#include <mbgl/test/util.hpp>
#include <mbgl/test/stub_file_source.hpp>

#include <mbgl/map/map.hpp>
#include <mbgl/platform/default/headless_display.hpp>
#include <mbgl/platform/default/headless_view.hpp>
#include <mbgl/layer/custom_layer.hpp>
#include <mbgl/util/io.hpp>
#include <mbgl/util/mat4.hpp>
#include <mbgl/util/run_loop.hpp>

using namespace mbgl;

static const GLchar * vertexShaderSource = "attribute vec2 a_pos; void main() { gl_Position = vec4(a_pos, 0, 1); }";
static const GLchar * fragmentShaderSource = "void main() { gl_FragColor = vec4(0, 1, 0, 1); }";

// Not using any mbgl-specific stuff (other than a basic error-checking macro) in the
// layer implementation because it is intended to reflect how someone using custom layers
// might actually write their own implementation.

class TestLayer {
public:
    ~TestLayer() {
        if (program) {
            MBGL_CHECK_ERROR(glDeleteBuffers(1, &buffer));
            MBGL_CHECK_ERROR(glDetachShader(program, vertexShader));
            MBGL_CHECK_ERROR(glDetachShader(program, fragmentShader));
            MBGL_CHECK_ERROR(glDeleteShader(vertexShader));
            MBGL_CHECK_ERROR(glDeleteShader(fragmentShader));
            MBGL_CHECK_ERROR(glDeleteProgram(program));
        }
    }

    void initialize() {
        program = MBGL_CHECK_ERROR(glCreateProgram());
        vertexShader = MBGL_CHECK_ERROR(glCreateShader(GL_VERTEX_SHADER));
        fragmentShader = MBGL_CHECK_ERROR(glCreateShader(GL_FRAGMENT_SHADER));

        MBGL_CHECK_ERROR(glShaderSource(vertexShader, 1, &vertexShaderSource, nullptr));
        MBGL_CHECK_ERROR(glCompileShader(vertexShader));
        MBGL_CHECK_ERROR(glAttachShader(program, vertexShader));
        MBGL_CHECK_ERROR(glShaderSource(fragmentShader, 1, &fragmentShaderSource, nullptr));
        MBGL_CHECK_ERROR(glCompileShader(fragmentShader));
        MBGL_CHECK_ERROR(glAttachShader(program, fragmentShader));
        MBGL_CHECK_ERROR(glLinkProgram(program));
        a_pos = glGetAttribLocation(program, "a_pos");

        GLfloat background[] = { -1,-1, 1,-1, -1,1, 1,1 };
        MBGL_CHECK_ERROR(glGenBuffers(1, &buffer));
        MBGL_CHECK_ERROR(glBindBuffer(GL_ARRAY_BUFFER, buffer));
        MBGL_CHECK_ERROR(glBufferData(GL_ARRAY_BUFFER, 8 * sizeof(GLfloat), background, GL_STATIC_DRAW));
    }

    void render() {
        MBGL_CHECK_ERROR(glUseProgram(program));
        MBGL_CHECK_ERROR(glBindBuffer(GL_ARRAY_BUFFER, buffer));
        MBGL_CHECK_ERROR(glEnableVertexAttribArray(a_pos));
        MBGL_CHECK_ERROR(glVertexAttribPointer(a_pos, 2, GL_FLOAT, GL_FALSE, 0, NULL));
        MBGL_CHECK_ERROR(glDisable(GL_STENCIL_TEST));
        MBGL_CHECK_ERROR(glDisable(GL_DEPTH_TEST));
        MBGL_CHECK_ERROR(glDrawArrays(GL_TRIANGLE_STRIP, 0, 4));
    }

    GLuint program = 0;
    GLuint vertexShader = 0;
    GLuint fragmentShader = 0;
    GLuint buffer = 0;
    GLuint a_pos = 0;
};

TEST(CustomLayer, Basic) {
    util::RunLoop loop;

    auto display = std::make_shared<mbgl::HeadlessDisplay>();
    HeadlessView view(display, 1);
    StubFileSource fileSource;

    Map map(view, fileSource, MapMode::Still);
    map.setStyleJSON(util::read_file("test/fixtures/api/empty.json"), "");
    map.addCustomLayer(
        "custom",
        [] (void* context) {
            reinterpret_cast<TestLayer*>(context)->initialize();
        },
        [] (void* context, const CustomLayerRenderParameters&) {
            reinterpret_cast<TestLayer*>(context)->render();
        },
        [] (void* context) {
            delete reinterpret_cast<TestLayer*>(context);
        }, new TestLayer());

    test::checkImage("test/fixtures/custom_layer/basic", test::render(map));
}