# Part of the A-A-P recipe executive: The parse position class

# Copyright (C) 2002 Stichting NLnet Labs
# Permission to copy and use this file is specified in the file COPYING.
# If this file is missing you can find it here: http://www.a-a-p.org/COPYING

# A ParsePos keeps the position in a file or string where the parser is
# working.

import string

from Error import *
from Util import *


class ParsePos:
    """Object to remember a file Or string being parsed, the last line read and
    the position in that line.
    Can't have a "file" and "string" at the same time."""

    def __init__(self, rpstack, file = '', string = ''):
	self.file = file	# file being read
	self.string = string	# string to be parsed
	self.string_idx = 0	# index in string, start of next line
	self.string_len = len(string)
	self.line = ''		# current line (concatenated file lines)
	self.idx = 0		# parsing index in "line"
	self.rpstack = rpstack	# stack of recipes, rpstack[-1] is the current
				# one and is the current line number in file;
				# when parsing a string it's offset by the line
				# number in the recipe where the string came
				# from

    def getlnum(self):
	"""Get the line number of the recipe being parsed."""
	return self.rpstack[-1].line_nr

    def nextline(self):
	"""Read a line from "self.file" and handle line continuation.
	   When reading a string use "self.string".
	   Puts the concatenated line in "self.line", with EOL and backslashes
	   removed.
	   Returns None in "self.line" when at the end of the file or string.
	   Increases the line number self.rpstack[-1].line_nr.
	   Skips over empty and comment lines.
	   Throws an exception when the last line has a backslash or when
	   there is a read error."""

	def getline(fp):
	    """Get one line from the file or the string.  Includes the newline
	       at the end of the line."""
	    if fp.string:
		i = string.find(fp.string, "\n", fp.string_idx)
		if i == fp.string_idx:	    # end of string
		    return ''
		l = fp.string[fp.string_idx:i + 1]
		fp.string_idx = i + 1
		return l
	    else:
		return fp.file.readline()


	try:
	    nonwhite = -1
	    while 1:
		self.line = getline(self)
		self.rpstack[-1].line_nr = self.rpstack[-1].line_nr + 1
		if not self.line:
		    # Reached end of file
		    self.line = None
		    break
		# concatenate lines ending in a backslash
		while 1:
		    # Remove the trailing NL or CR-NL.
		    # A CR-NL comes from reading a DOS file on Unix.
		    line_len = len(self.line) - 1
		    if line_len > 0 and self.line[line_len - 1] == '\r':
			self.line = self.line[:line_len - 1]
			line_len = line_len - 1
		    else:
			self.line = self.line[:line_len]
		    if line_len < 1 or self.line[line_len - 1] != '\\':
			break
		    nextline = getline(self)
		    self.rpstack[-1].line_nr = self.rpstack[-1].line_nr + 1
		    if not nextline:
			recipe_error(self.rpstack,
					       'last line ends in a backslash')

		    # When the line starts with '@' remove leading '@' from the
		    # continuation line.
		    if nonwhite < 0:
			nonwhite = skip_white(self.line, 0)
		    if self.line[nonwhite] == '@':
			i = skip_white(nextline, 0)
			if i < len(nextline) and nextline[i] == '@':
			    nextline = nextline[i + 1:]

		    self.line = self.line[:-1] + nextline

		# stop reading lines when found a non-blank non-comment line
		i = skip_white(self.line, 0)
		if i < len(self.line) and self.line[i] != '#':
		    break

	except IOError, e:
	    raise UserError, _('Cannot read from "') \
		    + self.file.name + '": ' + str(e)

	self.idx = 0
	if not self.line is None:
	    self.line_len = len(self.line)


# vim: set sw=4 sts=4 tw=79 fo+=l: