module YARP::LibRubyParser

def self.load_exported_functions_from(header, *functions)
  File.foreach(File.expand_path("../../include/#{header}", __dir__)) do |line|
    # We only want to attempt to load exported functions.
    next unless line.start_with?("YP_EXPORTED_FUNCTION ")
    # We only want to load the functions that we are interested in.
    next unless functions.any? { |function| line.include?(function) }
    # Parse the function declaration.
    unless /^YP_EXPORTED_FUNCTION (?<return_type>.+) (?<name>\w+)\((?<arg_types>.+)\);$/ =~ line
      raise "Could not parse #{line}"
    end
    # Delete the function from the list of functions we are looking for to
    # mark it as having been found.
    functions.delete(name)
    # Split up the argument types into an array, ensure we handle the case
    # where there are no arguments (by explicit void).
    arg_types = arg_types.split(",").map(&:strip)
    arg_types = [] if arg_types == %w[void]
    # Resolve the type of the argument by dropping the name of the argument
    # first if it is present.
    arg_types.map! { |type| resolve_type(type.sub(/\w+$/, "")) }
    # Attach the function using the FFI library.
    attach_function name, arg_types, resolve_type(return_type)
  end
  # If we didn't find all of the functions, raise an error.
  raise "Could not find functions #{functions.inspect}" unless functions.empty?
end

def self.resolve_type(type)
  type = type.strip.delete_prefix("const ")
  type.end_with?("*") ? :pointer : type.to_sym
end