# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2014 IBM Corporation
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# this will implement noderange grammar

# considered ast, but a number of things violate python grammar like [] in
# the middle of strings and use of @ for anything is not in their syntax


import itertools
import pyparsing as pp
import re

# construct custom grammar with pyparsing
_nodeword = pp.Word(pp.alphanums + '/=-:.*+')
_nodebracket = pp.QuotedString(quoteChar='[', endQuoteChar=']',
                               unquoteResults=False)
_nodeatom = pp.Group(pp.OneOrMore(_nodeword | _nodebracket))
_grammar = _nodeatom | ',-' | ',' | '@'
_parser = pp.nestedExpr(content=_grammar)

_numextractor = pp.OneOrMore(pp.Word(pp.alphas + '-') | pp.Word(pp.nums))

#TODO: pagination operators <pp.nums and >pp.nums for begin and end respective
class NodeRange(object):
    """Iterate over a noderange

    :param noderange: string representing a noderange to evaluate
    :param verify: whether or not to perform lookups in the config
    """

    def __init__(self, noderange, verify=True):
        self.verify = verify
        elements = _parser.parseString("(" + noderange + ")").asList()[0]
        self._noderange = self._evaluate(elements)

    @property
    def nodes(self):
        return self._noderange

    def _evaluate(self, parsetree):
        current_op = 0  # enum, 0 union, 1 subtract, 2 intersect
        current_range = set([])
        if not isinstance(parsetree[0], list):  # down to a plain text thing
            return self._expandstring(parsetree)
        for elem in parsetree:
            if elem == ',-':
                current_op = 1
            elif elem == ',':
                current_op = 0
            elif elem == '@':
                current_op = 2
            elif current_op == 0:
                current_range |= self._evaluate(elem)
            elif current_op == 1:
                current_range -= self._evaluate(elem)
            elif current_op == 2:
                current_range &= self._evaluate(elem)
        return current_range

    def failorreturn(self, atom):
        if self.verify:
            raise Exception(atom + " not valid")
        return set([atom])

    def expandrange(self, range, delimiter):
        pieces = range.split(delimiter)
        if len(pieces) % 2 != 0:
            return self.failorreturn(range)
        halflen = len(pieces) / 2
        left = delimiter.join(pieces[:halflen])
        right = delimiter.join(pieces[halflen:])
        leftbits = _numextractor.parseString(left).asList()
        rightbits = _numextractor.parseString(right).asList()
        if len(leftbits) != len(rightbits):
            return self.failorreturn(range)
        finalfmt = ''
        iterators = []
        for idx in xrange(len(leftbits)):
            if leftbits[idx] == rightbits[idx]:
                finalfmt += leftbits[idx]
            elif leftbits[idx][0] in pp.alphas:
                # if string portion unequal, not going to work
                return self.failorreturn(range)
            else:
                curseq = []
                finalfmt += '{%d}' % len(iterators)
                iterators.append(curseq)
                leftnum = int(leftbits[idx])
                rightnum = int(rightbits[idx])
                if leftnum > rightnum:
                    width = len(rightbits[idx])
                    minnum = rightnum
                    maxnum = leftnum + 1  # xrange goes to n-1...
                elif rightnum > leftnum:
                    width = len(leftbits[idx])
                    minnum = leftnum
                    maxnum = rightnum + 1
                else:  # differently padded, but same number...
                    return self.failorreturn(range)
                numformat = '{0:0%d}' % width
                for num in xrange(minnum, maxnum):
                    curseq.append(numformat.format(num))
        results = set([])
        for combo in itertools.product(*iterators):
            results.add(finalfmt.format(*combo))
        return results

    def _expandstring(self, element):
        prefix = ''
        for idx in xrange(len(element)):
            if element[idx][0] == '[':
                nodes = set([])
                for numeric in NodeRange(element[idx][1:-1], False).nodes:
                    nodes |= self._expandstring(
                            [prefix + numeric] + element[idx + 1:])
                return nodes
            else:
                prefix += element[idx]
        element = prefix
        nodes = set([])
        if self.verify:
            #this is where we would check for exactly this
            raise Exception("TODO: link with actual config")
        #this is where we would check for a literal groupname
        #ok, now time to understand the various things
        if '-' in element and ':' not in element:
            return self.expandrange(element, '-')
        elif ':' in element:  # : range for less ambiguity
            return self.expandrange(element, ':')
        elif '=' in element:
            raise Exception('TODO: criteria noderange')
        elif element[0] in ('/', '~'):
            raise Exception('TODO: regex noderange')
        elif '+' in element:
            raise Exception('TODO: plus range')
        if not self.verify:
            return set([element])