using ZB.MOM.WW.ScadaBridge.CentralUI.Components.Shared;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.Instances;

namespace ZB.MOM.WW.ScadaBridge.CentralUI.Tests.Shared;

/// <summary>
/// Unit tests for <see cref="InstanceTreeBuilder"/> — the pure area/instance forest
/// behind the Instance Picker combobox (design 2026-09-08).
/// </summary>
public class InstanceTreeBuilderTests
{
    private static Area MakeArea(int id, string name, int? parentAreaId = null) =>
        new(name) { Id = id, SiteId = 1, ParentAreaId = parentAreaId };

    private static Instance MakeInstance(int id, string uniqueName, int? areaId = null) =>
        new(uniqueName) { Id = id, SiteId = 1, AreaId = areaId };

    [Fact]
    public void Build_NestsAreasByParent_AndPutsRootInstancesAfterRootAreas()
    {
        var line1 = MakeArea(1, "Line1");
        var cellA = MakeArea(2, "Cell A", parentAreaId: 1);
        var p1 = MakeInstance(10, "P1", areaId: 2);
        var zulu = MakeInstance(11, "Zulu");
        var alpha = MakeInstance(12, "Alpha");

        var roots = InstanceTreeBuilder.Build([line1, cellA], [p1, zulu, alpha], filter: null);

        Assert.Equal(new[] { "a:1", "i:12", "i:11" }, roots.Select(n => n.Key));

        var areaNode = roots[0];
        Assert.Equal("Line1", areaNode.Label);
        Assert.False(areaNode.IsInstance);
        Assert.Same(line1, areaNode.Area);
        Assert.Null(areaNode.Instance);
        Assert.True(areaNode.HasChildren);

        var cellNode = Assert.Single(areaNode.Children);
        Assert.Equal("a:2", cellNode.Key);
        Assert.Equal("Cell A", cellNode.Label);
        Assert.Same(cellA, cellNode.Area);

        var p1Node = Assert.Single(cellNode.Children);
        Assert.Equal("i:10", p1Node.Key);
        Assert.Equal("P1", p1Node.Label);
        Assert.True(p1Node.IsInstance);
        Assert.Same(p1, p1Node.Instance);
        Assert.Null(p1Node.Area);
        Assert.False(p1Node.HasChildren);

        Assert.Equal("Alpha", roots[1].Label);
        Assert.Same(alpha, roots[1].Instance);
        Assert.Equal("Zulu", roots[2].Label);
        Assert.Same(zulu, roots[2].Instance);
    }

    [Fact]
    public void Build_SortsAreasAndInstancesCaseInsensitively()
    {
        var beta = MakeArea(1, "beta");
        var alphaArea = MakeArea(2, "Alpha");
        var zebra = MakeInstance(10, "zebra");
        var apple = MakeInstance(11, "Apple");

        var roots = InstanceTreeBuilder.Build([beta, alphaArea], [zebra, apple], filter: null);

        Assert.Equal(new[] { "Alpha", "beta", "Apple", "zebra" }, roots.Select(n => n.Label));
    }

    [Fact]
    public void Build_OrphanedArea_BecomesARoot()
    {
        // ParentAreaId points at an area that is not in the supplied list.
        var orphan = MakeArea(5, "Orphan", parentAreaId: 99);
        var child = MakeInstance(10, "OrphanChild", areaId: 5);

        var roots = InstanceTreeBuilder.Build([orphan], [child], filter: null);

        var root = Assert.Single(roots);
        Assert.Equal("a:5", root.Key);
        var leaf = Assert.Single(root.Children);
        Assert.Equal("i:10", leaf.Key);
    }

    [Fact]
    public void Build_InstanceWithUnknownArea_SurfacesAtRoot()
    {
        // AreaId points at an area that is not in the supplied list — the instance must not
        // vanish; it is listed at the root like an instance with no area at all.
        var line1 = MakeArea(1, "Line1");
        var stranded = MakeInstance(10, "Stranded", areaId: 99);

        var roots = InstanceTreeBuilder.Build([line1], [stranded], filter: null);

        Assert.Equal(new[] { "a:1", "i:10" }, roots.Select(n => n.Key));
        Assert.Same(stranded, roots[1].Instance);
    }

    [Fact]
    public void Build_InstanceWithUnknownArea_StaysFilterable()
    {
        var line1 = MakeArea(1, "Line1");
        var stranded = MakeInstance(10, "Stranded", areaId: 99);

        var matched = InstanceTreeBuilder.Build([line1], [stranded], filter: "rand");

        Assert.Equal("i:10", Assert.Single(matched).Key);
        Assert.Empty(InstanceTreeBuilder.Build([line1], [stranded], filter: "nomatch"));
    }

    [Fact]
    public void Build_DeepNesting_WiresChildrenAtEveryLevel()
    {
        var plant = MakeArea(1, "Plant");
        var line = MakeArea(2, "Line", parentAreaId: 1);
        var cell = MakeArea(3, "Cell", parentAreaId: 2);
        var deep = MakeInstance(10, "Deep", areaId: 3);

        var roots = InstanceTreeBuilder.Build([plant, line, cell], [deep], filter: null);

        var plantNode = Assert.Single(roots);
        Assert.Equal("a:1", plantNode.Key);
        var lineNode = Assert.Single(plantNode.Children);
        Assert.Equal("a:2", lineNode.Key);
        var cellNode = Assert.Single(lineNode.Children);
        Assert.Equal("a:3", cellNode.Key);
        var leaf = Assert.Single(cellNode.Children);
        Assert.Equal("i:10", leaf.Key);
        Assert.False(leaf.HasChildren);
    }

    [Fact]
    public void Build_CyclicParentAreaIds_DoNotLoopOrThrow()
    {
        // A bad row pair: each area names the other as its parent. Neither is reachable
        // from a root, so the forest is simply empty — and building it must terminate.
        var a = MakeArea(1, "A", parentAreaId: 2);
        var b = MakeArea(2, "B", parentAreaId: 1);
        var inA = MakeInstance(10, "InA", areaId: 1);
        var inB = MakeInstance(11, "InB", areaId: 2);

        var roots = InstanceTreeBuilder.Build([a, b], [inA, inB], filter: null);

        Assert.Empty(roots);
    }

    [Fact]
    public void Build_Filter_MatchesInstanceNamesOnly_AreaNameMatchIsNotEnough()
    {
        // "Line1" contains the needle but holds no matching instance — it is dropped.
        var line1 = MakeArea(1, "Line1");
        var line2 = MakeArea(2, "Line2");
        var other = MakeInstance(10, "Pump", areaId: 1);
        var hit = MakeInstance(11, "Line1Feeder", areaId: 2);

        var roots = InstanceTreeBuilder.Build([line1, line2], [other, hit], filter: "line1");

        var root = Assert.Single(roots);
        Assert.Equal("a:2", root.Key);
        Assert.Equal("i:11", Assert.Single(root.Children).Key);
    }

    [Fact]
    public void Build_Filter_KeepsMatchingInstancesWithAncestors_DropsEmptyBranches()
    {
        var line1 = MakeArea(1, "Line1");
        var cellA = MakeArea(2, "Cell A", parentAreaId: 1);
        var emptyArea = MakeArea(3, "Line2");
        var p1 = MakeInstance(10, "P1", areaId: 2);
        var zulu = MakeInstance(11, "Zulu");
        var alpha = MakeInstance(12, "Alpha");

        var roots = InstanceTreeBuilder.Build([line1, cellA, emptyArea], [p1, zulu, alpha], filter: "p1");

        var root = Assert.Single(roots);
        Assert.Equal("a:1", root.Key);
        var cellNode = Assert.Single(root.Children);
        Assert.Equal("a:2", cellNode.Key);
        var leaf = Assert.Single(cellNode.Children);
        Assert.Equal("i:10", leaf.Key);
    }

    [Fact]
    public void Build_Filter_WhitespaceMeansNoFilter()
    {
        var line1 = MakeArea(1, "Line1");
        var p1 = MakeInstance(10, "P1", areaId: 1);
        var zulu = MakeInstance(11, "Zulu");

        var roots = InstanceTreeBuilder.Build([line1], [p1, zulu], filter: "   ");

        Assert.Equal(new[] { "a:1", "i:11" }, roots.Select(n => n.Key));
        Assert.Single(roots[0].Children);
    }

    [Fact]
    public void Build_NullOrEmptyInputs_ReturnEmpty()
    {
        Assert.Empty(InstanceTreeBuilder.Build(null, null, filter: null));
        Assert.Empty(InstanceTreeBuilder.Build([], [], filter: null));
        Assert.Empty(InstanceTreeBuilder.Build(null, [], filter: "anything"));

        var orphanInstances = InstanceTreeBuilder.Build(null, [MakeInstance(1, "Solo")], filter: null);
        Assert.Equal("i:1", Assert.Single(orphanInstances).Key);

        var areasOnly = InstanceTreeBuilder.Build([MakeArea(1, "Line1")], null, filter: null);
        Assert.Equal("a:1", Assert.Single(areasOnly).Key);
    }

    [Fact]
    public void Build_AreaWithNoInstancesAndNoFilter_IsStillShown()
    {
        var empty = MakeArea(1, "Empty");

        var roots = InstanceTreeBuilder.Build([empty], [], filter: null);

        var root = Assert.Single(roots);
        Assert.Equal("a:1", root.Key);
        Assert.False(root.HasChildren);
    }
}