Crafter.Build/implementations/Crafter.Build-Asset.cpp

/*
Crafter® Build
Copyright (C) 2026 Catcrafts®
Catcrafts.net

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License version 3.0 as published by the Free Software Foundation;

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
*/

module Crafter.Build:Asset_impl;
import :Asset;
import std;
#ifdef CRAFTER_BUILD_HAS_ASSET
import Crafter.Asset;
import Crafter.Math;
#endif
namespace fs = std::filesystem;

namespace Crafter {
    std::string CompressAsset(const fs::path& input, const fs::path& output) {
        std::string ext = input.extension().string();
        // Case-insensitive extension match — Sponza's textures dir mixes
        // case (.tga and .TGA both appear in the wild).
        for (char& c : ext) c = static_cast<char>(std::tolower(static_cast<unsigned char>(c)));
#ifdef CRAFTER_BUILD_HAS_ASSET
        try {
            // stb_image (the loader behind LoadPNG) handles all of these,
            // so a single branch covers every raster format we ship. The
            // function is misnamed for historical reasons.
            if (ext == ".png" || ext == ".tga" || ext == ".jpg" || ext == ".jpeg" || ext == ".bmp") {
                auto tex = TextureAsset<Vector<std::uint8_t, 4, 4>>::LoadPNG<std::uint8_t>(input);
                tex.SaveCompressed(output);
            } else if (ext == ".obj") {
                auto mesh = MeshAsset<VertexNormalTangentUVPacked>::LoadOBJ(input);
                mesh.SaveCompressed(output);
            } else {
                return std::format("{}: unsupported asset extension '{}'", input.string(), ext);
            }
        } catch (const std::exception& e) {
            return std::format("{}: {}", input.string(), e.what());
        }
        return {};
#else
        return std::format(
            "{}: crafter-build was bootstrapped without Crafter.Asset linkage; "
            "rebuild via `./bin/crafter-build` so the self-host pass picks up the "
            "Crafter.Asset dep declared in project.cpp",
            input.string());
#endif
    }

    std::string BuildOBJBundle(
        const fs::path& objPath,
        const fs::path& mtlPath,
        const fs::path& outDir,
        std::uint16_t   albedoSize)
    {
#ifdef CRAFTER_BUILD_HAS_ASSET
        const fs::path manifest = outDir / "scene.txt";
        if (fs::exists(manifest)) return {};
        try {
            fs::create_directories(outDir);
            auto materials = LoadMTL(mtlPath);
            auto meshes    = MeshAsset<VertexNormalTangentUVPacked>::LoadOBJSplit(objPath);

            std::vector<std::string> uniqueAlbedos;
            std::unordered_map<std::string, std::uint32_t> albedoIndex;
            for (auto& [matName, _] : meshes) {
                auto matIt = materials.find(matName);
                if (matIt == materials.end() || matIt->second.mapKd.empty()) continue;
                const std::string& kd = matIt->second.mapKd;
                if (!albedoIndex.contains(kd)) {
                    albedoIndex.emplace(kd, static_cast<std::uint32_t>(uniqueAlbedos.size()));
                    uniqueAlbedos.push_back(kd);
                }
            }

            std::vector<std::int32_t> meshAlbedoIdx;
            std::uint32_t emitted = 0;
            for (auto& [matName, mesh] : meshes) {
                if (mesh.vertexes.empty() || mesh.indexes.empty()) continue;
                mesh.SaveCompressed(outDir / std::format("mesh_{}.cmesh", emitted));
                std::int32_t a = -1;
                if (auto it = materials.find(matName);
                    it != materials.end() && !it->second.mapKd.empty())
                    a = static_cast<std::int32_t>(albedoIndex.at(it->second.mapKd));
                meshAlbedoIdx.push_back(a);
                ++emitted;
            }

            for (std::uint32_t i = 0; i < uniqueAlbedos.size(); ++i) {
                const fs::path texPath = mtlPath.parent_path() / uniqueAlbedos[i];
                auto tex = TextureAsset<Vector<std::uint8_t, 4, 4>>::LoadPNG<std::uint8_t>(texPath);
                tex.Resize(albedoSize, albedoSize);
                tex.SaveCompressed(outDir / std::format("tex_{}.ctex", i));
            }

            std::ofstream m(manifest);
            m << uniqueAlbedos.size() << "\n" << emitted << "\n";
            for (std::int32_t a : meshAlbedoIdx) m << a << "\n";
        } catch (const std::exception& e) {
            return std::format("BuildOBJBundle: {}", e.what());
        }
        return {};
#else
        return "BuildOBJBundle: crafter-build was bootstrapped without Crafter.Asset linkage; "
               "rebuild via crafter-build itself to pick up the Crafter.Asset dep";
#endif
    }
}