Source code for sirepo.template.line_parser

# -*- coding: utf-8 -*-
"""Simple line parser.

Parses a line of input one character at a time.

:copyright: Copyright (c) 2016 RadiaSoft LLC.  All Rights Reserved.
:license: http://www.apache.org/licenses/LICENSE-2.0.html
"""
from __future__ import absolute_import, division, print_function
import re

class LineParser(object):
    """Parses a line of input one character at a time.
    Call set_line() prior to other metho calls.
    """
    def __init__(self, next_id=0):
        self._id = next_id
        self.index = 0
        self.line = ''
        self.line_number = 0


    def assert_char(self, char):
        """Raises an Error unless the current character matches"""
        if self.next_char() != char:
            self.raise_error('expected {}'.format(char))
        self.ignore_whitespace()


    def assert_end_of_line(self, comment_char='!'):
        """Raises an error unless the remaining line is empty"""
        self.ignore_whitespace()
        if self.has_char() and self.peek_char() != comment_char:
            self.raise_error('left-over input')


    def has_char(self):
        return self.index < len(self.line)


    def ignore_whitespace(self):
        """Skip whitespace"""
        while self.has_char() and re.search(r'\s', self.peek_char()):
            self.next_char()


    def increment_line_number(self):
        self.line_number += 1


    def get_index(self):
        return self.index


    def next_char(self):
        """Advance to the next character. Returns None if end of line"""
        if self.has_char():
            current = self.line[self.index]
            self.index += 1
            return current
        return None


    def next_id(self):
        self._id += 1
        return self._id


    def parse_quoted_value(self):
        self.assert_char('"')
        value = self.read_until('"')
        if self.line[self.index - 1] == '\\':
            value += '\"' + self.parse_quoted_value()
        else:
            self.assert_char('"')
        return value


    def parse_value(self, end_regex=r'[\s,=\!)*]'):
        """Parses a value, possibly quoted."""
        if self.peek_char() == '"':
            return self.parse_quoted_value()
        return self.read_until(end_regex)


    def peek_char(self):
        if self.has_char():
            return self.line[self.index]
        return None


    def raise_error(self, message):
        raise IOError('line {}, {}: {}'.format(
            self.line_number, message, self.line[self.index:]))


    def read_until(self, regex):
        """Reads until the end-of-line or the character regex is matched"""
        value = ''
        while self.has_char() and not re.search(regex, self.peek_char()):
            value += self.next_char()
        self.ignore_whitespace()
        return value


    def reset_index(self, index):
        """Reset the character index"""
        self.index = index


    def set_line(self, line):
        """Prepares a line for parsing."""
        self.line = line
        self.index = 0