# R overlay -- config package, loader
# -*- coding: utf-8 -*-
# Copyright (C) 2012 André Erdmann <dywi@mailerd.de>
# Distributed under the terms of the GNU General Public License;
# either version 2 of the License, or (at your option) any later version.

"""
Loads config data from files (including field definitions).

This module defines the following classes:
* ConfigLoader -- config loader
"""

__all__ = [ 'ConfigLoader', ]

import re
import shlex
import os.path

from roverlay.strutil         import unquote, str_to_bool
from roverlay.config          import fielddef
from roverlay.config.util     import get_config_path
from roverlay.config.entrymap import CONFIG_ENTRY_MAP

import roverlay.ebuild.useflagmap


def listlike ( var ):
   return hasattr ( var, '__iter__' ) and not isinstance ( var, str )
# --- end of listlike (...) ---

class ConfigLoader ( object ):
   """Loads config data from files."""

   # often used regexes
   WHITESPACE         = re.compile ( '\s+' )


   def __init__ ( self, config_tree, logger=None ):
      """Initializes a ConfigLoader.

      arguments:
      * config_tree -- ConfigTree
      * logger      -- logger to use, defaults to config_tree's logger
      """
      self.ctree = config_tree

      self.config_root = None

      self.logger   = self.ctree.logger if logger is None else logger
      self.fielddef = None

   # --- end of __init__ (...) ---

   def _setval ( self, path, value, allow_empty_value=False ):
      """Sets a value in the config tree.

      arguments:
      * path              -- config path
      * value             -- config value
      * allow_empty_value --
      """
      self.ctree._findpath (
         path,
         value=value,
         root=self.config_root,
         create=True,
         forceval=allow_empty_value,
         forcepath=False
      )
   # --- end of _setval (...) ---

   def _config_entry ( self, cref, option, value, config_root ):
      """Adds a normal config entry to the assigned ConfigTree.

      arguments:
      * cref        -- reference to the config option's entry in the
                        CONFIG_ENTRY_MAP
      * option      -- name of the config option
      * value       -- value read from a config file (will be verified here)
      * config_root -- ignored;
      """
      def uppercase_if_in_iterable ( s, iterable ):
         """Returns s.upper() if s.upper() in iterable else None.

         arguments:
         * s        -- string
         * iterable -- items
         """
         s_up = s.upper()
         return s_up if s_up in iterable else None
      # --- end of uppercase_if_in_iterable (...) ---

      # determine the config path
      path = get_config_path (
         cref.get ( "path", None ) or option.split ( '_' )
      )

      # need a valid path
      if path:

         # verify and convert value if value_type is set
         value = self._make_and_verify_value (
            cref.get ( 'value_type', str ), value
         )
         # --- end prepare value;

         value_choices = cref.get ( "choices", None )

         if value_choices:
            if listlike ( value ):

               # create value_invalid for logging
               # * also used as condition whether value is valid or not
               value_invalid = None

               if 'flags' in cref and 'CAPSLOCK' in cref ['flags']:
                  value_valid = list (
                     filter (
                        None,
                        (
                           uppercase_if_in_iterable ( v, value_choices )
                           for v in value
                        )
                     )
                  )

                  if len ( value_valid ) != len ( value ):

                     value_invalid = [
                        v for v in value if v.upper() not in value_choices
                     ]
               else:
                  value_valid = [ v for v in value if v in value_choices ]

                  if len ( value_valid ) != len ( value ):
                     value_invalid = [
                        v for v in value if v not in value_choices
                     ]


               if not value_invalid:
                  value = value_valid
               else:
                  # mark value as invalid
                  self.logger.error (
                     "Option {o!r} has unusable value(s): {v!r}.".format (
                        o=option,
                        v=', '.join ( value_invalid )
                     )
                  )
                  #value = None
                  # return immediately, no need to log about that twice
                  return False


            elif 'flags' in cref and 'CAPSLOCK' in cref ['flags']:
               value = uppercase_if_in_iterable ( value, value_choices )

            elif value not in value_choices:
               value = None

            # else value is valid

         elif 'flags' in cref and 'CAPSLOCK' in cref ['flags']:
            if listlike ( value ):
               value = [ s.upper() for s in value ]
            else:
               value = value.upper()
         # --- end verify choices / apply flags;

         # need a valid value
         if value is not None:

            if listlike ( value ) and 'f_convert_item' in cref:
               # or use map()
               value = [ cref ['f_convert_item'] ( v ) for v in value ]

            # not elif (use both functions for iterables if specified)
            if 'f_convert' in cref:
               # func should expect an iterable if value_type has/is "list"
               value = cref ['f_convert'] ( value )

         if value is not None and (
            'f_verify' not in cref
            or cref ['f_verify'] (
               value,
               logger=self.logger.getChild ( option )
            )
         ):

            self.logger.debug (
               "New config entry {o} with path {p} and value {v}.".format (
                  o=option, p=path, v=value
            ) )

            # add option/value to the config
            self._setval ( path, value )

            return True
         else:
            self.logger.error (
               "Option {o!r} has an unusable value {v!r}.".format (
                  o=option, v=value
            ) )
            return False
      # ---
   # --- end of _config_enty (...) ---

   def _add_entry ( self, option, value=None, config_root=None ):
      """Adds an option to the config.

      arguments:
      * option      -- name of the option as it appears in the config file
      * value       -- value to assign, defaults to None
      * config_root -- root of the config (a dict), defaults to None which is
                       later understood as self._config
      """

      real_option = option
      low_option = option.lower()

      # known option? option not empty and its lowercase repr in the entry map
      if option and low_option in CONFIG_ENTRY_MAP:

         original_cref = cref = CONFIG_ENTRY_MAP [low_option]
         cref_level = 0

         # check if cref is a link to another entry in CONFIG_ENTRY_MAP
         while isinstance ( cref, str ) and cref != '':
            if cref == original_cref and cref_level:
               self.logger.critical (
                  "CONFIG_ENTRY_MAP is invalid! circular cref detected."
               )
               raise Exception ( "CONFIG_ENTRY_MAP is invalid!" )

            elif cref in CONFIG_ENTRY_MAP:
               option = low_option = cref
               cref = CONFIG_ENTRY_MAP [cref]
               cref_level += 1
            else:
               self.logger.critical (
                  'CONFIG_ENTRY_MAP is invalid! '
                  'last cref = %s, current cref = %s.' % ( option, cref )
               )
               raise Exception ( "CONFIG_ENTRY_MAP is invalid!" )

         # check if config entry is disabled
         if cref is not None:
            return self._config_entry ( cref, option, value, config_root )
         else:
            # deftly ignored
            return True
      # ---

      self.logger.warning ( "Option '%s' is unknown." % real_option )
      return False

   # --- end of _add_entry (...) ---

   def parse_config ( self, fh_or_str, config_file='input' ):
      reader = shlex.shlex ( fh_or_str, config_file )
      reader.wordchars       += ' ,./$()[]:+-@*~'
      reader.whitespace_split = False

      nextline = lambda: [ reader.get_token() for n in range(3) ]

      option, equal, value = nextline()

      while equal == '=' or not ( option == value == reader.eof ):
         if equal == '=':
            self._add_entry ( option, value )
         else:
            self.logger.warning (
               "In {!r}, cannot parse this line: '{}{}{}'.".format (
                  config_file, option, equal, value
               )
            )

         option, equal, value = nextline()
   # --- end of parse_config (...) ---

   def load_config ( self, config_file ):
      """Loads a config file and integrates its content into the config tree.
      Older config entries may be overwritten.

      arguments:
      config_file   -- path to the file that should be read
      """
      with open ( config_file, 'rt' ) as FH:
         self.parse_config ( FH, config_file )
   # --- end of load_config (...) ---

   def load_use_expand_map ( self, map_file ):
      """Loads the USE_EXPAND flag rename 'map'.

      arguments:
      * map_file --
      """
      if map_file:
         # a is a map in file "format": dict { flag => *alias }
         a = roverlay.ebuild.useflagmap.UseFlagAliasMap ( from_file=map_file )

         # a dict { alias => flag } is required here:
         if self.ctree._use_extend_map:
            self.ctree._use_extend_map.update ( ~a )
         else:
            self.ctree._use_extend_map = ~a
   # --- end of load_use_expand_map

   def load_field_definition ( self, def_file, lenient=False ):
      """Loads a field definition file.
      Please see the example file for format details.

      arguments:
      * def_file -- file (str) to read,
                     this can be a list of str if lenient is True
      * lenient  -- if True: do not fail if a file cannot be read;
                     defaults to False
      """
      if self.fielddef is None:
         # field def loads the license map
         self.fielddef = fielddef.DescriptionFieldDefinition (
            self.logger, self.ctree
         )

      self.fielddef.load_file ( def_file, lenient=lenient )

      self.ctree._field_definition = self.fielddef.get()
   # --- end of load_field_definition (...) ---

   def _make_and_verify_value ( self, value_type, value ):
      """Prepares the value of a config option so that it can be used
      in the config.

      arguments:
      * value_type -- type of the value,
                       look above for explanation concerning this
      * value      -- value to verify and transform
      """

      def to_int ( val, fallback_value=-1 ):
         """Tries to convert val to an int, returning a fallback value
         on any error.

         arguments:
         * val --
         * fallback_value --

         catches: ValueError in case of an unsuccesful int conversion
         raises: nothing
         """
         try:
            ret = int ( val )
            return ret
         except ValueError as verr:
            return fallback_value
      # --- end of to_int (...) ---

      def yesno ( val ):
         """Tries to canonize an yes or no value to its integer
         representation. Returns 1 if val means 'yes', 0 if 'no' and
         -1 otherwise.

         arguments:
         * val --
         """
         ret = str_to_bool ( val, nofail=True )
         if ret is None:
            self.logger.warning ( str(val) + " is not a valid yesno value." )
            return -1
         else:
            return int(ret)
      # --- end of yesno (...) ---

      def fs_path ( val ):
         """val is a filesystem path - returns expanded path (~ -> HOME).

         arguments:
         * val --
         """
         return os.path.expanduser ( val ) if val else None
      # --- end of fs_path (...) ---

      def fs_abs ( val ):
         """val is a filesystem path - returns absolute + expanded path."""
         if val:
            return os.path.abspath ( os.path.expanduser ( val ) )
         else:
            return None

      def fs_file ( val ):
         """"val is a file - returns expanded path if it is
         an existent file or it does not exist.

         arguments:
         * val --
         """
         retval = fs_abs ( val )
         if retval:
            if os.path.isfile ( retval ) or not os.path.exists ( retval ):
               return retval

         return None
      # --- end of fs_file (...) ---

      def fs_dir ( val ):
         """val is a directory -- returns expanded path if it is
         an existent dir or it does not exist.

         arguments:
         * val --
         """
         retval = fs_abs ( val )
         if retval:
            if os.path.isdir ( retval ) or not os.path.exists ( retval ):
               return retval

         return None
      # --- end of fs_dir (...) ---

      def _regex ( val ):
         """val is a regex -- compile it if possible

         arguments:
         * val --
         """
         return re.compile ( val ) if not val is None else None
      # --- end of _regex (...) ---

      # replace whitespace with a single ' '
      if value_type is False:
         return ConfigLoader.WHITESPACE.sub ( ' ', value )
      else:
         value = unquote ( ConfigLoader.WHITESPACE.sub ( ' ', value ) )

      # convert value_type into a list of value types
      if not value_type:
         return value
      elif isinstance ( value_type, list ):
         vtypes = value_type
      elif isinstance ( value_type, str ):
         vtypes = value_type.split ( ':' )
      elif hasattr ( value_type, '__call__' ) or type ( value_type ) is type:
         try:
            return value_type ( value )
         except ValueError:
            return None
      else:
         self.logger.error (
            "Unknown value type {!r}.".format ( value_type )
         )
         return value

      # value_type -> function where function accepts one parameter
      funcmap = {
         'yesno'   : yesno,
         'int'     : to_int,
         'fs_dir'  : fs_dir,
         'fs_path' : fs_path,
         'fs_file' : fs_file,
         'fs_abs'  : fs_abs,
         'regex'   : _regex,
         'str'     : str,
      }

      # dofunc ( function f, <list or str> v) calls f(x) for every str in v
      dofunc = lambda f, v : [ f(x) for x in v ] \
         if isinstance ( v, list ) else f(v)

      retval = value.strip()

      for vtype in vtypes:
         if vtype == "slist" or vtype == "list":
            retval = list ( filter (
               None, self.__class__.WHITESPACE.split ( retval )
            ) )
         elif vtype in funcmap:
            retval = dofunc ( funcmap [vtype], retval )
         else:
            self.logger.warning ( "unknown value type '" + vtype + "'." )

      return retval
   # --- end of _make_and_verify_value (...) ---