using AppScaffolding;
using Dinah.Core.Net.Http;
using LibationFileManager;
using System;
using System.IO;
using System.Net.Http;
using System.Threading.Tasks;

namespace LibationUiBase;

public class UpgradeEventArgs
{
	public required UpgradeProperties UpgradeProperties { get; init; }
	public bool CapUpgrade { get; internal init; }
	private bool _ignore = false;
	private bool _installUpgrade = true;
	public bool Ignore
	{
		get => _ignore;
		set
		{
			_ignore = value;
			_installUpgrade &= !Ignore;
		}
	}
	public bool InstallUpgrade
	{
		get => _installUpgrade;
		set
		{
			_installUpgrade = value;
			_ignore &= !InstallUpgrade;
		}
	}
}

public class Upgrader : UpgraderBase
{
	protected override async Task<VersionCheckResult> CheckForUpgradeAsync()
	{
		try
		{
			return await Task.Run(LibationScaffolding.GetLatestRelease);
		}
		catch (Exception ex)
		{
			string message = "An error occurred while checking for app upgrades.";
			Serilog.Log.Logger.Error(ex, message);
			OnUpgradeFailed(message, ex);
			return new VersionCheckResult(VersionCheckOutcome.UnableToDetermine);
		}
	}

	protected override async Task<string?> DownloadUpgradeAsync(UpgradeProperties upgradeProperties)
	{
		if (upgradeProperties.ZipUrl is null)
		{
			string message = "Download link for new version not found.";
			Serilog.Log.Logger.Warning(message);
			OnUpgradeFailed(message, null);
			return null;
		}

		//Silently download the upgrade in the background, save it to a temp file.
		var zipFile = GetUpgradeDownloadPath(upgradeProperties.ZipUrl);
		if (zipFile is null)
			return null;

		Serilog.Log.Logger.Information($"Downloading {zipFile}");

		try
		{
			using var dlClient = new HttpClient();
			using var response = await dlClient.GetAsync(upgradeProperties.ZipUrl, HttpCompletionOption.ResponseHeadersRead);
			using var dlStream = await response.Content.ReadAsStreamAsync();
			using var tempFile = File.OpenWrite(zipFile);

			int read;
			long totalRead = 0;
			Memory<byte> buffer = new byte[128 * 1024];
			long contentLength = response.Content.Headers.ContentLength ?? 0;

			while ((read = await dlStream.ReadAsync(buffer)) > 0)
			{
				await tempFile.WriteAsync(buffer[..read]);
				totalRead += read;

				OnDownloadProgress(
					new DownloadProgress
					{
						BytesReceived = totalRead,
						TotalBytesToReceive = contentLength,
						ProgressPercentage = contentLength > 0 ? 100d * totalRead / contentLength : 0
					});
			}

			return zipFile;
		}
		catch (Exception ex)
		{
			var message = $"Failed to download the upgrade: {upgradeProperties.ZipUrl}";
			Serilog.Log.Logger.Error(ex, message);
			OnUpgradeFailed(message, ex);
			return null;
		}
	}

	/// <summary>
	/// Allocate a fresh per-run temp directory for the upgrade zip and return the full path
	/// the zip should be downloaded to. Uses a random subdirectory name (and 0700 perms on
	/// Unix) so we never extract or execute from a predictable, shared-temp location.
	/// </summary>
	/// <returns>Destination path for the upgrade zip, or <c>null</c> if the temp directory
	/// could not be created (in which case the upgrade-failed event has already been raised).</returns>
	private string? GetUpgradeDownloadPath(string zipUrl)
	{
		try
		{
			var stagingDir = Directory.CreateTempSubdirectory("Libation-upgrade-").FullName;
			return Path.Combine(stagingDir, Path.GetFileName(zipUrl));
		}
		catch (Exception ex)
		{
			var message = "Failed to create a temp directory for the upgrade download.";
			Serilog.Log.Logger.Error(ex, message);
			OnUpgradeFailed(message, ex);
			return null;
		}
	}
}

public class MockUpgrader : UpgraderBase
{
	public int DownloadTimeMs { get; set; } = 3000;
	public int DownloadSizeInBytes { get; set; } = 150 * 1024 * 1024;
	public bool CheckForUpgradeSucceeds { get; set; } = true;
	public bool DownloadUpgradeSucceeds { get; set; } = true;
	public string? MockUpgradeBundle { get; set; }

	protected override Task<VersionCheckResult> CheckForUpgradeAsync()
	{
		if (!CheckForUpgradeSucceeds)
		{
			OnUpgradeFailed("Mock Check For Upgrade Failed", null);
			return Task.FromResult(new VersionCheckResult(VersionCheckOutcome.UnableToDetermine));
		}
		return Task.FromResult(new VersionCheckResult(VersionCheckOutcome.UpdateAvailable, new UpgradeProperties(
					"http://fake.url/to/bundle.zip",
					"",
					Path.GetFileName(MockUpgradeBundle) ?? "",
					LibationScaffolding.BuildVersion ?? new(1, 0, 0, 0),
					"<RELEASE NOTES>")));
	}

	protected override async Task<string?> DownloadUpgradeAsync(UpgradeProperties upgradeProperties)
	{
		if (!File.Exists(MockUpgradeBundle))
		{
			OnUpgradeFailed("Mock Download bundle file not found", null);
			return null;
		}

		for (int i = 1; i <= 100; i++)
		{
			await Task.Delay(DownloadTimeMs / 100);
			OnDownloadProgress(new()
			{
				BytesReceived = DownloadSizeInBytes / 100,
				ProgressPercentage = i,
				TotalBytesToReceive = DownloadSizeInBytes * i / 100
			});
		}
		if (!DownloadUpgradeSucceeds)
		{
			OnUpgradeFailed("Mock Download Upgrade Failed", null);
			return null;
		}

		return MockUpgradeBundle;
	}
}

public abstract class UpgraderBase
{
	public event EventHandler? DownloadBegin;
	public event EventHandler<DownloadProgress>? DownloadProgress;
	public event EventHandler<bool>? DownloadCompleted;
	public event EventHandler<string>? UpgradeFailed;

	protected void OnDownloadProgress(DownloadProgress args) => DownloadProgress?.Invoke(this, args);
	protected void OnUpgradeFailed(string message, Exception? ex)
		=> UpgradeFailed?.Invoke(this, (message + Environment.NewLine + Environment.NewLine + ex?.Message).Trim());
	protected abstract Task<VersionCheckResult> CheckForUpgradeAsync();
	protected abstract Task<string?> DownloadUpgradeAsync(UpgradeProperties upgradeProperties);

	/// <summary>Check for upgrade and invoke <paramref name="upgradeAvailableHandler"/> if an update is available. Returns the check outcome so the UI can show "up to date", "update available", or "unable to determine".</summary>
	public async Task<VersionCheckResult> CheckForUpgradeAsync(Func<UpgradeEventArgs, Task> upgradeAvailableHandler)
	{
		try
		{
			var result = await CheckForUpgradeAsync();

			if (result.Outcome != VersionCheckOutcome.UpdateAvailable || result.UpgradeProperties is not UpgradeProperties upgradeProperties)
				return result;

			const string ignoreUpgrade = "IgnoreUpgrade";
			var config = Configuration.Instance;

			if (config.GetString(propertyName: ignoreUpgrade) == upgradeProperties.LatestRelease.ToString())
				return result;

			var interop = InteropFactory.Create();

			if (!interop.CanUpgrade)
				Serilog.Log.Logger.Information("Can't perform upgrade automatically");

			var upgradeEventArgs = new UpgradeEventArgs
			{
				UpgradeProperties = upgradeProperties,
				CapUpgrade = interop.CanUpgrade
			};

			await upgradeAvailableHandler(upgradeEventArgs);

			if (upgradeEventArgs.Ignore)
				config.SetString(upgradeProperties.LatestRelease.ToString(), ignoreUpgrade);

			if (!upgradeEventArgs.InstallUpgrade) return result;

			//Download the upgrade file in the background,
			DownloadBegin?.Invoke(this, EventArgs.Empty);
			string? upgradeBundle = await DownloadUpgradeAsync(upgradeProperties);

			if (string.IsNullOrEmpty(upgradeBundle) || !File.Exists(upgradeBundle))
			{
				DownloadCompleted?.Invoke(this, false);
			}
			else
			{
				DownloadCompleted?.Invoke(this, true);

				Serilog.Log.Logger.Information($"Begin running auto-upgrader");
				try
				{
					await interop.InstallUpgradeAsync(upgradeBundle);
					Serilog.Log.Logger.Information($"Completed running auto-upgrader");
				}
				catch (Exception ex)
				{
					Serilog.Log.Logger.Error(ex, "Auto-upgrader did not complete successfully");
					OnUpgradeFailed("The upgrade installer did not complete successfully. You can install the downloaded package manually from your temp folder.", ex);
				}
			}

			return result;
		}
		catch (Exception ex)
		{
			var message = "An error occurred while checking for app upgrades.";
			Serilog.Log.Logger.Error(ex, message);
			OnUpgradeFailed(message, ex);
			return new VersionCheckResult(VersionCheckOutcome.UnableToDetermine);
		}
	}
}