using System.Diagnostics;
using System.IO;
using System.Net.Http;
using System.Text.Json.Nodes;

namespace PamhagenSysCtrl.Helpers {
    public sealed record UpdateInstaller(Version Version, Uri Url, long Size);

    public static class UpdateService {

        private static readonly HttpClient HttpClient = new() {
            Timeout = Timeout.InfiniteTimeSpan,
        };

        public static async Task<UpdateInstaller> GetLatestInstallerAsync(string feedUrl, CancellationToken cancellationToken = default) {
            using var response = await HttpClient.GetAsync(feedUrl, cancellationToken);
            response.EnsureSuccessStatusCode();

            var json = JsonNode.Parse(await response.Content.ReadAsStringAsync(cancellationToken));
            var latest = json!["data"]!.AsArray()[^1]!;
            return new(
                new Version((string)latest["version"]!),
                new Uri((string)latest["url"]!),
                (long)latest["size"]!
            );
        }

        public static async Task<string> DownloadInstallerAsync(UpdateInstaller installer, string targetDirectory, IProgress<double>? progress = null, CancellationToken cancellationToken = default) {
            Directory.CreateDirectory(targetDirectory);
            var fileName = Path.Combine(targetDirectory, $"PamhagenSysCtrl-{installer.Version}.msi");

            try {
                using var response = await HttpClient.GetAsync(installer.Url, HttpCompletionOption.ResponseHeadersRead, cancellationToken);
                response.EnsureSuccessStatusCode();
                var contentLength = response.Content.Headers.ContentLength;

                await using (var destination = new FileStream(fileName, FileMode.Create)) {
                    await using var source = await response.Content.ReadAsStreamAsync(cancellationToken);
                    var buffer = new byte[81920];
                    long downloaded = 0;
                    int read;
                    while ((read = await source.ReadAsync(buffer, cancellationToken)) != 0) {
                        await destination.WriteAsync(buffer.AsMemory(0, read), cancellationToken);
                        downloaded += read;
                        if (contentLength.HasValue) {
                            progress?.Report((double)downloaded / contentLength.Value);
                        }
                    }
                }

                progress?.Report(1);
                return fileName;
            } catch {
                File.Delete(fileName);
                throw;
            }
        }

        public static void StartInstaller(string fileName) {
            var startInfo = new ProcessStartInfo {
                FileName = "msiexec.exe",
                UseShellExecute = true,
                Verb = "runas",
            };
            startInfo.ArgumentList.Add("/i");
            startInfo.ArgumentList.Add(Path.GetFullPath(fileName));

            if (Process.Start(startInfo) == null) {
                throw new InvalidOperationException("Der Installer konnte nicht gestartet werden.");
            }
        }

    }
}