#include <mbgl/gl/fence.hpp>
#include <mbgl/gl/defines.hpp>
#include <mbgl/util/instrumentation.hpp>
#include <cassert>
#include <stdexcept>
#include <string>

namespace mbgl {
namespace gl {

using namespace platform;

namespace {
std::string glErrors() {
    std::string error_list = "";
    for (auto error = glGetError(); error != GL_NO_ERROR; error = glGetError()) {
        error_list += std::to_string(error) + " ";
    }
    if (error_list.empty()) {
        return error_list;
    }
    return "GL error codes: " + error_list;
}
} // namespace

Fence::Fence() {}

Fence::~Fence() {
    MLN_TRACE_FUNC();

    if (fence) {
        glDeleteSync(fence);
    }
}

void Fence::insert() noexcept {
    MLN_TRACE_FUNC();

    assert(!fence);
    fence = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
}

bool Fence::isSignaled() const {
    MLN_TRACE_FUNC();

    if (!fence) {
        return false;
    }

    GLenum fenceStatus = glClientWaitSync(fence, GL_SYNC_FLUSH_COMMANDS_BIT, 0);

    switch (fenceStatus) {
        case GL_ALREADY_SIGNALED:
            [[fallthrough]];
        case GL_CONDITION_SATISFIED:
            return true;
        case GL_TIMEOUT_EXPIRED:
            return false;
        case GL_WAIT_FAILED:
            throw std::runtime_error("glClientWaitSync failed. " + glErrors());
            return false;
        default:
            assert(false); // unreachable
            return false;
    }
}

} // namespace gl
} // namespace mbgl