using System.Security.Claims;
using System.Security.Cryptography;
using Bunit;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Components.Authorization;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Diagnostics;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Options;
using NSubstitute;
using NSubstitute.ExceptionExtensions;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.Sites;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Services;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Transport;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Transport;
using ZB.MOM.WW.ScadaBridge.ConfigurationDatabase;
using ZB.MOM.WW.ScadaBridge.Security;
using ZB.MOM.WW.ScadaBridge.Transport;
using TransportImportPage = ZB.MOM.WW.ScadaBridge.CentralUI.Components.Pages.Design.TransportImport;

namespace ZB.MOM.WW.ScadaBridge.CentralUI.Tests.Pages.Design;

/// <summary>
/// bUnit + logic tests for the TransportImport wizard (Component #24, Task T22).
///
/// <para>
/// The wizard has five steps (Upload / Passphrase / Diff / Confirm / Result).
/// Selecting a file via <c>InputFile</c> is hard to drive cleanly from bUnit
/// (JS interop + DotNetStreamReference), so the state-machine tests reach into
/// the page instance via <c>cut.Instance</c> and the <c>InternalsVisibleTo</c>
/// declaration on <c>ZB.MOM.WW.ScadaBridge.CentralUI.csproj</c>. The <c>BundleImporter</c>
/// mock controls every load/preview/apply contract so each step's behaviour can
/// be exercised in isolation. The full happy-path round-trip is covered by the
/// integration tests in <c>ZB.MOM.WW.ScadaBridge.Transport.IntegrationTests</c>.
/// </para>
/// </summary>
public class TransportImportPageTests : BunitContext
{
    private readonly IBundleImporter _importer = Substitute.For<IBundleImporter>();
    private readonly IAuditService _auditService = Substitute.For<IAuditService>();
    // M8 E2: the Map step injects ISiteRepository to populate target-site +
    // target-connection dropdowns. Register a substitute so every test (not just
    // the Map tests) can render the wizard without a missing-service failure.
    private readonly ISiteRepository _siteRepo = Substitute.For<ISiteRepository>();

    public TransportImportPageTests()
    {
        JSInterop.Mode = JSRuntimeMode.Loose;

        Services.AddSingleton(_importer);
        Services.AddSingleton(_auditService);

        _siteRepo.GetAllSitesAsync(Arg.Any<CancellationToken>())
            .Returns(Array.Empty<Site>());
        _siteRepo.GetDataConnectionsBySiteIdAsync(Arg.Any<int>(), Arg.Any<CancellationToken>())
            .Returns(Array.Empty<DataConnection>());
        Services.AddSingleton(_siteRepo);
        Services.AddSingleton<IOptions<TransportOptions>>(
            Microsoft.Extensions.Options.Options.Create(new TransportOptions
            {
                MaxBundleSizeMb = 10,
                MaxUnlockAttemptsPerSession = 3,
            }));

        // Provide a SQLite in-memory ScadaBridgeDbContext so the page's
        // DbContext.SaveChangesAsync() calls in the audit path succeed.
        var dbOptions = new DbContextOptionsBuilder<ScadaBridgeDbContext>()
            .UseSqlite("DataSource=:memory:")
            .ConfigureWarnings(w => w.Ignore(RelationalEventId.AmbientTransactionWarning))
            .Options;
        var dbContext = new ScadaBridgeDbContext(dbOptions);
        dbContext.Database.OpenConnection();
        dbContext.Database.EnsureCreated();
        Services.AddSingleton(dbContext);

        var principal = BuildPrincipal("alice", "Administrator");
        Services.AddSingleton<AuthenticationStateProvider>(new TestAuthStateProvider(principal));
        Services.AddAuthorizationCore();
    }

    private static ClaimsPrincipal BuildPrincipal(string username, params string[] roles)
    {
        var claims = new List<Claim> { new(JwtTokenService.UsernameClaimType, username) };
        claims.AddRange(roles.Select(r => new Claim(JwtTokenService.RoleClaimType, r)));
        return new ClaimsPrincipal(new ClaimsIdentity(claims, "TestAuth"));
    }

    private static BundleSession BuildEncryptedSession(string sourceEnv = "prod-cluster") =>
        new()
        {
            SessionId = Guid.NewGuid(),
            Manifest = new BundleManifest(
                BundleFormatVersion: 1,
                SchemaVersion: "1.0",
                CreatedAtUtc: DateTimeOffset.UtcNow,
                SourceEnvironment: sourceEnv,
                ExportedBy: "bob",
                ScadaBridgeVersion: "1.0.0",
                ContentHash: "sha256:0000",
                Encryption: new EncryptionMetadata(
                    Algorithm: "AES-256-GCM",
                    Kdf: "PBKDF2-SHA256",
                    Iterations: 600_000,
                    SaltB64: "abc",
                    IvB64: "def"),
                Summary: new BundleSummary(0, 0, 0, 0, 0, 0, 0, 0),
                Contents: Array.Empty<ManifestContentEntry>()),
            DecryptedContent = Array.Empty<byte>(),
            ExpiresAt = DateTimeOffset.UtcNow.AddMinutes(30),
        };

    // ─────────────────────────────────────────────────────────────────────
    // Test 1: Step 1 renders the InputFile upload control.
    // ─────────────────────────────────────────────────────────────────────
    [Fact]
    public void Renders_step1_upload_input()
    {
        var cut = Render<TransportImportPage>();
        // Bootstrap classes are applied by InputFile via the CSS class attribute.
        Assert.NotNull(cut.Find("input[type='file']"));
        // The Bootstrap step indicator should highlight Step 1.
        Assert.Contains("Upload", cut.Markup);
    }

    // ─────────────────────────────────────────────────────────────────────
    // Test 2: Wrong passphrase increments the failure counter without
    // advancing past Step 2.
    // ─────────────────────────────────────────────────────────────────────
    [Fact]
    public async Task Decryption_failure_increments_attempt_counter()
    {
        // Set up the importer to throw CryptographicException for wrong passphrases.
        _importer.LoadAsync(Arg.Any<Stream>(), Arg.Any<string>(), Arg.Any<CancellationToken>())
            .Throws(new CryptographicException("authentication tag mismatch"));

        var cut = Render<TransportImportPage>();
        await cut.InvokeAsync(() =>
        {
            // Seed the wizard at the passphrase step with cached bytes.
            SeedAtPassphraseStep(cut.Instance, new byte[] { 0x01, 0x02 });
            SetField(cut.Instance, "_passphrase", "wrong-pass");
        });

        // Drive a passphrase submission.
        await cut.InvokeAsync(async () =>
        {
            await InvokeAsyncMethod(cut.Instance, "SubmitPassphraseAsync");
        });

        Assert.Equal(1, GetField<int>(cut.Instance, "_failedUnlockAttempts"));
        Assert.Equal(
            TransportImportPage.ImportWizardStep.Passphrase,
            GetField<TransportImportPage.ImportWizardStep>(cut.Instance, "_step"));
    }

    // ─────────────────────────────────────────────────────────────────────
    // Test 3: After MaxUnlockAttemptsPerSession failures the wizard returns
    // to Step 1 with an explanatory error.
    // ─────────────────────────────────────────────────────────────────────
    [Fact]
    public async Task Three_failed_unlocks_force_reupload()
    {
        _importer.LoadAsync(Arg.Any<Stream>(), Arg.Any<string>(), Arg.Any<CancellationToken>())
            .Throws(new CryptographicException("authentication tag mismatch"));

        var cut = Render<TransportImportPage>();
        await cut.InvokeAsync(() =>
        {
            SeedAtPassphraseStep(cut.Instance, new byte[] { 0x01, 0x02 });
        });

        for (var i = 0; i < 3; i++)
        {
            await cut.InvokeAsync(async () =>
            {
                SetField(cut.Instance, "_passphrase", $"wrong-{i}");
                await InvokeAsyncMethod(cut.Instance, "SubmitPassphraseAsync");
            });
        }

        Assert.Equal(
            TransportImportPage.ImportWizardStep.Upload,
            GetField<TransportImportPage.ImportWizardStep>(cut.Instance, "_step"));
        var errorMessage = GetField<string?>(cut.Instance, "_errorMessage");
        Assert.NotNull(errorMessage);
        Assert.Contains("Too many failed unlock attempts", errorMessage);
    }

    // ─────────────────────────────────────────────────────────────────────
    // Test 4: Confirm step requires an exact match (case-sensitive) on the
    // source environment name before Apply is enabled.
    // ─────────────────────────────────────────────────────────────────────
    [Fact]
    public async Task Confirm_step_requires_exact_environment_name_match()
    {
        var session = BuildEncryptedSession(sourceEnv: "prod-cluster");
        _importer.PreviewAsync(session.SessionId, Arg.Any<CancellationToken>())
            .Returns(new ImportPreview(session.SessionId, new List<ImportPreviewItem>
            {
                new("Template", "Pump", null, 1, ConflictKind.New, null, null),
            }));

        var cut = Render<TransportImportPage>();
        await cut.InvokeAsync(() =>
        {
            SetField(cut.Instance, "_session", session);
            SetField(cut.Instance, "_preview", new ImportPreview(session.SessionId, new List<ImportPreviewItem>
            {
                new("Template", "Pump", null, 1, ConflictKind.New, null, null),
            }));
            SetField(cut.Instance, "_resolutions", new Dictionary<(string EntityType, string Name), ImportResolution>
            {
                [("Template", "Pump")] = new("Template", "Pump", ResolutionAction.Add, null),
            });
            SetField(cut.Instance, "_step", TransportImportPage.ImportWizardStep.Confirm);
        });

        // Wrong text → Apply button is disabled.
        await cut.InvokeAsync(() => SetField(cut.Instance, "_confirmEnvironmentText", "wrong"));
        cut.Render();
        var applyBtn = cut.FindAll("button").First(b => b.TextContent.Trim().StartsWith("Apply Import"));
        Assert.True(applyBtn.HasAttribute("disabled"));

        // Case mismatch → still disabled.
        await cut.InvokeAsync(() => SetField(cut.Instance, "_confirmEnvironmentText", "PROD-CLUSTER"));
        cut.Render();
        applyBtn = cut.FindAll("button").First(b => b.TextContent.Trim().StartsWith("Apply Import"));
        Assert.True(applyBtn.HasAttribute("disabled"));

        // Exact match → enabled.
        await cut.InvokeAsync(() => SetField(cut.Instance, "_confirmEnvironmentText", "prod-cluster"));
        cut.Render();
        applyBtn = cut.FindAll("button").First(b => b.TextContent.Trim().StartsWith("Apply Import"));
        Assert.False(applyBtn.HasAttribute("disabled"));
    }

    // ─────────────────────────────────────────────────────────────────────
    // Test 5: ApplyAsync is invoked with the chosen resolutions and the
    // authenticated user identity.
    // ─────────────────────────────────────────────────────────────────────
    [Fact]
    public async Task Apply_step_invokes_BundleImporter_ApplyAsync_with_resolutions()
    {
        var session = BuildEncryptedSession(sourceEnv: "prod-cluster");
        var resolutions = new Dictionary<(string EntityType, string Name), ImportResolution>
        {
            [("Template", "Pump")] = new("Template", "Pump", ResolutionAction.Overwrite, null),
        };
        var expectedResult = new ImportResult(
            BundleImportId: Guid.NewGuid(),
            Added: 0,
            Overwritten: 1,
            Skipped: 0,
            Renamed: 0,
            StaleInstanceIds: Array.Empty<int>(),
            AuditEventCorrelation: Guid.NewGuid().ToString());

        _importer.ApplyAsync(
                session.SessionId,
                Arg.Any<IReadOnlyList<ImportResolution>>(),
                "alice",
                Arg.Any<CancellationToken>(),
                Arg.Any<BundleNameMap>())
            .Returns(expectedResult);

        var cut = Render<TransportImportPage>();
        await cut.InvokeAsync(() =>
        {
            SetField(cut.Instance, "_session", session);
            SetField(cut.Instance, "_preview", new ImportPreview(session.SessionId, new List<ImportPreviewItem>
            {
                new("Template", "Pump", 1, 2, ConflictKind.Modified, null, null),
            }));
            SetField(cut.Instance, "_resolutions", resolutions);
            SetField(cut.Instance, "_step", TransportImportPage.ImportWizardStep.Confirm);
            SetField(cut.Instance, "_confirmEnvironmentText", "prod-cluster");
        });

        await cut.InvokeAsync(async () =>
        {
            await InvokeAsyncMethod(cut.Instance, "ApplyAsync");
        });

        await _importer.Received(1).ApplyAsync(
            session.SessionId,
            Arg.Is<IReadOnlyList<ImportResolution>>(rs =>
                rs.Any(r => r.EntityType == "Template" && r.Name == "Pump"
                    && r.Action == ResolutionAction.Overwrite)),
            "alice",
            Arg.Any<CancellationToken>(),
            Arg.Any<BundleNameMap>());

        Assert.Equal(
            TransportImportPage.ImportWizardStep.Result,
            GetField<TransportImportPage.ImportWizardStep>(cut.Instance, "_step"));
        Assert.Equal(expectedResult, GetField<ImportResult?>(cut.Instance, "_result"));
    }

    // ─────────────────────────────────────────────────────────────────────
    // Test 6: A user without the Admin role fails the RequireAdmin policy.
    // The router enforces [Authorize(Policy=...)] at request time — bUnit
    // doesn't model routing, so we verify the policy itself denies the
    // principal.
    // ─────────────────────────────────────────────────────────────────────
    [Fact]
    public async Task Page_returns_unauthorized_for_user_without_Admin_role()
    {
        var services = new ServiceCollection();
        services.AddLogging();
        services.AddScadaBridgeAuthorization();
        using var provider = services.BuildServiceProvider();
        var authService = provider.GetRequiredService<IAuthorizationService>();

        // Design-only user — has a role but it isn't Admin.
        var principal = BuildPrincipal("bob", "Designer");
        var result = await authService.AuthorizeAsync(
            principal, null, AuthorizationPolicies.RequireAdmin);

        Assert.False(result.Succeeded);
    }

    // ─────────────────────────────────────────────────────────────────────
    // Test 7 (helper coverage): BuildDefaultResolutions maps each kind to the
    // expected default ResolutionAction.
    // ─────────────────────────────────────────────────────────────────────
    [Fact]
    public void BuildDefaultResolutions_maps_kinds_to_actions()
    {
        var preview = new ImportPreview(Guid.NewGuid(), new List<ImportPreviewItem>
        {
            new("Template", "A", 1, 1, ConflictKind.Identical, null, null),
            new("Template", "B", null, 1, ConflictKind.New, null, null),
            new("Template", "C", 1, 2, ConflictKind.Modified, null, null),
            new("Reference", "D", null, null, ConflictKind.Blocker, null, "missing dep"),
        });

        var map = TransportImportPage.BuildDefaultResolutions(preview);

        Assert.Equal(ResolutionAction.Skip, map[("Template", "A")].Action);
        Assert.Equal(ResolutionAction.Add, map[("Template", "B")].Action);
        Assert.Equal(ResolutionAction.Overwrite, map[("Template", "C")].Action);
        Assert.Equal(ResolutionAction.Skip, map[("Reference", "D")].Action);
    }

    // ─────────────────────────────────────────────────────────────────────
    // Test 8 (M8 E2): the Map sub-section renders one row per required site /
    // connection mapping with the auto-match defaults pre-selected, and the
    // section is hidden entirely when the preview carries no required mappings.
    // ─────────────────────────────────────────────────────────────────────
    [Fact]
    public async Task Map_section_renders_required_rows_with_automatch_defaults()
    {
        // Target environment has one site (site-b) with one connection (opc-main),
        // which the bundle's source site "site-a" / connection "opc-a" auto-match to.
        _siteRepo.GetAllSitesAsync(Arg.Any<CancellationToken>())
            .Returns(new List<Site> { new("Site B", "site-b") { Id = 7 } });
        _siteRepo.GetDataConnectionsBySiteIdAsync(7, Arg.Any<CancellationToken>())
            .Returns(new List<DataConnection> { new("opc-main", "OpcUa", 7) { Id = 11 } });

        var session = BuildEncryptedSession(sourceEnv: "prod-cluster");
        var preview = new ImportPreview(
            session.SessionId,
            new List<ImportPreviewItem>(),
            new List<RequiredSiteMapping> { new("site-a", "Site A", "site-b") },
            new List<RequiredConnectionMapping> { new("site-a", "opc-a", "opc-main") });
        _importer.PreviewAsync(session.SessionId, Arg.Any<CancellationToken>()).Returns(preview);

        var cut = Render<TransportImportPage>();
        await cut.InvokeAsync(() => SetField(cut.Instance, "_session", session));
        await cut.InvokeAsync(async () =>
            await InvokeAsyncMethod(cut.Instance, "LoadPreviewAndAdvanceAsync"));
        cut.Render();

        // Section present with one site row and one connection row.
        Assert.NotNull(cut.Find("[data-testid='map-section']"));
        Assert.Single(cut.FindAll("[data-testid='map-site-row']"));
        Assert.Single(cut.FindAll("[data-testid='map-conn-row']"));

        // Auto-match defaults: site-a → site-b, opc-a → opc-main.
        var siteSelect = cut.Find("[data-testid='map-site-select-site-a']");
        var selectedSiteOpt = siteSelect.QuerySelectorAll("option").Single(o => o.HasAttribute("selected"));
        Assert.Equal("site-b", selectedSiteOpt.GetAttribute("value"));

        var connSelect = cut.Find("[data-testid='map-conn-select-site-a-opc-a']");
        var selectedConnOpt = connSelect.QuerySelectorAll("option").Single(o => o.HasAttribute("selected"));
        Assert.Equal("opc-main", selectedConnOpt.GetAttribute("value"));
    }

    [Fact]
    public async Task Map_section_hidden_when_no_required_mappings()
    {
        var session = BuildEncryptedSession(sourceEnv: "prod-cluster");
        var preview = new ImportPreview(session.SessionId, new List<ImportPreviewItem>
        {
            new("Template", "Pump", null, 1, ConflictKind.New, null, null),
        });
        _importer.PreviewAsync(session.SessionId, Arg.Any<CancellationToken>()).Returns(preview);

        var cut = Render<TransportImportPage>();
        await cut.InvokeAsync(() => SetField(cut.Instance, "_session", session));
        await cut.InvokeAsync(async () =>
            await InvokeAsyncMethod(cut.Instance, "LoadPreviewAndAdvanceAsync"));
        cut.Render();

        Assert.Empty(cut.FindAll("[data-testid='map-section']"));
    }

    // ─────────────────────────────────────────────────────────────────────
    // Test 9 (M8 E2): the operator's Map choices fold into the BundleNameMap
    // passed to ApplyAsync — a chosen target → MapToExisting, "Create new" →
    // CreateNew. Captured via the substituted IBundleImporter.
    // ─────────────────────────────────────────────────────────────────────
    [Fact]
    public async Task Apply_passes_BundleNameMap_built_from_map_choices()
    {
        _siteRepo.GetAllSitesAsync(Arg.Any<CancellationToken>())
            .Returns(new List<Site> { new("Site B", "site-b") { Id = 7 } });
        _siteRepo.GetDataConnectionsBySiteIdAsync(7, Arg.Any<CancellationToken>())
            .Returns(new List<DataConnection> { new("opc-main", "OpcUa", 7) { Id = 11 } });

        var session = BuildEncryptedSession(sourceEnv: "prod-cluster");
        var preview = new ImportPreview(
            session.SessionId,
            new List<ImportPreviewItem>(),
            // site-a auto-matches site-b; site-c has no auto-match (→ Create new default).
            new List<RequiredSiteMapping>
            {
                new("site-a", "Site A", "site-b"),
                new("site-c", "Site C", null),
            },
            // opc-a (under site-a) auto-matches opc-main.
            new List<RequiredConnectionMapping> { new("site-a", "opc-a", "opc-main") });
        _importer.PreviewAsync(session.SessionId, Arg.Any<CancellationToken>()).Returns(preview);

        var expectedResult = new ImportResult(
            Guid.NewGuid(), 0, 0, 0, 0, Array.Empty<int>(), Guid.NewGuid().ToString());
        _importer.ApplyAsync(
                session.SessionId,
                Arg.Any<IReadOnlyList<ImportResolution>>(),
                "alice",
                Arg.Any<CancellationToken>(),
                Arg.Any<BundleNameMap>())
            .Returns(expectedResult);

        var cut = Render<TransportImportPage>();
        await cut.InvokeAsync(() => SetField(cut.Instance, "_session", session));
        await cut.InvokeAsync(async () =>
            await InvokeAsyncMethod(cut.Instance, "LoadPreviewAndAdvanceAsync"));
        await cut.InvokeAsync(() => SetField(cut.Instance, "_confirmEnvironmentText", "prod-cluster"));
        await cut.InvokeAsync(async () => await InvokeAsyncMethod(cut.Instance, "ApplyAsync"));

        await _importer.Received(1).ApplyAsync(
            session.SessionId,
            Arg.Any<IReadOnlyList<ImportResolution>>(),
            "alice",
            Arg.Any<CancellationToken>(),
            Arg.Is<BundleNameMap>(m =>
                m.Sites.Count == 2
                && m.Sites.Any(s => s.SourceSiteIdentifier == "site-a"
                    && s.Action == MappingAction.MapToExisting && s.TargetSiteIdentifier == "site-b")
                && m.Sites.Any(s => s.SourceSiteIdentifier == "site-c"
                    && s.Action == MappingAction.CreateNew && s.TargetSiteIdentifier == null)
                && m.Connections.Count == 1
                && m.Connections.Any(c => c.SourceSiteIdentifier == "site-a"
                    && c.SourceConnectionName == "opc-a"
                    && c.Action == MappingAction.MapToExisting && c.TargetConnectionName == "opc-main")));
    }

    // ─────────────────────────────────────────────────────────────────────
    // Test 10 (M8 E2): a Modified row whose FieldDiffJson carries a code
    // lineDiff renders +/- lines via LineDiffView.
    // ─────────────────────────────────────────────────────────────────────
    [Fact]
    public async Task Modified_row_with_code_lineDiff_renders_add_and_remove_lines()
    {
        const string fieldDiffJson = """
            {
              "changes": [
                {
                  "field": "Code",
                  "oldValue": "a\nb\nc",
                  "newValue": "a\nB\nc",
                  "lineDiff": {
                    "hunks": [
                      { "op": "context", "text": "a", "oldLineNo": 1, "newLineNo": 1 },
                      { "op": "remove", "text": "b", "oldLineNo": 2 },
                      { "op": "add", "text": "B", "newLineNo": 2 },
                      { "op": "context", "text": "c", "oldLineNo": 3, "newLineNo": 3 }
                    ],
                    "truncated": false,
                    "addedCount": 1,
                    "removedCount": 1
                  }
                }
              ]
            }
            """;

        var session = BuildEncryptedSession(sourceEnv: "prod-cluster");
        var preview = new ImportPreview(session.SessionId, new List<ImportPreviewItem>
        {
            new("Template", "Pump", 1, 2, ConflictKind.Modified, fieldDiffJson, null),
        });
        _importer.PreviewAsync(session.SessionId, Arg.Any<CancellationToken>()).Returns(preview);

        var cut = Render<TransportImportPage>();
        await cut.InvokeAsync(() => SetField(cut.Instance, "_session", session));
        await cut.InvokeAsync(async () =>
            await InvokeAsyncMethod(cut.Instance, "LoadPreviewAndAdvanceAsync"));
        cut.Render();

        // The code line-diff block is present and shows one add + one remove line.
        Assert.NotNull(cut.Find("[data-testid='code-line-diff']"));
        Assert.NotNull(cut.Find("[data-testid='line-diff']"));
        Assert.Single(cut.FindAll("[data-testid='line-diff-add']"));
        Assert.Single(cut.FindAll("[data-testid='line-diff-remove']"));
        // The raw JSON <pre> fallback is NOT used for code-field diffs.
        Assert.DoesNotContain("\"lineDiff\"", cut.Find("[data-testid='code-line-diff']").InnerHtml);
        // No truncation marker for a complete diff.
        Assert.Empty(cut.FindAll("[data-testid='line-diff-truncated']"));
    }

    // ─────────────────────────────────────────────────────────────────────
    // Test 11 (M8 E2): truncation marker shows when the lineDiff is truncated.
    // ─────────────────────────────────────────────────────────────────────
    [Fact]
    public async Task Modified_row_with_truncated_lineDiff_shows_truncation_marker()
    {
        const string fieldDiffJson = """
            {
              "changes": [
                {
                  "field": "Code",
                  "oldValue": "x",
                  "newValue": "y",
                  "lineDiff": {
                    "hunks": [
                      { "op": "remove", "text": "x", "oldLineNo": 1 },
                      { "op": "add", "text": "y", "newLineNo": 1 }
                    ],
                    "truncated": true,
                    "addedCount": 12,
                    "removedCount": 8
                  }
                }
              ]
            }
            """;

        var session = BuildEncryptedSession(sourceEnv: "prod-cluster");
        var preview = new ImportPreview(session.SessionId, new List<ImportPreviewItem>
        {
            new("Template", "Pump", 1, 2, ConflictKind.Modified, fieldDiffJson, null),
        });
        _importer.PreviewAsync(session.SessionId, Arg.Any<CancellationToken>()).Returns(preview);

        var cut = Render<TransportImportPage>();
        await cut.InvokeAsync(() => SetField(cut.Instance, "_session", session));
        await cut.InvokeAsync(async () =>
            await InvokeAsyncMethod(cut.Instance, "LoadPreviewAndAdvanceAsync"));
        cut.Render();

        var marker = cut.Find("[data-testid='line-diff-truncated']");
        Assert.Contains("truncated", marker.TextContent);
        Assert.Contains("+12", marker.TextContent);
        Assert.Contains("-8", marker.TextContent);
    }

    // ─────────────────────────────────────────────────────────────────────
    // Test 12 (M8 E2 Fix 1): changing a source site's dropdown to a target
    // that lacks the previously auto-matched connection name resets that
    // connection choice to CreateNew (""), and BuildNameMap therefore emits
    // a CreateNew entry — not a MapToExisting for an absent connection.
    // ─────────────────────────────────────────────────────────────────────
    [Fact]
    public async Task OnSiteChoiceChanged_resets_stale_connection_choices_when_new_target_lacks_connection()
    {
        // Target environment: site-b has connection "opc-main"; site-c has NO connections.
        var siteB = new Site("Site B", "site-b") { Id = 7 };
        var siteC = new Site("Site C", "site-c") { Id = 8 };
        _siteRepo.GetAllSitesAsync(Arg.Any<CancellationToken>())
            .Returns(new List<Site> { siteB, siteC });
        _siteRepo.GetDataConnectionsBySiteIdAsync(7, Arg.Any<CancellationToken>())
            .Returns(new List<DataConnection> { new("opc-main", "OpcUa", 7) { Id = 11 } });
        _siteRepo.GetDataConnectionsBySiteIdAsync(8, Arg.Any<CancellationToken>())
            .Returns(Array.Empty<DataConnection>());

        // Bundle: source site "site-a" auto-matches site-b; connection "opc-a" auto-matches "opc-main".
        var session = BuildEncryptedSession(sourceEnv: "prod-cluster");
        var preview = new ImportPreview(
            session.SessionId,
            new List<ImportPreviewItem>(),
            new List<RequiredSiteMapping> { new("site-a", "Site A", "site-b") },
            new List<RequiredConnectionMapping> { new("site-a", "opc-a", "opc-main") });
        _importer.PreviewAsync(session.SessionId, Arg.Any<CancellationToken>()).Returns(preview);

        var cut = Render<TransportImportPage>();
        await cut.InvokeAsync(() => SetField(cut.Instance, "_session", session));
        // Drive LoadPreviewAndAdvanceAsync to seed auto-match state (site-a → site-b, opc-a → opc-main).
        await cut.InvokeAsync(async () =>
            await InvokeAsyncMethod(cut.Instance, "LoadPreviewAndAdvanceAsync"));

        // Verify the auto-match seed: connection choice is "opc-main".
        var connChoicesBefore = GetField<Dictionary<(string, string), string>>(
            cut.Instance, "_connectionChoices");
        Assert.Equal("opc-main", connChoicesBefore[("site-a", "opc-a")]);

        // Operator changes site-a's target from site-b → site-c (which has no connections).
        await cut.InvokeAsync(async () =>
        {
            var method = cut.Instance.GetType().GetMethod(
                "OnSiteChoiceChangedAsync",
                System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic)!;
            await (Task)method.Invoke(cut.Instance, new object[] { "site-a", "site-c" })!;
        });

        // Connection choice for (site-a, opc-a) must now be CreateNew ("").
        var connChoicesAfter = GetField<Dictionary<(string, string), string>>(
            cut.Instance, "_connectionChoices");
        Assert.Equal(string.Empty, connChoicesAfter[("site-a", "opc-a")]);

        // BuildNameMap must NOT emit MapToExisting for "opc-a" — it should emit CreateNew.
        var nameMap = TransportImportPageTests.InvokeBuildNameMap(cut.Instance);
        var connMapping = nameMap.Connections.Single(c => c.SourceConnectionName == "opc-a");
        Assert.Equal(MappingAction.CreateNew, connMapping.Action);
        Assert.Null(connMapping.TargetConnectionName);
    }

    // ─────────────────────────────────────────────────────────────────────
    // Test 13 (M8 E2 Fix 2): BackToUpload clears session/preview/Map state
    // so a subsequent re-upload flow cannot inherit stale data.
    // ─────────────────────────────────────────────────────────────────────
    [Fact]
    public async Task BackToUpload_clears_session_and_preview_state()
    {
        // Seed the wizard at the Diff step with non-trivial session + preview + Map state.
        var session = BuildEncryptedSession(sourceEnv: "prod-cluster");
        var preview = new ImportPreview(
            session.SessionId,
            new List<ImportPreviewItem>
            {
                new("Template", "Pump", null, 1, ConflictKind.New, null, null),
            },
            new List<RequiredSiteMapping> { new("site-a", "Site A", null) },
            new List<RequiredConnectionMapping> { new("site-a", "conn-x", null) });

        var cut = Render<TransportImportPage>();
        await cut.InvokeAsync(() =>
        {
            SetField(cut.Instance, "_session", session);
            SetField(cut.Instance, "_preview", preview);
            SetField(cut.Instance, "_resolutions",
                new Dictionary<(string, string), ImportResolution>
                {
                    [("Template", "Pump")] = new("Template", "Pump", ResolutionAction.Add, null),
                });
            SetField(cut.Instance, "_siteChoices",
                new Dictionary<string, string> { ["site-a"] = "site-b" });
            SetField(cut.Instance, "_connectionChoices",
                new Dictionary<(string, string), string> { [("site-a", "conn-x")] = "conn-y" });
            SetField(cut.Instance, "_step", TransportImportPage.ImportWizardStep.Diff);
        });

        // Invoke BackToUpload.
        await cut.InvokeAsync(() =>
        {
            var method = cut.Instance.GetType().GetMethod(
                "BackToUpload",
                System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic)!;
            method.Invoke(cut.Instance, Array.Empty<object?>());
        });

        // Step must be back to Upload.
        Assert.Equal(
            TransportImportPage.ImportWizardStep.Upload,
            GetField<TransportImportPage.ImportWizardStep>(cut.Instance, "_step"));

        // Session, preview, resolutions, and Map state must all be cleared.
        Assert.Null(GetField<object?>(cut.Instance, "_session"));
        Assert.Null(GetField<object?>(cut.Instance, "_preview"));
        Assert.Null(GetField<object?>(cut.Instance, "_resolutions"));

        var siteChoices = GetField<Dictionary<string, string>>(cut.Instance, "_siteChoices");
        Assert.Empty(siteChoices);

        var connChoices = GetField<Dictionary<(string, string), string>>(cut.Instance, "_connectionChoices");
        Assert.Empty(connChoices);
    }

    // ─────────────────────────────────────────────────────────────────────
    // Reflection helpers — the wizard's per-instance state is private (the
    // razor partial pattern). We poke at it via reflection rather than
    // widening the surface of the production class with test-only accessors.
    // ─────────────────────────────────────────────────────────────────────

    private static void SetField(object obj, string name, object? value)
    {
        var field = obj.GetType().GetField(
            name,
            System.Reflection.BindingFlags.Instance
            | System.Reflection.BindingFlags.NonPublic
            | System.Reflection.BindingFlags.Public)
            ?? throw new InvalidOperationException($"Field '{name}' not found on {obj.GetType()}.");
        field.SetValue(obj, value);
    }

    private static T GetField<T>(object obj, string name)
    {
        var field = obj.GetType().GetField(
            name,
            System.Reflection.BindingFlags.Instance
            | System.Reflection.BindingFlags.NonPublic
            | System.Reflection.BindingFlags.Public)
            ?? throw new InvalidOperationException($"Field '{name}' not found on {obj.GetType()}.");
        return (T)field.GetValue(obj)!;
    }

    private static async Task InvokeAsyncMethod(object obj, string name)
    {
        var method = obj.GetType().GetMethod(
            name,
            System.Reflection.BindingFlags.Instance
            | System.Reflection.BindingFlags.NonPublic
            | System.Reflection.BindingFlags.Public)
            ?? throw new InvalidOperationException($"Method '{name}' not found on {obj.GetType()}.");
        var task = (Task)method.Invoke(obj, Array.Empty<object?>())!;
        await task;
    }

    /// <summary>
    /// Invokes the private <c>BuildNameMap()</c> method on the page instance and
    /// returns the resulting <see cref="BundleNameMap"/>. Used by Test 12 to assert
    /// the map shape after a site-choice change without going through ApplyAsync.
    /// </summary>
    private static BundleNameMap InvokeBuildNameMap(TransportImportPage instance)
    {
        var method = instance.GetType().GetMethod(
            "BuildNameMap",
            System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic)
            ?? throw new InvalidOperationException("Method 'BuildNameMap' not found.");
        return (BundleNameMap)method.Invoke(instance, Array.Empty<object?>())!;
    }

    /// <summary>
    /// Seeds the wizard at Step 2 (Passphrase) with a staged bundle file — the
    /// shape after an encrypted-bundle upload completed Step 1's peek and
    /// surfaced an ArgumentException ("passphrase required"). CentralUI-031:
    /// the wizard now stages the upload to a temp file and only retains the
    /// path on the component, so the test helper writes the bytes to a per-
    /// test temp file and sets the path field instead of the byte[] field.
    /// </summary>
    private static void SeedAtPassphraseStep(TransportImportPage instance, byte[] bytes)
    {
        var dir = Path.Combine(Path.GetTempPath(), "scadabridge-transport-staging");
        Directory.CreateDirectory(dir);
        var path = Path.Combine(dir, $"test-{Guid.NewGuid():N}.scadabundle");
        File.WriteAllBytes(path, bytes);
        SetField(instance, "_bundleTempPath", path);
        SetField(instance, "_session", null);
        SetField(instance, "_step", TransportImportPage.ImportWizardStep.Passphrase);
        SetField(instance, "_failedUnlockAttempts", 0);
    }
}
