using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using FluentAssertions;
using Microsoft.Data.Sqlite;
using Microsoft.EntityFrameworkCore;
using Moq;
using NexusReader.Application.Features.Books.Commands;
using NexusReader.Data.Persistence;
using NexusReader.Domain.Entities;
using NexusReader.Domain.Exceptions;
using Xunit;

namespace NexusReader.Application.Tests.Commands;

public class PublishBookVersionTests : IDisposable
{
    private readonly SqliteConnection _connection;
    private readonly DbContextOptions<AppDbContext> _contextOptions;
    private readonly Mock<IDbContextFactory<AppDbContext>> _dbContextFactoryMock;

    public PublishBookVersionTests()
    {
        _connection = new SqliteConnection("DataSource=:memory:");
        _connection.Open();

        _contextOptions = new DbContextOptionsBuilder<AppDbContext>()
            .UseSqlite(_connection)
            .Options;

        // Seed initial database schema
        using var context = new AppDbContext(_contextOptions);
        context.Database.EnsureCreated();

        _dbContextFactoryMock = new Mock<IDbContextFactory<AppDbContext>>();
        _dbContextFactoryMock.Setup(f => f.CreateDbContextAsync(It.IsAny<CancellationToken>()))
            .ReturnsAsync(() => new AppDbContext(_contextOptions));
    }

    [Fact]
    public async Task Handle_WithValidBookAndChapters_CorrectlyPublishesAndClonesChaptersWithNewGuids()
    {
        // Arrange
        var bookId = Guid.NewGuid();
        var userId = "test-user-123";
        var tenantId = "test-tenant-456";

        var user = new NexusUser
        {
            Id = userId,
            UserName = "testuser",
            Email = "test@example.com",
            TenantId = tenantId,
            SubscriptionPlanId = 1
        };

        var book = new Book
        {
            Id = bookId,
            Title = "My Epic Book",
            UserId = userId,
            TenantId = tenantId
        };

        var originalDraftRevision = new BookRevision
        {
            Id = Guid.NewGuid(),
            BookId = bookId,
            VersionString = "Working Draft",
            IsPublished = false,
            CreatedAt = DateTime.UtcNow
        };

        var oldChapterId1 = Guid.NewGuid();
        var oldChapterId2 = Guid.NewGuid();

        var chapter1 = new Chapter
        {
            Id = oldChapterId1,
            BookRevisionId = originalDraftRevision.Id,
            Title = "Chapter 1: The Beginning",
            MarkdownContent = "Once upon a time...",
            SortOrder = 1
        };

        var chapter2 = new Chapter
        {
            Id = oldChapterId2,
            BookRevisionId = originalDraftRevision.Id,
            Title = "Chapter 2: The Middle",
            MarkdownContent = "Interesting things happened.",
            SortOrder = 2
        };

        using (var context = new AppDbContext(_contextOptions))
        {
            context.Users.Add(user);
            context.Books.Add(book);
            context.BookRevisions.Add(originalDraftRevision);
            context.Chapters.Add(chapter1);
            context.Chapters.Add(chapter2);
            await context.SaveChangesAsync();

            // Link the book's draft revision
            var dbBook = await context.Books.FindAsync(bookId);
            dbBook!.CurrentDraftRevisionId = originalDraftRevision.Id;
            await context.SaveChangesAsync();
        }

        var command = new PublishBookVersionCommand(
            BookId: bookId,
            CustomVersionString: "v1.0.0",
            UserId: userId,
            TenantId: tenantId
        );

        var handler = new PublishBookVersionCommandHandler(_dbContextFactoryMock.Object);

        // Act
        var result = await handler.Handle(command, CancellationToken.None);

        // Assert
        result.IsSuccess.Should().BeTrue();

        using (var context = new AppDbContext(_contextOptions))
        {
            var updatedBook = await context.Books
                .Include(b => b.Revisions)
                    .ThenInclude(r => r.Chapters)
                .FirstOrDefaultAsync(b => b.Id == bookId);

            updatedBook.Should().NotBeNull();
            updatedBook!.LivePublishedRevisionId.Should().Be(originalDraftRevision.Id);
            updatedBook.CurrentDraftRevisionId.Should().NotBeNull();
            updatedBook.CurrentDraftRevisionId.Should().NotBe(originalDraftRevision.Id);

            // Fetch the old draft revision (now frozen / published)
            var oldDraft = updatedBook.Revisions.FirstOrDefault(r => r.Id == originalDraftRevision.Id);
            oldDraft.Should().NotBeNull();
            oldDraft!.IsPublished.Should().BeTrue();
            oldDraft.VersionString.Should().Be("v1.0.0");
            oldDraft.PublishedAt.Should().NotBeNull();

            // Fetch the new working draft revision
            var newDraft = updatedBook.Revisions.FirstOrDefault(r => r.Id == updatedBook.CurrentDraftRevisionId);
            newDraft.Should().NotBeNull();
            newDraft!.IsPublished.Should().BeFalse();
            newDraft.VersionString.Should().Be("Working Draft");

            // Verify chapters were deep copied and received brand new GUIDs (Identity Reset)
            newDraft.Chapters.Should().HaveCount(2);

            var clonedChapter1 = newDraft.Chapters.FirstOrDefault(c => c.SortOrder == 1);
            clonedChapter1.Should().NotBeNull();
            clonedChapter1!.Title.Should().Be("Chapter 1: The Beginning");
            clonedChapter1.MarkdownContent.Should().Be("Once upon a time...");
            clonedChapter1.Id.Should().NotBe(oldChapterId1); // GUID must be regenerated
            clonedChapter1.BookRevisionId.Should().Be(newDraft.Id);

            var clonedChapter2 = newDraft.Chapters.FirstOrDefault(c => c.SortOrder == 2);
            clonedChapter2.Should().NotBeNull();
            clonedChapter2!.Title.Should().Be("Chapter 2: The Middle");
            clonedChapter2.MarkdownContent.Should().Be("Interesting things happened.");
            clonedChapter2.Id.Should().NotBe(oldChapterId2); // GUID must be regenerated
            clonedChapter2.BookRevisionId.Should().Be(newDraft.Id);
        }
    }

    [Fact]
    public async Task Handle_WithMismatchedTenantId_ReturnsFailure()
    {
        // Arrange
        var bookId = Guid.NewGuid();
        var userId = "test-user-123";
        var tenantId = "test-tenant-456";

        var user = new NexusUser
        {
            Id = userId,
            UserName = "testuser",
            Email = "test@example.com",
            TenantId = tenantId,
            SubscriptionPlanId = 1
        };

        var book = new Book
        {
            Id = bookId,
            Title = "My Epic Book",
            UserId = userId,
            TenantId = tenantId
        };

        using (var context = new AppDbContext(_contextOptions))
        {
            context.Users.Add(user);
            context.Books.Add(book);
            await context.SaveChangesAsync();
        }

        // Send command with a different TenantId to check multi-tenancy isolation
        var command = new PublishBookVersionCommand(
            BookId: bookId,
            CustomVersionString: "v1.0.0",
            UserId: userId,
            TenantId: "different-tenant-789"
        );

        var handler = new PublishBookVersionCommandHandler(_dbContextFactoryMock.Object);

        // Act
        var result = await handler.Handle(command, CancellationToken.None);

        // Assert
        result.IsSuccess.Should().BeFalse();
        result.Errors.Should().Contain(e => e.Message.Contains("was not found"));
    }

    [Fact]
    public async Task Handle_WithMismatchedUserId_ReturnsFailure()
    {
        // Arrange
        var bookId = Guid.NewGuid();
        var userId = "test-user-123";
        var tenantId = "test-tenant-456";

        var user = new NexusUser
        {
            Id = userId,
            UserName = "testuser",
            Email = "test@example.com",
            TenantId = tenantId,
            SubscriptionPlanId = 1
        };

        var book = new Book
        {
            Id = bookId,
            Title = "My Epic Book",
            UserId = userId,
            TenantId = tenantId
        };

        using (var context = new AppDbContext(_contextOptions))
        {
            context.Users.Add(user);
            context.Books.Add(book);
            await context.SaveChangesAsync();
        }

        // Send command with a different UserId to check multi-tenancy isolation
        var command = new PublishBookVersionCommand(
            BookId: bookId,
            CustomVersionString: "v1.0.0",
            UserId: "different-user-789",
            TenantId: tenantId
        );

        var handler = new PublishBookVersionCommandHandler(_dbContextFactoryMock.Object);

        // Act
        var result = await handler.Handle(command, CancellationToken.None);

        // Assert
        result.IsSuccess.Should().BeFalse();
        result.Errors.Should().Contain(e => e.Message.Contains("was not found"));
    }

    [Fact]
    public async Task Handle_WithNonExistentBook_ReturnsFailure()
    {
        // Arrange
        var command = new PublishBookVersionCommand(
            BookId: Guid.NewGuid(),
            CustomVersionString: "v1.0.0",
            UserId: "user-1",
            TenantId: "tenant-1"
        );

        var handler = new PublishBookVersionCommandHandler(_dbContextFactoryMock.Object);

        // Act
        var result = await handler.Handle(command, CancellationToken.None);

        // Assert
        result.IsSuccess.Should().BeFalse();
        result.Errors.Should().Contain(e => e.Message.Contains("was not found"));
    }

    public void Dispose()
    {
        _connection.Close();
        _connection.Dispose();
    }
}