using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Jellyfin.Database.Implementations.Entities;
using Jellyfin.Plugin.WatchedTogether.Auth;
using Jellyfin.Plugin.WatchedTogether.Configuration;
using Jellyfin.Plugin.WatchedTogether.Services;
using MediaBrowser.Controller.Authentication;
using MediaBrowser.Model.Cryptography;
using Microsoft.Extensions.Logging.Abstractions;
using Moq;
using Xunit;

namespace Jellyfin.Plugin.WatchedTogether.Tests;

/// <summary>
/// Covers the rule that makes this plugin work: any member's password unlocks the shared account,
/// and nothing else does.
/// </summary>
public class AuthenticationTests
{
    // PasswordHash.Parse requires hex-encoded salt and hash segments, so these fixtures use real
    // hex rather than readable placeholders.
    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)
    {
        var user = new User(name, "Prov", "ResetProv") { Password = password! };
        return user;
    }

    /// <summary>
    /// Builds a provider whose crypto accepts exactly the (hash, password) pairs given.
    /// </summary>
    private static SharedAccountAuthenticationProvider MakeProvider(
        SharedGroup? group,
        IReadOnlyList<User> members,
        params (string Hash, string Password)[] validPairs)
        => MakeProvider(group, members, null, validPairs);

    /// <summary>
    /// Builds a provider, optionally with a dynamic-group service that returns
    /// <paramref name="dynamicResult"/> for an unresolved username.
    /// </summary>
    private static SharedAccountAuthenticationProvider MakeProvider(
        SharedGroup? group,
        IReadOnlyList<User> members,
        DynamicGroupResult? dynamicResult,
        params (string Hash, string Password)[] validPairs)
    {
        // ICryptoProvider.Verify takes a ReadOnlySpan<char>, which Moq cannot express as a generic
        // argument, so the crypto provider is stubbed by hand.
        var crypto = new StubCryptoProvider(validPairs);

        var groups = new Mock<IGroupService>();
        groups.Setup(g => g.GetGroupForSharedUser(It.IsAny<Guid>())).Returns(group);
        groups.Setup(g => g.GetEligibleMembers(It.IsAny<SharedGroup>())).Returns(members);

        var dynamic = new Mock<IDynamicGroupService>();
        dynamic.Setup(d => d.TryCreateFromLoginAsync(It.IsAny<string>(), It.IsAny<string>()))
            .ReturnsAsync(dynamicResult);

        return new SharedAccountAuthenticationProvider(
            crypto,
            new Lazy<IGroupService>(() => groups.Object),
            new Lazy<IDynamicGroupService>(() => dynamic.Object),
            NullLogger<SharedAccountAuthenticationProvider>.Instance);
    }

    [Fact]
    public async Task Authenticate_WithFirstMemberPassword_Succeeds()
    {
        var alice = MakeUser("alice", AliceHash);
        var bob = MakeUser("bob", BobHash);
        var shared = MakeUser("alice+bob", null);
        var group = new SharedGroup { SharedUserId = shared.Id, MemberUserIds = [alice.Id, bob.Id] };

        var provider = MakeProvider(group, [alice, bob], (AliceHash, "alice-pw"));

        var result = await provider.Authenticate("alice+bob", "alice-pw", shared);

        Assert.Equal("alice+bob", result.Username);
    }

    [Fact]
    public async Task Authenticate_WithLaterMemberPassword_Succeeds()
    {
        // The second member's password must work even though the first member's check failed
        // first - that loop is the whole point of the plugin.
        var alice = MakeUser("alice", AliceHash);
        var bob = MakeUser("bob", BobHash);
        var shared = MakeUser("alice+bob", null);
        var group = new SharedGroup { SharedUserId = shared.Id, MemberUserIds = [alice.Id, bob.Id] };

        var provider = MakeProvider(group, [alice, bob], (BobHash, "bob-pw"));

        var result = await provider.Authenticate("alice+bob", "bob-pw", shared);

        Assert.Equal("alice+bob", result.Username);
    }

    [Fact]
    public async Task Authenticate_WithWrongPassword_Throws()
    {
        var alice = MakeUser("alice", AliceHash);
        var bob = MakeUser("bob", BobHash);
        var shared = MakeUser("alice+bob", null);
        var group = new SharedGroup { SharedUserId = shared.Id, MemberUserIds = [alice.Id, bob.Id] };

        var provider = MakeProvider(group, [alice, bob], (AliceHash, "alice-pw"));

        await Assert.ThrowsAsync<AuthenticationException>(
            () => provider.Authenticate("alice+bob", "not-the-password", shared));
    }

    [Fact]
    public async Task Authenticate_WhenGroupDisabledOrUnknown_Throws()
    {
        // GetGroupForSharedUser returns null both for accounts we do not manage and for groups an
        // admin has suspended. Neither may be unlocked.
        var shared = MakeUser("alice+bob", null);
        var provider = MakeProvider(null, [], (AliceHash, "alice-pw"));

        await Assert.ThrowsAsync<AuthenticationException>(
            () => provider.Authenticate("alice+bob", "alice-pw", shared));
    }

    [Fact]
    public async Task Authenticate_WhenNoEligibleMembers_Throws()
    {
        // Every member disabled or deleted: a correct password for a now-disabled member must not
        // still open the account.
        var shared = MakeUser("alice+bob", null);
        var group = new SharedGroup { SharedUserId = shared.Id, MemberUserIds = [Guid.NewGuid()] };

        var provider = MakeProvider(group, [], (AliceHash, "alice-pw"));

        await Assert.ThrowsAsync<AuthenticationException>(
            () => provider.Authenticate("alice+bob", "alice-pw", shared));
    }

    [Fact]
    public async Task Authenticate_MemberWithNoPassword_IsSkipped()
    {
        // A passwordless member contributes no credential; an empty submitted password must not
        // match them and unlock the account.
        var ghost = MakeUser("ghost", null);
        var bob = MakeUser("bob", BobHash);
        var shared = MakeUser("ghost+bob", null);
        var group = new SharedGroup { SharedUserId = shared.Id, MemberUserIds = [ghost.Id, bob.Id] };

        var provider = MakeProvider(group, [ghost, bob], (BobHash, "bob-pw"));

        await Assert.ThrowsAsync<AuthenticationException>(
            () => provider.Authenticate("ghost+bob", string.Empty, shared));
    }

    [Fact]
    public async Task Authenticate_WithNullResolvedUser_AndNoDynamicMatch_Throws()
    {
        // Nothing resolved and the name is not a valid member combination.
        var provider = MakeProvider(null, [], dynamicResult: null, (AliceHash, "alice-pw"));

        await Assert.ThrowsAsync<AuthenticationException>(
            () => provider.Authenticate("whoever", "alice-pw", null));
    }

    [Fact]
    public async Task Authenticate_WithNullResolvedUser_CreatesGroupOnDemand()
    {
        // Typing "alice+bob" with a member's password provisions the shared account and logs in.
        var group = new SharedGroup { SharedUserId = Guid.NewGuid() };
        var provider = MakeProvider(
            null,
            [],
            new DynamicGroupResult(group, "alice+bob"),
            (AliceHash, "alice-pw"));

        var result = await provider.Authenticate("alice+bob", "alice-pw", null);

        Assert.Equal("alice+bob", result.Username);
    }

    [Fact]
    public async Task Authenticate_TwoArgOverload_AlsoCreatesGroupOnDemand()
    {
        // The two-argument overload is equivalent to passing a null resolved user.
        var group = new SharedGroup { SharedUserId = Guid.NewGuid() };
        var provider = MakeProvider(
            null,
            [],
            new DynamicGroupResult(group, "alice+bob"),
            (AliceHash, "alice-pw"));

        var result = await provider.Authenticate("alice+bob", "alice-pw");

        Assert.Equal("alice+bob", result.Username);
    }

    [Fact]
    public void HasPassword_IsAlwaysTrue()
    {
        // Returning false would let a client offer a passwordless login for the shared account.
        var provider = MakeProvider(null, []);
        Assert.True(provider.HasPassword(MakeUser("alice+bob", null)));
    }

    [Fact]
    public async Task ChangePassword_IsNotSupported()
    {
        var provider = MakeProvider(null, []);
        await Assert.ThrowsAsync<NotSupportedException>(
            () => provider.ChangePassword(MakeUser("alice+bob", null), "new-pw"));
    }
}