using System.Security.Cryptography;
using System.Text.Json;
using Launcher.Next.Core;
namespace Launcher.Next.Infrastructure;

public sealed class Sha256FileHasher : IFileHasher
{ public async Task<string> Sha256Async(string path, CancellationToken cancellationToken) { await using var s = File.OpenRead(path); return Convert.ToHexString(await SHA256.HashDataAsync(s, cancellationToken)); } }
public sealed class LocalPackageStore(string root, IFileHasher hasher) : ILocalPackageStore, IPackageActivator, IRollbackManager, IPackageSynchronizer
{
    private sealed record Pointer(string Current, string? Previous);
    private string PackageRoot(string id) => Path.Combine(root, "Applications", id);
    private string PointerPath(string id) => Path.Combine(PackageRoot(id), "current.json");
    private async Task<Pointer?> ReadPointer(string id, CancellationToken ct) => File.Exists(PointerPath(id)) ? await JsonSerializer.DeserializeAsync<Pointer>(File.OpenRead(PointerPath(id)), cancellationToken: ct) : null;
    public async Task<string?> GetCurrentVersionAsync(string id, CancellationToken ct) => (await ReadPointer(id, ct))?.Current;
    public async Task<string?> GetPreviousVersionAsync(string id, CancellationToken ct) => (await ReadPointer(id, ct))?.Previous;
    public async Task<ActivationResult> ActivateAsync(string id, string version, CancellationToken ct)
    {
        var dir = Path.Combine(PackageRoot(id), "versions", version); if (!Directory.Exists(dir)) throw new DirectoryNotFoundException(dir);
        Directory.CreateDirectory(PackageRoot(id)); var prior = await ReadPointer(id, ct);
        var temp = PointerPath(id) + ".tmp"; await File.WriteAllTextAsync(temp, JsonSerializer.Serialize(new Pointer(version, prior?.Current)), ct); File.Move(temp, PointerPath(id), true);
        return new(version, prior?.Current);
    }
    public async Task<string?> RollbackAsync(string id, CancellationToken ct) { var p = await ReadPointer(id, ct); return p?.Previous is null ? null : (await ActivateAsync(id, p.Previous, ct)).CurrentVersion; }
    public async Task<ActivationResult> SynchronizeAsync(PackageManifest manifest, string sourceRoot, CancellationToken ct, IProgress<PackageProgress>? progress = null)
    {
        var staging = Path.Combine(root, "Launcher", "staging", manifest.PackageId + "-" + manifest.Version + "-" + Guid.NewGuid().ToString("N")); Directory.CreateDirectory(staging);
        try { var i = 0; foreach (var f in manifest.Files) { ct.ThrowIfCancellationRequested(); var source = Path.Combine(sourceRoot, f.Path); var dest = Path.GetFullPath(Path.Combine(staging, f.Path)); if (!dest.StartsWith(Path.GetFullPath(staging) + Path.DirectorySeparatorChar, StringComparison.OrdinalIgnoreCase)) throw new InvalidOperationException("PACKAGE_ROOT_ESCAPE"); Directory.CreateDirectory(Path.GetDirectoryName(dest)!); File.Copy(source, dest, true); if (!string.Equals(await hasher.Sha256Async(dest, ct), f.Sha256, StringComparison.OrdinalIgnoreCase)) throw new InvalidOperationException("HASH_MISMATCH"); progress?.Report(new("copy", ++i, manifest.Files.Count)); }
            var versionDir = Path.Combine(PackageRoot(manifest.PackageId), "versions", manifest.Version); Directory.CreateDirectory(Path.GetDirectoryName(versionDir)!); if (Directory.Exists(versionDir)) Directory.Delete(staging, true); else Directory.Move(staging, versionDir); return await ActivateAsync(manifest.PackageId, manifest.Version, ct); }
        catch { if (Directory.Exists(staging)) Directory.Delete(staging, true); throw; }
    }
}