using System;
using System.IO;

namespace LibationFileManager;

/// <summary>
/// Ensures OS interop assembly resolution and required dependency files are ready before background library load.
/// </summary>
public static class StartupAssemblyBootstrap
{
	public const string EntityFrameworkCoreSqliteAssemblyFileName = "Microsoft.EntityFrameworkCore.Sqlite.dll";
	public const int ApplicationControlBlockedHResult = unchecked((int)0x800711C7);
	private const string TroubleshootApplicationControlUrl = "https://getlibation.com/docs/advanced/troubleshoot#windows-smart-app-control-and-in-app-upgrades";

	/// <summary>
	/// Registers <see cref="InteropFactory"/> assembly resolution and verifies required install-folder assemblies exist.
	/// Call before <c>Task.Run</c> loads the library or opens the database on a thread-pool thread.
	/// </summary>
	public static void PrepareForBackgroundDataAccess()
	{
		_ = InteropFactory.InteropFunctionsType;
		ValidateEntityFrameworkCoreSqlitePresent();
		TrySyncWindowsInstallMetadata();
	}

	private static void TrySyncWindowsInstallMetadata()
	{
		if (!Configuration.IsWindows || InteropFactory.InteropFunctionsType is null)
			return;

		try
		{
			InteropFactory.Create().TrySyncInstallMetadata();
		}
		catch (Exception ex)
		{
			Serilog.Log.Logger.Warning(ex, "Could not run install metadata sync at startup");
		}
	}

	public static string GetLibraryLoadFailureMessage() =>
		$"""
		Libation could not load its database components (Entity Framework Core for SQLite).

		This often happens after an incomplete in-app upgrade. Quit Libation completely, then install a fresh copy of the latest release to a new folder (do not overlay files on top of the old install).

		If the error mentions an Application Control policy or Smart App Control, see:
		{TroubleshootApplicationControlUrl}

		Install folder:
		{Configuration.ProcessDirectory}

		Expected file:
		{Path.Combine(Configuration.ProcessDirectory, EntityFrameworkCoreSqliteAssemblyFileName)}
		""";

	public static string GetApplicationControlBlockedMessage(Exception? ex = null)
	{
		var blockedFile = TryGetBlockedAssemblyPath(ex) ?? "(unknown)";

		return $"""
			Windows blocked Libation from loading a required file in its install folder. This often happens after an in-app upgrade when Smart App Control or another Application Control policy is enabled.

			Blocked file:
			{blockedFile}

			Install folder:
			{Configuration.ProcessDirectory}

			Your library database, accounts, and settings are stored separately and should be unaffected.

			To recover:
			1. Quit Libation completely.
			2. Download the latest release zip from GitHub and extract it to a new folder (do not copy files on top of the old install).
			3. Run Libation from the new folder.

			If Windows still blocks the app, review Smart App Control under Windows Security -> App & browser control, or run this in PowerShell (replace the path if needed):
			Unblock-File -Path '{Configuration.ProcessDirectory}\*' -Recurse

			More help:
			{TroubleshootApplicationControlUrl}
			""";
	}

	public static bool IsApplicationControlBlockedAssembly(Exception ex)
	{
		for (var current = ex; current is not null; current = current.InnerException)
		{
			if (current is FileLoadException fileLoadException)
			{
				if (fileLoadException.HResult == ApplicationControlBlockedHResult)
					return true;

				if (fileLoadException.Message.Contains("Application Control policy", StringComparison.OrdinalIgnoreCase))
					return true;
			}

			if (current.Message.Contains("Application Control policy", StringComparison.OrdinalIgnoreCase))
				return true;
		}

		return false;
	}

	public static bool IsInstallFolderAssemblyLoadFailure(Exception ex) =>
		IsApplicationControlBlockedAssembly(ex) || IsMissingDependencyAssembly(ex);

	public static bool TryGetStartupFailureMessage(Exception ex, out string title, out string body)
	{
		if (IsApplicationControlBlockedAssembly(ex))
		{
			title = "Libation blocked by Windows security";
			body = GetApplicationControlBlockedMessage(ex);
			return true;
		}

		if (IsMissingDependencyAssembly(ex))
		{
			title = "Library load failed";
			body = GetLibraryLoadFailureMessage();
			return true;
		}

		title = string.Empty;
		body = string.Empty;
		return false;
	}

	public static bool IsMissingDependencyAssembly(Exception ex)
	{
		for (var current = ex; current is not null; current = current.InnerException)
		{
			if (current is not FileNotFoundException and not FileLoadException)
				continue;

			var name = (current as FileNotFoundException)?.FileName ?? current.Message;
			if (name.Contains("EntityFrameworkCore", StringComparison.OrdinalIgnoreCase)
				|| name.Contains("Microsoft.Data.Sqlite", StringComparison.OrdinalIgnoreCase))
				return true;
		}

		return false;
	}

	private static string? TryGetBlockedAssemblyPath(Exception? ex)
	{
		for (var current = ex; current is not null; current = current.InnerException)
		{
			if (current is FileLoadException { FileName: { Length: > 0 } blockedPath })
				return blockedPath;

			if (current is FileNotFoundException { FileName: { Length: > 0 } missingPath })
				return missingPath;
		}

		return null;
	}

	private static void ValidateEntityFrameworkCoreSqlitePresent()
	{
		var path = Path.Combine(Configuration.ProcessDirectory, EntityFrameworkCoreSqliteAssemblyFileName);
		if (File.Exists(path))
			return;

		throw new FileNotFoundException(
			$"Required file '{EntityFrameworkCoreSqliteAssemblyFileName}' was not found in the Libation install folder.{Environment.NewLine}{Environment.NewLine}{GetLibraryLoadFailureMessage()}",
			path);
	}
}