using System.Text.Json;
using ZB.MOM.WW.CBDDC.Core.Cache;
using ZB.MOM.WW.CBDDC.Core.Network;

namespace ZB.MOM.WW.CBDDC.Core.Tests;

public class DocumentCacheTests
{
    /// <summary>
    ///     Verifies cache hit/miss statistics after get and set operations.
    /// </summary>
    [Fact]
    public async Task GetAndSet_ShouldTrackCacheHitsAndMisses()
    {
        var cache = new DocumentCache(CreateConfigProvider(maxDocumentCacheSize: 2));

        Document? missing = await cache.Get("users", "1");
        missing.ShouldBeNull();

        var document = CreateDocument("users", "1");
        await cache.Set("users", "1", document);
        Document? hit = await cache.Get("users", "1");

        hit.ShouldNotBeNull();
        hit.Key.ShouldBe("1");
        var stats = cache.GetStatistics();
        stats.Hits.ShouldBe(1);
        stats.Misses.ShouldBe(1);
        stats.Size.ShouldBe(1);
        stats.HitRate.ShouldBe(0.5d);
    }

    /// <summary>
    ///     Verifies least-recently-used eviction when cache capacity is reached.
    /// </summary>
    [Fact]
    public async Task Set_WhenCacheIsFull_EvictsLeastRecentlyUsedEntry()
    {
        var cache = new DocumentCache(CreateConfigProvider(maxDocumentCacheSize: 2));
        await cache.Set("users", "1", CreateDocument("users", "1"));
        await cache.Set("users", "2", CreateDocument("users", "2"));

        // Touch key 1 so key 2 becomes the LRU entry.
        (await cache.Get("users", "1")).ShouldNotBeNull();

        await cache.Set("users", "3", CreateDocument("users", "3"));

        (await cache.Get("users", "2")).ShouldBeNull();
        (await cache.Get("users", "1")).ShouldNotBeNull();
        (await cache.Get("users", "3")).ShouldNotBeNull();
    }

    /// <summary>
    ///     Verifies remove and clear operations delete entries from the cache.
    /// </summary>
    [Fact]
    public async Task RemoveAndClear_ShouldDeleteEntriesFromCache()
    {
        var cache = new DocumentCache(CreateConfigProvider(maxDocumentCacheSize: 3));
        await cache.Set("users", "1", CreateDocument("users", "1"));
        await cache.Set("users", "2", CreateDocument("users", "2"));
        cache.GetStatistics().Size.ShouldBe(2);

        cache.Remove("users", "1");
        (await cache.Get("users", "1")).ShouldBeNull();
        cache.GetStatistics().Size.ShouldBe(1);

        cache.Clear();
        cache.GetStatistics().Size.ShouldBe(0);
    }

    private static Document CreateDocument(string collection, string key)
    {
        using var json = JsonDocument.Parse("""{"name":"test"}""");
        return new Document(collection, key, json.RootElement.Clone(), new HlcTimestamp(1, 0, "node-a"), false);
    }

    private static IPeerNodeConfigurationProvider CreateConfigProvider(int maxDocumentCacheSize)
    {
        var configProvider = Substitute.For<IPeerNodeConfigurationProvider>();
        configProvider.GetConfiguration().Returns(new PeerNodeConfiguration
        {
            MaxDocumentCacheSize = maxDocumentCacheSize
        });
        return configProvider;
    }
}