/*
 * Copyright (C) 2010 David McPaul
 *
 * All rights reserved. Distributed under the terms of the MIT License.
 */

// This class merges buffers together
// Merge is called everytime a primary buffer needs to be passed downstream
// This should allow different framerates to be handled by buffering slower 
// buffer producers and discarding buffers from faster producers
// TODO ColorConversion

#include "BufferMixer.h"

BufferMixer::BufferMixer() {
}

BufferMixer::~BufferMixer() {
}

bool
BufferMixer::isBufferAvailable() {
        return groupedBuffers[0] != NULL;
}

// Should only be called after checking with isBufferAvailable
BBuffer *
BufferMixer::GetOutputBuffer() {
        // Do the merging of all buffers in the groupedBuffers map
        // into the primary buffer and return that buffer.
        // The primary buffer is removed;
        
        BBuffer *outputBuffer = groupedBuffers[0];
        groupedBuffers[0] = NULL;
        
        std::map<int32, BBuffer*>::iterator each;
        
        for (each=groupedBuffers.begin(); each != groupedBuffers.end(); each++) {
                if (each->second != outputBuffer) {
                        if (each->second != NULL) {
                                Merge(each->second, outputBuffer);
                        }
                }
        }
        
        return outputBuffer;
}

#define ALPHABLEND(source, destination, alpha) (((destination) * (256 - (alpha)) + (source) * (alpha)) >> 8)

void
BufferMixer::Merge(BBuffer *input, BBuffer *output) {
        // Currently only deals with RGBA32
        
        uint8 *source = (uint8 *)input->Data();
        uint8 *destination = (uint8 *)output->Data();
        uint32 size = input->Header()->size_used / 4;
        uint8 alpha = 0;
        uint8 c1, c2, c3;

        for (uint32 i=0; i<size; i++) {
                c1    = *source++;
                c2    = *source++;
                c3    = *source++;
                alpha = *source++;
                destination[0] = ALPHABLEND(c1, destination[0], alpha);
                destination[1] = ALPHABLEND(c2, destination[1], alpha);
                destination[2] = ALPHABLEND(c3, destination[2], alpha);
                destination[3] = 0x00;
                destination += 4;
        }
}

void
BufferMixer::AddBuffer(int32 id, BBuffer *buffer, bool isPrimary) {
        BBuffer *oldBuffer;
        
        if (isPrimary) {
                oldBuffer = groupedBuffers[0];
                groupedBuffers[0] = buffer;
        } else {
                oldBuffer = groupedBuffers[id];
                groupedBuffers[id] = buffer;
        }

        if (oldBuffer != NULL) {
                oldBuffer->Recycle();
        }
}

void 
BufferMixer::RemoveBuffer(int32 id) {
        BBuffer *oldBuffer;

        if (uint32(id) < groupedBuffers.size()) {
                oldBuffer = groupedBuffers[id];
                groupedBuffers[id] = NULL;
        
                if (oldBuffer != NULL) {
                        oldBuffer->Recycle();
                }
        }       
}