import.lua

-- Copied/modified from LTN 11: http://www.lua.org/notes/ltn011.html

    local imported = {}

    local function package_stub(name)
      local stub = {}
      local stub_meta = {
        __index = function(_, index)
          error(string.format("member `%s' is accessed before package `%s' is fully imported", index, name))
        end,
        __newindex = function(_, index, _)
          error(string.format("member `%s' is assigned a value before package `%s' is fully imported", index, name))
        end,
      }
      setmetatable(stub, stub_meta)
      return stub
    end

    local function locate(name)
      local path = LUA_PATH
      if type(path) ~= "string" then
        path = os.getenv "LUA_PATH" or "./?.lua"
      end
      for path in string.gfind(path, "[^;]+") do
        path = string.gsub(path, "?", name)
        local chunk = loadfile(path)
        if chunk then return chunk, path end
      end
      return nil, path
    end

    function import(name)
      local package = imported[name]
      if package then return package end
      local chunk, path = locate(name)
      if not chunk then
        error(string.format("could not locate package `%s' in `%s'", name, path))
      end
      package = package_stub(name)
      imported[name] = package
      setfenv(chunk, getfenv(2))
      chunk = chunk()
      setmetatable(package, nil)
      if type(chunk) == "function" then
        chunk(package, name, path)
      end
      return package
    end