"""Configuration file parser.

A setup file consists of sections, lead by a "[section]" header,
and followed by "name: value" entries, with continuations and such in
the style of rfc822.

The option values can contain format strings which refer to other
values in the same section, or values in a special [DEFAULT] section.
For example:

    something: %(dir)s/whatever

would resolve the "%(dir)s" to the value of dir.  All reference
expansions are done late, on demand.

Intrinsic defaults can be specified by passing them into the
ConfigParser constructor as a dictionary.

class:

ConfigParser -- responsible for for parsing a list of
                configuration files, and managing the parsed database.

    methods:

    __init__(defaults=None) -- create the parser and specify a
                               dictionary of intrinsic defaults.  The
                               keys must be strings, the values must
                               be appropriate for %()s string
                               interpolation.  Note that `name' is
                               always an intrinsic default; it's value
                               is the section's name.

    sections() -- return all the configuration section names, sans DEFAULT

    options(section) -- return list of configuration options for the named
                        section

    read(*filenames) -- read and parse the list of named configuration files

    get(section, option, raw=0) -- return a string value for the named
                                   option.  All % interpolations are
                                   expanded in the return values, based on
                                   the defaults passed into the constructor
                                   and the DEFAULT section.

    getint(section, options) -- like get(), but convert value to an integer

    getfloat(section, options) -- like get(), but convert value to a float

    getboolean(section, options) -- like get(), but convert value to
                                    a boolean (currently defined as 0
                                    or 1, only)
"""

import sys
import string
import regex
from types import ListType


SECTHEAD_RE = "^\[\([-A-Za-z0-9]*\)\][" + string.whitespace + "]*$"
secthead_cre = regex.compile(SECTHEAD_RE)
OPTION_RE = "^\([-A-Za-z0-9.]+\)\(:\|[" + string.whitespace + "]*=\)\(.*\)$"
option_cre = regex.compile(OPTION_RE)

DEFAULTSECT = "DEFAULT"


# exception classes
class Error:
    def __init__(self, msg=''):
        self.__msg = msg
    def __repr__(self):
        return self.__msg

class NoSectionError(Error):
    def __init__(self, section):
        Error.__init__(self, 'No section: %s' % section)
        self.section = section

class DuplicateSectionError(Error):
    def __init__(self, section):
        Error.__init__(self, "Section %s already exists" % section)
        self.section = section

class NoOptionError(Error):
    def __init__(self, option, section):
        Error.__init__(self, "No option `%s' in section: %s" %
                       (option, section))
        self.option = option
        self.section = section

class InterpolationError(Error):
    def __init__(self, reference, option, section):
        Error.__init__(self,
                       "Bad value substitution: sect `%s', opt `%s', ref `%s'"
                       % (section, option, reference))
        self.reference = reference
        self.option = option
        self.section = section


class ConfigParser:
    def __init__(self, defaults=None):
        self.__sections = {}
        if defaults is None:
            self.__defaults = {}
        else:
            self.__defaults = defaults

    def defaults(self):
        return self.__defaults

    def sections(self):
        """Return a list of section names, excluding [DEFAULT]"""
        # self.__sections will never have [DEFAULT] in it
        return self.__sections.keys()

    def add_section(self, section):
        """Create a new section in the configuration.

        Raise DuplicateSectionError if a section by the specified name
        already exists.
        """
        if self.__sections.has_key(section):
            raise DuplicateSectionError(section)
        self.__sections[section] = {}

    def has_section(self, section):
        """Indicate whether the named section is present in the configuration.

        The DEFAULT section is not acknowledged.
        """
        return self.__sections.has_key(section)

    def options(self, section):
        try:
            opts = self.__sections[section].copy()
        except KeyError:
            raise NoSectionError(section)
        opts.update(self.__defaults)
        return opts.keys()

    def read(self, filenames):
        """Read and parse a list of filenames."""
        if type(filenames) is type(''):
            filenames = [filenames]
        for file in filenames:
            try:
                fp = open(file, 'r')
                self.__read(fp)
            except IOError:
                pass

    def get(self, section, option, raw=0):
        """Get an option value for a given section.

        All % interpolations are expanded in the return values, based
        on the defaults passed into the constructor.

        The section DEFAULT is special.
        """
        try:
            sectdict = self.__sections[section].copy()
        except KeyError:
            if section == DEFAULTSECT:
                sectdict = {}
            else:
                raise NoSectionError(section)
        d = self.__defaults.copy()
        d.update(sectdict)
        option = string.lower(option)
        try:
            rawval = d[option]
        except KeyError:
            raise NoOptionError(option, section)
        # do the string interpolation
        if raw:
            return rawval
        try:
            return rawval % d
        except KeyError, key:
            raise InterpolationError(key, option, section)

    def __get(self, section, conv, option):
        return conv(self.get(section, option))

    def getint(self, section, option):
        return self.__get(section, string.atoi, option)

    def getfloat(self, section, option):
        return self.__get(section, string.atof, option)

    def getboolean(self, section, option):
        v = self.get(section, option)
        val = string.atoi(v)
        if val not in (0, 1):
            raise ValueError, 'Not a boolean: %s' % v
        return val

    def __read(self, fp):
        """Parse a sectioned setup file.

        The sections in setup file contains a title line at the top,
        indicated by a name in square brackets (`[]'), plus key/value
        options lines, indicated by `name: value' format lines.
        Continuation are represented by an embedded newline then
        leading whitespace.  Blank lines, lines beginning with a '#',
        and just about everything else is ignored.
        """
        cursect = None                  # None, or a dictionary
        optname = None
        lineno = 0
        while 1:
            line = fp.readline()
            if not line:
                break
            lineno = lineno + 1
            # comment or blank line?
            if string.strip(line) == '' or line[0] in '#;':
                continue
            if string.lower(string.split(line)[0]) == 'rem' \
               and line[0] == "r":      # no leading whitespace
                continue
            # continuation line?
            if line[0] in ' \t' and cursect <> None and optname:
                value = string.strip(line)
                if value:
                    cursect = cursect[optname] + '\n ' + value
            # a section header?
            elif secthead_cre.match(line) >= 0:
                sectname = secthead_cre.group(1)
                if self.__sections.has_key(sectname):
                    cursect = self.__sections[sectname]
                elif sectname == DEFAULTSECT:
                    cursect = self.__defaults
                else:
                    cursect = {'name': sectname}
                    self.__sections[sectname] = cursect
                # So sections can't start with a continuation line.
                optname = None
            # an option line?
            elif option_cre.match(line) >= 0:
                optname, optval = option_cre.group(1, 3)
                optname = string.lower(optname)
                optval = string.strip(optval)
                # allow empty values
                if optval == '""':
                    optval = ''
                cursect[optname] = optval
            # an error
            else:
                print 'Error in %s at %d: %s', (fp.name, lineno, `line`)