#include "Mesh.h"
#include "Utilities.h"
#include "Vertex.h"

UINT Mesh::init(IDirect3DDevice9* pD3DDevice)
{
    UINT error = 0;

    error = createVertexBuffer(pD3DDevice);
    CheckError(error);

    error = createIndexBuffer(pD3DDevice);
    CheckError(error);

    return 0;
}

void Mesh::update(FLOAT dt)
{
}

void Mesh::render(IDirect3DDevice9* pD3DDevice)
{
    // 1. set mesh data
    pD3DDevice->SetStreamSource(0, _pVertexBuffer, 0, _vertexStride);
    pD3DDevice->SetFVF(FVF);

    // 2. draw call
    // vertex buffer only 
    pD3DDevice->DrawPrimitive(D3DPT_TRIANGLELIST, 0, _vertexCount / 3); 
}

void Mesh::deInit()
{
    safeRelease(_pIndexBuffer);
    safeRelease(_pVertexBuffer);
}

UINT Mesh::createVertexBuffer(IDirect3DDevice9* pD3DDevice)
{
    // 1. define mesh parameters
    _vertexCount = 3;
    _vertexStride = sizeof(Vertex);

    // 2. create vertex buffer object WITHOUT data
    HRESULT hr = pD3DDevice->CreateVertexBuffer(
        _vertexCount * _vertexStride, // vertex buffer size in bytes
        D3DUSAGE_WRITEONLY, // how to access the buffer
        FVF, // FVF - Flexible Vertex Format
        D3DPOOL_MANAGED, // video memory management
        &_pVertexBuffer, // vertex buffer object
        nullptr // not used anymore
    );
    CheckFailed(hr, 300);

    // 3. set vertex data
    Vertex* pVertices = nullptr;

    hr = _pVertexBuffer->Lock(0, 0, reinterpret_cast<void**>(&pVertices), 0); // transfer vertex buffer from video memory to cpu memory
    CheckFailed(hr, 310);

    // fill vertex buffer with data
    pVertices[0] = Vertex(0.0f, 0.5f, 0.0f);
    pVertices[1] = Vertex(0.5f, -0.5f, 0.0f);
    pVertices[2] = Vertex(-0.5f, -0.5f, 0.0f);

    hr = _pVertexBuffer->Unlock(); // transfer vertex buffer back from cpu memory to video memory
    CheckFailed(hr, 320);

    pVertices = nullptr;

    return 0;
}

UINT Mesh::createIndexBuffer(IDirect3DDevice9* pD3DDevice)
{
    return 0;
}