using Microsoft.Extensions.Configuration;

namespace URLNotesGrabberCORE
{
    // Inverse of OutputMode. For each Blog with a TTFolderPath, restores every *.bak back
    // to its *.txt, first preserving the current *.txt as the next-free *.bkN. Consumes
    // the *.bak (File.Move). Filesystem-only; reads the DB only to enumerate folders.
    public static class RevertMode
    {
        public static int Run(IConfiguration config, string? blogFilter = null)
        {
            DataAccess.EnsureTTFileHelperColumnsExist();

            var blogs = DataAccess.GetAllBlogsWithTTFolderPath();
            if (!string.IsNullOrWhiteSpace(blogFilter))
                blogs = blogs.Where(b => string.Equals(b.BlogName, blogFilter, StringComparison.OrdinalIgnoreCase)).ToList();

            Console.WriteLine($"Found {blogs.Count} blog(s) to process.");

            // Count total *.bak files up front so the confirmation prompt is meaningful.
            int totalBakFiles = 0;
            foreach (var (_, ttFolderPath) in blogs)
            {
                if (string.IsNullOrWhiteSpace(ttFolderPath) || !Directory.Exists(ttFolderPath))
                    continue;
                try { totalBakFiles += Directory.GetFiles(ttFolderPath, "*.bak").Length; }
                catch { }
            }

            if (totalBakFiles == 0)
            {
                Console.WriteLine("No .bak files found in any blog folder. Nothing to revert.");
                return 0;
            }

            Console.Write($"WARNING: This will restore {totalBakFiles} .bak file(s) over their .txt files across {blogs.Count} blog folder(s). " +
                          $"Current .txt files are preserved as the next-free .bkN. Continue? (yes/no): ");
            string? response = Console.ReadLine();
            if (string.IsNullOrWhiteSpace(response) || !response.Equals("yes", StringComparison.OrdinalIgnoreCase))
            {
                Console.WriteLine("Operation cancelled.");
                return 0;
            }

            foreach (var (blogName, ttFolderPath) in blogs)
            {
                Console.WriteLine($"\nProcessing blog: {blogName}");

                if (string.IsNullOrWhiteSpace(ttFolderPath) || !Directory.Exists(ttFolderPath))
                {
                    Console.WriteLine($"  TTFolderPath does not exist or is not set. Skipping.");
                    continue;
                }

                Console.WriteLine($"  TTFolderPath: {ttFolderPath}");

                var (restored, backedUp) = RevertFolder(ttFolderPath);
                Console.WriteLine($"  Restored {restored} file(s); backed up {backedUp} current .txt file(s).");
            }

            Console.WriteLine("\nRevert mode complete.");
            return 0;
        }

        // For each *.bak: back up the current *.txt to the next-free *.bkN, then File.Move(bak -> txt).
        private static (int restored, int backedUp) RevertFolder(string folderPath)
        {
            int restored = 0, backedUp = 0;

            var bakFiles = Directory.GetFiles(folderPath, "*.bak");
            if (bakFiles.Length == 0)
            {
                Console.WriteLine("    Nothing to revert (no .bak files).");
                return (restored, backedUp);
            }

            foreach (var bakFile in bakFiles)
            {
                try
                {
                    string txtPath = Path.ChangeExtension(bakFile, ".txt");

                    if (File.Exists(txtPath))
                    {
                        string bkPath = NextFreeBkPath(txtPath);
                        File.Move(txtPath, bkPath);
                        backedUp++;
                        Console.WriteLine($"    Backed up {Path.GetFileName(txtPath)} -> {Path.GetFileName(bkPath)}");
                    }

                    File.Move(bakFile, txtPath);
                    restored++;
                    Console.WriteLine($"    Restored {Path.GetFileName(bakFile)} -> {Path.GetFileName(txtPath)}");
                }
                catch (Exception ex)
                {
                    Console.WriteLine($"    Error reverting {Path.GetFileName(bakFile)}: {ex.Message}");
                }
            }

            return (restored, backedUp);
        }

        // Returns the lowest unused .bkN path for a given .txt file (.bk1, .bk2, ...).
        private static string NextFreeBkPath(string txtFile)
        {
            for (int n = 1; ; n++)
            {
                string candidate = Path.ChangeExtension(txtFile, $".bk{n}");
                if (!File.Exists(candidate)) return candidate;
            }
        }
    }
}