using FluentAssertions;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;
using NSubstitute;
using ProposalSystem.Application.Interfaces;
using ProposalSystem.Domain.Entities;
using ProposalSystem.Infrastructure.Services;
using ProposalSystem.Tests.Helpers;
using Xunit;

namespace ProposalSystem.Tests.Services;

/// <summary>
/// QA-C2: Proposal state machine transition tests.
/// Verifies that only valid state transitions succeed and invalid ones throw.
/// State machine: InReview -> Approved -> Sent -> Revised (creates new proposal).
/// </summary>
public class ProposalStateMachineTests : IDisposable
{
    private readonly Infrastructure.Data.ProposalDbContext _db;
    private readonly ICurrentUserService _currentUser;
    private readonly IAuditService _audit;
    private readonly IJobPublisher _jobPublisher;
    private readonly IProposalNumberGenerator _numberGenerator;
    private readonly IEmailService _emailService;
    private readonly IS3Service _s3Service;
    private readonly ProposalService _sut;

    public ProposalStateMachineTests()
    {
        _db = DbContextFactory.Create();
        _currentUser = Substitute.For<ICurrentUserService>();
        _audit = Substitute.For<IAuditService>();
        _jobPublisher = Substitute.For<IJobPublisher>();
        _numberGenerator = Substitute.For<IProposalNumberGenerator>();
        _emailService = Substitute.For<IEmailService>();
        _s3Service = Substitute.For<IS3Service>();

        var userId = Guid.NewGuid();
        _currentUser.UserId.Returns(userId);
        _currentUser.Role.Returns(UserRole.Admin);

        // InMemory provider enforces FK constraints; create the required User entity
        _db.Users.Add(new User
        {
            Id = userId,
            CognitoSub = $"sub-{userId}",
            Email = "admin@test.com",
            DisplayName = "Test Admin",
            Role = UserRole.Admin,
            CreatedAt = DateTime.UtcNow,
            UpdatedAt = DateTime.UtcNow,
        });
        _db.SaveChanges();

        var config = new ConfigurationBuilder()
            .AddInMemoryCollection(new Dictionary<string, string?>
            {
                { "GENERATED_BUCKET", "test-bucket" },
            })
            .Build();

        _sut = new ProposalService(_db, _currentUser, _numberGenerator, _audit, _jobPublisher,
            _emailService, _s3Service, config,
            Substitute.For<ILogger<ProposalService>>());
    }

    public void Dispose()
    {
        _db.Dispose();
    }

    #region Valid Transitions

    [Fact(DisplayName = "QA-C2: InReview -> Approved succeeds when line items have prices")]
    public async Task ApproveAsync_InReview_TransitionsToApproved()
    {
        // Arrange
        var proposal = CreateProposal(ProposalStatus.InReview);
        proposal.LineItems.Add(new LineItem
        {
            Id = Guid.NewGuid(),
            ProposalId = proposal.Id,
            Description = "HVAC duct replacement",
            Quantity = 1,
            Unit = "each",
            TotalPrice = 5000m,
            PricingMode = PricingMode.TotalPrice,
            Source = LineItemSource.AI,
        });
        _db.Proposals.Add(proposal);
        await _db.SaveChangesAsync();

        // Act
        var result = await _sut.ApproveAsync(proposal.Id);

        // Assert
        result.Status.Should().Be(ProposalStatus.Approved);
        result.ApprovedById.Should().Be(_currentUser.UserId);
        result.TotalBidAmount.Should().Be(5000m);
    }

    [Fact(DisplayName = "QA-C2: Approved -> Sent succeeds")]
    public async Task MarkSentAsync_Approved_TransitionsToSent()
    {
        // Arrange
        var proposal = CreateProposal(ProposalStatus.Approved);
        _db.Proposals.Add(proposal);
        await _db.SaveChangesAsync();

        // Act
        var result = await _sut.MarkSentAsync(proposal.Id);

        // Assert
        result.Status.Should().Be(ProposalStatus.Sent);
        result.SentAt.Should().NotBeNull();
    }

    [Fact(DisplayName = "QA-C2: Sent -> Revised creates new revision proposal")]
    public async Task ReviseAsync_Sent_CreatesNewProposalInReview()
    {
        // Arrange
        var proposal = CreateProposal(ProposalStatus.Sent);
        proposal.LineItems.Add(new LineItem
        {
            Id = Guid.NewGuid(),
            ProposalId = proposal.Id,
            Description = "Pipe repair",
            Quantity = 2,
            Unit = "hours",
            UnitPrice = 150m,
            TotalPrice = 300m,
            PricingMode = PricingMode.UnitPrice,
            Source = LineItemSource.Manual,
        });
        _db.Proposals.Add(proposal);
        await _db.SaveChangesAsync();

        // Act
        var result = await _sut.ReviseAsync(proposal.Id);

        // Assert
        result.Status.Should().Be(ProposalStatus.InReview);
        result.ParentProposalId.Should().Be(proposal.Id);
        result.CurrentRevision.Should().Be(proposal.CurrentRevision + 1);
        result.ProposalNumber.Should().Contain("-R");

        // Original proposal should now be Revised
        var original = await _db.Proposals.FindAsync(proposal.Id);
        original!.Status.Should().Be(ProposalStatus.Revised);
    }

    [Fact(DisplayName = "QA-C2: Approve is idempotent on already-approved proposal")]
    public async Task ApproveAsync_AlreadyApproved_ReturnsWithoutError()
    {
        // Arrange
        var proposal = CreateProposal(ProposalStatus.Approved);
        _db.Proposals.Add(proposal);
        await _db.SaveChangesAsync();

        // Act
        var result = await _sut.ApproveAsync(proposal.Id);

        // Assert
        result.Status.Should().Be(ProposalStatus.Approved);
    }

    [Fact(DisplayName = "QA-C2: MarkSent is idempotent on already-sent proposal")]
    public async Task MarkSentAsync_AlreadySent_ReturnsWithoutError()
    {
        // Arrange
        var proposal = CreateProposal(ProposalStatus.Sent);
        _db.Proposals.Add(proposal);
        await _db.SaveChangesAsync();

        // Act
        var result = await _sut.MarkSentAsync(proposal.Id);

        // Assert
        result.Status.Should().Be(ProposalStatus.Sent);
    }

    #endregion

    #region Invalid Transitions

    [Fact(DisplayName = "QA-C2: InReview -> Sent is invalid, must approve first")]
    public async Task MarkSentAsync_InReview_ThrowsInvalidOperation()
    {
        // Arrange
        var proposal = CreateProposal(ProposalStatus.InReview);
        _db.Proposals.Add(proposal);
        await _db.SaveChangesAsync();

        // Act
        var act = () => _sut.MarkSentAsync(proposal.Id);

        // Assert
        await act.Should().ThrowAsync<InvalidOperationException>()
            .WithMessage("*approved*");
    }

    [Fact(DisplayName = "QA-C2: Approved -> Revised is invalid, must send first")]
    public async Task ReviseAsync_Approved_ThrowsInvalidOperation()
    {
        // Arrange
        var proposal = CreateProposal(ProposalStatus.Approved);
        _db.Proposals.Add(proposal);
        await _db.SaveChangesAsync();

        // Act
        var act = () => _sut.ReviseAsync(proposal.Id);

        // Assert
        await act.Should().ThrowAsync<InvalidOperationException>()
            .WithMessage("*sent*");
    }

    [Fact(DisplayName = "QA-C2: Draft -> Approved is invalid")]
    public async Task ApproveAsync_Draft_ThrowsInvalidOperation()
    {
        // Arrange
        var proposal = CreateProposal(ProposalStatus.Draft);
        proposal.LineItems.Add(new LineItem
        {
            Id = Guid.NewGuid(),
            ProposalId = proposal.Id,
            Description = "Some work",
            Quantity = 1,
            Unit = "each",
            TotalPrice = 100m,
            PricingMode = PricingMode.TotalPrice,
            Source = LineItemSource.Manual,
        });
        _db.Proposals.Add(proposal);
        await _db.SaveChangesAsync();

        // Act
        var act = () => _sut.ApproveAsync(proposal.Id);

        // Assert
        await act.Should().ThrowAsync<InvalidOperationException>()
            .WithMessage("*in review*");
    }

    [Fact(DisplayName = "QA-C2: InReview -> Revised is invalid")]
    public async Task ReviseAsync_InReview_ThrowsInvalidOperation()
    {
        // Arrange
        var proposal = CreateProposal(ProposalStatus.InReview);
        _db.Proposals.Add(proposal);
        await _db.SaveChangesAsync();

        // Act
        var act = () => _sut.ReviseAsync(proposal.Id);

        // Assert
        await act.Should().ThrowAsync<InvalidOperationException>()
            .WithMessage("*sent*");
    }

    [Fact(DisplayName = "QA-C2: Sent -> Approved is invalid")]
    public async Task MarkSentAsync_Sent_StaysIdempotent_But_ApproveThrows()
    {
        // Sent cannot go back to Approved
        var proposal = CreateProposal(ProposalStatus.Sent);
        _db.Proposals.Add(proposal);
        await _db.SaveChangesAsync();

        var act = () => _sut.ApproveAsync(proposal.Id);

        await act.Should().ThrowAsync<InvalidOperationException>()
            .WithMessage("*in review*");
    }

    [Fact(DisplayName = "QA-C2: Cannot approve proposal without priced line items")]
    public async Task ApproveAsync_NoLineItems_ThrowsInvalidOperation()
    {
        // Arrange - proposal InReview but no line items
        var proposal = CreateProposal(ProposalStatus.InReview);
        _db.Proposals.Add(proposal);
        await _db.SaveChangesAsync();

        // Act
        var act = () => _sut.ApproveAsync(proposal.Id);

        // Assert
        await act.Should().ThrowAsync<InvalidOperationException>()
            .WithMessage("*priced line items*");
    }

    [Fact(DisplayName = "QA-C2: Cannot approve proposal with zero-price line items only")]
    public async Task ApproveAsync_AllZeroPriceLineItems_ThrowsInvalidOperation()
    {
        // Arrange
        var proposal = CreateProposal(ProposalStatus.InReview);
        proposal.LineItems.Add(new LineItem
        {
            Id = Guid.NewGuid(),
            ProposalId = proposal.Id,
            Description = "Unprice item",
            Quantity = 1,
            Unit = "each",
            TotalPrice = 0m,
            PricingMode = PricingMode.TotalPrice,
            Source = LineItemSource.AI,
        });
        _db.Proposals.Add(proposal);
        await _db.SaveChangesAsync();

        // Act
        var act = () => _sut.ApproveAsync(proposal.Id);

        // Assert
        await act.Should().ThrowAsync<InvalidOperationException>()
            .WithMessage("*priced line items*");
    }

    [Fact(DisplayName = "QA-C2: Approve/Send/Revise on nonexistent proposal throws KeyNotFoundException")]
    public async Task StateTransitions_NonexistentProposal_ThrowsKeyNotFound()
    {
        var missingId = Guid.NewGuid();

        var approveAct = () => _sut.ApproveAsync(missingId);
        var sendAct = () => _sut.MarkSentAsync(missingId);
        var reviseAct = () => _sut.ReviseAsync(missingId);

        await approveAct.Should().ThrowAsync<KeyNotFoundException>();
        await sendAct.Should().ThrowAsync<KeyNotFoundException>();
        await reviseAct.Should().ThrowAsync<KeyNotFoundException>();
    }

    #endregion

    #region Revision Edge Cases

    [Fact(DisplayName = "QA-C2: Revision copies line items from parent")]
    public async Task ReviseAsync_CopiesLineItems()
    {
        // Arrange
        var proposal = CreateProposal(ProposalStatus.Sent);
        proposal.LineItems.Add(new LineItem
        {
            Id = Guid.NewGuid(),
            ProposalId = proposal.Id,
            Description = "Item 1",
            Quantity = 5,
            Unit = "sq ft",
            UnitPrice = 10m,
            TotalPrice = 50m,
            PricingMode = PricingMode.UnitPrice,
            SortOrder = 1,
            Source = LineItemSource.Manual,
        });
        proposal.LineItems.Add(new LineItem
        {
            Id = Guid.NewGuid(),
            ProposalId = proposal.Id,
            Description = "Item 2",
            Quantity = 1,
            Unit = "each",
            TotalPrice = 200m,
            PricingMode = PricingMode.TotalPrice,
            SortOrder = 2,
            Source = LineItemSource.AI,
        });
        _db.Proposals.Add(proposal);
        await _db.SaveChangesAsync();

        // Act
        var result = await _sut.ReviseAsync(proposal.Id);

        // Assert
        var revision = await _db.Proposals.FindAsync(result.Id);
        var revisionItems = _db.LineItems.Where(li => li.ProposalId == result.Id).ToList();
        revisionItems.Should().HaveCount(2);
        revisionItems.Should().AllSatisfy(li => li.ProposalId.Should().Be(result.Id));
        revisionItems.Select(li => li.Description).Should().BeEquivalentTo("Item 1", "Item 2");
    }

    [Fact(DisplayName = "QA-C2: Audit is logged for approve transition")]
    public async Task ApproveAsync_LogsAuditEvent()
    {
        // Arrange
        var proposal = CreateProposal(ProposalStatus.InReview);
        proposal.LineItems.Add(new LineItem
        {
            Id = Guid.NewGuid(),
            ProposalId = proposal.Id,
            Description = "Work item",
            Quantity = 1,
            Unit = "each",
            TotalPrice = 1000m,
            PricingMode = PricingMode.TotalPrice,
            Source = LineItemSource.Manual,
        });
        _db.Proposals.Add(proposal);
        await _db.SaveChangesAsync();

        // Act
        await _sut.ApproveAsync(proposal.Id);

        // Assert
        await _audit.Received(1).LogAsync(AuditAction.Approve, proposal.Id, Arg.Any<string?>(), Arg.Any<CancellationToken>());
    }

    [Fact(DisplayName = "QA-C2: MarkSent publishes library-ingest job")]
    public async Task MarkSentAsync_PublishesLibraryIngestJob()
    {
        // Arrange
        var proposal = CreateProposal(ProposalStatus.Approved);
        _db.Proposals.Add(proposal);
        await _db.SaveChangesAsync();

        // Act
        await _sut.MarkSentAsync(proposal.Id);

        // Assert
        await _jobPublisher.Received(1).PublishAsync("library-ingest", Arg.Any<object>(), Arg.Any<CancellationToken>());
    }

    #endregion

    private Proposal CreateProposal(ProposalStatus status)
    {
        return new Proposal
        {
            Id = Guid.NewGuid(),
            ProposalNumber = $"P-{Guid.NewGuid():N}".Substring(0, 12),
            WorkOrderNumber = "WO-001",
            CustomerName = "Test Customer",
            CustomerAddress = "123 Test St",
            ScopeOfWork = "Test scope of work",
            ServiceCategory = ServiceCategory.HVAC,
            Priority = Priority.Standard,
            Status = status,
            Notes = "",
            SubmittedById = _currentUser.UserId,
            SubmittedAt = DateTime.UtcNow.AddDays(-1),
            CurrentRevision = 1,
            CreatedAt = DateTime.UtcNow.AddDays(-1),
            UpdatedAt = DateTime.UtcNow.AddDays(-1),
        };
    }
}