using AcDream.App.Studio;
using AcDream.App.UI;

namespace AcDream.App.Tests.Studio;

/// <summary>
/// Tests for <see cref="DumpLayout"/> — parsing the retail UI dump JSON and
/// building a <see cref="UiElement"/> tree from it.
///
/// These tests load the real dump file from the source tree
/// (<c>docs/research/2026-06-25-retail-ui-layout-dump.json</c>). The test
/// skips cleanly when the file is absent (should not happen in a normal dev
/// checkout, but guards against stripped CI machines).
/// </summary>
public class DumpLayoutTests
{
    private static string DumpPath()
    {
        // Walk up from the test output directory to the solution root,
        // mirroring ConformanceDats.SolutionRoot().
        var dir = AppContext.BaseDirectory;
        while (!string.IsNullOrEmpty(dir))
        {
            if (File.Exists(Path.Combine(dir, "AcDream.slnx")))
                return Path.Combine(dir, "docs", "research",
                    "2026-06-25-retail-ui-layout-dump.json");
            dir = Path.GetDirectoryName(dir);
        }
        // Fallback: try a relative path (won't find it but skip rather than throw)
        return Path.Combine(AppContext.BaseDirectory,
            "docs", "research", "2026-06-25-retail-ui-layout-dump.json");
    }

    private static (uint, int, int) NoTex(uint _) => (1u, 1, 1);

    // ── Helpers ──────────────────────────────────────────────────────────

    /// <summary>Depth-first search for an element with the given EventId.</summary>
    private static UiElement? FindById(UiElement root, uint id)
    {
        if (root.EventId == id) return root;
        foreach (var c in root.Children)
        {
            var found = FindById(c, id);
            if (found is not null) return found;
        }
        return null;
    }

    /// <summary>Count the total elements in the tree (self + all descendants).</summary>
    private static int CountAll(UiElement root)
    {
        int n = 1;
        foreach (var c in root.Children) n += CountAll(c);
        return n;
    }

    // ── Tests ─────────────────────────────────────────────────────────────

    /// <summary>
    /// Loading the "inventory" slug should succeed and the returned tree should
    /// contain an element with EventId == 0x100001D5 (the doll viewport node)
    /// and at least 40 elements in total.
    /// </summary>
    [Fact]
    public void Load_Inventory_ReturnsTreeWithDollViewport()
    {
        var path = DumpPath();
        if (!File.Exists(path))
            return; // Skip: dump not available.

        var root = DumpLayout.Load(path, "inventory", NoTex, out var err);

        Assert.NotNull(root);
        Assert.Null(err);

        // The doll viewport element must appear somewhere in the tree.
        const uint dollViewportId = 0x100001D5u;
        var found = FindById(root!, dollViewportId);
        Assert.NotNull(found);

        // The full tree must be reasonably deep — 59 dump nodes → >= 40 elements.
        int total = CountAll(root!);
        Assert.True(total >= 40,
            $"Expected >= 40 elements in inventory tree; got {total}");
    }

    /// <summary>
    /// Loading an unknown slug must return null and a non-empty error string.
    /// </summary>
    [Fact]
    public void Load_UnknownSlug_ReturnsNullWithError()
    {
        var path = DumpPath();
        if (!File.Exists(path))
            return; // Skip.

        var root = DumpLayout.Load(path, "this_slug_does_not_exist", NoTex, out var err);

        Assert.Null(root);
        Assert.NotNull(err);
        Assert.NotEmpty(err!);
    }

    /// <summary>
    /// The root element's Left/Top should be (0,0) (the panel's rect offset has
    /// been stripped so the tree sits at the window origin), and its Width/Height
    /// should match the dump panel dimensions.
    /// </summary>
    [Fact]
    public void Load_Inventory_RootAtOrigin()
    {
        var path = DumpPath();
        if (!File.Exists(path))
            return; // Skip.

        var root = DumpLayout.Load(path, "inventory", NoTex, out _);
        Assert.NotNull(root);

        // Root always placed at (0,0) by DumpLayout (origin of the UiHost).
        Assert.Equal(0f, root!.Left);
        Assert.Equal(0f, root.Top);
        // Width/Height come from the panel record in the dump.
        Assert.True(root.Width > 0,  "Root width must be > 0");
        Assert.True(root.Height > 0, "Root height must be > 0");
    }

    /// <summary>
    /// Children must use parent-relative coordinates (the dump rects are absolute;
    /// DumpLayout subtracts the parent rect to produce parent-local offsets).
    /// Verify that at least the direct children of the root have Left/Top values
    /// that are NOT equal to the absolute rect they had in the dump (since the root
    /// was at x>0 in screen space but we place it at 0,0).
    /// </summary>
    [Fact]
    public void Load_Inventory_ChildrenAreParentRelative()
    {
        var path = DumpPath();
        if (!File.Exists(path))
            return; // Skip.

        var root = DumpLayout.Load(path, "inventory", NoTex, out _);
        Assert.NotNull(root);

        // If the dump has children at absolute x>=500 but the root is at 0,
        // a correct parent-relative placement will give children x < 500.
        // (The inventory panel root is at absolute x=500; children in the dump
        // also start at x=500 — after subtraction they should land near x=0.)
        bool anyChildAtAbsoluteX = false;
        foreach (var child in root!.Children)
        {
            if (child.Left >= 490f) // would indicate absolute not relative
            {
                anyChildAtAbsoluteX = true;
                break;
            }
        }
        Assert.False(anyChildAtAbsoluteX,
            "Children appear to have absolute coords (Left >= 490) — " +
            "DumpLayout must subtract the parent rect.");
    }

    /// <summary>
    /// Every panel slug known in the dump must load without error.
    /// This is a smoke test that the JSON parse + tree build does not
    /// crash on any of the 26 panels.
    /// </summary>
    [Fact]
    public void Load_AllSlugs_Succeed()
    {
        var path = DumpPath();
        if (!File.Exists(path))
            return; // Skip.

        var slugs = UiDumpModel.ListSlugs(path);
        Assert.True(slugs.Count >= 20,
            $"Expected >= 20 panel slugs in dump; got {slugs.Count}");

        foreach (var slug in slugs)
        {
            var root = DumpLayout.Load(path, slug, NoTex, out var err);
            Assert.True(root is not null || err is not null,
                $"Load('{slug}') returned both null root AND null error — one must be set.");
            if (root is null)
                Assert.Fail($"Slug '{slug}' failed with error: {err}");
        }
    }
}