using System.Diagnostics;
using System.Globalization;
using SQLInsight.Rules.Lifecycle;
using SQLInsight.Updates;

namespace SQLInsight.Agent.Updates;

/// <summary>
/// Command line:
/// <list type="bullet">
/// <item><c>update check</c>: show what the feed offers.</item>
/// <item><c>update apply [--feed &lt;url|mappe&gt;]</c>: download and install the newest version now (administrator).</item>
/// <item><c>apply-update</c>: for the scheduled update task; installs a staged version when the mode is Automatic and
/// the maintenance window is open.</item>
/// </list>
/// Installing runs from a copy of the program in the updater's folder, so no file in the installation is in use.
/// </summary>
public static class UpdateCommands
{
    private const string RunnerFlag = "--runner";

    public static bool Handles(string[] args) => args.FirstOrDefault() is "update" or "apply-update";

    public static async Task<int> RunAsync(string[] args)
    {
        ArgumentNullException.ThrowIfNull(args);
        var agentFolder = Option(args, "--install-dir") ?? AppContext.BaseDirectory;
        var settings = LoadOptions(agentFolder);
        if (Option(args, "--feed") is { } feed)
        {
            settings.Feed = feed;
        }

        using var http = new HttpClient { Timeout = TimeSpan.FromMinutes(10) };
        try
        {
            return (args.ElementAtOrDefault(0), args.ElementAtOrDefault(1)) switch
            {
                ("update", "check") => await CheckAsync(settings, http).ConfigureAwait(false),
                ("update", "apply") => await ApplyNowAsync(args, settings, agentFolder, http).ConfigureAwait(false),
                ("apply-update", _) when args.Contains(RunnerFlag) => await RunApplierAsync(args, settings, agentFolder).ConfigureAwait(false),
                ("apply-update", _) => ScheduledApply(args, settings, agentFolder),
                _ => Usage(),
            };
        }
        catch (Exception ex) when (ex is UpdateException or IOException or UnauthorizedAccessException or FormatException)
        {
            Console.Error.WriteLine(ex.Message);
            return 2;
        }
    }

    private static async Task<int> CheckAsync(UpdateOptions settings, HttpClient http)
    {
        var checker = Checker(settings, http);
        var manifest = (await checker.FetchAsync(CancellationToken.None).ConfigureAwait(false)).Manifest;
        var installed = AppVersion.Running;
        var pack = RulePack.Embedded();
        Console.WriteLine($"Feed:         {settings.Feed} ({settings.Channel}, udgivet {manifest.PublishedAt:yyyy-MM-dd HH:mm} UTC)");
        Console.WriteLine($"Installeret:  {installed}");
        Console.WriteLine($"Tilgængelig:  {manifest.Release?.Version ?? "-"}{(UpdateChecker.NewerRelease(manifest, installed) is { Security: true } ? " (sikkerhedsopdatering)" : string.Empty)}");
        Console.WriteLine($"Regelpakke:   {manifest.RulePack?.Version ?? "-"} (indbygget {pack.Version})");
        return 0;
    }

    /// <summary>Administrator: download and install now, regardless of mode and maintenance window.</summary>
    private static async Task<int> ApplyNowAsync(string[] args, UpdateOptions settings, string agentFolder, HttpClient http)
    {
        var checker = Checker(settings, http);
        var manifest = await checker.FetchAsync(CancellationToken.None).ConfigureAwait(false);
        if (!await checker.StageAsync(manifest, AppVersion.Running, CancellationToken.None).ConfigureAwait(false))
        {
            Console.WriteLine($"Version {AppVersion.Running} er den nyeste på {settings.Channel}-kanalen.");
            return 0;
        }

        Console.WriteLine($"Version {manifest.Manifest.Release!.Version} er hentet og verificeret.");
        return LaunchRunner(args, settings, agentFolder);
    }

    /// <summary>Scheduled task: only in Automatic mode, only in the maintenance window, only if something is staged.</summary>
    private static int ScheduledApply(string[] args, UpdateOptions settings, string agentFolder)
    {
        if (settings.Application != AppUpdateMode.Automatic)
        {
            Console.WriteLine($"Automatisk installation er slået fra (Application = {settings.Application}).");
            return 0;
        }

        if (!settings.InMaintenanceWindow(TimeOnly.FromDateTime(DateTime.Now)))
        {
            Console.WriteLine($"Uden for vedligeholdelsesvinduet {settings.MaintenanceWindow}.");
            return 0;
        }

        if (!File.Exists(Path.Combine(settings.Directories.Pending, UpdateFeed.ManifestFile)))
        {
            Console.WriteLine("Ingen opdatering venter.");
            return 0;
        }

        return LaunchRunner(args, settings, agentFolder);
    }

    /// <summary>
    /// Copies the program to the updater's folder and runs <c>apply-update --runner</c> from there. On Windows the
    /// installation's files are locked while this process runs, so it does not wait; on Linux it waits, so a systemd
    /// oneshot unit does not kill the updater when it exits.
    /// </summary>
    private static int LaunchRunner(string[] args, UpdateOptions settings, string agentFolder)
    {
        var runner = Path.Combine(settings.UpdaterRoot(agentFolder), "runner");
        if (Directory.Exists(runner))
        {
            Directory.Delete(runner, recursive: true);
        }

        foreach (var file in Directory.EnumerateFiles(agentFolder, "*", SearchOption.AllDirectories))
        {
            var target = Path.Combine(runner, Path.GetRelativePath(agentFolder, file));
            Directory.CreateDirectory(Path.GetDirectoryName(target)!);
            File.Copy(file, target);
        }

        var host = Environment.ProcessPath ?? throw new InvalidOperationException("Programmets sti er ukendt.");
        var viaDotnet = Path.GetFileNameWithoutExtension(host).Equals("dotnet", StringComparison.OrdinalIgnoreCase);
        var start = new ProcessStartInfo(viaDotnet ? host : Path.Combine(runner, Path.GetFileName(host))) { UseShellExecute = false };
        if (viaDotnet)
        {
            start.ArgumentList.Add(Path.Combine(runner, "SQLInsight.Agent.dll"));
        }

        string[] runnerArgs = ["apply-update", RunnerFlag, "--install-dir", agentFolder, "--wait-pid", Environment.ProcessId.ToString(CultureInfo.InvariantCulture)];
        foreach (var arg in runnerArgs.Concat(Option(args, "--feed") is { } feed ? ["--feed", feed] : []))
        {
            start.ArgumentList.Add(arg);
        }

        using var process = Process.Start(start) ?? throw new UpdateException("Opdateringen kunne ikke startes.");
        if (OperatingSystem.IsWindows())
        {
            Console.WriteLine($"Opdateringen kører nu i baggrunden. Resultatet skrives i {settings.Directories.ResultFile} og vises i webbrugerfladen.");
            return 0;
        }

        process.WaitForExit();
        return process.ExitCode;
    }

    private static async Task<int> RunApplierAsync(string[] args, UpdateOptions settings, string agentFolder)
    {
        // On Windows the process that started us holds the installation's files open until it exits.
        if (OperatingSystem.IsWindows() && int.TryParse(Option(args, "--wait-pid"), NumberStyles.None, CultureInfo.InvariantCulture, out var parent))
        {
            try
            {
                using var launcher = Process.GetProcessById(parent);
                using var timeout = new CancellationTokenSource(TimeSpan.FromMinutes(1));
                await launcher.WaitForExitAsync(timeout.Token).ConfigureAwait(false);
            }
            catch (Exception ex) when (ex is ArgumentException or OperationCanceledException)
            {
                // Already gone, or still running after a minute: go ahead, a locked file triggers a rollback.
            }
        }

        var root = settings.UpdaterRoot(agentFolder);
        var logFile = Path.Combine(root, "update.log");
        void Log(string line)
        {
            var stamped = $"{DateTimeOffset.Now:yyyy-MM-dd HH:mm:ss} {line}";
            Console.WriteLine(stamped);
            File.AppendAllText(logFile, stamped + Environment.NewLine);
        }

        var applier = new UpdateApplier(
            new UpdateApplierOptions
            {
                Channel = settings.Channel,
                PrivateRoot = Path.Combine(root, "work"),
                Components = settings.ComponentsFor(agentFolder),
                HealthCheckDuration = settings.HealthCheckDuration,
            },
            settings.Directories, settings.Keys, ServiceControl.ForCurrentOs(), TimeProvider.System, Log);
        var result = await applier.ApplyAsync(AppVersion.Running, CancellationToken.None).ConfigureAwait(false);
        return result.Outcome is UpdateOutcome.Applied or UpdateOutcome.NothingToDo ? 0 : 2;
    }

    private static UpdateChecker Checker(UpdateOptions settings, HttpClient http)
    {
        if (string.IsNullOrWhiteSpace(settings.Feed))
        {
            throw new UpdateException("Der er intet opdateringsfeed. Angiv SQLInsight:Updates:Feed eller --feed <url|mappe>.");
        }

        return new UpdateChecker(new UpdateFeed(settings.Feed, http), settings.Keys, settings.Directories, settings.Channel, TimeProvider.System);
    }

    private static UpdateOptions LoadOptions(string agentFolder)
    {
        var environment = Environment.GetEnvironmentVariable("DOTNET_ENVIRONMENT") ?? "Production";
        var configuration = new ConfigurationBuilder()
            .SetBasePath(agentFolder)
            .AddJsonFile("appsettings.json", optional: true)
            .AddJsonFile($"appsettings.{environment}.json", optional: true)
            .AddEnvironmentVariables()
            .Build();
        return configuration.GetSection(UpdateOptions.SectionName).Get<UpdateOptions>() ?? new UpdateOptions();
    }

    private static string? Option(string[] args, string name)
    {
        var i = Array.IndexOf(args, name);
        return i >= 0 && i + 1 < args.Length ? args[i + 1] : null;
    }

    private static int Usage()
    {
        Console.Error.WriteLine("""
            SQLInsight.Agent update check                        Vis hvad opdateringsfeedet tilbyder
            SQLInsight.Agent update apply [--feed <url|mappe>]   Hent og installér nyeste version nu (administrator)
            SQLInsight.Agent apply-update                        Til den planlagte opdateringsopgave
            """);
        return 1;
    }
}