#include "HydraLightBufferManager.h"
#include "../scheduler/HydraTaskScheduler.h"
#include "../engine/HydraEngine.h"
#include "../task/buffer/HydraCreateGPUBufferTask.hpp"
#include "../task/buffer/HydraDeleteGPUBufferTask.hpp"
#include "../task/buffer/HydraUpdatePartialGPUBufferTask.hpp"
#include "../ecs/components/HydraLightComponent.h"

void HydraLightBufferManager::Initialise()
{
    m_light_lookup.resize(MAX_LIGHTS);
    
    for(uint32_t i = 0; i < MAX_LIGHTS; i ++)
    {
        m_available_lights.push(i);
        m_light_lookup[i] = INVALID_HYDRA_ID;
    }
    
    HydraTaskScheduler *task_scheduler = GetEngine()->TaskScheduler();
    HydraID create_gpu_buffer_task_id = task_scheduler->CreateTask<HydraCreateGPUBufferTask>(HydraThreadAffinity::Render);
    HydraCreateGPUBufferTask *task = static_cast<HydraCreateGPUBufferTask *>(task_scheduler->GetTask(create_gpu_buffer_task_id));
    task->Intialise("LightBuffer", 1, MAX_LIGHTS * sizeof(HydraLightComponent), &m_light_buffer_id, HYDRA_BUFFER_TYPE::HYDRA_SSBO_BUFFER);
    task_scheduler->WaitForTask(create_gpu_buffer_task_id);
}

void HydraLightBufferManager::Shutdown()
{
    HydraTaskScheduler *task_scheduler = GetEngine()->TaskScheduler();
    HydraID delete_gpu_buffer_task_id = task_scheduler->CreateTask<HydraDeleteGPUBufferTask>(HydraThreadAffinity::Render);
    HydraDeleteGPUBufferTask *task = static_cast<HydraDeleteGPUBufferTask *>(task_scheduler->GetTask(delete_gpu_buffer_task_id));
    task->Intialise(m_light_buffer_id);
    task_scheduler->WaitForTask(delete_gpu_buffer_task_id);
}

void HydraLightBufferManager::UpdateBuffer()
{
    void *buffer = static_cast<void *>(m_lights.data());
    HydraTaskScheduler *task_scheduler = GetEngine()->TaskScheduler();

    HydraID update_buffer_task_id = task_scheduler->CreateTask<HydraUpdatePartialGPUBufferTask>(HydraThreadAffinity::Render);
    HydraUpdatePartialGPUBufferTask *task = static_cast<HydraUpdatePartialGPUBufferTask *>(task_scheduler->GetTask(update_buffer_task_id));
    task->Intialise(m_light_buffer_id, 0, sizeof(HydraLightComponent) * m_lights.size(), buffer);
    task_scheduler->WaitForTask(update_buffer_task_id);
}

void HydraLightBufferManager::AddLight(HydraLightComponent light)
{
    std::lock_guard<std::mutex> lock(m_mutex);
    if(m_available_lights.size() == 0)
    {
        return;
    }

    auto it = std::find(m_light_lookup.begin(), m_light_lookup.end(), light.entity_id);
    
    if(it == m_light_lookup.end())
    {
        //light ID is not the index in the light buffer - this has to stay contiguous       
        m_lights.push_back(light);
        m_light_lookup[m_light_count] = light.entity_id;
        m_light_count++;
    }
    else
    {
        m_lights[m_light_lookup[*it]] = light;
    }
    
}

//Remove the light from the buffer and shuffle all of the others down to keep 
//the light buffer contiguous.
void HydraLightBufferManager::RemoveLight(HydraID entity_id)
{
    std::lock_guard<std::mutex> lock(m_mutex);
    auto it = std::find(m_light_lookup.begin(), m_light_lookup.end(), entity_id);
    if(it != m_light_lookup.end())
    {
        uint32_t remove_idx = it - m_light_lookup.begin();
        //end one - easy
        if(remove_idx == m_light_count-1)
        {
            m_lights.erase(m_lights.end()-1);
            m_light_count--;
            return;
        }


        HydraLightComponent light_to_delete = m_lights[remove_idx];
        HydraLightComponent light_to_move = m_lights[m_light_count-1];

        m_lights[remove_idx] = light_to_move;
        m_lights.erase(m_lights.end()-1);
        m_light_lookup[m_light_count-1] = INVALID_HYDRA_ID;
        m_light_lookup[remove_idx] = light_to_move.entity_id;
        m_light_count--;
    }
}

uint32_t HydraLightBufferManager::GetLightCount()
{
    return m_light_count;
}