JsonGlobalSettingsStore.cs

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using System.IO;
using System.Text.Json;
using FamiliesApp.Models;
 
namespace FamiliesApp.Services;

public sealed class JsonGlobalSettingsStore : IGlobalSettingsStore
{
    private readonly string _path;
    private static readonly SemaphoreSlim _gate = new(1, 1);
    private GlobalSettings? _cache;

    private static readonly JsonSerializerOptions _jsonOpts = new() { WriteIndented = true };

    public JsonGlobalSettingsStore(FamilyOptions opts)
    {
        var dataRoot = Path.GetDirectoryName(opts.ResolvedDataPath.TrimEnd(Path.DirectorySeparatorChar))
            ?? Path.Combine(AppContext.BaseDirectory, "App_Data");
        Directory.CreateDirectory(dataRoot);
        _path = Path.Combine(dataRoot, "global-settings.json");
    }

    public async Task<GlobalSettings> GetAsync(CancellationToken ct = default)
    {
        if (_cache is not null) return _cache;
 
        await _gate.WaitAsync(ct).ConfigureAwait(false);
        try
        {
            if (_cache is not null) return _cache;
 
            if (!File.Exists(_path))
            {
                _cache = new GlobalSettings();
                return _cache;
            }
 
            await using var fs = File.OpenRead(_path);
            _cache = await JsonSerializer.DeserializeAsync<GlobalSettings>(fs, _jsonOpts, ct).ConfigureAwait(false)
                ?? new GlobalSettings();
            return _cache;
        }
        finally { _gate.Release(); }
    }

    public async Task SaveAsync(GlobalSettings settings, CancellationToken ct = default)
    {
        await _gate.WaitAsync(ct).ConfigureAwait(false);
        try
        {
            var tmp = _path + ".tmp";
            await using (var fs = File.Create(tmp))
                await JsonSerializer.SerializeAsync(fs, settings, _jsonOpts, ct).ConfigureAwait(false);
 
            File.Copy(tmp, _path, overwrite: true);
            File.Delete(tmp);
            _cache = settings;
        }
        finally { _gate.Release(); }
    }
}