"""Demonstrate the use of a writer output class with Pyana

This example demonstrates using a writer object (an object implementing
a "write" method and, optionally, a "flush" method) as the output target
of the transformationn.

The actual example implements a writer that compresses the output as it
receives it using zlib. At the end of the script, the size of the actual
XSL output and the size of the compessed output are displayed.
"""

import sys
import zlib
import Pyana

class CompressionWriter: 
    def __init__(self, compressionLevel = 9):
        self.compressor = zlib.compressobj(compressionLevel)
        self.actualSize = 0
        self.compressedData = ''
        
    def write(self, buffer):
        self.actualSize += len(buffer)
        self.compressedData += self.compressor.compress(buffer)
        
    def transformFinished(self):
        self.compressedData += self.compressor.flush()
        self.compressedSize = len(self.compressedData)

# All this transformation does it generate the source document. You can
# change it to something more interesting if you like.
identityTransform = r'''
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <!-- Whenever you match any node or any attribute -->
  <xsl:template match="node()|@*">
    <!-- Copy the current node -->
    <xsl:copy>
      <!-- Including any attributes it has and any child nodes -->
      <xsl:apply-templates select="@*|node()"/>
    </xsl:copy>
  </xsl:template>
</xsl:stylesheet>
'''

def getXMLCompressability(url):
    compressionWriter = CompressionWriter()
    Pyana.transform2Writer(source=Pyana.URI(url), style=identityTransform, writer=compressionWriter)
    compressionWriter.transformFinished()

    print 'The actual XML output was: %d bytes' % compressionWriter.actualSize
    print 'The compressed XML output was: %d bytes' % compressionWriter.compressedSize
    print 'Compression ratio: %.2f%%' % (float(compressionWriter.compressedSize)/float(compressionWriter.actualSize) * 100)

if __name__ == '__main__':
    if len(sys.argv) == 1:
        print 'usage: %s url1 [url2] .. [urln]\n'\
              'e.g. %s http://pyana.sourceforge.net/' % (sys.argv[0], sys.argv[0])
    else:
        for url in sys.argv[1:]:
            getXMLCompressability(url)