using FluentAssertions;
using Microsoft.Data.Sqlite;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;
using NSubstitute;
using ProposalSystem.Application.Common;
using ProposalSystem.Application.DTOs;
using ProposalSystem.Application.Interfaces;
using ProposalSystem.Domain.Entities;
using ProposalSystem.Infrastructure.Data;
using ProposalSystem.Infrastructure.Services;
using ProposalSystem.Tests.Helpers;
using Xunit;

namespace ProposalSystem.Tests.Services;

/// <summary>
/// Optimistic-concurrency tests for the proposal aggregate (ADR 0004, SHOC
/// double-guard). Covers the pre-check path, both 422 token codes, the
/// DB-level race window (two writers over one SQLite database), version
/// bumping, and audit atomicity (staged rows must not survive a failed save).
/// </summary>
public class ProposalConcurrencyTests : IDisposable
{
    private readonly SqliteConnection _connection;
    private readonly Func<ProposalDbContext> _contextFactory;
    private readonly ProposalDbContext _db;
    private readonly ICurrentUserService _currentUser;
    private readonly ProposalService _sut;
    private readonly LineItemService _lineItems;
    private readonly Guid _userId = Guid.NewGuid();

    public ProposalConcurrencyTests()
    {
        (_connection, _contextFactory) = SqliteDbContextFactory.CreateShared();
        _db = _contextFactory();

        _currentUser = Substitute.For<ICurrentUserService>();
        _currentUser.UserId.Returns(_userId);
        _currentUser.Role.Returns(UserRole.Admin);

        _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();

        // Real AuditService on the SAME context so staged-audit atomicity is exercised.
        var audit = new AuditService(_db, _currentUser);
        _sut = new ProposalService(_db, _currentUser, Substitute.For<IProposalNumberGenerator>(), audit,
            Substitute.For<IJobPublisher>(), Substitute.For<IEmailService>(), Substitute.For<IS3Service>(),
            config, Substitute.For<ILogger<ProposalService>>());
        _lineItems = new LineItemService(_db, audit, Substitute.For<ILogger<LineItemService>>());
    }

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

    private Proposal SeedProposal(ProposalStatus status = ProposalStatus.InReview)
    {
        var proposal = new Proposal
        {
            Id = Guid.NewGuid(),
            ProposalNumber = $"P-{Guid.NewGuid():N}"[..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 = _userId,
            SubmittedAt = DateTime.UtcNow.AddDays(-1),
            CurrentRevision = 1,
            CreatedAt = DateTime.UtcNow.AddDays(-1),
            UpdatedAt = DateTime.UtcNow.AddDays(-1),
        };
        _db.Proposals.Add(proposal);
        _db.SaveChanges();
        return proposal;
    }

    private static UpdateProposalRequest UpdateNotes(string notes, string? version) =>
        new(null, notes, null, null, null, version);

    [Fact(DisplayName = "Missing proposalVersion -> 422 ProposalVersionRequired")]
    public async Task MissingVersion_ThrowsVersionRequired()
    {
        var proposal = SeedProposal();

        var act = () => _sut.UpdateAsync(proposal.Id, UpdateNotes("x", null));

        var ex = await act.Should().ThrowAsync<BusinessRuleException>();
        ex.Which.Code.Should().Be("ProposalVersionRequired");
    }

    [Fact(DisplayName = "Malformed proposalVersion -> 422 InvalidRowVersion")]
    public async Task MalformedVersion_ThrowsInvalidRowVersion()
    {
        var proposal = SeedProposal();

        var act = () => _sut.UpdateAsync(proposal.Id, UpdateNotes("x", "not-a-token!"));

        var ex = await act.Should().ThrowAsync<BusinessRuleException>();
        ex.Which.Code.Should().Be("InvalidRowVersion");
    }

    [Fact(DisplayName = "Stale token fails the pre-check and carries currentState")]
    public async Task StaleToken_PreCheck_ThrowsWithCurrentState()
    {
        var proposal = SeedProposal();

        var act = () => _sut.UpdateAsync(proposal.Id, UpdateNotes("x", RowVersionCodec.Encode(99)));

        var ex = await act.Should().ThrowAsync<ProposalConcurrencyException>();
        var state = ex.Which.CurrentState.Should().BeOfType<ProposalResponse>().Subject;
        state.Id.Should().Be(proposal.Id);
        state.RowVersion.Should().Be(RowVersionCodec.Encode(1));
    }

    [Fact(DisplayName = "DB-level race: concurrent writer wins, loser gets 409 state with the winner's values")]
    public async Task LostRace_ReloadsCurrentState()
    {
        var proposal = SeedProposal();
        var token = RowVersionCodec.Encode(1);

        // Load into the service context first (pre-check will pass against version 1)...
        var tracked = await _db.Proposals.FirstAsync(p => p.Id == proposal.Id);
        tracked.Should().NotBeNull();

        // ...then a second writer commits between the pre-check read and our save.
        await using (var other = _contextFactory())
        {
            var competing = await other.Proposals.FirstAsync(p => p.Id == proposal.Id);
            other.Entry(competing).Property(p => p.Version).OriginalValue = 1L;
            competing.Notes = "the winner's notes";
            competing.Version = 2;
            await other.SaveChangesAsync();
        }

        var act = () => _sut.UpdateAsync(proposal.Id, UpdateNotes("the loser's notes", token));

        var ex = await act.Should().ThrowAsync<ProposalConcurrencyException>();
        var state = ex.Which.CurrentState.Should().BeOfType<ProposalResponse>().Subject;
        state.Notes.Should().Be("the winner's notes");
        state.RowVersion.Should().Be(RowVersionCodec.Encode(2));
    }

    [Fact(DisplayName = "Audit atomicity: a save lost to a concurrent writer persists no audit row")]
    public async Task LostRace_PersistsNoAuditRow()
    {
        var proposal = SeedProposal();
        await _db.Proposals.FirstAsync(p => p.Id == proposal.Id);

        await using (var other = _contextFactory())
        {
            var competing = await other.Proposals.FirstAsync(p => p.Id == proposal.Id);
            competing.Notes = "winner";
            competing.Version = 2;
            await other.SaveChangesAsync();
        }

        var act = () => _sut.UpdateAsync(proposal.Id, UpdateNotes("loser", RowVersionCodec.Encode(1)));
        await act.Should().ThrowAsync<ProposalConcurrencyException>();

        await using var check = _contextFactory();
        (await check.AuditLogs.CountAsync()).Should().Be(0);
    }

    [Fact(DisplayName = "Successful update bumps the version and commits exactly one audit row atomically")]
    public async Task SuccessfulUpdate_BumpsVersionAndCommitsAudit()
    {
        var proposal = SeedProposal();

        var result = await _sut.UpdateAsync(proposal.Id, UpdateNotes("new notes", RowVersionCodec.Encode(1)));

        result.RowVersion.Should().Be(RowVersionCodec.Encode(2));
        await using var check = _contextFactory();
        (await check.AuditLogs.CountAsync(a => a.ProposalId == proposal.Id)).Should().Be(1);
        (await check.Proposals.SingleAsync(p => p.Id == proposal.Id)).Version.Should().Be(2);
    }

    [Fact(DisplayName = "Bulk line-item update is guarded by the proposal token")]
    public async Task BulkUpdate_StaleProposalToken_Conflicts()
    {
        var proposal = SeedProposal();
        var request = new BulkUpdateLineItemsRequest(
            new List<UpdateLineItemEntry>
            {
                new(null, "Item", 1, "each", null, 100m, PricingMode.TotalPrice, 0, LineItemSource.Manual),
            },
            RowVersionCodec.Encode(42));

        var act = () => _lineItems.BulkUpdateAsync(proposal.Id, request);

        await act.Should().ThrowAsync<ProposalConcurrencyException>();
    }

    [Fact(DisplayName = "Line-item create bumps the proposal aggregate version")]
    public async Task LineItemCreate_BumpsProposalVersion()
    {
        var proposal = SeedProposal();

        var created = await _lineItems.CreateAsync(proposal.Id,
            new CreateLineItemRequest("Item", 1, "each", null, 50m, PricingMode.TotalPrice, 0, LineItemSource.Manual));

        created.RowVersion.Should().Be(RowVersionCodec.Encode(1));
        await using var check = _contextFactory();
        (await check.Proposals.SingleAsync(p => p.Id == proposal.Id)).Version.Should().Be(2);
    }

    [Fact(DisplayName = "Approve with the current token succeeds and returns the bumped token")]
    public async Task Approve_WithCurrentToken_Succeeds()
    {
        var proposal = SeedProposal();
        _db.LineItems.Add(new LineItem
        {
            Id = Guid.NewGuid(),
            ProposalId = proposal.Id,
            Description = "Priced item",
            Quantity = 1,
            Unit = "each",
            TotalPrice = 500m,
            PricingMode = PricingMode.TotalPrice,
            Source = LineItemSource.Manual,
        });
        _db.SaveChanges();

        var result = await _sut.ApproveAsync(proposal.Id, RowVersionCodec.Encode(1));

        result.Status.Should().Be(ProposalStatus.Approved);
        result.RowVersion.Should().Be(RowVersionCodec.Encode(2));
    }
}