SRB2 require.lua

-- The complete package library as relevant to possible SRB2 implementation --
-- (pseudocode, but reference Lua 5.3)

-- global package table
package = {
  preload = {},
  loaded = {},
  searchers = {}
}

-- These searcher functions will be used below.
-- They are intended to return a Lua function that represents the script file, and an optional error message.

local function search_preload(name)
  return package.preload[name]
end

local function search_lumps(name)
  -- load Lua script lump from loaded wads
  local chunk, msg = load(name)
  return chunk, msg or "lump '"..name.."' not found"
end

-- Lua users can add their own script finders to the list.
-- This is probably not useful to SRB2.
package.searchers = { search_preload, search_lumps }

function require(name)
  -- check package.loaded first
  if package.loaded[name] then
    -- return previous value
    return package.loaded[name]
  end

  local chunk, elist = nil, "Search for '"..name.."' failed:"
  for i, search in ipairs(package.searchers) do
    local msg

    chunk, msg = search(name)

    if chunk then
      -- found a chunk!
      break
    end

    if msg then
      -- append an error
      elist = elist .. "\n\t" .. msg
    end
  end

  -- if we've exhausted our list of searchers and not found a chunk,
  -- then admit failure and dump all the combined errors we've been saving.
  if not chunk then
    error(elist)
  end

  -- Do make sure to check that chunk is a function,
  -- and not some random value a user threw into package.preload
  assert(type(chunk) == "function")

  -- run the script and save its return value
  package.loaded[name] = chunk()

  -- package.loaded must only contain non-false values,
  -- even if the script explicitly returns false or 0
  if not package.loaded[name] then
    package.loaded[name] = true
  end

  -- return the value the script gave us
  return package.loaded[name]
end