repl.py

import rdfscript.rdfscriptparser as parser
from rdfscript.env import Env

import sys


class REPL:

    def __init__(self,
                 serializer='nt',
                 out=None,
                 optpaths=[],
                 optextensions=[],
                 debug_lvl=1):

        self.env = Env(repl=True,
                       serializer=serializer,
                       paths=optpaths,
                       extensions=optextensions)

        self.parser = parser.RDFScriptParser(debug_lvl=debug_lvl)
        self.reader = self.parser.scanner
        self.out_file = out

    def start(self):

        try:
            while True:
                self.read()
                self.evaluate()
        except EOFError:
            self.finish()

    def read(self):
        prompt = self.get_prompt_string()

        if sys.version_info >= (3, 0):
            s = input(prompt + '  > ')
        else:
            s = raw_input(prompt + '  > ')

        if not s:
            self.read()

        self.reader.input(s)

    def evaluate(self):
        form = self.parser.parser.parse(lexer=self.reader)
        result = self.env.interpret(form)

        self.pprint(result)

    def pprint(self, value):
        if value is not None:
            string = format("%s" % value)
            print(string)

    def finish(self):

        if not self.out_file:
            self.pprint(self.env)
        else:
            with open(self.out_file, 'w') as out:
                out.write(str(self.env))

    def get_prompt_string(self):
        if self.env.prefix is not None:
            prompt = self.env.prefix
        else:
            prompt = 'RDF'

        return prompt