ContainerWeightedPlayer

package com.happykiller.weightlimit.player.inventory.container;

import com.happykiller.weightlimit.items.ItemBackpack;
import com.happykiller.weightlimit.player.inventory.InventoryWeightLimit;

import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.entity.player.InventoryPlayer;
import net.minecraft.inventory.Container;
import net.minecraft.inventory.Slot;
import net.minecraft.item.ItemArmor;
import net.minecraft.item.ItemStack;
import net.minecraftforge.fml.relauncher.Side;
import net.minecraftforge.fml.relauncher.SideOnly;

public class ContainerWeightedPlayer extends Container {

    private static final int ARMOR_START = InventoryWeightLimit.INV_SIZE, ARMOR_END = ARMOR_START + 3,
            INV_START = ARMOR_END + 1, INV_END = INV_START + 26,
            HOTBAR_START = INV_END + 1, HOTBAR_END = HOTBAR_START + 8;

    private final EntityPlayer thePlayer;

    public ContainerWeightedPlayer(EntityPlayer player, InventoryPlayer invPlayer, InventoryWeightLimit invW) {
        thePlayer = player;

        int i;
        int j;

        this.addSlotToContainer(new SlotWeightLimit(invW, 0, 80, 8));

        for (i = 0; i < 4; ++i) {

            final int k = i;

            this.addSlotToContainer(new Slot(invPlayer, invPlayer.getSizeInventory() - 1 - i, 8, 8 + i * 18) {

                public int getSlotStackLimit() {
                    return 1;
                }

                public boolean isItemValid(ItemStack stack) {
                    if (stack == null) return false;
                    return stack.getItem().isValidArmor(stack, k, thePlayer);
                }

                @SideOnly(Side.CLIENT)
                public String getSlotTexture() {
                    return ItemArmor.EMPTY_SLOT_NAMES[k];
                }
            });
        }

        for (i = 0; i < 3; ++i) {
            for (j = 0; j < 9; ++j) {
                this.addSlotToContainer(new Slot(invPlayer, j + (i + 1) * 9, 8 + j * 18, 84 + i * 18));
            }
        }

        for (i = 0; i < 9; ++i) {
            this.addSlotToContainer(new Slot(invPlayer, i, 8 + i * 18, 142));
        }
    }

    public boolean canInteractWith(EntityPlayer playerIn) {
        return true;
    }

    public ItemStack transferStackInSlot(EntityPlayer player, int i) {
        ItemStack stack = null;

        Slot slot = (Slot)this.inventorySlots.get(i);

        if(slot != null && slot.getHasStack()) {
            ItemStack stack1 = slot.getStack();

            stack = stack1.copy();

            if(i < INV_START) {
                if(!this.mergeItemStack(stack1, INV_START, HOTBAR_END + 1, true)) {
                    return null;
                }

                slot.onSlotChange(stack1, stack);
            }else {
                if(stack1.getItem() instanceof ItemBackpack) {
                    if(!this.mergeItemStack(stack1, 0, InventoryWeightLimit.INV_SIZE, false)) {
                        return null;
                    }
                }else if(stack1.getItem() instanceof ItemArmor) {
                    int type = ((ItemArmor)stack1.getItem()).armorType;

                    if(!this.mergeItemStack(stack1, ARMOR_START + type, ARMOR_START + type + 1, false)) {
                        return null;
                    }
                }else if(i >= INV_START && i < HOTBAR_START) {
                    if(!this.mergeItemStack(stack1, HOTBAR_START, HOTBAR_START + 1, false)) {
                        return null;
                    }
                }else if(i >= HOTBAR_START && i < HOTBAR_END + 1) {
                    if(!this.mergeItemStack(stack1, INV_START, INV_END + 1, false)) {
                        return null;
                    }
                }
            }

            if(stack1.stackSize == 0) {
                slot.putStack((ItemStack)null);
            }else {
                slot.onSlotChanged();
            }

            if(stack1.stackSize == stack.stackSize) {
                return null;
            }

            slot.onPickupFromSlot(thePlayer, stack1); //TODO If problems are caused, change to player.
        }

        return stack;
    }
}