"""
Reads a JSON file and uses it to call into a datatype class to extract
a subset of a dataset for processing.

Used by jobs that split large files into pieces to be processed concurrently
on a gid in a scatter-gather mode. This does part of the scatter.

"""
import json
import logging
import os
import sys
logging.basicConfig()
log = logging.getLogger( __name__ )

new_path = [ os.path.join( os.getcwd(), "lib" ) ]
new_path.extend( sys.path[1:] ) # remove scripts/ from the path
sys.path = new_path

# This junk is here to prevent loading errors
import galaxy.model.mapping #need to load this before we unpickle, in order to setup properties assigned by the mappers
galaxy.model.Job() #this looks REAL stupid, but it is REQUIRED in order for SA to insert parameters into the classes defined by the mappers --> it appears that instantiating ANY mapper'ed class would suffice here

def __main__():
    """
    Argument: a JSON file
    """
    file_path = sys.argv.pop( 1 )
    if not os.path.isfile(file_path):
        #Nothing to do - some splitters don't write a JSON file
        sys.exit(0)
    data = json.load(open(file_path, 'r'))
    try:
        class_name_parts = data['class_name'].split('.')
        module_name = '.'.join(class_name_parts[:-1])
        class_name = class_name_parts[-1]
        mod = __import__(module_name, globals(),  locals(),  [class_name])
        cls = getattr(mod,  class_name)
        if not cls.process_split_file(data):
            sys.stderr.write('Writing split file failed\n')
            sys.exit(1)
    except Exception, e:
        sys.stderr.write(str(e))
        sys.exit(1)
        
__main__()