// Copyright (C) 2025, The Duplicati Team
// https://duplicati.com, hello@duplicati.com
//
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// copy of this software and associated documentation files (the "Software"),
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// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
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//
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// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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using System.CommandLine;
using System.CommandLine.NamingConventionBinder;
using Duplicati.Library.AutoUpdater;
using Duplicati.Library.Interface;
using Duplicati.Library.Main.Database;
using Duplicati.Library.SQLiteHelper;
using Duplicati.Library.Utility;

namespace Duplicati.CommandLine.DatabaseTool.Commands;

/// <summary>
/// The downgrade command
/// </summary>
public static class Downgrade
{
    /// <summary>
    /// Creates the downgrade command
    /// </summary>
    /// <returns>The downgrade command</returns>
    public static Command Create() =>
        new Command("downgrade", "Downgrades one or more databases to a prior version")
        {
            new Argument<string[]>("databases", "The databases to downgrade") {
                Arity = ArgumentArity.ZeroOrMore
            },
            new Option<DirectoryInfo>("--server-datafolder", description: "The folder with databases", getDefaultValue: () => new DirectoryInfo(DataFolderLocator.GetDefaultStorageFolder(DataFolderManager.SERVER_DATABASE_FILENAME, false, true))),
            new Option<int>("--server-version", description: "The version to downgrade the server database to", getDefaultValue: () => 8),
            new Option<int>("--local-version", description: "The version to downgrade local databases to", getDefaultValue: () => 14),
            new Option<bool>("--no-backups", description: "Do not create backups before downgrade", getDefaultValue: () => false),
            new Option<bool>("--include-untracked-databases", description: "Include untracked databases in the downgrade process", getDefaultValue: () => false)
        }
        .WithHandler(CommandHandler.Create<string[], DirectoryInfo, int, int, bool, bool>((databases, serverdatafolder, serverversion, localversion, nobackups, includeuntrackeddatabases) =>
            {
                databases = Helper.FindAllDatabases(databases, serverdatafolder.FullName, includeuntrackeddatabases).Await();
                if (databases.Length == 0)
                {
                    Console.WriteLine("No databases found to downgrade");
                    return;
                }

                static string ReadStream(string path)
                {
                    using var reader = new StreamReader(typeof(Downgrade).Assembly.GetManifestResourceStream(path) ?? throw new InvalidOperationException());
                    return reader.ReadToEnd();
                }

                static string ResourceNameToPath(string resourcename)
                {
                    var prefixes = new[] {
                        typeof(Program).Namespace + ".Scripts.Local.",
                        typeof(Program).Namespace + ".Scripts.Server."
                    };

                    foreach (var prefix in prefixes)
                        if (resourcename.StartsWith(prefix))
                            return resourcename.Substring(prefix.Length);

                    throw new Exception($"Unexpected resource name: {resourcename}");
                }

                var serverVersions = typeof(Downgrade).Assembly.GetManifestResourceNames()
                    .Where(x => x.Contains(".Scripts.Server."))
                    .Select(x => new DowngradeScript(Version: int.Parse(ResourceNameToPath(x).Split('.').First()), Filename: ResourceNameToPath(x), Content: ReadStream(x)))
                    .ToList();

                var localVersions = typeof(Downgrade).Assembly.GetManifestResourceNames()
                    .Where(x => x.Contains(".Scripts.Local."))
                    .Select(x => new DowngradeScript(Version: int.Parse(ResourceNameToPath(x).Split('.').First()), Filename: ResourceNameToPath(x), Content: ReadStream(x)))
                    .ToList();

                foreach (var db in databases)
                {
                    Console.WriteLine($"Examining {db} ...");
                    if (!File.Exists(db))
                    {
                        Console.WriteLine($"Database {db} does not exist");
                        continue;
                    }

                    int version;
                    bool isserverdb;
                    try
                    {
                        (version, isserverdb) = Helper.ExamineDatabase(db).Await();
                    }
                    catch (Exception ex)
                    {
                        Console.WriteLine($"Error reading database {db}: {ex.Message}");
                        continue;
                    }

                    Console.WriteLine($"Database {db} is version {version} and is a {(isserverdb ? "server" : "local")} database");
                    ApplyDowngrade(db, version,
                        isserverdb ? serverversion : localversion,
                        isserverdb ? serverVersions : localVersions,
                    nobackups)
                        .Await();
                }
            }));

    /// <summary>
    /// The downgrade script
    /// </summary>
    /// <param name="Filename">The path to the assembly resource</param>
    /// <param name="Version">The script version</param>
    /// <param name="Content">The script contents</param>
    private sealed record DowngradeScript(string Filename, int Version, string Content);

    /// <summary>
    /// Applies the downgrade scripts to the database
    /// </summary>
    /// <param name="db">The database path</param>
    /// <param name="dbversion">The current database version</param>
    /// <param name="targetversion">The target database version</param>
    /// <param name="scripts">The downgrade scripts</param>
    /// <param name="nobackups">Flag to disable backups</param>
    /// <returns>A task that completes when the downgrade is done.</returns>
    private static async Task ApplyDowngrade(string db, int dbversion, int targetversion, IEnumerable<DowngradeScript> scripts, bool nobackups)
    {
        if (dbversion > targetversion)
        {
            var requiredVersions = Enumerable.Range(targetversion + 1, dbversion - targetversion)
                .Reverse()
                .ToList();

            var missingScripts = requiredVersions
                .Where(x => !scripts.Any(y => y.Version == x))
                .ToList();

            if (missingScripts.Count > 0)
            {
                Console.WriteLine($"Missing downgrade scripts for versions: {string.Join(", ", missingScripts)}");
                return;
            }

            var downgradeScripts = requiredVersions
                .Select(x => scripts.First(y => y.Version == x))
                .ToList();

            Console.WriteLine($"Downgrading {db} from version {dbversion} to {targetversion}");
            if (!nobackups)
                Helper.CreateFileBackup(db);

            await using var con = await SQLiteLoader.LoadConnectionAsync(db)
                .ConfigureAwait(false);
            await using var tr = con.BeginTransaction();
            await using var cmd = con.CreateCommand(tr);
            foreach (var script in downgradeScripts)
            {
                Console.WriteLine($"Applying downgrade script {script.Filename} ...");
                try
                {
                    cmd.SetCommandAndParameters(script.Content);
                    var r = await cmd.ExecuteScalarAsync().ConfigureAwait(false);
                    if (r != null)
                        throw new UserInformationException($"{r}", "DowngradeScriptFailure");

                    await cmd.SetCommandAndParameters(@"
                        UPDATE ""Version""
                        SET ""Version"" = @Version
                    ")
                        .SetParameterValue("@Version", script.Version - 1)
                        .ExecuteNonQueryAsync()
                        .ConfigureAwait(false);
                }
                catch (Exception ex)
                {
                    throw new UserInformationException($"Failed applying downgrade script {script.Filename}: {ex.Message}", "DowngradeScriptFailure", ex);
                }
            }

            await tr.CommitAsync().ConfigureAwait(false);
            Console.WriteLine($"Downgraded {db} to version {targetversion}");
        }
        else if (dbversion == targetversion)
        {
            Console.WriteLine($"Database {db} is already at version {targetversion}");
        }
        else
        {
            Console.WriteLine($"Database {db} is already at version {dbversion} (cannot downgrade to {targetversion})");
        }
    }
}