import gll

@gll.parser("expression")
def expression(string):
    parser = gll.seq(ws, func_call | literal, ws, tag="expression")

    return parser(string)

ws = gll.skipmany(gll.string(" "))
skipped = lambda pat: gll.skip(gll.string(pat), tag="skip_{}".format(pat))
variable = gll.regex("\w+", tag="variable_name")
type_decl = gll.regex("\w+", tag="type")
comma = gll.skip(gll.regex(r"\s*,\s*"))

number = gll.many1(gll.digit(), tag="number")
string = gll.seq(skipped("\""), gll.regex(r'[^"\\]+'), skipped("\""), tag="string")
lst    = gll.seq(skipped("["), gll.sep_by(comma, expression | variable),
                 skipped("]"), tag="list")

declaration = gll.seq(skipped("var"), ws, variable, ws, type_decl, tag="declaration")

assignment = gll.seq(variable, ws, skipped("="), ws, expression, tag="assignment")

return_statement = gll.seq(skipped("return"), ws, expression,
                           tag="return")

func_call = gll.seq(variable, skipped("("),
                    gll.sep_by(comma, expression | variable, tag="arguments"),
                    skipped(")"), tag="call")

literal = number | string | lst

special = gll.seq(ws, return_statement | declaration | assignment, ws)

body = gll.seq(skipped("{"), skipped("\n"),
               gll.sep_by(gll.regex(r"\s*\n+\s*"), expression | special, tag="body"),
               gll.opt(skipped("\n")), skipped("}"))

argument = gll.seq(variable, ws, type_decl, tag="parameter")
arguments_list = gll.seq(skipped("("), gll.sep_by(comma, argument),
                         skipped(")"), tag="parameters")

function = gll.seq(skipped("func"), ws, gll.regex("\w+", tag="function_name"),
                   ws, arguments_list, ws, type_decl, ws, body, ws,
                   tag="function")

package_name = gll.seq(skipped("package"), ws, variable,
                       gll.skipmany(gll.string(" ")), skipped("\n"),
                       tag="package_name")

package = gll.seq(package_name, gll.sep_by(gll.string("\n"), function,
                                           tag="package_body"),
                  gll.many(skipped("\n")),
                  tag="package")

parser = gll.all(package)