# Copyright (c) 2006,2007 Mitch Garnaat http://garnaat.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,
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# IN THE SOFTWARE.

"""
Represents an SQS Queue
"""

import xml.sax
import urlparse
from boto.exception import SQSError
from boto.handler import XmlHandler
from boto.sqs.message import Message
from boto.resultset import ResultSet

class Queue:
    
    def __init__(self, connection=None, url=None, message_class=Message):
        self.connection = connection
        self.url = url
        self.message_class = message_class
        self.visibility_timeout = None

    def startElement(self, name, attrs, connection):
        return None

    def endElement(self, name, value, connection):
        if name == 'QueueUrl':
            self.url = value
            if value:
                self.id = urlparse.urlparse(value)[2]
        elif name == 'VisibilityTimeout':
            self.visibility_timeout = int(value)
        else:
            setattr(self, name, value)

    def set_message_class(self, message_class):
        """
        Set the message class that should be used when instantiating messages read
        from the queue.  By default, the class boto.sqs.message.Message is used but
        this can be overriden with any class that behaves like a message.
        Inputs:
            message_class - The new message class
        Returns:
            Nothing
        """
        self.message_class = message_class

    def get_attributes(self, attributes='All'):
        """
        Retrieves attributes about this queue object and returns
        them in an Attribute instance (subclass of a Dictionary).
        Inputs:
            attributes - A string containing
                         All|ApproximateNumberOfMessages|VisibilityTimeout
                         Default value is "All"
        Returns:
            An Attribute object which is a mapping type holding the
            requested name/value pairs
        """
        return self.connection.get_queue_attributes(self.id, attributes)

    def set_attribute(self, attribute, value):
        """
        Set a new value for an attribute of the Queue.
        Inputs:
            attribute - The name of the attribute you want to set.  The
                        only valid value at this time is: VisibilityTimeout
                value - The new value for the attribute.
                        For VisibilityTimeout the value must be an
                        integer number of seconds from 0 to 86400.
        Returns:
            Boolean True if successful, otherwise False.
        """
        return self.connection.set_queue_attribute(self.id, attribute, value)

    def get_timeout(self):
        """
        Get the visibility timeout for the queue.
        Inputs:
            None
        Returns:
            The number of seconds as an integer.
        """
        a = self.get_attributes('VisibilityTimeout')
        return int(a['VisibilityTimeout'])

    def set_timeout(self, visibility_timeout):
        """
        Set the visibility timeout for the queue.
        Inputs:
            visibility_timeout - The desired timeout in seconds
        Returns:
            Nothing
        """
        retval = self.set_attribute('VisibilityTimeout', visibility_timeout)
        if retval:
            self.visibility_timeout = visibility_timeout
        return retval

    def read(self, visibility_timeout=None):
        """
        Read a single message from the queue.
        Inputs:
            visibility_timeout - The timeout for this message in seconds
        Returns:
            A single message or None if queue is empty
        """
        rs = self.get_messages(1, visibility_timeout)
        if len(rs) == 1:
            return rs[0]
        else:
            return None

    def write(self, message):
        """
        Add a single message to the queue.
        Inputs:
            message - The message to be written to the queue
        Returns:
            None
        """
        self.connection.send_message(self.url, message.get_body_encoded())
        return None

    def new_message(self, body=''):
        return self.message_class(self, body)

    # get a variable number of messages, returns a list of messages
    def get_messages(self, num_messages=1, visibility_timeout=None):
        return self.connection.receive_message(self.url, number_messages=num_messages,
                                               visibility_timeout=visibility_timeout,
                                               message_class=self.message_class)

    def delete_message(self, message):
        return self.connection.delete_message(self.url, message.id, message.receipt_handle)

    def delete(self):
        return self.connection.delete_queue(self)

    def clear(self, page_size=10, vtimeout=10):
        """Utility function to remove all messages from a queue"""
        n = 0
        l = self.get_messages(page_size, vtimeout)
        while l:
            for m in l:
                self.delete_message(m)
                n += 1
            l = self.get_messages(page_size, vtimeout)
        return n

    def count(self, page_size=10, vtimeout=10):
        """
        Utility function to count the number of messages in a queue.
        Note: This function now calls GetQueueAttributes to obtain
        an 'approximate' count of the number of messages in a queue.
        """
        a = self.get_attributes('ApproximateNumberOfMessages')
        return a['ApproximateNumberOfMessages']
    
    def count_slow(self, page_size=10, vtimeout=10):
        """
        Deprecated.  This is the old 'count' method that actually counts
        the messages by reading them all.  This gives an accurate count but
        is very slow for queues with non-trivial number of messasges.
        Instead, use get_attribute('ApproximateNumberOfMessages') to take
        advantage of the new SQS capability.  This is retained only for
        the unit tests.
        """
        n = 0
        l = self.get_messages(page_size, vtimeout)
        while l:
            for m in l:
                n += 1
            l = self.get_messages(page_size, vtimeout)
        return n
    
    def dump(self, file_name, page_size=100, vtimeout=10, sep='\n'):
        """Utility function to dump the messages in a queue to a file"""
        fp = open(file_name, 'wb')
        n = 0
        l = self.get_messages(page_size, vtimeout)
        while l:
            for m in l:
                fp.write(m.get_body())
                if sep:
                    fp.write(sep)
                n += 1
            l = self.get_messages(page_size, vtimeout)
        fp.close()
        return n

    def save(self, file_name, sep='\n'):
        """
        Read all messages from the queue and persist them to local file.
        Messages are written to the file and the 'sep' string is written
        in between messages.  Messages are deleted from the queue after
        being written to the file.
        Returns the number of messages saved.
        """
        fp = open(file_name, 'wb')
        n = 0
        m = self.read()
        while m:
            n += 1
            fp.write(m.get_body())
            if sep:
                fp.write(sep)
            self.delete_message(m)
            m = self.read()
        fp.close()
        return n

    def save_to_s3(self, bucket):
        """
        Read all messages from the queue and persist them to S3.
        Messages are stored in the S3 bucket using a naming scheme of:
            <queue_id>/<message_id>
        Messages are deleted from the queue after being saved to S3.
        Returns the number of messages saved.
        """
        n = 0
        m = self.read()
        while m:
            n += 1
            key = bucket.new_key('%s/%s' % (self.id, m.id))
            key.set_contents_from_string(m.get_body())
            self.delete_message(m)
            m = self.read()
        return n

    def load_from_s3(self, bucket, prefix=None):
        """
        Load messages previously saved to S3.
        """
        n = 0
        if prefix:
            prefix = '%s/' % prefix
        else:
            prefix = '%s/' % self.id
        rs = bucket.list(prefix=prefix)
        for key in rs:
            n += 1
            m = self.new_message(key.get_contents_as_string())
            self.write(m)
        return n

    def load(self, file_name, sep='\n'):
        """Utility function to load messages from a file to a queue"""
        fp = open(file_name, 'rb')
        n = 0
        body = ''
        l = fp.readline()
        while l:
            if l == sep:
                m = Message(self, body)
                self.write(m)
                n += 1
                print 'writing message %d' % n
                body = ''
            else:
                body = body + l
            l = fp.readline()
        fp.close()
        return n