#!/usr/bin/env python

"""

Parsing of vCard, vCalendar and iCalendar files.

Copyright (C) 2005, 2006, 2007, 2008 Paul Boddie <paul@boddie.org.uk>

This program is free software; you can redistribute it and/or modify it under

the terms of the GNU Lesser General Public License as published by the Free

Software Foundation; either version 3 of the License, or (at your option) any

later version.

This program is distributed in the hope that it will be useful, but WITHOUT

ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more

details.

You should have received a copy of the GNU Lesser General Public License along

with this program.  If not, see <http://www.gnu.org/licenses/>.

--------

References:

RFC 2445: Internet Calendaring and Scheduling Core Object Specification

          (iCalendar)

          http://rfc.net/rfc2445.html

RFC 2425: A MIME Content-Type for Directory Information

          http://rfc.net/rfc2425.html

RFC 2426: vCard MIME Directory Profile

          http://rfc.net/rfc2426.html

"""

# Encoding-related imports.

import base64, quopri

# Simple reader class.

class Reader:

    "A simple class wrapping a file, providing simple pushback capabilities."

    def __init__(self, f, non_standard_newline=0):

        """

        Initialise the object with the file 'f'. If 'non_standard_newline' is

        set to a true value (unlike the default), lines ending with CR will be

        treated as complete lines.

        """

        self.f = f

        self.non_standard_newline = non_standard_newline

        self.lines = []

        self.line_number = 0

    def pushback(self, line):

        """

        Push the given 'line' back so that the next line read is actually the

        given 'line' and not the next line from the underlying file.

        """

        self.lines.append(line)

        self.line_number -= 1

    def readline(self):

        """

        If no pushed-back lines exist, read a line directly from the file.

        Otherwise, read from the list of pushed-back lines.

        """

        self.line_number += 1

        if self.lines:

            return self.lines.pop()

        else:

            # NOTE: Sanity check for broken lines (\r instead of \r\n or \n).

            line = self.f.readline()

            while line.endswith("\r") and not self.non_standard_newline:

                line += self.f.readline()

            if line.endswith("\r") and self.non_standard_newline:

                return line + "\n"

            else:

                return line

    def read_until(self, targets):

        """

        Read from the stream until one of the 'targets' is seen. Return the

        string from the current position up to the target found, along with the

        target string, using a tuple of the form (string, target). If no target

        was found, return the entire string together with a target of None.

        """

        indexes = {}

        # Remember the entire text read and the index of the current line in

        # that text.

        lines = []

        line = self.readline()

        lines.append(line)

        start = 0

        while indexes == {} and line != "":

            for target in targets:

                index = line.find(target)

                # Always choose the first matching target.

                if index != -1 and not indexes.has_key(start + index):

                    indexes[start + index] = target

            start += len(line)

            line = self.readline()

            lines.append(line)

        text = "".join(lines)

        if indexes:

            min_index = reduce(min, indexes.keys())

            target = indexes[min_index]

            # Skip the target.

            # Since the end of the buffer should always be a newline, ignore the

            # last element.

            lines = text[min_index + len(target):].split("\n")[:]

            if not lines[-1]:

                del lines[-1]

            lines.reverse()

            for line in lines:

                self.pushback(line + "\n")

            return text[:min_index], target

        else:

            return text, None

class StreamParser:

    "A stream parser for content in vCard/vCalendar/iCalendar-like formats."

    def __init__(self, f):

        "Initialise the parser for the given file 'f'."

        self.f = f

    def __iter__(self):

        "Return self as the iterator."

        return self

    def next(self):

        """

        Return the next content item in the file as a tuple of the form

        (name, parameters, values).

        """

        return self.parse_content_line()

    def parse_content_line(self):

        """

        Return the name, parameters and a list containing value information for

        the current content line in the file being parsed.

        """

        f = self.f

        parameters = {}

        name, sep = f.read_until([";", ":"])

        name = name.strip()

        if not name and sep is None:

            raise StopIteration

        while sep == ";":

            # Find the actual modifier.

            parameter_name, sep = f.read_until(["=", ";", ":"])

            parameter_name = parameter_name.strip()

            if sep == "=":

                parameter_value, sep = f.read_until([";", ":"])

                parameter_value = parameter_value.strip()

            else:

                parameter_value = None

            # Append a key, value tuple to the parameters list.

            parameters[parameter_name] = parameter_value

        # Get the value content.

        if sep != ":":

            raise ValueError, f.line_number

        # Strip all appropriate whitespace from the right end of each line.

        # For subsequent lines, remove the first whitespace character.

        # See section 4.1 of the iCalendar specification.

        line = f.readline()

        value_lines = [line.rstrip("\r\n")]

        line = f.readline()

        while line != "" and line[0] in [" ", "\t"]:

            value_lines.append(line.rstrip("\r\n")[1:])

            line = f.readline()

        # Since one line too many will have been read, push the line back into the

        # file.

        f.pushback(line)

        # Decode the value.

        value = self.decode("".join(value_lines), parameters.get("ENCODING"))

        return name, parameters, value

    def decode(self, value, encoding):

        "Decode the 'value' with the given 'encoding'."

        # NOTE: Assuming ISO 8869-1 for the character set.

        if encoding == "QUOTED-PRINTABLE":

            return unicode(quopri.decodestring(value), "iso-8859-1")

        elif encoding == "BASE64":

            return base64.decodestring(value)

        else:

            # NOTE: Introducing newline conversions.

            # Replace quoted characters (see 4.3.11 in RFC 2445).

            return value.replace("\r", "").replace("\\N", "\n").replace("\\n", "\n").replace("\\,", ",").replace("\\;", ";")

class Parser:

    "A parser for content in vCard/vCalendar/iCalendar-like formats."

    def __init__(self):

        "Initialise the parser."

        self.elements = [] # also known as components

        self.document = []

        self.current = self.document

    def parse(self, f):

        "Parse the contents of the file 'f'."

        parser = StreamParser(f)

        for name, parameters, value in parser:

            # Add new elements/components to the current position in the

            # document, recording the element as the active element.

            if name == "BEGIN":

                children = []

                element = (value, parameters, children)

                self.elements.append(element)

                self.current.append(element)

                self.current = children

            # End elements by removing them from the active element stack and

            # making the next element's children the current position for new

            # content.

            elif name == "END":

                start_element = self.elements.pop()

                start_value, start_parameters, children = start_element

                if start_value != value:

                    raise ParseError, "Mismatch in BEGIN and END declarations (%r and %r) at line %d." % (

                        start_value, value, f.line_number)

                if self.elements:

                    parent_value, parent_parameters, children = self.elements[-1]

                    self.current = children

                else:

                    self.current = self.document

            else:

                self.current.append((name, parameters, value))

        return self.document

# Public functions.

def parse(f, non_standard_newline=0):

    """

    Parse the resource data found through the use of the file object 'f', which

    should provide Unicode data, and put the resource information in the given

    'store'. (The codecs module can be used to open files or to wrap streams in

    order to provide Unicode data.)

    The optional 'non_standard_newline' can be set to a true value (unlike the

    default) in order to attempt to process files with CR as the end of line

    character.

    As a result of parsing the resource, the root node of the imported resource

    is returned.

    """

    reader = Reader(f, non_standard_newline=non_standard_newline)

    parser = Parser()

    return parser.parse(reader)

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