using System.IO.Compression;
using System.Text.Json;

namespace LehrerApp.Templating;

public static class TemplatePackage
{
    public const string Extension = ".lavorlage";

    public static void Create(string outputPath, TemplateManifest manifest, string layoutSource,
        IReadOnlyDictionary<string, byte[]> assets, string? continuationLayoutSource = null)
    {
        if (!TemplateLoader.IsSafeRelativePath(manifest.MetadataFile))
            throw new InvalidDataException("metadataFile enthält einen unsicheren Pfad.");
        if (TemplateLoader.Normalize(manifest.MetadataFile).Equals(
                TemplateLoader.Normalize(manifest.LayoutFile), StringComparison.OrdinalIgnoreCase))
            throw new InvalidDataException("metadataFile und layoutFile dürfen nicht identisch sein.");
        var reservedPaths = new HashSet<string>(StringComparer.OrdinalIgnoreCase)
        { "manifest.json", TemplateLoader.Normalize(manifest.LayoutFile), TemplateLoader.Normalize(manifest.MetadataFile) };
        if (manifest.ContinuationLayoutFile is { } continuationPath)
        {
            if (!TemplateLoader.IsSafeRelativePath(continuationPath))
                throw new InvalidDataException("continuationLayoutFile enthält einen unsicheren Pfad.");
            reservedPaths.Add(TemplateLoader.Normalize(continuationPath));
            if (continuationLayoutSource is null)
                throw new InvalidDataException("Das Folgeseiten-Layout fehlt.");
        }
        if (!string.Equals(Path.GetExtension(outputPath), Extension, StringComparison.OrdinalIgnoreCase))
            outputPath += Extension;
        var directory = Path.GetDirectoryName(outputPath);
        if (!string.IsNullOrEmpty(directory)) Directory.CreateDirectory(directory);
        var temporary = outputPath + ".tmp";
        try
        {
            using (var archive = ZipFile.Open(temporary, ZipArchiveMode.Create))
            {
                WriteText(archive, "manifest.json", JsonSerializer.Serialize(manifest, TemplateLoader.JsonOptions));
                WriteText(archive, manifest.LayoutFile, layoutSource);
                if (manifest.ContinuationLayoutFile is { } continuationFile)
                    WriteText(archive, continuationFile, continuationLayoutSource!);
                WriteText(archive, manifest.MetadataFile, TemplateMetadataText.Serialize(manifest.Metadata));
                foreach (var asset in assets)
                {
                    if (!TemplateLoader.IsSafeRelativePath(asset.Key))
                        throw new InvalidDataException($"Unsicherer Assetpfad „{asset.Key}“.");
                    if (reservedPaths.Contains(TemplateLoader.Normalize(asset.Key)))
                        throw new InvalidDataException($"Assetpfad „{asset.Key}“ ist für Paketdaten reserviert.");
                    var entry = archive.CreateEntry(TemplateLoader.Normalize(asset.Key), CompressionLevel.Optimal);
                    using var stream = entry.Open(); stream.Write(asset.Value);
                }
            }
            using (var verify = File.OpenRead(temporary)) new TemplateLoader().LoadFromPackage(verify, Path.GetFileName(outputPath));
            File.Move(temporary, outputPath, overwrite: true);
        }
        finally { if (File.Exists(temporary)) File.Delete(temporary); }
    }

    private static void WriteText(ZipArchive archive, string path, string content)
    {
        var entry = archive.CreateEntry(TemplateLoader.Normalize(path), CompressionLevel.Optimal);
        using var writer = new StreamWriter(entry.Open()); writer.Write(content);
    }
}

public sealed record InstalledTemplate(string Id, string Name, string Description, string PackagePath,
    DateTime ImportedAtUtc);

public sealed class TemplateStore
{
    private readonly string _directory;
    private readonly ITemplateLoader _loader;

    public TemplateStore(string appDataPath, ITemplateLoader? loader = null, string subfolder = "letter-template-packages")
    {
        _directory = Path.Combine(appDataPath, subfolder);
        Directory.CreateDirectory(_directory);
        _loader = loader ?? new TemplateLoader();
    }

    public IReadOnlyList<InstalledTemplate> GetTemplates()
    {
        var result = new List<InstalledTemplate>();
        foreach (var path in Directory.EnumerateFiles(_directory, $"*{TemplatePackage.Extension}"))
        {
            try
            {
                var loaded = _loader.LoadFromPackage(path);
                result.Add(new(loaded.Manifest.Id, loaded.Manifest.Name, loaded.Manifest.Description, path,
                    File.GetLastWriteTimeUtc(path)));
            }
            catch (Exception ex) when (ex is InvalidDataException or TemplateValidationException) { }
        }
        return result.OrderBy(x => x.Name, StringComparer.CurrentCultureIgnoreCase).ToList();
    }

    public InstalledTemplate Import(string sourcePath)
    {
        var loaded = _loader.LoadFromPackage(sourcePath);
        var safeId = string.Concat(loaded.Manifest.Id.Select(c => char.IsAsciiLetterOrDigit(c) || c == '-' ? c : '-')).Trim('-');
        if (safeId.Length == 0) throw new InvalidDataException("Die Vorlagen-ID ist ungültig.");
        var destination = Path.Combine(_directory, safeId + TemplatePackage.Extension);
        var temporary = destination + ".tmp";
        File.Copy(sourcePath, temporary, overwrite: true);
        File.Move(temporary, destination, overwrite: true);
        return new(loaded.Manifest.Id, loaded.Manifest.Name, loaded.Manifest.Description, destination, DateTime.UtcNow);
    }

    public LoadedTemplate Load(InstalledTemplate template) => _loader.LoadFromPackage(template.PackagePath);
    public void Delete(string id)
    {
        var match = GetTemplates().FirstOrDefault(x => x.Id == id);
        if (match is not null && File.Exists(match.PackagePath)) File.Delete(match.PackagePath);
    }
}

/// <summary>Getrennter Vorlagen-Speicher für Arbeitsblätter (eigener Unterordner) - reiner
/// Marker-Typ, damit DI die Elternbrief- und die Arbeitsblatt-Vorlagenbibliothek als zwei
/// unabhängige <see cref="TemplateStore"/>-Instanzen registrieren kann.</summary>
public sealed class WorksheetTemplateStore(TemplateStore store)
{
    public TemplateStore Store { get; } = store;
}