##############################################################################
#
# Copyright (c) 2002 Zope Foundation and Contributors.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE
#
##############################################################################
'''Sequence insertion

       A sequence may be inserted using an 'in' command.  The 'in'
       command specifies the name of a sequence object and text to
       be inserted for each element in the sequence.

       The EPFS syntax for the in command is::

          %(in name)[
               text
          %(in name)]

       The HTML syntax for the in command is::

          <!--#in name-->
               text
          <!--#/in name-->

      See the example below that shows how 'if', 'else', and 'in' commands
      may be combined to display a possibly empty list of objects.

      The text included within an 'in' command will be refered to
      as an 'in' block.

    Synopsis

      If the variable 'sequence' exists as a sequence, a simple case
      of the 'in' tag is used as follows::

         <!--#in sequence-->some markup<!--#/in-->

      A more complete case is used as follows::

        <!--#in sequence sort=age-->
          <!--#var sequence-number-->) <!--#var age-->
        <!--#/in-->

    Attributes

      sort -- Define the sort order for sequence items.  Parameter to the
      attribute is either a sort option, or list of sort options separated
      by comma.  Every sort option consists of variable name, optional
      comparison function name (default is cmp) and optional sort order
      (default is asc).
          Examples: sort="date" or sort="date,time" or
      sort="title/locale,date/cmp/desc". If you want to specify sort order,
      you cannot omit the function; use cmp for standard comparison.
          Few predefined comparison functions available: standard cmp,
      nocase (ignore string case), strcoll (alias "locale"),
      strcoll_nocase (alias "locale_nocase"). Locale functions are
      available only if module locale is already imported (you started Zope
      with -L locale).

      sort_expr -- The "sort" attribute accepts only static list of
      sort options. This calculated parameter allows you to calculate the
      list of sort options on the fly.

      sort_expr -- This allows an expression to control sort order.

      reverse -- Reverse the sequence (may be combined with sort).  Note
      that this can cause a huge memory use in lazy activation instances.

      reverse_expr -- This calculated parameter allows you to calculate the
      need of reversing on the fly.

      Within an 'in' block, variables are substituted from the
      elements of the iteration unless the 'no_push_item' optional
      is specified.  The elements may be either instance or mapping
      objects.  In addition, the variables:

         'sequence-item' -- The element.

         'sequence-var-nnn' -- The value of a specific named attribute
           of the item, where 'nnn' is the name.  For example, to get
           an items 'title' attribute, use 'sequence-var-title'.  This
           construct is most useful in an 'if' tag to test whether an
           attribute is present, because the attribute lookup will be
           extended to the full document template namespace.

         'sequence-key' -- The key associated with the element in an
           items list. See below.

         'sequence-index' -- The index, starting from 0, of the
           element within the sequence.

         'sequence-number' -- The index, starting from 1, of the
           element within the sequence.

         'sequence-letter' -- The index, starting from 'a', of the
           element within the sequence.

         'sequence-Letter' -- The index, starting from 'A', of the
           element within the sequence.

         'sequence-roman' -- The index, starting from 'i', of the
           element within the sequence.

         'sequence-Roman' -- The index, starting from 'I', of the
           element within the sequence.

         'sequence-start' -- A variable that is true if the element
           being displayed is the first of the displayed elements,
           and false otherwise.

         'sequence-end' -- A variable that is true if the element
           being displayed is the last of the displayed elements,
           and false otherwise.

      are defined for each element.

      Normally, 'in' blocks are used to iterate over sequences of
      instances.  If the optional parameter 'mapping' is specified
      after the sequence name, then the elements of the sequence
      will be treated as mapping objects.

      An 'in' command may be used to iterate over a sequence of
      dictionary items.  If the elements of the iteration are
      two-element tuples, then then the template code given in the
      'in' block will be applied to the second element of each
      tuple and may use a variable, 'sequence-key' to access the
      first element in each tuple.

    Batch sequence insertion

      When displaying a large number of objects, it is sometimes
      desirable to display just a sub-sequence of the data.
      An 'in' command may have optional parameters,
      as in::

          <!--#in values start=start_var size=7-->

      The parameter values may be either integer literals or
      variable names.

      Up to five parameters may be set:

          'start'   -- The number of the first element to be shown,
                       where elements are numbered from 1.

          'end'     -- The number of the last element to be shown,
                       where elements are numbered from 1.

          'size'    -- The desired number of elements to be shown at
                       once.

          'orphan'  -- The desired minimum number of objects to be
                       displayed.  The default value for this
                       parameter is 0.

          'overlap' -- The desired overlap between batches. The
                       default is no overlap.

      Typically, only 'start' and 'size' will be specified.

      When batch insertion is used, several additional variables are
      defined for use within the sequence insertion text:

          'sequence-query' -- The original query string given in a get
             request with the form variable named in the 'start'
             attribute removed.  This is extremely useful when
             building URLs to fetch another batch.

             To see how this is used, consider the following example::

                 <!--#in search_results size=20 start=batch_start-->

                    ... display rows

                    <!--#if sequence-end--> <!--#if next-sequence-->
                      <a href="&dtml-URL;/&dtml-sequence-query;batch_start=&dtml-next-sequence-start-number;">
                      (Next &dtml-next-sequence-size; results)
                      </a>
                    <!--#/if--> <!--#/if-->

                 <!--#/in-->

             If the original URL is: 'foo/bar?x=1&y=2', then the
             rendered text (after row data are displayed) will be::

                      <a href="foo/bar?x=1&amp;y=2&amp;batch_start=20">
                      (Next 20 results)
                      </a>

             If the original URL is: 'foo/bar?batch_start=10&x=1&y=2',
             then the rendered text (after row data are displayed)
             will be::

                      <a href="foo/bar?x=1&amp;y=2&amp;batch_start=30">
                      (Next 20 results)
                      </a>

          'sequence-step-start-index' -- The index, starting from 0,
             of the start of the current batch.

          'sequence-step-end-index' -- The index, starting from 0, of
             the end of the current batch.

          'sequence-step-size' -- The batch size used.

          'previous-sequence' -- This variable will be true when the
             first element is displayed and when the first element
             displayed is not the first element in the sequence.

          'previous-sequence-start-index' -- The index, starting from
             0, of the start of the batch previous to the current
             batch.

          'previous-sequence-end-index' -- The index, starting from
             0, of the end of the batch previous to the current
             batch.

          'previous-sequence-size' -- The size of the batch previous to
             the current batch.

          'previous-batches' -- A sequence of mapping objects
             containing information about all of the batches prior
             to the batch being displayed.

             Each of these mapping objects include the following
             variables:

                batch-start-index -- The index, starting from
                   0, of the beginning of the batch.

                batch-end-index -- The index, starting from
                   0, of the end of the batch.

                batch-size -- The size of the batch.

          'next-sequence' -- This variable will be true when the last
             element is displayed and when the last element
             displayed is not the last element in the sequence.

          'next-sequence-start-index' -- The index, starting from
             0, of the start of the batch after the current
             batch.

          'next-sequence-end-index' -- The index, starting from
             0, of the end of the batch after the current
             batch.

          'next-sequence-size' -- The size of the batch after
             the current batch.

          'next-batches' -- A sequence of mapping objects
             containing information about all of the batches after
             the batch being displayed.

             Each of these mapping objects include the following
             variables:

                batch-start-index -- The index, starting from
                   0, of the beginning of the batch.

                batch-end-index -- The index, starting from
                   0, of the end of the batch.

                batch-size -- The size of the batch.

      For each of the variables listed above with names ending in
      "-index", there are variables with names ending in "-number",
      "-roman", "-Roman", "-letter", and "-Letter" that are indexed
      from 1, "i", "I", "a", and "A", respectively.  In addition,
      for every one of these variables there are variables with
      names ending in "-var-xxx", where "xxx" is an element
      attribute name or key.

    Summary statistics

      When performing sequence insertion, special variables may be
      used to obtain summary statistics.  To obtain a summary
      statistic for a variable, use the variable name:
      'statistic-name', where 'statistic' is a statistic name and
      'name' is the name of a data variable.

      Currently supported statistic names are:

        total -- The total of numeric values.

        count -- The total number of non-missing values.

        min -- The minimum of non-missing values.

        max -- The maximum of non-missing values.

        median -- The median of non-missing values.

        mean -- The mean of numeric values values.

        variance -- The variance of numeric values computed with a
          degrees of freedom equal to the count - 1.

        variance-n -- The variance of numeric values computed with a
          degrees of freedom equal to the count.

        standard-deviation -- The standard deviation of numeric values
          computed with a degrees of freedom equal to the count - 1.

        standard-deviation-n -- The standard deviation of numeric
          values computed with a degrees of freedom equal to the count.

      Missing values are either 'None' or the attribute 'Value'
      of the module 'Missing', if present.

    'else' continuation tag within in

      An 'else' tag may be used as a continuation tag in the 'in' tag.
      The source after the 'else' tag is inserted if:

        - The sequence given to the 'in' tag is of zero length, or

        - The 'previous' attribute was used and their are no
          previous batches, or

        - The 'next' attribute was used and their are no
          next batches, or

''' #'

__rcs_id__='$Id: DT_In.py 112186 2010-05-08 05:47:04Z tseaver $'
__version__='$Revision: 1.62 $'[11:-2]

import sys
import re

from DocumentTemplate.DT_Util import ParseError, parse_params, name_param
from DocumentTemplate.DT_Util import str, join_unicode
from DocumentTemplate.DT_Util import render_blocks, InstanceDict
from DocumentTemplate.DT_Util import ValidationError, Eval
from DocumentTemplate.DT_Util import simple_name, add_with_prefix
from DocumentTemplate.DT_InSV import sequence_variables, opt

TupleType = tuple
StringTypes = (str, unicode)

class InFactory:
    blockContinuations=('else',)
    name='in'

    def __call__(self, blocks):
        i=InClass(blocks)
        if i.batch: return i.renderwb
        else: return i.renderwob

In=InFactory()

class InClass:
    elses=None
    expr=sort=batch=mapping=no_push_item=None
    start_name_re=None
    reverse=None
    sort_expr=reverse_expr=None

    def __init__(self, blocks):
        tname, args, section = blocks[0]
        args=parse_params(args, name='', start='1',end='-1',size='10',
                          orphan='0',overlap='1',mapping=1,
                          no_push_item=1,
                          skip_unauthorized=1,
                          previous=1, next=1, expr='', sort='',
                          reverse=1, sort_expr='', reverse_expr='',
                          prefix='')
        self.args=args
        has_key=args.has_key

        if has_key('sort'):
            self.sort=sort=args['sort']
            if sort=='sequence-item': self.sort=''

        if has_key('sort_expr'):
            self.sort_expr=Eval(args['sort_expr'])

        if has_key('reverse_expr'):
            self.reverse_expr=Eval(args['reverse_expr'])

        if has_key('reverse'):
            self.reverse=args['reverse']

        if has_key('no_push_item'):
            self.no_push_item=args['no_push_item']

        if has_key('mapping'): self.mapping=args['mapping']
        for n in 'start', 'size', 'end':
            if has_key(n): self.batch=1

        prefix = args.get('prefix')
        if prefix and not simple_name(prefix):
            raise ParseError, _tm(
                'prefix is not a simple name', 'in')

        for n in 'orphan','overlap','previous','next':
            if has_key(n) and not self.batch:
                raise ParseError, (
                    """
                    The %s attribute was used but neither of the
                    <code>start</code>, <code>end</code>, or <code>size</code>
                    attributes were used.
                    """ % n, 'in')

        if has_key('start'):
            v=args['start']
            if type(v)==type(''):
                try: int(v)
                except:

                    self.start_name_re=re.compile(
                        '&+'+
                        ''.join(["[%s]" % c for c in v])+
                        '=[0-9]+&+')

        name,expr=name_param(args,'in',1)
        if expr is not None: expr=expr.eval
        self.__name__, self.expr = name, expr
        self.section=section.blocks
        if len(blocks) > 1:
            if len(blocks) != 2: raise ParseError, (
                'too many else blocks', 'in')
            tname, args, section = blocks[1]
            args=parse_params(args, name='')
            if args:
                ename=name_param(args)
                if ename != name:
                    raise ParseError, (
                        'name in else does not match in', 'in')
            self.elses=section.blocks


    def renderwb(self, md):
        expr=self.expr
        name=self.__name__
        if expr is None:
            sequence=md[name]
            cache={ name: sequence }
        else:
            sequence=expr(md)
            cache=None

        if not sequence:
            if self.elses: return render_blocks(self.elses, md)
            return ''

        if type(sequence) is type(''):
            raise ValueError, (
                'Strings are not allowed as input to the in tag.')


        section=self.section
        params=self.args

        mapping=self.mapping
        no_push_item=self.no_push_item

        if self.sort_expr is not None:
            self.sort=self.sort_expr.eval(md)
            sequence=self.sort_sequence(sequence, md)
        elif self.sort is not None:
            sequence=self.sort_sequence(sequence, md)

        if self.reverse_expr is not None and self.reverse_expr.eval(md):
            sequence=self.reverse_sequence(sequence)
        elif self.reverse is not None:
            sequence=self.reverse_sequence(sequence)

        next=previous=0
        try: start=int_param(params,md,'start',0)
        except: start=1
        end=int_param(params,md,'end',0)
        size=int_param(params,md,'size',0)
        overlap=int_param(params,md,'overlap',0)
        orphan=int_param(params,md,'orphan','0')
        start,end,sz=opt(start,end,size,orphan,sequence)
        if params.has_key('next'): next=1
        if params.has_key('previous'): previous=1

        last=end-1
        first=start-1

        try: query_string=md['QUERY_STRING']
        except: query_string=''
        prefix = params.get('prefix')
        vars = sequence_variables(sequence, '?'+query_string,
                                  self.start_name_re, prefix)
        kw=vars.data
        pkw = add_with_prefix(kw, 'sequence', prefix)
        for k, v in kw.items():
            pkw[k] = v
        pkw['sequence-step-size']=sz
        pkw['sequence-step-overlap']=overlap
        pkw['sequence-step-start']=start
        pkw['sequence-step-end']=end
        pkw['sequence-step-start-index']=start-1
        pkw['sequence-step-end-index']=end-1
        pkw['sequence-step-orphan']=orphan

        kw['mapping']=mapping

        push=md._push
        pop=md._pop
        render=render_blocks

        if cache: push(cache)
        push(vars)
        try:
            if previous:
                if first > 0:
                    pstart,pend,psize=opt(0,first+overlap,
                                          sz,orphan,sequence)
                    pkw['previous-sequence']=1
                    pkw['previous-sequence-start-index']=pstart-1
                    pkw['previous-sequence-end-index']=pend-1
                    pkw['previous-sequence-size']=pend+1-pstart
                    result=render(section,md)

                elif self.elses: result=render(self.elses, md)
                else: result=''
            elif next:
                try:
                    # The following line is a sneaky way to test whether
                    # there are more items, without actually
                    # computing a length:
                    sequence[end]
                except IndexError:
                    if self.elses: result=render(self.elses, md)
                    else: result=''
                else:
                    pstart,pend,psize=opt(end+1-overlap,0,
                                          sz,orphan,sequence)
                    pkw['next-sequence']=1
                    pkw['next-sequence-start-index']=pstart-1
                    pkw['next-sequence-end-index']=pend-1
                    pkw['next-sequence-size']=pend+1-pstart
                    result=render(section,md)
            else:
                result = []
                append=result.append
                guarded_getitem = getattr(md, 'guarded_getitem', None)
                for index in range(first,end):
                    # preset
                    pkw['previous-sequence']= 0
                    pkw['next-sequence']= 0 # now more often defined then previously
                    #
                    if index==first or index==last:
                        # provide batching information
                        if first > 0:
                            pstart,pend,psize=opt(0,first+overlap,
                                                  sz,orphan,sequence)
                            if index==first: pkw['previous-sequence']=1
                            pkw['previous-sequence-start-index']=pstart-1
                            pkw['previous-sequence-end-index']=pend-1
                            pkw['previous-sequence-size']=pend+1-pstart
                        try:
                            # The following line is a sneaky way to
                            # test whether there are more items,
                            # without actually computing a length:
                            sequence[end]
                            pstart,pend,psize=opt(end+1-overlap,0,
                                                  sz,orphan,sequence)
                            if index==last: pkw['next-sequence']=1
                            pkw['next-sequence-start-index']=pstart-1
                            pkw['next-sequence-end-index']=pend-1
                            pkw['next-sequence-size']=pend+1-pstart
                        except: pass

                    if index==last: pkw['sequence-end']=1

                    if guarded_getitem is not None:
                        try: client = guarded_getitem(sequence, index)
                        except ValidationError, vv:
                            if (params.has_key('skip_unauthorized') and
                                params['skip_unauthorized']):
                                if index==first: pkw['sequence-start']=0
                                continue
                            raise ValidationError, '(item %s): %s' % (
                                index, vv), sys.exc_info()[2]
                    else:
                        client = sequence[index]

                    pkw['sequence-index']=index
                    t = type(client)
                    if t is TupleType and len(client)==2:
                        client=client[1]

                    if no_push_item:
                        pushed = 0
                    elif mapping:
                        pushed = 1
                        push(client)
                    elif t in StringTypes:
                        pushed = 0
                    else:
                        pushed = 1
                        push(InstanceDict(client, md))

                    try: append(render(section, md))
                    finally:
                        if pushed:
                            pop()

                    if index==first: pkw['sequence-start']=0


                result = join_unicode(result)

        finally:
            if cache: pop()
            pop()

        return result

    def renderwob(self, md):
        """RENDER WithOutBatch"""
        expr=self.expr
        name=self.__name__
        if expr is None:
            sequence=md[name]
            cache={ name: sequence }
        else:
            sequence=expr(md)
            cache=None

        if not sequence:
            if self.elses: return render_blocks(self.elses, md)
            return ''

        if type(sequence) is type(''):
            raise ValueError, (
                'Strings are not allowed as input to the in tag.')

        section=self.section
        mapping=self.mapping
        no_push_item=self.no_push_item

        if self.sort_expr is not None:
            self.sort=self.sort_expr.eval(md)
            sequence=self.sort_sequence(sequence, md)
        elif self.sort is not None:
            sequence=self.sort_sequence(sequence, md)

        if self.reverse_expr is not None and self.reverse_expr.eval(md):
            sequence=self.reverse_sequence(sequence)
        elif self.reverse is not None:
            sequence=self.reverse_sequence(sequence)

        prefix = self.args.get('prefix')
        vars=sequence_variables(sequence, alt_prefix=prefix)
        kw=vars.data
        pkw = add_with_prefix(kw, 'sequence', prefix)
        for k, v in kw.items():
            pkw[k] = v
        kw['mapping']=mapping

        l=len(sequence)
        last=l-1

        push=md._push
        pop=md._pop
        render=render_blocks

        if cache: push(cache)
        push(vars)
        try:
            result = []
            append=result.append
            guarded_getitem = getattr(md, 'guarded_getitem', None)
            for index in range(l):
                if index==last: pkw['sequence-end']=1
                if guarded_getitem is not None:
                    try: client = guarded_getitem(sequence, index)
                    except ValidationError, vv:
                        if (self.args.has_key('skip_unauthorized') and
                            self.args['skip_unauthorized']):
                            if index==1: pkw['sequence-start']=0
                            continue
                        raise ValidationError, '(item %s): %s' % (
                            index, vv), sys.exc_info()[2]
                else:
                    client = sequence[index]

                pkw['sequence-index']=index
                t = type(client)
                if t is TupleType and len(client)==2:
                    client=client[1]

                if no_push_item:
                    pushed = 0
                elif mapping:
                    pushed = 1
                    push(client)
                elif t in StringTypes:
                    pushed = 0
                else:
                    pushed = 1
                    push(InstanceDict(client, md))

                try: append(render(section, md))
                finally:
                    if pushed:
                        pop()
                if index==0: pkw['sequence-start']=0

            result = join_unicode(result)

        finally:
            if cache: pop()
            pop()

        return result

    def sort_sequence(self, sequence, md):

        # Modified with multiple sort fields by Ross Lazarus
        # April 7 2000 rossl@med.usyd.edu.au
        # eg <dtml-in "foo" sort="akey,anotherkey">

        # Modified with advanced sort functions by
        # Oleg Broytmann <phd@phd.pp.ru> 30 Mar 2001
        # eg <dtml-in "foo" sort="akey/nocase,anotherkey/cmp/desc">

        sort=self.sort
        need_sortfunc = sort.find('/') >= 0

        sortfields = sort.split(',')   # multi sort = key1,key2
        multsort = len(sortfields) > 1 # flag: is multiple sort

        if need_sortfunc:
            # prepare the list of functions and sort order multipliers
            sf_list = make_sortfunctions(sortfields, md)

            # clean the mess a bit
            if multsort: # More than one sort key.
                sortfields = map(lambda x: x[0], sf_list)
            else:
                sort = sf_list[0][0]

        mapping=self.mapping
        isort=not sort

        s=[]
        for client in sequence:
            k = None
            if type(client)==TupleType and len(client)==2:
                if isort: k=client[0]
                v=client[1]
            else:
                if isort: k=client
                v=client

            if sort:
                if multsort: # More than one sort key.
                    k = []
                    for sk in sortfields:
                        if mapping: akey = v.get(sk)
                        else: akey = getattr(v, sk, None)
                        if not basic_type(akey):
                            try: akey = akey()
                            except: pass
                        k.append(akey)
                else: # One sort key.
                    if mapping: k = v.get(sort)
                    else: k = getattr(v, sort, None)
                    if not basic_type(type(k)):
                        try: k = k()
                        except: pass

            s.append((k,client))

        if need_sortfunc:
            by = SortBy(multsort, sf_list)
            s.sort(by)
        else:
            s.sort()

        sequence=[]
        for k, client in s:
            sequence.append(client)
        return sequence

    def reverse_sequence(self, sequence):
        s=list(sequence)
        s.reverse()
        return s


basic_type={type(''): 1, type(0): 1, type(0.0): 1, type(()): 1, type([]): 1,
            type(None) : 1 }.has_key

def int_param(params,md,name,default=0, st=type('')):
    try: v=params[name]
    except: v=default
    if v:
        try: v=int(v)
        except:
            v=md[v]
            if type(v) is st: v=int(v)
    return v


# phd: Advanced sort support

def nocase(str1, str2):
    return cmp(str1.lower(), str2.lower())

if sys.modules.has_key("locale"): # only if locale is already imported
    from locale import strcoll

    def strcoll_nocase(str1, str2):
        return strcoll(str1.lower(), str2.lower())


def make_sortfunctions(sortfields, md):
    """Accepts a list of sort fields; splits every field, finds comparison
    function. Returns a list of 3-tuples (field, cmp_function, asc_multplier)"""

    sf_list = []
    for field in sortfields:
        f = field.split('/')
        l = len(f)

        if l == 1:
            f.append("cmp")
            f.append("asc")
        elif l == 2:
            f.append("asc")
        elif l == 3:
            pass
        else:
            raise SyntaxError, "sort option must contain no more than 2 slashes"

        f_name = f[1]

        # predefined function?
        if f_name == "cmp":
            func = cmp # builtin
        elif f_name == "nocase":
            func = nocase
        elif f_name in ("locale", "strcoll"):
            func = strcoll
        elif f_name in ("locale_nocase", "strcoll_nocase"):
            func = strcoll_nocase
        else: # no - look it up in the namespace
            func = md.getitem(f_name, 0)

        sort_order = f[2].lower()

        if sort_order == "asc":
            multiplier = +1
        elif sort_order == "desc":
            multiplier = -1
        else:
            raise SyntaxError, "sort oder must be either ASC or DESC"

        sf_list.append((f[0], func, multiplier))

    return sf_list


class SortBy:
    def __init__(self, multsort, sf_list):
        self.multsort = multsort
        self.sf_list = sf_list

    def __call__(self, o1, o2):
        multsort = self.multsort
        if multsort:
            o1 = o1[0] # if multsort - take the first element (key list)
            o2 = o2[0]

        sf_list = self.sf_list
        l = len(sf_list)

        # assert that o1 and o2 are tuples of apropriate length
        assert len(o1) == l + 1 - multsort, "%s, %d" % (o1, l + multsort)
        assert len(o2) == l + 1 - multsort, "%s, %d" % (o2, l + multsort)

        # now run through the list of functions in sf_list and
        # compare every object in o1 and o2
        for i in range(l):
            # if multsort - we already extracted the key list
            # if not multsort - i is 0, and the 0th element is the key
            c1, c2 = o1[i], o2[i]
            func, multiplier = sf_list[i][1:3]
            n = func(c1, c2)
            if n: return n*multiplier

        # all functions returned 0 - identical sequences
        return 0
