using Avalonia.Controls;
using DodoSSH.Client.App.ViewModels;
using DodoSSH.Client.App.Views;
using DodoSSH.Client.Session;
using DodoSSH.Client.Session.Tests;
using DodoSSH.Client.Ssh;
using DodoSSH.Client.Storage;
using DodoSSH.Client.Terminal;
using DodoSSH.Crypto;
using NSubstitute;

namespace DodoSSH.Client.App.Layout.Tests;

/// <summary>
/// Whether the vault column fits in the space the window gives it.
/// </summary>
/// <remarks>
/// <para>
/// The column is 340 pixels wide and holds a list and an editor per item type, of which it shows one type at a
/// time. This suite is the measurement behind that arrangement: the column used to stack both types and keep
/// itself from clipping its own Save button with a state rule — one editor open at a time — and that rule was
/// added on the strength of an argument. The argument was right about the stacked column and is now moot,
/// which is a thing this suite found rather than assumed. See
/// <see cref="BothEditorsOpen_NowFit_BecauseOnlyOneSectionIsLaidOut" />.
/// </para>
/// <para>
/// One test per section, and one per section with its editor open, because that is the full set of shapes a
/// user can put this column into. A third section will add two more.
/// </para>
/// <para>
/// A real <c>VaultViewModel</c> over a real unlocked vault, rather than a stand-in. Compiled bindings resolve
/// against the declared data type, so a stand-in would have to be the same type anyway — and the editors'
/// height depends on real content: a key with a real armour block in the box is taller than an empty one.
/// </para>
/// </remarks>
public sealed class VaultColumnLayoutTests : IAsyncLifetime
{
    private const string Passphrase = "a sufficiently long passphrase";
    private const string ServerUrl = "https://dodossh.example";

    /// <remarks>Far below the shipped profile: nothing here attacks a wrap.</remarks>
    private static readonly Argon2Profile CheapProfile =
        Argon2Profile.FromStoredParameters(memoryKibibytes: 8 * 1024, passes: 1, parallelism: 1);

    private readonly FakeAccountServer server = new();
    private readonly StubKeyBinding keyBinding = new();
    private readonly VaultKnownHostStore knownHosts = new();

    private ClientCacheFactory caches = null!;
    private TerminalWorkspace workspace = null!;
    private VaultSession session = null!;
    private VaultViewModel vault = null!;

    private static CancellationToken Token => TestContext.Current.CancellationToken;

    /// <inheritdoc />
    public async ValueTask InitializeAsync()
    {
        caches = ClientCacheFactory.ForMemory($"layout-{Guid.CreateVersion7():N}");
        await caches.MigrateAsync(Token);

        await new AccountProvisioner(server, keyBinding, caches, TimeProvider.System, CheapProfile)
            .EnrollAsync(ServerUrl, Passphrase, "laptop", "Personal", Token);

        var outcome = await new SessionOpener(caches, TimeProvider.System).UnlockAsync(Passphrase, Token);
        outcome.IsUnlocked.ShouldBeTrue(outcome.Message);
        session = outcome.Session!;

        // Never started and never connected through: the column's layout does not depend on the terminal, and
        // the substitute is here only because the view model's constructor asks for one.
        workspace = new TerminalWorkspace(
            new InMemoryTerminalAssetProvider(new Dictionary<string, TerminalAsset>(StringComparer.Ordinal)),
            Substitute.For<ISshConnectionFactory>(),
            TimeProvider.System);

        await knownHosts.OpenAsync(session, Token);

        // Offline. A null connection is what the column shows on a laptop with no network, and it keeps every
        // sync pass out of a suite that is only measuring rectangles.
        vault = new VaultViewModel(session, workspace, knownHosts, static () => null);

        await SeedAsync();
    }

    /// <inheritdoc />
    public async ValueTask DisposeAsync()
    {
        await vault.DisposeAsync();
        knownHosts.Close();
        await workspace.DisposeAsync();
        await session.DisposeAsync();
        caches.Dispose();
    }

    [Fact]
    public async Task TheHostsSectionFitsWithNoEditorOpen()
    {
        await MeasureAsync(faults => faults.ShouldBeEmpty());
    }

    [Fact]
    public async Task TheHostsSectionFitsWithItsEditorOpen()
    {
        vault.NewHostCommand.Execute(null);
        vault.IsEditing.ShouldBeTrue();

        await MeasureAsync(faults => faults.ShouldBeEmpty());
    }

    [Fact]
    public async Task TheKeysSectionFitsWithNoEditorOpen()
    {
        vault.ShowSectionCommand.Execute(VaultSection.Keys);
        vault.ShowsKeys.ShouldBeTrue();

        await MeasureAsync(faults => faults.ShouldBeEmpty());
    }

    [Fact]
    public async Task TheKeysSectionFitsWithItsEditorOpen()
    {
        // The tall one: a private key needs a real text area, and this editor is what the key list used to
        // hide itself and cap its own height for. Both workarounds are gone, so this measurement is now the
        // only thing saying they were not needed.
        vault.NewKeyCommand.Execute(null);
        vault.IsEditingKey.ShouldBeTrue();
        vault.ShowsKeys.ShouldBeTrue("opening an editor has to bring its own section into view");

        vault.KeyEditorPrivateKey = string.Join(
            '\n',
            Enumerable.Repeat("b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gt", 6));

        await MeasureAsync(faults => faults.ShouldBeEmpty());
    }

    [Fact]
    public async Task TheCredentialsSectionFitsWithNoEditorOpen()
    {
        vault.ShowSectionCommand.Execute(VaultSection.Credentials);
        vault.ShowsCredentials.ShouldBeTrue();

        await MeasureAsync(faults => faults.ShouldBeEmpty());
    }

    [Fact]
    public async Task TheCredentialsSectionFitsWithItsEditorOpen()
    {
        vault.NewCredentialCommand.Execute(null);
        vault.IsEditingCredential.ShouldBeTrue();
        vault.ShowsCredentials.ShouldBeTrue("opening an editor has to bring its own section into view");

        await MeasureAsync(faults => faults.ShouldBeEmpty());
    }

    /// <remarks>
    /// The only section with no editor, so it has only the one shape — but the tallest rows, because each
    /// carries a full fingerprint on a wrapped monospace line rather than a one-word description.
    /// </remarks>
    [Fact]
    public async Task TheHostKeysSectionFits()
    {
        vault.ShowSectionCommand.Execute(VaultSection.KnownHosts);
        vault.ShowsKnownHosts.ShouldBeTrue();

        vault.KnownHostPins.ShouldNotBeEmpty("an empty list is the easy case and proves nothing here");

        await MeasureAsync(faults => faults.ShouldBeEmpty());
    }

    /// <remarks>
    /// The host editor is the one a third item type made taller: its authentication picker is now a ComboBox
    /// with a two-line-capable item template, and the section it sits in is the only one holding a
    /// <c>NumericUpDown</c>, a <c>CheckBox</c> and two paragraphs of hint text. Measured with the picker
    /// populated, because an empty ComboBox is shorter than one showing a qualifier beside a label.
    /// </remarks>
    [Fact]
    public async Task TheHostEditorFitsWithTheAuthenticationPickerFull()
    {
        vault.SelectedHost = vault.Hosts[0];
        vault.EditSelectedHostCommand.Execute(null);

        vault.EditorAuthenticationChoices.Count
            .ShouldBeGreaterThan(1, "the picker has to be populated for this to measure anything");

        vault.EditorSelectedAuthentication = vault.EditorAuthenticationChoices
            .First(choice => choice.Kind is AuthenticationKind.Credential);

        await MeasureAsync(faults => faults.ShouldBeEmpty());
    }

    [Fact]
    public async Task BothEditorsOpen_NowFit_BecauseOnlyOneSectionIsLaidOut()
    {
        // This test used to assert the opposite, and its own comment said that if it ever started passing the
        // rule it justified had become unnecessary. That has happened, and this is the record of it: the two
        // editors are in different sections now and only one section is laid out, so the sizing argument for
        // one-editor-at-a-time is dead.
        //
        // The rule itself is not, and AnEditorIsInTheWay says why — an open key editor holds a pasted private
        // key, and moving on would leave it in a form nobody can see. That is a state rule with a state
        // reason, so it belongs in the shell's tests and not here. This suite's job was the sizing claim, and
        // the honest thing to do with a measurement that has flipped is to keep measuring it.
        vault.IsEditing = true;
        vault.IsEditingKey = true;

        await MeasureAsync(faults => faults.ShouldBeEmpty(
            "one section at a time means two open editors are never laid out together"));

        vault.Section = VaultSection.Keys;

        await MeasureAsync(faults => faults.ShouldBeEmpty(
            "and the same holds from the other side, where the taller editor is the visible one"));
    }

    /// <remarks>
    /// <para>
    /// The one thing a wrong answer here breaks is unrecoverable from the keyboard: <c>MainWindow</c> takes the
    /// keyboard off the terminal's native child window first and then focuses this target, so a target that
    /// cannot take focus leaves the user with no focused element and no way back except the mouse.
    /// </para>
    /// <para>
    /// Which is why this asserts that focus was <i>taken</i> rather than that the right control was named.
    /// Naming is the cheap half and it was already right; taking it was not — a <c>ListBox</c> is not focusable
    /// by default, so this call returned false against the column as it stood and the shipped release-the-
    /// keyboard path did nothing. Two ways to fail, and only the assertion that runs the call sees both: a
    /// control in the section that is not showing is collapsed, and <c>Focus()</c> on a collapsed control is a
    /// no-op that is not replayed when it is revealed.
    /// </para>
    /// </remarks>
    [Fact]
    public async Task TheKeyboardTargetIsTheListThatIsOnScreenAndItTakesFocus()
    {
        await OnTheColumnAsync((column, _) =>
        {
            column.KeyboardTarget.ShouldBeSameAs(column.HostList);
            column.KeyboardTarget.Focus().ShouldBeTrue("the hosts section is showing");
        });

        vault.ShowSectionCommand.Execute(VaultSection.Keys);

        await OnTheColumnAsync((column, _) =>
        {
            column.KeyboardTarget.ShouldBeSameAs(column.KeyList);
            column.KeyboardTarget.Focus().ShouldBeTrue("the keys section is showing");
        });

        vault.ShowSectionCommand.Execute(VaultSection.Credentials);

        await OnTheColumnAsync((column, _) =>
        {
            column.KeyboardTarget.ShouldBeSameAs(column.CredentialList);
            column.KeyboardTarget.Focus().ShouldBeTrue("the credentials section is showing");
        });

        vault.ShowSectionCommand.Execute(VaultSection.KnownHosts);

        await OnTheColumnAsync((column, _) =>
        {
            column.KeyboardTarget.ShouldBeSameAs(column.KnownHostList);
            column.KeyboardTarget.Focus().ShouldBeTrue("the host keys section is showing");
        });
    }

    /// <remarks>
    /// The same call in the state the section rule allows: an editor open, its own list still on screen behind
    /// it. The key list used to collapse itself whenever its editor opened, so a target that followed the
    /// section would have been a no-op in exactly the state a user is most likely to leave the terminal in.
    /// </remarks>
    [Fact]
    public async Task TheKeyboardTargetStillTakesFocusWithAnEditorOpen()
    {
        vault.NewKeyCommand.Execute(null);

        await OnTheColumnAsync((column, _) =>
        {
            column.KeyList.IsEffectivelyVisible.ShouldBeTrue();
            column.KeyboardTarget.Focus().ShouldBeTrue();
        });
    }

    /// <remarks>
    /// The claim the whole arrangement rests on, and the one nothing else here would notice breaking: two
    /// sections left visible at once would overlap in the row they share rather than clip, so every fit test
    /// above would still pass while the column showed one list through another.
    /// </remarks>
    [Fact]
    public async Task OnlyOneSectionIsOnScreenAtOnce()
    {
        await AssertOnlyVisibleAsync(VaultSection.Hosts);
        await AssertOnlyVisibleAsync(VaultSection.Keys);
        await AssertOnlyVisibleAsync(VaultSection.Credentials);
        await AssertOnlyVisibleAsync(VaultSection.KnownHosts);
    }

    /// <summary>Shows one section and checks that it is the only one a user can see.</summary>
    private async Task AssertOnlyVisibleAsync(VaultSection section)
    {
        vault.Section = section;

        await OnTheColumnAsync((column, _) =>
        {
            var lists = new Dictionary<VaultSection, ListBox>
            {
                [VaultSection.Hosts] = column.HostList,
                [VaultSection.Keys] = column.KeyList,
                [VaultSection.Credentials] = column.CredentialList,
                [VaultSection.KnownHosts] = column.KnownHostList,
            };

            foreach (var (owner, list) in lists)
            {
                list.IsEffectivelyVisible.ShouldBe(
                    owner == section,
                    $"{owner} showing while {section} is selected");
            }
        });
    }

    /// <remarks>
    /// The selector is the only way to reach a section, so a click that lands on nothing is a column with one
    /// half of it walled off. Its buttons are covered by every fit test above — the harness treats a
    /// <see cref="Button"/> as interactive — but that only proves they are inside the window. This proves they
    /// are the size a pointer can find, which a zero-height row of buttons in a collapsed border would not be.
    /// </remarks>
    [Fact]
    public async Task TheSelectorIsBigEnoughToClick()
    {
        await OnTheColumnAsync((column, _) =>
        {
            var buttons = column.SectionSelector.Children.OfType<Button>().ToList();

            buttons.Count.ShouldBe(4, "one per section that exists");

            foreach (var button in buttons)
            {
                button.Bounds.Height.ShouldBeGreaterThan(20);
                button.Bounds.Width.ShouldBeGreaterThan(40);
            }

            // How much room a fifth section would have. The row is a horizontal StackPanel in a 340-pixel
            // column, so the four labels are close to filling it — and the fit tests above would catch an
            // overflow only as "a button falls outside the window", which reads as a mysterious layout fault
            // rather than as "the selector has run out of room". Stated as a number so it reads as itself.
            var used = buttons.Sum(button => button.Bounds.Width);

            used.ShouldBeLessThan(
                LayoutHarness.VaultColumnWidth,
                $"the selector needs {used:0} of {LayoutHarness.VaultColumnWidth:0} pixels; a fifth section "
                + "means shorter labels or a second row");
        });
    }

    /// <summary>Lays the column out at the size the window gives it and hands the faults to an assertion.</summary>
    private Task MeasureAsync(Action<IReadOnlyList<string>> assert) =>
        OnTheColumnAsync((_, window) => assert(LayoutHarness.Unreachable(window)));

    /// <summary>Shows the column at the size the window gives it and runs one body against it.</summary>
    private Task OnTheColumnAsync(Action<VaultColumn, Window> body) =>
        LayoutHarness.OnTheUiThreadAsync(
            () =>
            {
                var column = new VaultColumn { DataContext = vault };

                var window = LayoutHarness.HostAtMinimumSize(
                    column,
                    LayoutHarness.VaultColumnWidth,
                    LayoutHarness.VaultColumnHeight);

                try
                {
                    body(column, window);
                }
                finally
                {
                    window.Close();
                }
            },
            Token);

    /// <remarks>
    /// Enough rows in both lists that neither is empty, because an empty list is the easiest case and the one
    /// least worth certifying — and since the selector arrived, the keys section has a whole column of its own
    /// to fill rather than a capped strip at the bottom of the hosts one.
    /// </remarks>
    private async Task SeedAsync()
    {
        for (var i = 0; i < 6; i++)
        {
            vault.NewHostCommand.Execute(null);
            vault.EditorLabel = $"host-{i}";
            vault.EditorHostname = $"host-{i}.internal";
            vault.EditorUsername = "deploy";
            await vault.SaveHostCommand.ExecuteAsync(null);
        }

        for (var i = 0; i < 4; i++)
        {
            vault.NewKeyCommand.Execute(null);
            vault.KeyEditorLabel = $"key-{i}";
            vault.KeyEditorPrivateKey =
                $"-----BEGIN OPENSSH PRIVATE KEY-----\nMATERIAL-{i}\n-----END OPENSSH PRIVATE KEY-----\n";
            await vault.SaveKeyCommand.ExecuteAsync(null);
        }

        for (var i = 0; i < 3; i++)
        {
            vault.NewCredentialCommand.Execute(null);
            vault.CredentialEditorLabel = $"credential-{i}";
            vault.CredentialEditorPassword = $"password-{i}";
            vault.CredentialEditorUsername = $"account-{i}";
            await vault.SaveCredentialCommand.ExecuteAsync(null);
        }

        // Pins come from approving a fingerprint at connect time, not from an editor, so they are seeded
        // through the store the connect path writes to. Two for one endpoint, because a host offering keys
        // of two algorithms is ordinary and the duplicate is one of the things this list has to show.
        foreach (var (host, algorithm) in new[]
        {
            ("host-0.internal", "ssh-ed25519"),
            ("host-0.internal", "ecdsa-sha2-nistp256"),
            ("gone.internal", "ssh-ed25519"),
        })
        {
            await knownHosts.TrustAsync(
                new HostKeyPresentation(
                    host, 22, algorithm, $"SHA256:{algorithm}-fingerprint-0123456789abcdefghijklmnop"),
                Token);
        }

        // Back to where the column opens, so every test starts from the state a user would see.
        vault.Section = VaultSection.Hosts;

        await vault.LoadAsync(Token);
    }
}