using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using StellaOps.Scheduler.Models;
using StellaOps.Scheduler.Worker;
using StellaOps.Scheduler.Worker.Options;
using StellaOps.Scheduler.Worker.Policy;
using Xunit;

namespace StellaOps.Scheduler.Worker.Tests;

public sealed class PolicyRunTargetingServiceTests
{
    [Fact]
    public async Task EnsureTargetsAsync_ReturnsUnchanged_ForNonIncrementalJob()
    {
        var service = CreateService();
        var job = CreateJob(mode: PolicyRunMode.Full);

        var result = await service.EnsureTargetsAsync(job, CancellationToken.None);

        Assert.Equal(PolicyRunTargetingStatus.Unchanged, result.Status);
        Assert.Equal(job, result.Job);
    }

    [Fact]
    public async Task EnsureTargetsAsync_ReturnsUnchanged_WhenSbomSetAlreadyPresent()
    {
        var service = CreateService();
        var inputs = new PolicyRunInputs(sbomSet: new[] { "sbom:S-1" });
        var job = CreateJob(inputs: inputs);

        var result = await service.EnsureTargetsAsync(job, CancellationToken.None);

        Assert.Equal(PolicyRunTargetingStatus.Unchanged, result.Status);
    }

    [Fact]
    public async Task EnsureTargetsAsync_ReturnsNoWork_WhenNoCandidatesResolved()
    {
        var impact = new StubImpactTargetingService();
        var service = CreateService(impact);
        var metadata = ImmutableSortedDictionary<string, string>.Empty.Add("delta.purls", "pkg:npm/leftpad");
        var job = CreateJob(metadata: metadata, inputs: PolicyRunInputs.Empty);

        var result = await service.EnsureTargetsAsync(job, CancellationToken.None);

        Assert.Equal(PolicyRunTargetingStatus.NoWork, result.Status);
        Assert.Equal("no_matches", result.Reason);
    }

    [Fact]
    public async Task EnsureTargetsAsync_TargetsDirectSboms()
    {
        var service = CreateService();
        var metadata = ImmutableSortedDictionary<string, string>.Empty.Add("delta.sboms", "sbom:S-2, sbom:S-1, sbom:S-2");
        var job = CreateJob(metadata: metadata, inputs: PolicyRunInputs.Empty);

        var result = await service.EnsureTargetsAsync(job, CancellationToken.None);

        Assert.Equal(PolicyRunTargetingStatus.Targeted, result.Status);
        Assert.Equal(new[] { "sbom:S-1", "sbom:S-2" }, result.Job.Inputs.SbomSet);
    }

    [Fact]
    public async Task EnsureTargetsAsync_TargetsUsingImpactIndex()
    {
        var impact = new StubImpactTargetingService
        {
            OnResolveByPurls = (keys, usageOnly, selector, _) =>
            {
                var image = new ImpactImage(
                    "sha256:111",
                    "registry",
                    "repo",
                    labels: ImmutableSortedDictionary.Create<string, string>(StringComparer.Ordinal).Add("sbomId", "sbom:S-42"));
                var impactSet = new ImpactSet(
                    selector,
                    new[] { image },
                    usageOnly,
                    DateTimeOffset.UtcNow,
                    total: 1,
                    snapshotId: null,
                    schemaVersion: SchedulerSchemaVersions.ImpactSet);
                return ValueTask.FromResult(impactSet);
            }
        };

        var service = CreateService(impact);
        var metadata = ImmutableSortedDictionary<string, string>.Empty.Add("delta.purls", "pkg:npm/example");
        var job = CreateJob(metadata: metadata, inputs: PolicyRunInputs.Empty);

        var result = await service.EnsureTargetsAsync(job, CancellationToken.None);

        Assert.Equal(PolicyRunTargetingStatus.Targeted, result.Status);
        Assert.Equal(new[] { "sbom:S-42" }, result.Job.Inputs.SbomSet);
    }

    [Fact]
    public async Task EnsureTargetsAsync_FallsBack_WhenLimitExceeded()
    {
        var service = CreateService(configure: options => options.MaxSboms = 1);
        var metadata = ImmutableSortedDictionary<string, string>.Empty.Add("delta.sboms", "sbom:S-1,sbom:S-2");
        var job = CreateJob(metadata: metadata, inputs: PolicyRunInputs.Empty);

        var result = await service.EnsureTargetsAsync(job, CancellationToken.None);

        Assert.Equal(PolicyRunTargetingStatus.Unchanged, result.Status);
    }

    [Fact]
    public async Task EnsureTargetsAsync_FallbacksToDigest_WhenLabelMissing()
    {
        var impact = new StubImpactTargetingService
        {
            OnResolveByVulnerabilities = (ids, usageOnly, selector, _) =>
            {
                var image = new ImpactImage("sha256:aaa", "registry", "repo");
                var impactSet = new ImpactSet(
                    selector,
                    new[] { image },
                    usageOnly,
                    DateTimeOffset.UtcNow,
                    total: 1,
                    snapshotId: null,
                    schemaVersion: SchedulerSchemaVersions.ImpactSet);
                return ValueTask.FromResult(impactSet);
            }
        };

        var service = CreateService(impact);
        var metadata = ImmutableSortedDictionary<string, string>.Empty.Add("delta.vulns", "CVE-2025-1234");
        var job = CreateJob(metadata: metadata, inputs: PolicyRunInputs.Empty);

        var result = await service.EnsureTargetsAsync(job, CancellationToken.None);

        Assert.Equal(PolicyRunTargetingStatus.Targeted, result.Status);
        Assert.Equal(new[] { "sbom:sha256:aaa" }, result.Job.Inputs.SbomSet);
    }

    private static PolicyRunTargetingService CreateService(
        IImpactTargetingService? impact = null,
        Action<SchedulerWorkerOptions.PolicyOptions.TargetingOptions>? configure = null)
    {
        impact ??= new StubImpactTargetingService();
        var options = CreateOptions(configure);
        return new PolicyRunTargetingService(
            impact,
            Microsoft.Extensions.Options.Options.Create(options),
            timeProvider: null,
            NullLogger<PolicyRunTargetingService>.Instance);
    }

    private static SchedulerWorkerOptions CreateOptions(Action<SchedulerWorkerOptions.PolicyOptions.TargetingOptions>? configure)
    {
        var options = new SchedulerWorkerOptions
        {
            Policy =
            {
                Api =
                {
                    BaseAddress = new Uri("https://policy.example.com"),
                    RunsPath = "/runs",
                    SimulatePath = "/simulate"
                }
            }
        };

        configure?.Invoke(options.Policy.Targeting);
        return options;
    }

    private static PolicyRunJob CreateJob(
        PolicyRunMode mode = PolicyRunMode.Incremental,
        ImmutableSortedDictionary<string, string>? metadata = null,
        PolicyRunInputs? inputs = null)
    {
        return new PolicyRunJob(
            SchemaVersion: SchedulerSchemaVersions.PolicyRunJob,
            Id: "job-1",
            TenantId: "tenant-alpha",
            PolicyId: "P-7",
            PolicyVersion: 4,
            Mode: mode,
            Priority: PolicyRunPriority.Normal,
            PriorityRank: 0,
            RunId: null,
            RequestedBy: null,
            CorrelationId: null,
            Metadata: metadata ?? ImmutableSortedDictionary<string, string>.Empty,
            Inputs: inputs ?? PolicyRunInputs.Empty,
            QueuedAt: DateTimeOffset.UtcNow,
            Status: PolicyRunJobStatus.Dispatching,
            AttemptCount: 0,
            LastAttemptAt: null,
            LastError: null,
            CreatedAt: DateTimeOffset.UtcNow,
            UpdatedAt: DateTimeOffset.UtcNow,
            AvailableAt: DateTimeOffset.UtcNow,
            SubmittedAt: null,
            CompletedAt: null,
            LeaseOwner: "lease",
            LeaseExpiresAt: DateTimeOffset.UtcNow.AddMinutes(1),
            CancellationRequested: false,
            CancellationRequestedAt: null,
            CancellationReason: null,
            CancelledAt: null);
    }

    private sealed class StubImpactTargetingService : IImpactTargetingService
    {
        public Func<IEnumerable<string>, bool, Selector, CancellationToken, ValueTask<ImpactSet>>? OnResolveByPurls { get; set; }

        public Func<IEnumerable<string>, bool, Selector, CancellationToken, ValueTask<ImpactSet>>? OnResolveByVulnerabilities { get; set; }

        public ValueTask<ImpactSet> ResolveByPurlsAsync(IEnumerable<string> productKeys, bool usageOnly, Selector selector, CancellationToken cancellationToken = default)
        {
            if (OnResolveByPurls is null)
            {
                return ValueTask.FromResult(CreateEmptyImpactSet(selector, usageOnly));
            }

            return OnResolveByPurls(productKeys, usageOnly, selector, cancellationToken);
        }

        public ValueTask<ImpactSet> ResolveByVulnerabilitiesAsync(IEnumerable<string> vulnerabilityIds, bool usageOnly, Selector selector, CancellationToken cancellationToken = default)
        {
            if (OnResolveByVulnerabilities is null)
            {
                return ValueTask.FromResult(CreateEmptyImpactSet(selector, usageOnly));
            }

            return OnResolveByVulnerabilities(vulnerabilityIds, usageOnly, selector, cancellationToken);
        }

        public ValueTask<ImpactSet> ResolveAllAsync(Selector selector, bool usageOnly, CancellationToken cancellationToken = default)
            => ValueTask.FromResult(CreateEmptyImpactSet(selector, usageOnly));

        private static ImpactSet CreateEmptyImpactSet(Selector selector, bool usageOnly)
        {
            return new ImpactSet(
                selector,
                ImmutableArray<ImpactImage>.Empty,
                usageOnly,
                DateTimeOffset.UtcNow,
                total: 0,
                snapshotId: null,
                schemaVersion: SchedulerSchemaVersions.ImpactSet);
        }
    }
}