using System.Xml.Serialization;
using ControlPlane.Core.Models;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;

namespace ControlPlane.Core.Services;

/// <summary>
/// Reads and writes per-tenant XML config files under the ClientAssets folder.
/// One file per tenant: {subdomain}.xml
/// Thread-safe for concurrent reads; writes are serialized per subdomain via per-file locking.
/// </summary>
public class TenantRegistryService
{
    private readonly string _folder;
    private readonly ILogger<TenantRegistryService> _logger;
    private static readonly XmlSerializer Serializer = new(typeof(TenantRecord));

    // One lock object per subdomain so writes to different tenants never block each other
    private readonly System.Collections.Concurrent.ConcurrentDictionary<string, object> _locks = new(StringComparer.OrdinalIgnoreCase);

    public TenantRegistryService(IConfiguration configuration, ILogger<TenantRegistryService> logger)
    {
        _folder = configuration["ClientAssets__Folder"] ?? configuration["ClientAssets:Folder"]
                  ?? Path.GetFullPath(Path.Combine(AppContext.BaseDirectory, "..", "ClientAssets"));
        _logger = logger;
        Directory.CreateDirectory(_folder);
    }

    // -- Write --

    public void Save(TenantRecord record)
    {
        var path = FilePath(record.Subdomain);
        var gate = _locks.GetOrAdd(record.Subdomain, _ => new object());
        lock (gate)
        {
            using var writer = new StreamWriter(path, append: false, System.Text.Encoding.UTF8);
            Serializer.Serialize(writer, record);
        }
        _logger.LogInformation("Saved tenant record: {Path}", path);
    }

    // -- Read --

    public TenantRecord? TryGet(string subdomain)
    {
        var path = FilePath(subdomain);
        if (!File.Exists(path)) return null;
        using var reader = new StreamReader(path, System.Text.Encoding.UTF8);
        return (TenantRecord?)Serializer.Deserialize(reader);
    }

    public IReadOnlyList<TenantRecord> GetAll()
    {
        var results = new List<TenantRecord>();
        foreach (var file in Directory.EnumerateFiles(_folder, "*.xml"))
        {
            try
            {
                using var reader = new StreamReader(file, System.Text.Encoding.UTF8);
                if (Serializer.Deserialize(reader) is TenantRecord record)
                    results.Add(record);
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "Skipping malformed tenant file: {File}", file);
            }
        }
        return results;
    }

    public bool Exists(string subdomain) => File.Exists(FilePath(subdomain));

    private string FilePath(string subdomain) =>
        Path.Combine(_folder, $"{subdomain.ToLowerInvariant()}.xml");
}