#include <gtest/gtest.h>
#include <fstream>
#include <cstdio>
#include "vde/foundation/io_gltf.h"
#include "vde/brep/modeling.h"
#include "vde/brep/modeling.h"

using namespace vde::foundation;
using namespace vde::mesh;
using namespace vde::core;

// ── Helper: build a simple tetrahedron mesh ──
static HalfedgeMesh make_tetrahedron() {
    HalfedgeMesh mesh;
    mesh.build_from_triangles(
        {
            Point3D(0, 0, 0), Point3D(1, 0, 0), Point3D(0.5, 0.866, 0), Point3D(0.5, 0.289, 0.816)
        },
        {
            {0, 1, 2}, {0, 3, 1}, {1, 3, 2}, {0, 2, 3}
        }
    );
    return mesh;
}

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

TEST(IoGltfTest, ExportTetToGltfJson) {
    auto mesh = make_tetrahedron();
    GltfOptions opt;
    opt.binary = false;
    opt.include_normals = false;

    const char* path = "/tmp/test_tet.gltf";
    std::remove(path);  // clean up from previous run
    ASSERT_TRUE(write_gltf(path, mesh, opt));

    std::ifstream f(path);
    ASSERT_TRUE(f.good());
    std::string content((std::istreambuf_iterator<char>(f)), std::istreambuf_iterator<char>());
    EXPECT_NE(content.find("\"asset\""), std::string::npos);
    EXPECT_NE(content.find("\"meshes\""), std::string::npos);
    EXPECT_NE(content.find("ViewDesignEngine"), std::string::npos);

    std::remove(path);
    std::remove("/tmp/test_tet.bin");
}

TEST(IoGltfTest, ExportTetToGlbBinary) {
    auto mesh = make_tetrahedron();
    GltfOptions opt;
    opt.binary = true;
    opt.include_normals = false;

    const char* path = "/tmp/test_tet.glb";
    std::remove(path);
    ASSERT_TRUE(write_gltf(path, mesh, opt));

    // Verify GLB magic bytes
    std::ifstream f(path, std::ios::binary);
    ASSERT_TRUE(f.good());

    uint32_t magic = 0, version = 0;
    f.read(reinterpret_cast<char*>(&magic), 4);
    f.read(reinterpret_cast<char*>(&version), 4);

    EXPECT_EQ(magic, 0x46546C67u) << "GLB magic should be 'glTF'";
    EXPECT_EQ(version, 2u) << "GLB version should be 2";

    uint32_t total_len = 0;
    f.read(reinterpret_cast<char*>(&total_len), 4);

    // Should contain "JSON" chunk marker
    uint32_t chunk_len = 0, chunk_type = 0;
    f.read(reinterpret_cast<char*>(&chunk_len), 4);
    f.read(reinterpret_cast<char*>(&chunk_type), 4);
    EXPECT_EQ(chunk_type, 0x4E4F534Au) << "First chunk should be JSON";

    std::remove(path);
}

TEST(IoGltfTest, ExportWithNormals) {
    auto mesh = make_tetrahedron();
    GltfOptions opt;
    opt.binary = true;
    opt.include_normals = true;

    const char* path = "/tmp/test_tet_normals.glb";
    std::remove(path);
    ASSERT_TRUE(write_gltf(path, mesh, opt));

    // Read GLB and verify it contains JSON with NORMAL attribute
    std::ifstream f(path, std::ios::binary);
    ASSERT_TRUE(f.good());

    // Read header
    uint32_t magic = 0, version = 0, total_len = 0;
    f.read(reinterpret_cast<char*>(&magic), 4);
    f.read(reinterpret_cast<char*>(&version), 4);
    f.read(reinterpret_cast<char*>(&total_len), 4);
    EXPECT_EQ(magic, 0x46546C67u);

    // Read JSON chunk header
    uint32_t chunk_len = 0, chunk_type = 0;
    f.read(reinterpret_cast<char*>(&chunk_len), 4);
    f.read(reinterpret_cast<char*>(&chunk_type), 4);
    EXPECT_EQ(chunk_type, 0x4E4F534Au);

    // Read unpadded JSON data + skip padding
    std::string json(chunk_len, '\0');
    f.read(&json[0], chunk_len);
    size_t padding = (4 - (chunk_len % 4)) % 4;
    f.seekg(static_cast<std::streamoff>(padding), std::ios::cur);

    EXPECT_NE(json.find("\"NORMAL\""), std::string::npos)
        << "JSON should include NORMAL attribute when normals enabled";

    // File should also have a BIN chunk (larger because of normals)
    uint32_t bin_len = 0, bin_type = 0;
    if (f.read(reinterpret_cast<char*>(&bin_len), 4)) {
        f.read(reinterpret_cast<char*>(&bin_type), 4);
        EXPECT_EQ(bin_type, 0x004E4942u) << "Second chunk should be BIN";
        EXPECT_GT(bin_len, 0u) << "BIN chunk should have data";
    }

    std::remove(path);
}

TEST(IoGltfTest, ExportBrepBoxToGlb) {
    auto box = vde::brep::make_box(2.0, 2.0, 2.0);

    const char* path = "/tmp/test_brep_box.glb";
    std::remove(path);
    ASSERT_TRUE(write_brep_gltf(path, box, 32));

    // Verify file exists and has magic
    std::ifstream f(path, std::ios::binary);
    ASSERT_TRUE(f.good());

    uint32_t magic = 0;
    f.read(reinterpret_cast<char*>(&magic), 4);
    EXPECT_EQ(magic, 0x46546C67u);

    std::remove(path);
}

TEST(IoGltfTest, EmptyMeshFailsGracefully) {
    HalfedgeMesh empty;
    GltfOptions opt;
    opt.binary = true;

    const char* path = "/tmp/test_empty.glb";
    std::remove(path);
    EXPECT_FALSE(write_gltf(path, empty, opt))
        << "Exporting empty mesh should return false";
}

TEST(IoGltfTest, EmptyBrepFailsGracefully) {
    vde::brep::BrepModel empty;

    const char* path = "/tmp/test_empty_brep.glb";
    std::remove(path);
    EXPECT_FALSE(write_brep_gltf(path, empty, 32))
        << "Exporting empty B-Rep should return false";
}