using ClaudeDo.Data;
using ClaudeDo.Data.Models;
using ClaudeDo.Ui.ViewModels.Islands;
using Microsoft.EntityFrameworkCore;
using TaskStatus = ClaudeDo.Data.Models.TaskStatus;

namespace ClaudeDo.Ui.Tests.ViewModels;

// Phase 3 reconcile tick: a periodic, awaitable-for-tests diff of the flat `Items` master
// collection against SQLite that patches properties in place. It must never rebuild a row and
// never fall back to LoadForList — see
// docs/superpowers/specs/2026-08-07-ui-reaktivitaet-und-listen-performance-design.md.
// It DOES Regroup, but only when a patch changed a grouping input: healing a row's data while
// leaving it in the wrong section would fix nothing the user can see.
public class TasksIslandReconcileTickTests : IDisposable
{
    private readonly string _dbPath;

    public TasksIslandReconcileTickTests()
    {
        _dbPath = Path.Combine(Path.GetTempPath(), $"claudedo_ui_reconcile_{Guid.NewGuid():N}.db");
        using var ctx = NewContext();
        ctx.Database.EnsureCreated();
    }

    public void Dispose()
    {
        try { File.Delete(_dbPath); } catch { }
        try { File.Delete(_dbPath + "-wal"); } catch { }
        try { File.Delete(_dbPath + "-shm"); } catch { }
    }

    private ClaudeDoDbContext NewContext()
    {
        var opts = new DbContextOptionsBuilder<ClaudeDoDbContext>()
            .UseSqlite($"Data Source={_dbPath}")
            .Options;
        return new ClaudeDoDbContext(opts);
    }

    private sealed class CountingDbFactory : IDbContextFactory<ClaudeDoDbContext>
    {
        private readonly Func<ClaudeDoDbContext> _create;
        public int CreateCalls { get; private set; }
        public CountingDbFactory(Func<ClaudeDoDbContext> create) => _create = create;
        public ClaudeDoDbContext CreateDbContext()
        {
            CreateCalls++;
            return _create();
        }
    }

    private static ListNavItemViewModel UserList(string listEntityId, string name) =>
        new() { Id = $"user:{listEntityId}", Kind = ListKind.User, Name = name };

    private static async Task LoadAndWaitAsync(TasksIslandViewModel vm, ListNavItemViewModel list, int expectedCount = 1)
    {
        vm.LoadForList(list);
        var deadline = DateTime.UtcNow.AddSeconds(5);
        while (DateTime.UtcNow < deadline)
        {
            await Task.Delay(25);
            if (vm.Items.Count >= expectedCount) break;
        }
        await Task.Delay(50);
    }

    private async Task SeedListAsync()
    {
        await using var db = NewContext();
        db.Lists.Add(new ListEntity { Id = "L1", Name = "Work", CreatedAt = DateTime.UtcNow });
        await db.SaveChangesAsync();
    }

    private async Task SeedTaskAsync(string id, string title, TaskStatus status, int sortOrder)
    {
        await using var db = NewContext();
        db.Tasks.Add(new TaskEntity
        {
            Number = TestTaskNumbers.Next(),
            Id = id, ListId = "L1", Title = title,
            Status = status, CreatedAt = DateTime.UtcNow, SortOrder = sortOrder,
        });
        await db.SaveChangesAsync();
    }

    [Fact]
    public async Task Tick_patches_a_diverging_property()
    {
        await SeedListAsync();
        await SeedTaskAsync("T1", "Original title", TaskStatus.Idle, 0);

        var vm = new TasksIslandViewModel(new CountingDbFactory(NewContext), worker: null);
        await LoadAndWaitAsync(vm, UserList("L1", "Work"));
        Assert.Equal("Original title", vm.Items.Single(r => r.Id == "T1").Title);

        await using (var db = NewContext())
        {
            var t = await db.Tasks.FirstAsync(x => x.Id == "T1");
            t.Title = "Renamed elsewhere";
            await db.SaveChangesAsync();
        }

        await vm.ReconcileTickAsync();

        Assert.Equal("Renamed elsewhere", vm.Items.Single(r => r.Id == "T1").Title);
    }

    [Fact]
    public async Task Tick_never_creates_a_new_row_instance()
    {
        await SeedListAsync();
        await SeedTaskAsync("T1", "Task one", TaskStatus.Idle, 0);

        var vm = new TasksIslandViewModel(new CountingDbFactory(NewContext), worker: null);
        await LoadAndWaitAsync(vm, UserList("L1", "Work"));
        var rowBefore = vm.Items.Single(r => r.Id == "T1");

        await using (var db = NewContext())
        {
            var t = await db.Tasks.FirstAsync(x => x.Id == "T1");
            t.Status = TaskStatus.Running;
            await db.SaveChangesAsync();
        }

        await vm.ReconcileTickAsync();

        var rowAfter = vm.Items.Single(r => r.Id == "T1");
        Assert.True(ReferenceEquals(rowBefore, rowAfter));
        Assert.Equal(TaskStatus.Running, rowAfter.Status);
    }

    [Fact]
    public async Task Tick_with_no_changes_raises_no_property_changed()
    {
        await SeedListAsync();
        await SeedTaskAsync("T1", "Task one", TaskStatus.Idle, 0);

        var vm = new TasksIslandViewModel(new CountingDbFactory(NewContext), worker: null);
        await LoadAndWaitAsync(vm, UserList("L1", "Work"));
        var row = vm.Items.Single(r => r.Id == "T1");

        var changedProperties = new List<string?>();
        row.PropertyChanged += (_, e) => changedProperties.Add(e.PropertyName);

        await vm.ReconcileTickAsync();

        Assert.Empty(changedProperties);
    }

    [Fact]
    public async Task Tick_discards_a_stale_result_when_a_newer_refresh_wins_the_race()
    {
        await SeedListAsync();
        await SeedTaskAsync("T1", "Task one", TaskStatus.Queued, 0);

        var vm = new TasksIslandViewModel(new CountingDbFactory(NewContext), worker: null);
        await LoadAndWaitAsync(vm, UserList("L1", "Work"));
        Assert.Equal(TaskStatus.Queued, vm.Items.Single(r => r.Id == "T1").Status);

        var barrierReached = new TaskCompletionSource();
        var proceed = new TaskCompletionSource();
        vm.ReconcileTickTestBarrier = async () =>
        {
            barrierReached.TrySetResult();
            await proceed.Task;
        };

        // Tick reads "Queued" (nothing has changed yet), then parks at the barrier before
        // applying its (about to become stale) result.
        var tickTask = vm.ReconcileTickAsync();
        await barrierReached.Task;

        // A fresher broadcast lands and wins: the DB flips to Running and the delta path applies
        // it with a newer sequence number while the tick is still parked.
        await using (var db = NewContext())
        {
            var t = await db.Tasks.FirstAsync(x => x.Id == "T1");
            t.Status = TaskStatus.Running;
            await db.SaveChangesAsync();
        }
        await vm.RefreshTaskFromWorkerAsync("T1");
        Assert.Equal(TaskStatus.Running, vm.Items.Single(r => r.Id == "T1").Status);

        // Let the tick's stale "Queued" apply attempt run — the sequence guard must discard it.
        proceed.TrySetResult();
        await tickTask;

        Assert.Equal(TaskStatus.Running, vm.Items.Single(r => r.Id == "T1").Status);
    }

    [Fact]
    public async Task Tick_caps_reconciliation_at_the_row_limit()
    {
        await SeedListAsync();
        var total = TasksIslandViewModel.ReconcileRowCap + 1;
        for (var i = 0; i < total; i++)
            await SeedTaskAsync($"T{i}", $"Task {i}", TaskStatus.Queued, i);

        var factory = new CountingDbFactory(NewContext);
        var vm = new TasksIslandViewModel(factory, worker: null);
        await LoadAndWaitAsync(vm, UserList("L1", "Work"), expectedCount: total);
        Assert.Equal(total, vm.Items.Count);

        await using (var db = NewContext())
        {
            await db.Tasks.ExecuteUpdateAsync(s => s.SetProperty(t => t.Status, TaskStatus.Running));
        }

        var createCallsBefore = factory.CreateCalls;
        await vm.ReconcileTickAsync();
        Assert.Equal(createCallsBefore + 1, factory.CreateCalls); // exactly one DB query for the whole tick

        var reconciled = vm.Items.Count(r => r.Status == TaskStatus.Running);
        Assert.Equal(TasksIslandViewModel.ReconcileRowCap, reconciled);

        // The row beyond the cap (last one loaded, per SortOrder) must not have been touched.
        var lastRow = vm.Items.Single(r => r.Id == $"T{total - 1}");
        Assert.Equal(TaskStatus.Queued, lastRow.Status);
    }

    [Fact]
    public async Task Tick_moves_a_healed_done_task_into_the_completed_section()
    {
        await SeedListAsync();
        await SeedTaskAsync("T1", "Task one", TaskStatus.Idle, 0);
        await SeedTaskAsync("T2", "Task two", TaskStatus.Idle, 1);

        var vm = new TasksIslandViewModel(new CountingDbFactory(NewContext), worker: null);
        await LoadAndWaitAsync(vm, UserList("L1", "Work"), expectedCount: 2);
        vm.IsShowingCompleted = true;
        Assert.False(vm.HasCompleted);

        // The TaskUpdated broadcast goes missing: SQLite says Done, the row still reads open.
        await using (var db = NewContext())
        {
            var t = await db.Tasks.FirstAsync(x => x.Id == "T1");
            t.Status = TaskStatus.Done;
            await db.SaveChangesAsync();
        }

        await vm.ReconcileTickAsync();

        Assert.True(vm.HasCompleted);

        // Rows is the rendered order, so the healed row has to sit *under* the completed header
        // (the only one carrying an action command), not still be interleaved with the open rows.
        var rows = vm.Rows.ToList();
        var headerIndex = rows.FindIndex(r => r is HeaderRow { HasAction: true });
        var healedIndex = rows.FindIndex(r => r is TaskRowViewModel { Id: "T1" });
        Assert.True(headerIndex >= 0, "completed header was never emitted");
        Assert.True(healedIndex > headerIndex, $"healed row at {healedIndex}, completed header at {headerIndex}");
    }

    [Fact]
    public async Task Tick_reorders_the_chain_when_a_depends_on_link_is_healed()
    {
        await SeedListAsync();
        await SeedTaskAsync("HEAD", "Chain head", TaskStatus.Idle, 0);
        await SeedTaskAsync("MID", "Unrelated", TaskStatus.Idle, 1);
        await SeedTaskAsync("DEP", "Dependent", TaskStatus.Idle, 2);

        var vm = new TasksIslandViewModel(new CountingDbFactory(NewContext), worker: null);
        await LoadAndWaitAsync(vm, UserList("L1", "Work"), expectedCount: 3);
        Assert.Equal(new[] { "HEAD", "MID", "DEP" }, vm.Rows.OfType<TaskRowViewModel>().Select(r => r.Id));

        await using (var db = NewContext())
        {
            var t = await db.Tasks.FirstAsync(x => x.Id == "DEP");
            t.DependsOnTaskId = "HEAD";
            await db.SaveChangesAsync();
        }

        await vm.ReconcileTickAsync();

        // The dependent is pulled directly under its head and gets the rail, not just the data.
        Assert.Equal(new[] { "HEAD", "DEP", "MID" }, vm.Rows.OfType<TaskRowViewModel>().Select(r => r.Id));
        Assert.True(vm.Items.Single(r => r.Id == "DEP").ShowAsChainMember);
        Assert.Equal(1, vm.Items.Single(r => r.Id == "DEP").ChainStep);
    }
}