-- inventory management, trading and handling of quest items for talking to NPCs

-- cache the inventory of NPCs for easier access
yl_speak_up.npc_inventory = {}

-- where are they stored on the disk?
yl_speak_up.get_inventory_save_path = function(n_id)
    return yl_speak_up.worldpath .. yl_speak_up.inventory_path .. DIR_DELIM .. "inv_" .. n_id .. ".json"
end


-- access the inventory of the NPC (only possible for players with the right priv)
yl_speak_up.get_fs_inventory = function(player, n_id, npc_name)
	return "size[12,11]" ..
		"label[2,-0.2;Inventory of "..minetest.formspec_escape(npc_name)..
			" (ID: "..tostring(n_id).."):]"..
		"list[detached:yl_npc_"..tostring(n_id)..";npc_main;0,0.3;12,6;]" ..
		"list[current_player;main;2,6.85;8,1;]" ..
		"list[current_player;main;2,8.08;8,3;8]" ..
		"listring[detached:yl_npc_"..tostring(n_id)..";npc_main]" ..
		"listring[current_player;main]" ..
		"button[10.0,10.2;2,0.9;back_from_inventory;Back]"
end


-- save the inventory of the NPC with the id n_id
yl_speak_up.save_npc_inventory = function( n_id )
	-- only save something if we actually can
	if(not(n_id) or not(yl_speak_up.npc_inventory[ n_id ])) then
		return
	end
	-- convert the inventory data to something we can actually store
	local inv = yl_speak_up.npc_inventory[ n_id ]
	local inv_as_table = {}
	for i=1, inv:get_size("npc_main") do
		local stack = inv:get_stack("npc_main", i)
		-- only save those slots that are not empty
		if(not(stack:is_empty())) then
			inv_as_table[ i ] = stack:to_table()
		end
	end
	-- convert the table into json
	local json = minetest.write_json( inv_as_table )
	-- get a file name for storing the data
	local file_name = yl_speak_up.get_inventory_save_path(n_id)
	-- actually store it on disk
	minetest.safe_file_write(file_name, json)
end


-- create and load the detached inventory in yl_speak_up.after_activate;
-- direct access to this inventory is only possible for players with the right privs
yl_speak_up.load_npc_inventory = function(n_id)
	if(not(n_id)) then
		return
	end
	-- the inventory is already loaded
	if( yl_speak_up.npc_inventory[ n_id ]) then
		return
	end
	-- create the detached inventory (it is empty for now)
	local npc_inv = minetest.create_detached_inventory("yl_npc_"..tostring(n_id), {
		allow_move = function(inv, from_list, from_index, to_list, to_index, count, player)
			if(not(yl_speak_up.may_edit_npc(player, n_id))) then
				return 0
			end
			return count
		end,
	        -- Called when a player wants to move items inside the inventory.
	        -- Return value: number of items allowed to move.

	        allow_put = function(inv, listname, index, stack, player)
			if(not(yl_speak_up.may_edit_npc(player, n_id))) then
				return 0
			end
			return stack:get_count()
		end,
	        -- Called when a player wants to put something into the inventory.
	        -- Return value: number of items allowed to put.
	        -- Return value -1: Allow and don't modify item count in inventory.

	        allow_take = function(inv, listname, index, stack, player)
			if(not(yl_speak_up.may_edit_npc(player, n_id))) then
				return 0
			end
			return stack:get_count()
		end,
	        -- Called when a player wants to take something out of the inventory.
	        -- Return value: number of items allowed to take.
	        -- Return value -1: Allow and don't modify item count in inventory.

		-- log inventory changes (same way as modifications to chest inventories)
	        on_move = function(inv, from_list, from_index, to_list, to_index, count, player)
			minetest.log("action", "(yl_speak_up) "..player:get_player_name() ..
				" moves stuff in inventory of NPC " .. tostring(n_id))

		end,
	        on_put = function(inv, listname, index, stack, player)
			minetest.log("action", "(yl_speak_up) "..player:get_player_name() ..
				" moves " .. stack:get_name() ..
				" to inventory of NPC " .. tostring(n_id))

		end,
	        on_take = function(inv, listname, index, stack, player)
			minetest.log("action", "(yl_speak_up) "..player:get_player_name() ..
				" takes " .. stack:get_name() ..
				" from inventory of NPC " .. tostring(n_id))
		end,
	})
	-- the NPC needs enough room for trade items, payment and questitems
	npc_inv:set_size("npc_main", 6*12)

	-- cache a pointer to this inventory for easier access
	yl_speak_up.npc_inventory[ n_id ] = npc_inv

	-- find out where the inventory of the NPC is stored
	local file_name = yl_speak_up.get_inventory_save_path(n_id)

	-- load the data from the file
	local file, err = io.open(file_name, "r")
	if err then
		return
	end
	io.input(file)
	local text = io.read()
	local inv_as_table = minetest.parse_json(text)
	io.close(file)

	if(type(inv_as_table) ~= "table") then
		return
	end

	-- restore the inventory
	for i=1, npc_inv:get_size("npc_main") do
		npc_inv:set_stack("npc_main", i, ItemStack( inv_as_table[ i ]))
	end
end