-- show a list of all trades

-- the player is accessing the trade list
yl_speak_up.input_trade_list = function(player, formname, fields)
        local pname = player:get_player_name()
	local d_id = yl_speak_up.speak_to[pname].d_id
	local n_id = yl_speak_up.speak_to[pname].n_id

        local dialog = yl_speak_up.speak_to[pname].dialog

	if(not(dialog.trades)) then
		dialog.trades = {}
	end

	-- the player wants to add a new trade
	if(fields.trade_list_add_trade) then
		-- show the trade config dialog for a new trade
		yl_speak_up.show_fs(player, "add_trade_simple", "new")
		return
	end

	if(fields.trade_limit) then
		-- show a list of how much the NPC can buy and sell
		yl_speak_up.show_fs(player, "trade_limit")
		return
	end

	-- toggle between view of dialog option trades and trade list trades
	if(fields.show_dialog_option_trades
	  or fields.show_trade_list) then
		yl_speak_up.show_fs(player, "trade_list", fields.show_dialog_option_trades)
		return
	end

	-- go back to the main dialog
	if(fields.finished_trading) then
		yl_speak_up.show_fs(player, "talk", {n_id = n_id, d_id = d_id})
		return
	end

	-- normal mode: the player wants to see a particular trade
	for k,v in pairs(dialog.trades) do
		-- the "_" is necessary for the price button so that offer and price
		-- button can each have their tooltip *and* lead to the same dialog
		if(fields[ k ] or fields[ k.."_" ]) then
			yl_speak_up.show_fs(player, "trade_simple", k)
			return
		end
	end

	-- show the inventory of the NPC
	if(fields.show_inventory) then
		yl_speak_up.show_fs(player, "inventory")
		return
	end
	-- TODO: and otherwise?
end


-- show a list of all trades the NPC has to offer
-- if show_dialog_option_trades is set: show only those trades that are attached to options of dialogs;
--   otherwise show only those trades attached to the trade list
yl_speak_up.get_fs_trade_list = function(player, show_dialog_option_trades)
	if(not(player)) then
		return ""
	end
	local pname = player:get_player_name()

	-- which NPC is the player talking to?
	local n_id = yl_speak_up.speak_to[pname].n_id
	local dialog = yl_speak_up.speak_to[pname].dialog
	-- do we have all the necessary data?
	if(not(n_id) or not(dialog.n_npc)) then
		return "size[6,2]"..
			"label[0.2,0.5;Ups! This NPC lacks ID or name.]"..
		                "button_exit[2,1.5;1,0.9;exit;Exit]"
	end


	-- make sure the NPC has that table defined
	if(not(dialog.trades)) then
		dialog.trades = {}
	end

	yl_speak_up.load_npc_inventory(n_id)
	local npc_inv = minetest.get_inventory({type="detached", name="yl_speak_up_npc_"..tostring(n_id)})

	if(not(yl_speak_up.may_edit_npc(player, n_id))) then
		-- do not show trades attached to dialog options for players who cannot edit the NPC
		show_dialog_option_trades = false
	end

	local alternate_text = " I can offer you these trades.\n\n"..
				"Select one trade and then choose \"buy\" to actually buy something."..
				"\n\nThere may be more trades then those shown in the first row."..
				"\nPlease look at all my offers [that is, scroll down a bit]!"..
				"\n\n[$NPC_NAME$ looks expectantly at you.]"

	local pname_for_old_fs = yl_speak_up.get_pname_for_old_fs(pname)
	local formspec = {}
        local h = -0.8

	-- arrange the offers in yl_speak_up.trade_max_cols columns horizontally
	-- and yl_speak_up.trade_max_rows row vertically
	local row = 0
	local col = 0
	local anz_trades = 0

	-- the order in which the trades appear shall not change each time;
	-- but lua cannot sort the keys of a table by itself...
	local sorted_trades = {}
	for k in pairs(dialog.trades) do
		table.insert(sorted_trades, k)
	end
	table.sort(sorted_trades)

	for i, k in ipairs(sorted_trades) do
		local v = dialog.trades[ k ]
		  -- needs both to be negated because show_dialog_option_trades will most of the time be nil
		  -- and the actual value of v.d_id isn't of intrest here either
		if(   (not(show_dialog_option_trades) == not(v.d_id))
		  and v.pay and v.pay[1] and v.pay[1] ~= "" and v.buy and v.buy[1] and v.buy[1] ~= "") then
			local pay_stack = ItemStack(v.pay[1])
			local buy_stack = ItemStack(v.buy[1])
			-- do not show trades with nonexistant items
			if(  not(minetest.registered_items[ pay_stack:get_name() ])
			  or not(minetest.registered_items[ buy_stack:get_name() ])) then
				break
			end

			anz_trades = anz_trades + 1
			local kstr = tostring(minetest.formspec_escape(k))
			local sold_out = not(npc_inv:contains_item("npc_main", buy_stack))
			local color = "#a37e45" --"#777777"
			if(sold_out) then
				color = "#663333"
				-- still needs to contain kstr so that each button has a diffrent text
--				kstr = "sold out "..kstr
			end
			table.insert(formspec,
				"container["..tostring(0.5+(col*4.5))..","..
					      tostring(0.3+(row*6)).."]"..
				"style_type[button;bgcolor=#FF4444]"..
				"box[0,0;4.2,5.6;"..color.."]"..
				"item_image_button[1.0,0.2;3,3;"..
					tostring(v.buy[1])..";"..kstr..";]"..
				"item_image_button[2.0,3.4;2,2;"..
					-- the "_" at the end is necessary; we need a diffrent name
					-- here than kstr as that was used for another button (leading
					-- to the same result) just above
					tostring(v.pay[1])..";"..kstr.."_;]")
			if(sold_out) then
--				table.insert(formspec, "label[0,1.9;Sold out]\ncontainer_end[]")
				table.insert(formspec, "button[0,1.0;4.3,1.0;"..kstr.."__;Sold out]"..
							"\ncontainer_end[]")
			else
				-- show the price label only when the offer is in stock
				table.insert(formspec, "label[0,1.9;->]"..
							"label[0,4.4;Price:]\ncontainer_end[]")
			end
			col = col + 1
			if(col >= yl_speak_up.trade_max_cols) then
				col = 0
				row = row + 1
			end
		end
	end

	-- set button background color back to golden/brownish
	table.insert(formspec, "style_type[button;bgcolor=#a37e45]")
	h = (row+1) * 6 - 0.6
	h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
		"show_inventory",
		"Access and manage the inventory of the NPC. This is used for adding trade "..
			"items, getting collected payments and managing quest items.",
			"Show your inventory (only accessible to owner)!",
			true, nil, nil, pname_for_old_fs)

	-- allow players with the right priv to switch view between dialog option trades
	-- and those normal ones in the trade list
	if(yl_speak_up.may_edit_npc(player, n_id)) then
		if(not(show_dialog_option_trades)) then
			local text = "This is the trade list view (player view). "..
				"Show trades attached to dialog options."
			h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
				"show_dialog_option_trades",
				text, text,
				true, nil, nil, pname_for_old_fs)
		else
			local text = "These are trades attached to dialog options. "..
				"Show trade list trades (player view)."
			h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
				"show_trade_list",
				text, text,
				true, nil, nil, pname_for_old_fs)
		end
		-- button "add trade" for those who can edit the NPC (entering edit mode is not required)
		local text = "Add a new trade."
		h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
			"trade_list_add_trade",
			text, text,
			true, nil, nil, pname_for_old_fs)
		-- show a list of how much the NPC will buy and sell
		text = "Do not buy or sell more than what I will tell you."
		h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
			"trade_limit",
			text, text,
			true, nil, nil, pname_for_old_fs)
	end

	local text = "That was all. Let's continue talking."
	h = yl_speak_up.add_edit_button_fs_talkdialog(formspec, h,
		"finished_trading",
		text, text,
		true, nil, nil, pname_for_old_fs) -- button_exit

	-- if there are no trades, at least print a hint that there could be some here
	-- (a mostly empty formspec looks too boring and could irritate players)
	if(anz_trades == 0) then
		table.insert(formspec,
			"label[1,1;Sorry. There are currently no offers available.]")
	end

	-- edit mode makes no sense here in the trade list
	return yl_speak_up.show_fs_decorated(pname, nil, h, alternate_text, "",
                                        table.concat(formspec, "\n"), nil, h)
end