render_template

#! /usr/bin/env python
import os
import sys
import json
import argparse

from jinja2 import Environment, ChoiceLoader, FileSystemLoader
from jinja2.exceptions import TemplateNotFound

def render_template():
    ARG_PARSER = argparse.ArgumentParser()
    ARG_PARSER.add_argument('template',
            help='Name of a template file to load'
    )
    ARG_PARSER.add_argument(
        '-j',
        '--json',
        type=open,
        default=sys.stdin,
        dest='json',
        help='a file containing the json data to merge with the selected template'
    )
    ARG_PARSER.add_argument(
        '-d',
        '--template-dir',
        default=os.environ.get('TEMPLATE_DIR', None),
        dest='template_dir',
        help='directory to load templates from'
    )
    args = ARG_PARSER.parse_args()
    cwd = os.getcwd()
    loader_list =[
                FileSystemLoader(os.path.join(cwd, 'templates/')),    
            ]
    if args.template_dir:
        loader_list.insert(0, FileSystemLoader(args.template_dir))
    jinja_env = Environment( loader=ChoiceLoader(loader_list) )

    try:
        template = jinja_env.get_template(args.template)
    except TemplateNotFound as e:
        sys.stderr.write("Could find no template named: %s\n" % (args.template))
        sys.exit(1)

    for line in args.json:
        sys.stdout.write(template.render(json.loads(line)))

if __name__ == "__main__":
    render_template()