using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Jellyfin.Data;
using Jellyfin.Database.Implementations.Entities;
using Jellyfin.Database.Implementations.Enums;
using Jellyfin.Plugin.WatchedTogether.Configuration;
using Jellyfin.Plugin.WatchedTogether.Services;
using MediaBrowser.Controller.Library;
using Microsoft.Extensions.Logging.Abstractions;
using Moq;
using Xunit;

namespace Jellyfin.Plugin.WatchedTogether.Tests;

/// <summary>
/// Covers creating a shared account on the fly from a name typed at the login screen.
/// </summary>
/// <remarks>
/// These tests drive <see cref="DynamicGroupService"/> through a stubbed user manager. They rely on
/// <see cref="Plugin.Instance"/> configuration, which is set up per test via
/// <see cref="PluginTestContext"/>.
/// </remarks>
[Collection(nameof(PluginTestContext))]
public class DynamicGroupTests
{
    private const string AliceHash = "$PBKDF2-SHA512$iterations=210000$A1A1A1A1$AAAAAAAABBBBBBBB";
    private const string BobHash = "$PBKDF2-SHA512$iterations=210000$B2B2B2B2$CCCCCCCCDDDDDDDD";

    private static User MakeUser(string name, string? password = null, bool disabled = false)
    {
        var user = new User(name, "Prov", "ResetProv");
        if (password is not null)
        {
            user.Password = password;
        }

        if (disabled)
        {
            user.SetPermission(PermissionKind.IsDisabled, true);
        }

        return user;
    }

    private sealed record Harness(
        DynamicGroupService Service,
        Mock<IProvisioningService> Provisioning,
        StubCryptoProvider Crypto);

    private static Harness MakeService(
        IReadOnlyList<User> knownUsers,
        params (string Hash, string Password)[] validPairs)
    {
        var userManager = new Mock<IUserManager>();

        userManager.Setup(m => m.GetUserByName(It.IsAny<string>()))
            .Returns((string n) =>
            {
                foreach (var u in knownUsers)
                {
                    if (string.Equals(u.Username, n, StringComparison.OrdinalIgnoreCase))
                    {
                        return u;
                    }
                }

                return null!;
            });

        // Any known user must also resolve by id, so an existing group can be followed back to its
        // shared account.
        foreach (var u in knownUsers)
        {
            userManager.Setup(m => m.GetUserById(u.Id)).Returns(u);
        }

        var provisioning = new Mock<IProvisioningService>();
        var createdShared = MakeUser("created-shared");

        provisioning.Setup(p => p.CreateGroupAsync(
                It.IsAny<IReadOnlyList<Guid>>(),
                It.IsAny<string?>()))
            .ReturnsAsync((IReadOnlyList<Guid> ids, string? name) =>
                new SharedGroup { SharedUserId = createdShared.Id, MemberUserIds = [.. ids] });

        userManager.Setup(m => m.GetUserById(createdShared.Id)).Returns(createdShared);

        var crypto = new StubCryptoProvider(validPairs);

        var service = new DynamicGroupService(
            userManager.Object,
            provisioning.Object,
            crypto,
            NullLogger<DynamicGroupService>.Instance);

        return new Harness(service, provisioning, crypto);
    }

    [Fact]
    public async Task TypingTwoMemberNames_WithAMemberPassword_CreatesTheAccount()
    {
        using var ctx = PluginTestContext.Create();
        var alice = MakeUser("alice", AliceHash);
        var bob = MakeUser("bob", BobHash);
        var h = MakeService([alice, bob], (AliceHash, "alice-pw"));

        var result = await h.Service.TryCreateFromLoginAsync("alice+bob", "alice-pw");

        Assert.NotNull(result);
        // No name is passed: provisioning generates the canonical alphabetical one.
        h.Provisioning.Verify(
            p => p.CreateGroupAsync(
                It.Is<IReadOnlyList<Guid>>(ids => ids.Count == 2),
                null),
            Times.Once);
    }

    [Fact]
    public async Task ReversedNameOrder_ReusesTheExistingGroup()
    {
        // "john+jane" and "jane+john" are the same group. Jellyfin only calls this code when no
        // account matches the typed name, so without an order-independent lookup the reversed
        // spelling would quietly create a second account for the same two people.
        using var ctx = PluginTestContext.Create();
        var alice = MakeUser("alice", AliceHash);
        var bob = MakeUser("bob", BobHash);
        var shared = MakeUser("alice+bob");

        ctx.Configuration.Groups.Add(new SharedGroup
        {
            SharedUserId = shared.Id,
            MemberUserIds = [alice.Id, bob.Id]
        });

        var h = MakeService([alice, bob, shared], (BobHash, "bob-pw"));

        var result = await h.Service.TryCreateFromLoginAsync("bob+alice", "bob-pw");

        Assert.NotNull(result);
        Assert.Equal("alice+bob", result!.SharedUsername);
        h.Provisioning.VerifyNoOtherCalls();
    }

    [Fact]
    public async Task ANewGroup_IsNamedCanonically()
    {
        // Provisioning is asked for no particular name so it generates the canonical sorted one,
        // rather than preserving whatever order happened to be typed.
        using var ctx = PluginTestContext.Create();
        var alice = MakeUser("alice", AliceHash);
        var bob = MakeUser("bob", BobHash);
        var h = MakeService([alice, bob], (BobHash, "bob-pw"));

        await h.Service.TryCreateFromLoginAsync("bob+alice", "bob-pw");

        h.Provisioning.Verify(
            p => p.CreateGroupAsync(It.IsAny<IReadOnlyList<Guid>>(), null),
            Times.Once);
    }

    [Fact]
    public async Task ReversedNameOrder_WhenTheGroupIsDisabled_IsRejected()
    {
        using var ctx = PluginTestContext.Create();
        var alice = MakeUser("alice", AliceHash);
        var bob = MakeUser("bob", BobHash);
        var shared = MakeUser("alice+bob");

        ctx.Configuration.Groups.Add(new SharedGroup
        {
            SharedUserId = shared.Id,
            MemberUserIds = [alice.Id, bob.Id],
            IsDisabled = true
        });

        var h = MakeService([alice, bob, shared], (BobHash, "bob-pw"));

        Assert.Null(await h.Service.TryCreateFromLoginAsync("bob+alice", "bob-pw"));
        h.Provisioning.VerifyNoOtherCalls();
    }

    [Fact]
    public async Task TheFirstTypedMember_HasTheirPasswordCheckedFirst()
    {
        // Password verification is a deliberately slow hash comparison, so whoever puts their own
        // name first should be checked first.
        using var ctx = PluginTestContext.Create();
        var alice = MakeUser("alice", AliceHash);
        var bob = MakeUser("bob", BobHash);
        var h = MakeService([alice, bob], (BobHash, "bob-pw"));

        await h.Service.TryCreateFromLoginAsync("bob+alice", "bob-pw");

        // Bob was typed first and his password matched, so alice's hash is never touched.
        Assert.Equal(["B2B2B2B2"], h.Crypto.VerifiedSalts);
    }

    [Fact]
    public async Task ALaterMembersPassword_StillWorks()
    {
        // The first-typed member is only a preference: the second member's password must still
        // unlock the group once the first fails to match.
        using var ctx = PluginTestContext.Create();
        var alice = MakeUser("alice", AliceHash);
        var bob = MakeUser("bob", BobHash);
        var h = MakeService([alice, bob], (BobHash, "bob-pw"));

        Assert.NotNull(await h.Service.TryCreateFromLoginAsync("alice+bob", "bob-pw"));
        Assert.Equal(["A1A1A1A1", "B2B2B2B2"], h.Crypto.VerifiedSalts);
    }

    [Fact]
    public async Task AnyNamedMembersPassword_Works()
    {
        using var ctx = PluginTestContext.Create();
        var alice = MakeUser("alice", AliceHash);
        var bob = MakeUser("bob", BobHash);
        var h = MakeService([alice, bob], (BobHash, "bob-pw"));

        Assert.NotNull(await h.Service.TryCreateFromLoginAsync("alice+bob", "bob-pw"));
    }

    [Fact]
    public async Task WithoutAMatchingPassword_NothingIsCreated()
    {
        // Otherwise anyone who knows two usernames could conjure a shared account into existence.
        using var ctx = PluginTestContext.Create();
        var alice = MakeUser("alice", AliceHash);
        var bob = MakeUser("bob", BobHash);
        var h = MakeService([alice, bob], (AliceHash, "alice-pw"));

        Assert.Null(await h.Service.TryCreateFromLoginAsync("alice+bob", "guessing"));
        h.Provisioning.VerifyNoOtherCalls();
    }

    [Fact]
    public async Task AnUnknownNamePart_IsRejected()
    {
        using var ctx = PluginTestContext.Create();
        var alice = MakeUser("alice", AliceHash);
        var h = MakeService([alice], (AliceHash, "alice-pw"));

        Assert.Null(await h.Service.TryCreateFromLoginAsync("alice+nobody", "alice-pw"));
        h.Provisioning.VerifyNoOtherCalls();
    }

    [Fact]
    public async Task ADisabledMember_IsRejected()
    {
        using var ctx = PluginTestContext.Create();
        var alice = MakeUser("alice", AliceHash);
        var bob = MakeUser("bob", BobHash, disabled: true);
        var h = MakeService([alice, bob], (AliceHash, "alice-pw"));

        Assert.Null(await h.Service.TryCreateFromLoginAsync("alice+bob", "alice-pw"));
    }

    [Fact]
    public async Task ASingleName_IsNotAGroup()
    {
        using var ctx = PluginTestContext.Create();
        var alice = MakeUser("alice", AliceHash);
        var h = MakeService([alice], (AliceHash, "alice-pw"));

        Assert.Null(await h.Service.TryCreateFromLoginAsync("alice", "alice-pw"));
    }

    [Fact]
    public async Task TheSameMemberTwice_IsRejected()
    {
        using var ctx = PluginTestContext.Create();
        var alice = MakeUser("alice", AliceHash);
        var h = MakeService([alice], (AliceHash, "alice-pw"));

        Assert.Null(await h.Service.TryCreateFromLoginAsync("alice+alice", "alice-pw"));
    }

    [Fact]
    public async Task AnExistingSharedAccountNamedPart_IsRejected()
    {
        // Shared accounts must not nest inside other shared accounts.
        using var ctx = PluginTestContext.Create();
        var alice = MakeUser("alice", AliceHash);
        var existingShared = MakeUser("shared", BobHash);
        ctx.Configuration.Groups.Add(new SharedGroup { SharedUserId = existingShared.Id });

        var h = MakeService([alice, existingShared], (AliceHash, "alice-pw"));

        Assert.Null(await h.Service.TryCreateFromLoginAsync("alice+shared", "alice-pw"));
    }

    [Fact]
    public async Task WhenDisabledInConfiguration_NothingIsCreated()
    {
        using var ctx = PluginTestContext.Create();
        ctx.Configuration.EnableDynamicGroups = false;

        var alice = MakeUser("alice", AliceHash);
        var bob = MakeUser("bob", BobHash);
        var h = MakeService([alice, bob], (AliceHash, "alice-pw"));

        Assert.Null(await h.Service.TryCreateFromLoginAsync("alice+bob", "alice-pw"));
    }

    [Fact]
    public async Task AConfiguredSeparator_IsHonoured()
    {
        using var ctx = PluginTestContext.Create();
        ctx.Configuration.NameSeparator = "_";

        var alice = MakeUser("alice", AliceHash);
        var bob = MakeUser("bob", BobHash);
        var h = MakeService([alice, bob], (AliceHash, "alice-pw"));

        Assert.NotNull(await h.Service.TryCreateFromLoginAsync("alice_bob", "alice-pw"));
        Assert.Null(await h.Service.TryCreateFromLoginAsync("alice+bob", "alice-pw"));
    }

    [Fact]
    public async Task ThreeOrMoreMembers_AreSupported()
    {
        using var ctx = PluginTestContext.Create();
        var alice = MakeUser("alice", AliceHash);
        var bob = MakeUser("bob", BobHash);
        var carol = MakeUser("carol", BobHash);
        var h = MakeService([alice, bob, carol], (AliceHash, "alice-pw"));

        Assert.NotNull(await h.Service.TryCreateFromLoginAsync("alice+bob+carol", "alice-pw"));
        h.Provisioning.Verify(
            p => p.CreateGroupAsync(
                It.Is<IReadOnlyList<Guid>>(ids => ids.Count == 3),
                It.IsAny<string?>()),
            Times.Once);
    }
}