# Copyright (c) 2010 Chris Moyer http://coredumped.org/
#
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish, dis-
# tribute, sublicense, and/or sell copies of the Software, and to permit
# persons to whom the Software is furnished to do so, subject to the fol-
# lowing conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABIL-
# ITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
# SHALL THE AUTHOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, 
# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
# IN THE SOFTWARE.

from boto.exception import SDBResponseError

class SequenceGenerator(object):
    """Generic Sequence Generator object, this takes a single
    string as the "sequence" and uses that to figure out
    what the next value in a string is. For example
    if you give "ABC" and pass in "A" it will give you "B",
    and if you give it "C" it will give you "AA".

    If you set "rollover" to True in the above example, passing
    in "C" would give you "A" again.

    The Sequence string can be a string or any iterable
    that has the "index" function and is indexable.
    """
    __name__ = "SequenceGenerator"

    def __init__(self, sequence_string, rollover=False):
        """Create a new SequenceGenerator using the sequence_string
        as how to generate the next item.

        :param sequence_string: The string or list that explains
        how to generate the next item in the sequence
        :type sequence_string: str,iterable

        :param rollover: Rollover instead of incrementing when
        we hit the end of the sequence
        :type rollover: bool
        """
        self.sequence_string = sequence_string
        self.sequence_length = len(sequence_string[0])
        self.rollover = rollover
        self.last_item = sequence_string[-1]
        self.__name__ = "%s('%s')" % (self.__class__.__name__, sequence_string)

    def __call__(self, val, last=None):
        """Get the next value in the sequence"""
        # If they pass us in a string that's not at least
        # the lenght of our sequence, then return the
        # first element in our sequence
        if val == None or len(val) < self.sequence_length:
            return self.sequence_string[0]
        last_value = val[-self.sequence_length:]
        if (not self.rollover) and (last_value == self.last_item):
            val = "%s%s" % (self(val[:-self.sequence_length]), self._inc(last_value))
        else:
            val = "%s%s" % (val[:-self.sequence_length], self._inc(last_value))
        return val

    def _inc(self, val):
        """Increment a single value"""
        assert(len(val) == self.sequence_length)
        return self.sequence_string[(self.sequence_string.index(val)+1) % len(self.sequence_string)]



#
# Simple Sequence Functions
#
def increment_by_one(cv=None, lv=None):
    if cv == None:
        return 0
    return cv + 1

def double(cv=None, lv=None):
    if cv == None:
        return 1
    return cv * 2

def fib(cv=1, lv=0):
    """The fibonacci sequence, this incrementer uses the
    last value"""
    if cv == None:
        cv = 1
    if lv == None:
        lv = 0
    return cv + lv

increment_string = SequenceGenerator("ABCDEFGHIJKLMNOPQRSTUVWXYZ")



class Sequence(object):
    """A simple Sequence using the new SDB "Consistent" features
    Based largly off of the "Counter" example from mitch garnaat:
    http://bitbucket.org/mitch/stupidbototricks/src/tip/counter.py"""


    def __init__(self, id=None, domain_name=None, fnc=increment_by_one, init_val=None):
        """Create a new Sequence, using an optional function to 
        increment to the next number, by default we just increment by one.
        Every parameter here is optional, if you don't specify any options
        then you'll get a new SequenceGenerator with a random ID stored in the
        default domain that increments by one and uses the default botoweb 
        environment

        :param id: Optional ID (name) for this counter
        :type id: str

        :param domain_name: Optional domain name to use, by default we get this out of the
            environment configuration
        :type domain_name:str

        :param fnc: Optional function to use for the incrementation, by default we just increment by one
            There are several functions defined in this module.
            Your function must accept "None" to get the initial value
        :type fnc: function, str

        :param init_val: Initial value, by default this is the first element in your sequence, 
            but you can pass in any value, even a string if you pass in a function that uses
            strings instead of ints to increment
        """
        self._db = None
        self._value = None
        self.last_value = None
        self.domain_name = domain_name
        self.id = id
        if self.id == None:
            import uuid
            self.id = str(uuid.uuid4())
            if init_val == None:
                init_val = fnc(init_val)
            self.val = init_val

        self.item_type = type(fnc(None))
        self.timestamp = None
        # Allow us to pass in a full name to a function
        if type(fnc) == str:
            from boto.utils import find_class
            fnc = find_class(fnc)
        self.fnc = fnc

    def set(self, val):
        """Set the value"""
        import time
        now = time.time()
        expected_values = []
        new_val = {}
        new_val['timestamp'] = now
        if self._value != None:
            new_val['last_value'] = self._value
            expected_values = ['current_value', str(self._value)]
        new_val['current_value'] = val
        try:
            self.db.put_attributes(self.id, new_val, expected_values=expected_values)
            self.timestamp = new_val['timestamp']
        except SDBResponseError, e:
            if e.status == 409:
                raise ValueError, "Sequence out of sync"
            else:
                raise


    def get(self):
        """Get the value"""
        val = self.db.get_attributes(self.id, consistent_read=True)
        if val and val.has_key('timestamp'):
            self.timestamp = val['timestamp']
        if val and val.has_key('current_value'):
            self._value = self.item_type(val['current_value'])