using System;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace Schaad.Accounting.Repositories
{
    /// <summary>
    /// Per-scope cache of deserialized XML lists, keyed by absolute file path.
    ///
    /// Registered as Scoped so it lives for the SignalR circuit; each XML file is
    /// then loaded at most once per circuit. Writes go through <see cref="BaseRepository.SaveAsync"/>,
    /// which invalidates the corresponding entry so the next read reloads from disk.
    ///
    /// Not thread-safe — callers within a single Blazor Server circuit run serialized on the
    /// circuit's synchronization context, so no locking is needed.
    /// </summary>
    public class RepositoryCache
    {
        private readonly Dictionary<string, object> entries =
            new(StringComparer.OrdinalIgnoreCase);

        public async Task<List<T>> GetOrLoadAsync<T>(string cacheKey, Func<Task<List<T>>> loader)
        {
            if (entries.TryGetValue(cacheKey, out var cached))
            {
                return (List<T>)cached;
            }

            var list = await loader();
            entries[cacheKey] = list;
            return list;
        }

        public void Invalidate(string cacheKey)
        {
            entries.Remove(cacheKey);
        }
    }
}