Add basic support for progressive mode

What’s lacking: Saving held items, a game setting.

init.lua

@@ -300,7 +300,7 @@ local function get_formspec(player)
 	end
 
 	table.insert(fs, "container[0,5.6]")
-	if data.recipes then
+	if data.recipes and #data.recipes > 0 then
 		recipe_fs(fs, data)
 	elseif data.prev_item then
 		table.insert(fs, ("label[2,1;%s]"):format(esc(data.show_usages
@@ -319,12 +319,12 @@ end
 local function execute_search(data)
 	local filter = data.filter
 	if filter == "" then
-		data.items = init_items
+		data.items = visible_items(data)
 		return
 	end
 	data.items = {}
 
-	for _, item in ipairs(init_items) do
+	for _, item in ipairs(visible_items(data)) do
 		local def = minetest.registered_items[item]
 		local desc = def and minetest.get_translated_string(data.lang_code, def.description)
 
@@ -343,7 +343,7 @@ local function on_receive_fields(player, fields)
 		data.pagenum = 1
 		data.prev_item = nil
 		data.recipes = nil
-		data.items = init_items
+		data.items = visible_items(data)
 		return true
 
 	elseif (fields.key_enter_field == "filter" or fields.search)
@@ -398,9 +398,9 @@ local function on_receive_fields(player, fields)
 			data.show_usages = nil
 		end
 		if data.show_usages then
-			data.recipes = usages_cache[item]
+			data.recipes = known_recipes(data, usages_cache[item])
 		else
-			data.recipes = recipes_cache[item]
+			data.recipes = known_recipes(data, recipes_cache[item])
 		end
 		data.prev_item = item
 		data.rnum = 1
@@ -415,7 +415,10 @@ minetest.register_on_joinplayer(function(player)
 	player_data[name] = {
 		filter = "",
 		pagenum = 1,
-		items = init_items,
+		items = {},
+		held_items = {},
+		held_groups = {},
+		known_items = {},
 		lang_code = info.lang_code
 	}
 end)
@@ -436,3 +439,124 @@ sfinv.register_page("mtg_craftguide:craftguide", {
 		end
 	end
 })
+
+-- ~ Progressive-mode support ~
+-- [The vast majority of changes to mtg_craftguide are found here!]
+function table_to_str(table)
+	local ret = "["
+	for k,v in pairs(table) do
+		ret = ret .. "; " .. k .. " - "
+		if type(v) == "table" then
+			ret = ret .. table_to_str(v)
+		else
+			ret = ret .. v
+		end
+	end
+	return ret .. "]"
+end
+
+-- Given a player’s data and a recipe, return whether or not that recipe
+-- is “known” by the player. (That is, they have held all necessary inputs.)
+function known_recipe(data, recipe)
+	for _,input in pairs(recipe.items) do
+		if (not data.held_items[input:gsub(" .*", "")]) and (not data.held_groups[input])  then
+			return false
+		end
+	end
+	return true
+end
+
+-- From a table of recipes, return a sub-table of recipes that are “known.”
+function known_recipes(data, recipes)
+	local ret = {}
+	if recipes then
+		for _,recipe in pairs(recipes) do
+			if known_recipe(data, recipe) then
+				table.insert(ret, recipe)
+			end
+		end
+	end
+	return ret
+end
+
+-- Given a player’s data and an item-name, return a table of all items the
+-- player should “know of” that can be crafted from that item.
+function known_crafting_outputs(data, item_name)
+	local outputs = {}
+	local uses = usages_cache[item_name]
+	if uses then
+		for _,recipe in pairs(uses) do
+			if known_recipe(data, recipe) then
+				local out_name = recipe.output
+				out_name = out_name:gsub(" .*", "")
+				table.insert(outputs, out_name)
+			end
+		end
+	end
+	return outputs
+end
+
+-- Returns a table of all items that are “known” to the player; either they’ve
+-- been held by them, or they’re craftable using solely objects held previously.
+function visible_items(data)
+	local ret = {}
+	for item,_ in pairs(data.held_items) do
+		table.insert(ret, item)
+	end
+	for item,_ in pairs(data.known_items) do
+		table.insert(ret, item)
+	end
+	return ret
+end
+
+-- To be executed whenever a player gains/picks up an item.
+-- If the item is new, it is added to the player’s held_items table, and then
+-- possible outputs from it (and other known items) are added to known_items.
+function update_known_items(player, item_name)
+	local name = player:get_player_name()
+	local data = player_data[name]
+
+	if not data.held_items[item_name] then
+		-- Mark the new item as known.
+		data.held_items[item_name] = true
+
+		-- Mark the new item’s groups as known.
+		local groups = minetest.registered_items[item_name].groups
+		for group,rating in pairs(groups) do
+			if rating > 0 then
+				data.held_groups["group:" .. group] = true
+			end
+		end
+
+		-- Mark items craftable with this (and other) items as known.
+		for _,out_item_name in pairs(known_crafting_outputs(data, item_name)) do
+			data.known_items[out_item_name] = true
+		end
+
+		-- Reset item-list.
+		data.items = visible_items(data)
+
+		-- Notify the player.
+		minetest.chat_send_player(name, S("New recipes unlocked!"))
+	end
+end
+
+minetest.register_on_item_pickup(function(itemstack, picker)
+	update_known_items(picker, itemstack:get_name())
+end)
+
+minetest.register_on_player_inventory_action(function(player, action, inv, inv_info)
+	if action == "put" then
+		update_known_items(player, inv_info.stack:get_name())
+	end
+end)
+
+minetest.register_on_dignode(function(pos, oldnode, digger)
+	update_known_items(digger, oldnode.name)
+end)
+
+minetest.register_on_craft(function(itemstack, player)
+		update_known_items(player, itemstack:get_name())
+end)
+
+