#include "Draw.h"

namespace NB{

DrawWarning::DrawWarning(const std::string& msg) : std::runtime_error(msg) {}

uint8_t GLSLTypeSize(GLenum type) {
    switch(type) {
    case GL_SHORT:
    case GL_UNSIGNED_SHORT:
    case GL_HALF_FLOAT:
        return 2;
        break;
    case GL_INT:
    case GL_UNSIGNED_INT:
    case GL_FLOAT:
        return 4;
        break;
    case GL_DOUBLE:
        return 8;
        break;
    default:
        return 1;
        break;
    }
}

uint8_t GLSLPrimitiveVertexSize(GLenum type, unsigned int num_prims) {
    switch(type) {
    case GL_POINTS:
        return num_prims;
    case GL_LINES:
        return num_prims*2;
        break;
    case GL_LINE_STRIP:
        return num_prims+1;
        break;
    case GL_LINE_LOOP:
        return num_prims;
        break;
    case GL_TRIANGLES:
        return num_prims*3;
        break;
    case GL_TRIANGLE_STRIP:
    case GL_TRIANGLE_FAN:
        return num_prims+2;
        break;
    case GL_QUADS:
        return 4*num_prims;
        break;
    case GL_QUAD_STRIP:
        return 2*num_prims+2;
        break;
    default:
        return num_prims;
        break;
    }
}

DrawBuffer::DrawBuffer(
    std::vector<VertexAttribute> vas,
    const Shader& shader
) : _vertex_attributes(vas), _shader(shader),
    _vert_data(GL_ARRAY_BUFFER), _elmt_data(GL_ELEMENT_ARRAY_BUFFER) {}

unsigned int DrawBuffer::vertSize() const {
    size_t num_attrs = _vertex_attributes.size();
    size_t vert_size = 0;
    for (int i = 0; i < num_attrs; ++i) {
        vert_size += _vertex_attributes[i].GLSLSize*GLSLTypeSize(_vertex_attributes[i].GLSLType);
    }
    return vert_size;
}

std::vector<VertexAttributePointer> DrawBuffer::getLayout() const {
    unsigned int num_attrs = _vertex_attributes.size();
    std::vector<VertexAttributePointer> ret(num_attrs);
    for (int i = 0; i < num_attrs; ++i) {
        ret[i] = _vertex_attributes[i].ptr;
    }

    return ret;
}

void DrawBuffer::draw() const {
    _shader.use();
    glBindVertexArray(_VAO);
    glDrawElements(_gl_primitive_type, _elmt_data.size(), GL_UNSIGNED_INT, 0);
    glBindVertexArray(0);
}

const Shader DrawBuffer::shader() const {
    return _shader;
}

bool DrawBuffer::keepLocalElement() const { return _elmt_data.keepLocal(); }

bool DrawBuffer::keepLocalVertex() const { return _vert_data.keepLocal(); }

unsigned int DrawBuffer::elementBufferID() const { return _elmt_data.id(); }

unsigned int DrawBuffer::vertexBufferID() const { return _vert_data.id(); }

bool DrawBuffer::keepLocalElement(bool keep) { return _elmt_data.keepLocal(keep); }

bool DrawBuffer::keepLocalVertex(bool keep) { return _vert_data.keepLocal(keep); }

const Shader DrawBuffer::shader(const Shader& new_shader) {
    _shader = new_shader;
    return _shader;
}

std::vector<VertexAttributePointer> DrawBuffer::setLayout() {
    int vert_size = vertSize();
    unsigned int num_attrs = _vertex_attributes.size();
    std::vector<VertexAttributePointer> ret(num_attrs);
    unsigned int curr_byte = 0;
    for (int i = 0; i < num_attrs; ++i) {
        _vertex_attributes[i].ptr.stride = vert_size;
        _vertex_attributes[i].ptr.offset = curr_byte;
        curr_byte += _vertex_attributes[i].GLSLSize * GLSLTypeSize(_vertex_attributes[i].GLSLType);
        ret[i] = _vertex_attributes[i].ptr;
    }

    return getLayout();
}

std::vector<VertexAttributePointer> DrawBuffer::setLayout(std::vector<VertexAttributePointer> vap) {
    unsigned int num_attrs = _vertex_attributes.size();
    if (vap.size() != num_attrs) {
        throw DrawWarning("DrawBuffer Vertex Attributes and passed Vertex Attributes do not match.");
    }
    for (int i = 0; i < num_attrs; ++i) {
        if (vap[i].stride == -1) {
            throw DrawWarning("Unset Vertex Attribute Pointer in index " + std::to_string(i) + ".");
        }
        _vertex_attributes[i].ptr = vap[i];
    }

    return getLayout();
}

void DrawBuffer::generateElementBuffer(unsigned int num_prims, GLenum gl_primitive_type) {
    generateElementBuffer(std::vector<unsigned int>(GLSLPrimitiveVertexSize(gl_primitive_type, num_prims)));
}

void DrawBuffer::generateElementBuffer(std::vector<unsigned int> elements, GLenum gl_primitive_type) {
    _num_prims = elements.size();
    _gl_primitive_type = gl_primitive_type;
    _elmt_data.setData(elements);
}

void DrawBuffer::generateVertexBuffer(unsigned int num_verts) {
    generateVertexBuffer(std::vector<unsigned char>(num_verts * vertSize()));
}

void DrawBuffer::generateVertexBuffer(std::vector<unsigned char> vert_data) {
    int vert_size = vertSize();
    if (vert_data.size() % vert_size != 0) {
        throw DrawWarning("Starting data does not match vertex size of " + std::to_string(vert_size) + ".");
    }
    _num_verts = vert_data.size() / vert_size;
    unsigned int num_attrs = _vertex_attributes.size();
    for (int i = 0; i < num_attrs; ++i) {
        if (_vertex_attributes[i].ptr.stride == -1) {
            setLayout();
            i = num_attrs+1;
        }
    }

    // TODO: Make it not static draw all the time

    glGenVertexArrays(1, &_VAO);
    glBindVertexArray(_VAO);
    _vert_data.setData(vert_data);
    _elmt_data.bind();

    for (GLuint i = 0; i < num_attrs; ++i) {
        glVertexAttribPointer(
            i,
            _vertex_attributes[i].GLSLSize,
            _vertex_attributes[i].GLSLType,
            _vertex_attributes[i].GLSLNormalization,
            _vertex_attributes[i].ptr.stride,
            (void*)(_vertex_attributes[i].ptr.offset)
        );
        glEnableVertexAttribArray(i);
    }
    glBindVertexArray(0);
}

void DrawBuffer::loadElementBuffer(const std::vector<unsigned int>& elements, unsigned int offset, GLenum gl_primitive_type) {
    glBindVertexArray(_VAO);
    if (!_elmt_data.isInitialized()) {
        std::vector<unsigned int> load_data(offset);
        load_data.insert(load_data.end(), elements.begin(), elements.end());
        generateElementBuffer(load_data);
    } else {
        if (gl_primitive_type != _gl_primitive_type) {
            throw DrawWarning("Attempting to overload GL primitive type.");
        }
        _elmt_data.loadData(elements, offset);
    }
    glBindVertexArray(0);
}

void DrawBuffer::loadVertexBuffer(const std::vector<unsigned char>& data, unsigned int offset) {
    glBindVertexArray(_VAO);
    if (!_vert_data.isInitialized()) {
        std::vector<unsigned char> load_data(offset);
        load_data.insert(load_data.end(), data.begin(), data.end());
        generateVertexBuffer(load_data);
    } else {
        _vert_data.loadData(data, offset);
    }
    glBindVertexArray(0);
}

}