A Lua script to extract Minecraft's assets from the repository format used by the Mojang launcher and ForgeGradle into regular directories. Requires Lua 5.2+/LuaJIT, LuaJSON, Penlight and LuaFileSystem

ExtractMinecraftAssets.lua

-- Extracts Minecraft's assets from the repository format used by the Mojang launcher and ForgeGradle into regular directories.
-- Requires Lua 5.2+/LuaJIT, LuaJSON, Penlight and LuaFileSystem

---------------------
-- Start of Config --
---------------------

-- The location of the index JSON file
local INDEX_FILE = [[C:\Users\USER\.gradle\caches\minecraft\assets\indexes\1.11.json]]

-- The directory to extract the assets to
local OUTPUT_DIR = [[C:\Users\USER\Documents\Minecraft\Mods\TestMod3\TestMod3_1.11.2\vanilla_assets]]

-------------------
-- End of Config --
-------------------

local json = require("json")
local path = require("pl.path")
local file = require("pl.file")
local pretty = require("pl.pretty")

--- Calls string.format and prints the result.
local function printf(formatStr, ...)
	print(formatStr:format(...))
end

--- Formats a number with thousands comma separators.
local function formatNumber(number)
	return pretty.number(number, "T")
end

--- Creates a directory, also creating any intermediate directories if they don't exist.
-- @return true on success or nil, the directory that couldn't be created and an error message on failure
local function mkdirs(directoryPath)
	local baseDirectory, thisDir = path.splitpath(directoryPath)
	
	if not path.isdir(baseDirectory) then -- If the base directory doesn't exist, try to create it
		local success, failedDirectory, errorMessage = mkdirs(baseDirectory)
		if not success then -- If creating the base directory fails, we can't create this directory
			return nil, failedDirectory, errorMessage
		end
	end
	
	local success, errorMessage = path.mkdir(directoryPath)
	if success then
		return true
	else
		return nil, directoryPath, errorMessage
	end
end

local function extractRepository(indexFilePath, outputDirPath)
	print("Extracting files from repository")
	printf("Index file: %s", indexFilePath)
	printf("Output dir: %s", outputDirPath)
	print("\n")
	
	local numSucceeded, numFailed, numSkipped = 0, 0, 0

	local function succeeded(...)
		numSucceeded = numSucceeded + 1
		printf(...)
	end
	
	local function failed(...)
		numFailed = numFailed + 1
		printf(...)
	end
	
	local function skipped(...)
		numSkipped = numSkipped + 1
		printf(...)
	end
	
	local index = json.decode(file.read(indexFilePath))
	
	local indexesDirPath = path.splitpath(indexFilePath)
	local objectsDirPath = path.join(indexesDirPath, "../objects")
	
	for filePath, fileData in pairs(index.objects) do
		local hash = fileData.hash
		local repositoryFilePath = path.join(hash:sub(1, 2), hash)
		local fullRepositoryFilePath = path.join(objectsDirPath, repositoryFilePath)
		
		filePath = path.normpath(filePath)
		local outputFilePath = path.join(outputDirPath, filePath)
		local outputSubDirPath = path.join(outputDirPath, (path.splitpath(filePath)))
		
		printf("Copying %s to %s...", repositoryFilePath, filePath)
		
		if not path.isdir(outputSubDirPath) then
			local success, failedDirectory, errorMessage = mkdirs(outputSubDirPath)
			if not success then
				failed("Failed to create directory %s: %s", failedDirectory, errorMessage)
				goto continue
			end
		end
		
		if path.exists(outputFilePath) then
			skipped("Skipping file as it already exists")
		else
			local success, errorMessage = file.copy(fullRepositoryFilePath, outputFilePath)
			if success then
				succeeded("Successfully copied file")
			else
				failed("Failed to copy file: %s", errorMessage)
			end
		end
		
		::continue::
		
		print()
	end
	
	print()
	printf("Finished extracting %s files with %s successes, %s failures and %s skipped",  formatNumber(numSucceeded + numFailed + numSkipped), formatNumber(numSucceeded), formatNumber(numFailed), formatNumber(numSkipped))
end

extractRepository(INDEX_FILE, OUTPUT_DIR)