#include <catch2/catch_test_macros.hpp>
#include <catch2/matchers/catch_matchers_floating_point.hpp>
#include "engine/core/gui/uiComponent/layout/LayoutEngine.h"

using namespace LayoutEngine;
using Catch::Matchers::WithinAbs;
const float EPS = 0.001f;

static NodeLayout makeNode(float x, float y, float w, float h) {
    NodeLayout n;
    n.layoutStyle.width       = { w, SizeUnit::Percent };
    n.layoutStyle.height      = { h, SizeUnit::Percent };
    n.layoutStyle.margin.left = { x, SizeUnit::Percent };
    n.layoutStyle.margin.top  = { y, SizeUnit::Percent };
    return n;
}

static Dimensions screen800x600() {
    return { 0.f, 0.f, 1.0f, 1.0f };
}

// ── Basisfälle ───────────────────────────────────────────────────────────────

TEST_CASE("SizeUnit::Pixels wird korrekt normalisiert", "[layout][pixels]") {
    NodeLayout root;
    root.layoutStyle.width  = { 400.f, SizeUnit::Pixels };
    root.layoutStyle.height = { 300.f, SizeUnit::Pixels };

    auto result = compute(root, screen800x600(), 800.f, 600.f);

    REQUIRE_THAT(result.self.width,  WithinAbs(0.5f, EPS));  // 400/800
    REQUIRE_THAT(result.self.height, WithinAbs(0.5f, EPS));  // 300/600
}

TEST_CASE("Eigene Dimensionen werden korrekt berechnet", "[layout][self]") {
    NodeLayout root = makeNode(0.1f, 0.2f, 0.5f, 0.4f);
    auto result = compute(root, screen800x600(), 800.f, 600.f);

    REQUIRE_THAT(result.self.x,      WithinAbs(0.1f, EPS));
    REQUIRE_THAT(result.self.y,      WithinAbs(0.2f, EPS));
    REQUIRE_THAT(result.self.width,  WithinAbs(0.5f, EPS));
    REQUIRE_THAT(result.self.height, WithinAbs(0.4f, EPS));
}

TEST_CASE("Kein Kind → leere children-Liste", "[layout][children]") {
    NodeLayout root = makeNode(0.f, 0.f, 0.5f, 0.5f);
    auto result = compute(root, screen800x600(), 800.f, 600.f);
    REQUIRE(result.children.empty());
}

// ── JustifyContent ───────────────────────────────────────────────────────────

TEST_CASE("JustifyContent::Start – Kinder beginnen bei 0", "[layout][justify]") {
    NodeLayout root = makeNode(0.f, 0.f, 1.0f, 1.0f);
    root.layoutStyle.flexDirection  = FlexDirection::Row;
    root.layoutStyle.justifyContent = JustifyContent::Start;
    root.children.push_back(makeNode(0.f, 0.f, 0.2f, 1.0f));
    root.children.push_back(makeNode(0.f, 0.f, 0.2f, 1.0f));

    auto result = compute(root, screen800x600(), 800.f, 600.f);
    REQUIRE_THAT(result.children[0].self.x, WithinAbs(0.0f, EPS));
    REQUIRE_THAT(result.children[1].self.x, WithinAbs(0.2f, EPS));
}

TEST_CASE("JustifyContent::Center – Kind horizontal zentriert", "[layout][justify]") {
    NodeLayout root = makeNode(0.f, 0.f, 1.0f, 1.0f);
    root.layoutStyle.flexDirection  = FlexDirection::Row;
    root.layoutStyle.justifyContent = JustifyContent::Center;
    root.children.push_back(makeNode(0.f, 0.f, 0.4f, 1.0f));

    auto result = compute(root, screen800x600(), 800.f, 600.f);
    // remaining = 1.0 - 0.4 = 0.6 → offset = 0.3
    REQUIRE_THAT(result.children[0].self.x, WithinAbs(0.3f, EPS));
}

TEST_CASE("JustifyContent::SpaceBetween – Gap korrekt verteilt", "[layout][justify]") {
    NodeLayout root = makeNode(0.f, 0.f, 1.0f, 1.0f);
    root.layoutStyle.flexDirection  = FlexDirection::Row;
    root.layoutStyle.justifyContent = JustifyContent::SpaceBetween;
    root.children.push_back(makeNode(0.f, 0.f, 0.2f, 1.0f));
    root.children.push_back(makeNode(0.f, 0.f, 0.2f, 1.0f));
    root.children.push_back(makeNode(0.f, 0.f, 0.2f, 1.0f));

    auto result = compute(root, screen800x600(), 800.f, 600.f);
    // remaining = 1.0 - 0.6 = 0.4, gap = 0.2
    REQUIRE_THAT(result.children[0].self.x, WithinAbs(0.0f, EPS));
    REQUIRE_THAT(result.children[1].self.x, WithinAbs(0.4f, EPS));
    REQUIRE_THAT(result.children[2].self.x, WithinAbs(0.8f, EPS));
}

// ── AlignItems ───────────────────────────────────────────────────────────────

TEST_CASE("AlignItems::Center – Kind vertikal zentriert (Row)", "[layout][align]") {
    NodeLayout root = makeNode(0.f, 0.f, 1.0f, 1.0f);
    root.layoutStyle.flexDirection = FlexDirection::Row;
    root.layoutStyle.alignItems    = AlignItems::Center;
    root.children.push_back(makeNode(0.f, 0.f, 0.5f, 0.4f));

    auto result = compute(root, screen800x600(), 800.f, 600.f);
    // remaining = 1.0 - 0.4 = 0.6 → y = 0.3
    REQUIRE_THAT(result.children[0].self.y, WithinAbs(0.3f, EPS));
}

TEST_CASE("AlignItems::End – Kind am unteren Rand (Row)", "[layout][align]") {
    NodeLayout root = makeNode(0.f, 0.f, 1.0f, 1.0f);
    root.layoutStyle.flexDirection = FlexDirection::Row;
    root.layoutStyle.alignItems    = AlignItems::End;
    root.children.push_back(makeNode(0.f, 0.f, 0.5f, 0.4f));

    auto result = compute(root, screen800x600(), 800.f, 600.f);
    // remaining = 1.0 - 0.4 = 0.6 → y = 0.6
    REQUIRE_THAT(result.children[0].self.y, WithinAbs(0.6f, EPS));
}

// ── FlexDirection::Column ────────────────────────────────────────────────────

TEST_CASE("Column: Kinder werden vertikal gestapelt", "[layout][column]") {
    NodeLayout root = makeNode(0.f, 0.f, 1.0f, 1.0f);
    root.layoutStyle.flexDirection  = FlexDirection::Column;
    root.layoutStyle.justifyContent = JustifyContent::Start;
    root.children.push_back(makeNode(0.f, 0.f, 1.0f, 0.3f));
    root.children.push_back(makeNode(0.f, 0.f, 1.0f, 0.3f));

    auto result = compute(root, screen800x600(), 800.f, 600.f);
    REQUIRE_THAT(result.children[0].self.y, WithinAbs(0.0f, EPS));
    REQUIRE_THAT(result.children[1].self.y, WithinAbs(0.3f, EPS));
}