Add loot API and use it in tsm_railcorridors

mods/CORE/mcl_loot/description.txt

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+API for filling a chest with random treasures.

mods/CORE/mcl_loot/init.lua

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+mcl_loot = {}
+
+--[[
+Select a number of itemstacks out of a pool of treasure definitions randomly.
+
+Parameters:
+* loot_definitions: Probabilities and information about the loot to select. Syntax:
+
+{
+	stacks_min = 1,	-- Mamimum number of item stacks to get
+	stacks_max = 3, -- Number of repetitions, maximum
+	items = { -- Table of possible loot items. This function selects between stacks_min and stacks_max of these.
+		{
+		itemstring = "example:item1", -- Which item to select
+		amount_min = 1,		-- Minimum size of itemstack. Optional (default: 1)
+		amount_max = 10,	-- Maximum size of item stack. Must not exceed item definition's stack_max. Optional (default: 1)
+		wear_min = 1,		-- Minimum wear value. Must be at lest 1. Optional (default: no wear)
+		wear_max = 1,		-- Maxiumum wear value. Must be at lest 1. Optional (default: no wear)
+		weight = 5,		-- Likelihood of this item being selected
+		},
+		{ -- more tables like above, one table per item stack }
+	}
+}
+* pr: PseudoRandom object
+
+How weight works: The probability of a single item stack being selected is weight/total_weight, with
+total_weight being the sum of all weight values in the items table.
+
+Returns: Table of itemstrings
+]]
+function mcl_loot.get_loot(loot_definitions, pr)
+	local items = {}
+
+	local total_weight = 0
+	for i=1, #loot_definitions.items do
+		total_weight = total_weight + loot_definitions.items[i].weight
+	end
+
+	local stacks = pr:next(loot_definitions.stacks_min, loot_definitions.stacks_max)
+	for s=1, stacks do
+		local r = pr:next(1, total_weight)
+
+		local accumulated_weight = 0
+		local item
+		for i=1, #loot_definitions.items do
+			accumulated_weight = accumulated_weight + loot_definitions.items[i].weight
+			if accumulated_weight >= r then
+				item = loot_definitions.items[i]
+				break
+			end
+		end
+		if item then
+			local itemstring = item.itemstring
+			if item.amount_min and item.amount_max then
+				itemstring = itemstring .. " " .. pr:next(item.amount_min, item.amount_max)
+			end
+			if item.wear_min and item.wear_max then
+				if not item.amount_min and not item.amount_max then
+					itemstring = itemstring .. " 1"
+				end
+				itemstring = itemstring .. " " .. pr:next(item.wear_min, item.wear_max)
+			end
+			table.insert(items, itemstring)
+		else
+			minetest.log("error", "[mcl_loot] INTERNAL ERROR! Failed to select random loot item!")
+		end
+	end
+
+	return items
+end
+
+--[[
+Repeat mcl_loot.get_loot multiple times for various loot_definitions.
+Useful for filling chests.
+
+* multi_loot_definitions: Table of loot_definitions (see mcl_loot.get_loot)
+* pr: PseudoRandom object
+
+Returns: Table of itemstrings ]]
+function mcl_loot.get_multi_loot(multi_loot_definitions, pr)
+	local items = {}
+	for m=1, #multi_loot_definitions do
+		local group = mcl_loot.get_loot(multi_loot_definitions[m], pr)
+		for g=1, #group do
+			table.insert(items, group[g])
+		end
+	end
+	return items
+end

mods/CORE/mcl_loot/mod.conf

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+name = mcl_loot