using Xunit;
using System.Text.Json;
using System.Threading.Tasks;
using StellaOps.Policy.Engine.Overlay;
using StellaOps.Policy.Engine.Tests.Fakes;
using StellaOps.Policy.Engine.Services;
using StellaOps.Policy.Engine.Streaming;

using StellaOps.TestKit;
namespace StellaOps.Policy.Engine.Tests;

public sealed class PathScopeSimulationBridgeServiceTests
{
    private static readonly JsonSerializerOptions SerializerOptions = new(JsonSerializerDefaults.Web);

    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public async Task SimulateAsync_OrdersByInputAndProducesMetrics()
    {
        var bridge = CreateBridge();

        var request = new PathScopeSimulationBridgeRequest(
            Tenant: "acme",
            Rules: Array.Empty<string>(),
            Overlays: null,
            Paths: new[]
            {
                BuildPathRequest("b/file.js"),
                BuildPathRequest("a/file.js")
            },
            Mode: "preview",
            Seed: 123);

        var result = await bridge.SimulateAsync(request);

        Assert.Equal(2, result.Decisions.Count);
        Assert.Contains("\"filePath\":\"b/file.js\"", JsonSerializer.Serialize(result.Decisions[0].PathScope, SerializerOptions));
        Assert.Contains("\"filePath\":\"a/file.js\"", JsonSerializer.Serialize(result.Decisions[1].PathScope, SerializerOptions));
        Assert.Equal(2, result.Metrics.Evaluated);
    }

    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public async Task SimulateAsync_WhatIfProducesDeltas()
    {
        var bridge = CreateBridge();

        var request = new PathScopeSimulationBridgeRequest(
            Tenant: "acme",
            Rules: Array.Empty<string>(),
            Overlays: null,
            Paths: new[] { BuildPathRequest("a/file.js") },
            Mode: "whatif",
            Seed: 42);

        var result = await bridge.SimulateAsync(request);

        Assert.Single(result.Decisions);
        Assert.NotNull(result.Deltas);
        Assert.Single(result.Deltas!);
    }

    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public async Task SimulateAsync_PublishesEventsAndSavesOverlays()
    {
        var sink = new FakeOverlayEventSink();
        var store = new FakeOverlayStore();
        var bridge = CreateBridge(sink, store);

        var request = new PathScopeSimulationBridgeRequest(
            Tenant: "acme",
            Rules: Array.Empty<string>(),
            Overlays: null,
            Paths: new[] { BuildPathRequest("a/file.js") },
            Mode: "whatif",
            Seed: 99);

        await bridge.SimulateAsync(request);

        Assert.NotEmpty(sink.Published);
        Assert.NotEmpty(store.Saved);
    }

    private static PathScopeSimulationBridgeService CreateBridge(
        IOverlayEventSink? sink = null,
        IOverlayStore? store = null)
    {
        sink ??= new FakeOverlayEventSink();
        store ??= new FakeOverlayStore();

        var overlayService = new OverlayProjectionService(new PolicyEvaluationService(), TimeProvider.System);
        var publisher = new OverlayChangeEventPublisher(sink, TimeProvider.System);
        return new PathScopeSimulationBridgeService(overlayService, publisher, store);
    }

    private static PathScopeSimulationRequest BuildPathRequest(string filePath) =>
        new(
            SchemaVersion: "1.0.0",
            Tenant: "acme",
            BasePolicyRef: "policy://acme/main@sha256:1",
            CandidatePolicyRef: "policy://acme/feat@sha256:2",
            Subject: new PathScopeSubject("pkg:npm/lodash@4.17.21", null, "lib.js", null),
            Targets: new[]
            {
                new PathScopeTarget(filePath, "pat", "prefix", 0.9, null, null, null, "e1", null, null)
            },
            Options: new SimulationOptions("path,finding,verdict", 100, IncludeTrace: true, Deterministic: true));
}