                        xml.Append($"<d:response><d:href>/dav/{path}/</d:href></d:response>");
                        foreach (var child in children) xml.Append($"<d:response><d:href>/dav/{child}</d:href></d:response>");
                        xml.Append("</d:multistatus>");
                        ctx.Response.StatusCode = 207;
                        ctx.Response.ContentType = "application/xml";
                        await ctx.Response.WriteAsync(xml.ToString());
                        break;
                    }
                default: ctx.Response.StatusCode = 405; break;
            }
        });
    }

    public async Task StartAsync()
    {
        await _app.StartAsync();
        Url = _app.Services.GetRequiredService<IServer>().Features.Get<IServerAddressesFeature>()!.Addresses.First().TrimEnd('/') + "/dav";
    }

    public async ValueTask DisposeAsync()
    {
        await _app.StopAsync();
        await _app.DisposeAsync();
    }
}