# config.py
# Copyright (C) 2008, 2009 Michael Trier (mtrier@gmail.com) and contributors
#
# This module is part of GitPython and is released under
# the BSD License: http://www.opensource.org/licenses/bsd-license.php
"""Module containing module parser implementation able to properly read and write
configuration files"""

import re
import os
import ConfigParser as cp
import inspect
import cStringIO

from git.odict import OrderedDict
from git.util import LockFile

__all__ = ('GitConfigParser', 'SectionConstraint')

class MetaParserBuilder(type):
    """Utlity class wrapping base-class methods into decorators that assure read-only properties"""
    def __new__(metacls, name, bases, clsdict):
        """
        Equip all base-class methods with a needs_values decorator, and all non-const methods
        with a set_dirty_and_flush_changes decorator in addition to that."""
        kmm = '_mutating_methods_'
        if kmm in clsdict:
            mutating_methods = clsdict[kmm]
            for base in bases:
                methods = ( t for t in inspect.getmembers(base, inspect.ismethod) if not t[0].startswith("_") )
                for name, method in methods:
                    if name in clsdict:
                        continue
                    method_with_values = needs_values(method)
                    if name in mutating_methods:
                        method_with_values = set_dirty_and_flush_changes(method_with_values)
                    # END mutating methods handling
                    
                    clsdict[name] = method_with_values
                # END for each name/method pair
            # END for each base
        # END if mutating methods configuration is set
        
        new_type = super(MetaParserBuilder, metacls).__new__(metacls, name, bases, clsdict)
        return new_type
    
    

def needs_values(func):
    """Returns method assuring we read values (on demand) before we try to access them"""
    def assure_data_present(self, *args, **kwargs):
        self.read()
        return func(self, *args, **kwargs)
    # END wrapper method
    assure_data_present.__name__ = func.__name__
    return assure_data_present
    
def set_dirty_and_flush_changes(non_const_func):
    """Return method that checks whether given non constant function may be called.
    If so, the instance will be set dirty.
    Additionally, we flush the changes right to disk"""
    def flush_changes(self, *args, **kwargs):
        rval = non_const_func(self, *args, **kwargs)
        self.write()
        return rval
    # END wrapper method
    flush_changes.__name__ = non_const_func.__name__
    return flush_changes
    

class SectionConstraint(object):
    """Constrains a ConfigParser to only option commands which are constrained to 
    always use the section we have been initialized with.
    
    It supports all ConfigParser methods that operate on an option"""
    __slots__ = ("_config", "_section_name")
    _valid_attrs_ = ("get_value", "set_value", "get", "set", "getint", "getfloat", "getboolean", "has_option", 
                    "remove_section", "remove_option", "options")
    
    def __init__(self, config, section):
        self._config = config
        self._section_name = section
        
    def __getattr__(self, attr):
        if attr in self._valid_attrs_:
            return lambda *args, **kwargs: self._call_config(attr, *args, **kwargs)
        return super(SectionConstraint,self).__getattribute__(attr)
        
    def _call_config(self, method, *args, **kwargs):
        """Call the configuration at the given method which must take a section name 
        as first argument"""
        return getattr(self._config, method)(self._section_name, *args, **kwargs)
        
    @property
    def config(self):
        """return: Configparser instance we constrain"""
        return self._config
        

class GitConfigParser(cp.RawConfigParser, object):
    """Implements specifics required to read git style configuration files.
    
    This variation behaves much like the git.config command such that the configuration
    will be read on demand based on the filepath given during initialization.
    
    The changes will automatically be written once the instance goes out of scope, but 
    can be triggered manually as well.
    
    The configuration file will be locked if you intend to change values preventing other 
    instances to write concurrently.
    
    :note:
        The config is case-sensitive even when queried, hence section and option names
        must match perfectly."""
    __metaclass__ = MetaParserBuilder
    
    
    #{ Configuration
    # The lock type determines the type of lock to use in new configuration readers.
    # They must be compatible to the LockFile interface.
    # A suitable alternative would be the BlockingLockFile
    t_lock = LockFile
    re_comment = re.compile('^\s*[#;]')
    
    #} END configuration 
    
    OPTCRE = re.compile(
        r'\s*(?P<option>[^:=\s][^:=]*)'       # very permissive, incuding leading whitespace
        r'\s*(?P<vi>[:=])\s*'                 # any number of space/tab,
                                              # followed by separator
                                              # (either : or =), followed
                                              # by any # space/tab
        r'(?P<value>.*)$'                     # everything up to eol
        )
    
    # list of RawConfigParser methods able to change the instance
    _mutating_methods_ = ("add_section", "remove_section", "remove_option", "set")
    __slots__ = ("_sections", "_defaults", "_file_or_files", "_read_only","_is_initialized", '_lock')
    
    def __init__(self, file_or_files, read_only=True):
        """Initialize a configuration reader to read the given file_or_files and to 
        possibly allow changes to it by setting read_only False
        
        :param file_or_files:
            A single file path or file objects or multiple of these
        
        :param read_only:
            If True, the ConfigParser may only read the data , but not change it.
            If False, only a single file path or file object may be given."""
        super(GitConfigParser, self).__init__()
        # initialize base with ordered dictionaries to be sure we write the same 
        # file back 
        self._sections = OrderedDict()
        self._defaults = OrderedDict()
        
        self._file_or_files = file_or_files
        self._read_only = read_only
        self._is_initialized = False
        self._lock = None
        
        if not read_only:
            if isinstance(file_or_files, (tuple, list)):
                raise ValueError("Write-ConfigParsers can operate on a single file only, multiple files have been passed")
            # END single file check
            
            if not isinstance(file_or_files, basestring):
                file_or_files = file_or_files.name
            # END get filename from handle/stream
            # initialize lock base - we want to write
            self._lock = self.t_lock(file_or_files)
            
            self._lock._obtain_lock()
        # END read-only check
        
    
    def __del__(self):
        """Write pending changes if required and release locks"""
        # checking for the lock here makes sure we do not raise during write()
        # in case an invalid parser was created who could not get a lock
        if self.read_only or not self._lock._has_lock():
            return
        
        try:
            try:
                self.write()
            except IOError,e:
                print "Exception during destruction of GitConfigParser: %s" % str(e)
        finally:
            self._lock._release_lock()
    
    def optionxform(self, optionstr):
        """Do not transform options in any way when writing"""
        return optionstr
    
    def _read(self, fp, fpname):
        """A direct copy of the py2.4 version of the super class's _read method
        to assure it uses ordered dicts. Had to change one line to make it work.
        
        Future versions have this fixed, but in fact its quite embarassing for the 
        guys not to have done it right in the first place !
        
        Removed big comments to make it more compact.
        
        Made sure it ignores initial whitespace as git uses tabs"""
        cursect = None                            # None, or a dictionary
        optname = None
        lineno = 0
        e = None                                  # None, or an exception
        while True:
            line = fp.readline()
            if not line:
                break
            lineno = lineno + 1
            # comment or blank line?
            if line.strip() == '' or self.re_comment.match(line):
                continue
            if line.split(None, 1)[0].lower() == 'rem' and line[0] in "rR":
                # no leading whitespace
                continue
            else:
                # is it a section header?
                mo = self.SECTCRE.match(line.strip())
                if mo:
                    sectname = mo.group('header').strip()
                    if sectname in self._sections:
                        cursect = self._sections[sectname]
                    elif sectname == cp.DEFAULTSECT:
                        cursect = self._defaults
                    else:
                        # THE ONLY LINE WE CHANGED !
                        cursect = OrderedDict((('__name__', sectname),))
                        self._sections[sectname] = cursect
                    # So sections can't start with a continuation line
                    optname = None
                # no section header in the file?
                elif cursect is None:
                    raise cp.MissingSectionHeaderError(fpname, lineno, line)
                # an option line?
                else:
                    mo = self.OPTCRE.match(line)
                    if mo:
                        optname, vi, optval = mo.group('option', 'vi', 'value')
                        if vi in ('=', ':') and ';' in optval:
                            pos = optval.find(';')
                            if pos != -1 and optval[pos-1].isspace():
                                optval = optval[:pos]
                        optval = optval.strip()
                        if optval == '""':
                            optval = ''
                        optname = self.optionxform(optname.rstrip())
                        cursect[optname] = optval
                    else:
                        if not e:
                            e = cp.ParsingError(fpname)
                        e.append(lineno, repr(line))
                    # END  
                # END ? 
            # END ?
        # END while reading 
        # if any parsing errors occurred, raise an exception
        if e:
            raise e
    
    
    def read(self):
        """Reads the data stored in the files we have been initialized with. It will 
        ignore files that cannot be read, possibly leaving an empty configuration
        
        :return: Nothing
        :raise IOError: if a file cannot be handled"""
        if self._is_initialized:
            return
            
        files_to_read = self._file_or_files
        if not isinstance(files_to_read, (tuple, list)):
            files_to_read = [ files_to_read ]
        
        for file_object in files_to_read:
            fp = file_object
            close_fp = False
            # assume a path if it is not a file-object
            if not hasattr(file_object, "seek"):
                try:
                    fp = open(file_object)
                    close_fp = True
                except IOError,e:
                    continue
            # END fp handling
                
            try:
                self._read(fp, fp.name)
            finally:
                if close_fp:
                    fp.close()
            # END read-handling
        # END  for each file object to read
        self._is_initialized = True
        
    def _write(self, fp):
        """Write an .ini-format representation of the configuration state in 
        git compatible format"""
        def write_section(name, section_dict):
            fp.write("[%s]\n" % name)
            for (key, value) in section_dict.items():
                if key != "__name__":
                    fp.write("\t%s = %s\n" % (key, str(value).replace('\n', '\n\t')))
                # END if key is not __name__
        # END section writing 
        
        if self._defaults:
            write_section(cp.DEFAULTSECT, self._defaults)
        map(lambda t: write_section(t[0],t[1]), self._sections.items())

        
    @needs_values
    def write(self):
        """Write changes to our file, if there are changes at all
        
        :raise IOError: if this is a read-only writer instance or if we could not obtain 
            a file lock"""
        self._assure_writable("write")
        
        fp = self._file_or_files
        close_fp = False
        
        # we have a physical file on disk, so get a lock
        if isinstance(fp, (basestring, file)):
            self._lock._obtain_lock()
        # END get lock for physical files
        
        if not hasattr(fp, "seek"):
            fp = open(self._file_or_files, "w")
            close_fp = True
        else:
            fp.seek(0)
            # make sure we do not overwrite into an existing file
            if hasattr(fp, 'truncate'):
                fp.truncate()
            #END 
        # END handle stream or file
        
        # WRITE DATA
        try:
            self._write(fp)
        finally:
            if close_fp:
                fp.close()
        # END data writing
            
        # we do not release the lock - it will be done automatically once the 
        # instance vanishes
        
    def _assure_writable(self, method_name):
        if self.read_only:
            raise IOError("Cannot execute non-constant method %s.%s" % (self, method_name))
        
    @needs_values
    @set_dirty_and_flush_changes
    def add_section(self, section):
        """Assures added options will stay in order"""
        super(GitConfigParser, self).add_section(section)
        self._sections[section] = OrderedDict()
        
    @property
    def read_only(self):
        """:return: True if this instance may change the configuration file"""
        return self._read_only
        
    def get_value(self, section, option, default = None):
        """
        :param default:
            If not None, the given default value will be returned in case 
            the option did not exist
        :return: a properly typed value, either int, float or string
        
        :raise TypeError: in case the value could not be understood
            Otherwise the exceptions known to the ConfigParser will be raised."""
        try:
            valuestr = self.get(section, option)
        except Exception:
            if default is not None:
                return default
            raise
        
        types = ( long, float )
        for numtype in types:
            try:
                val = numtype( valuestr )

                # truncated value ?
                if val != float( valuestr ):
                    continue

                return val
            except (ValueError,TypeError):
                continue
        # END for each numeric type
        
        # try boolean values as git uses them
        vl = valuestr.lower() 
        if vl == 'false':
            return False
        if vl == 'true':
            return True
        
        if not isinstance( valuestr, basestring ):
            raise TypeError( "Invalid value type: only int, long, float and str are allowed", valuestr )
        
        return valuestr
    
    @needs_values
    @set_dirty_and_flush_changes
    def set_value(self, section, option, value):
        """Sets the given option in section to the given value.
        It will create the section if required, and will not throw as opposed to the default 
        ConfigParser 'set' method.
        
        :param section: Name of the section in which the option resides or should reside
        :param option: Name of the options whose value to set
            
        :param value: Value to set the option to. It must be a string or convertible 
            to a string"""
        if not self.has_section(section):
            self.add_section(section)
        self.set(section, option, str(value))
