#!/usr/bin/env python2.7
import os
import sys
from lib2to3 import pygram, pytree
from lib2to3.pgen2 import driver

BIN_DIR = os.path.dirname(__file__)

def find(node, leaf):
    if node == leaf:
        return node
    for c in node.children:
        if find(c, leaf):
            return find(c, leaf)

if __name__ == "__main__":
    if len(sys.argv) != 3:
        print "usage: %s settings_file target_file" % sys.argv[0]
        sys.exit(1)

    src     = sys.argv[1]
    dest    = sys.argv[2]
    patch   = os.path.join(BIN_DIR, "dbs.py.src")

    drv = driver.Driver(pygram.python_grammar, pytree.convert)
    root = drv.parse_file(src)

    node = find(root, pytree.Leaf(1, "DATABASES")) # Find node for DATABASES = { ... }
    end  = node.parent.next_sibling # calculate adjacent sibling

    with open(src) as _src:
        head = [_src.next() for x in xrange(end.lineno)]
        tail = [l for x,l in enumerate(_src)]

    with open(patch) as _patch:
        body = [l for x,l in enumerate(_patch)]

    with open(dest, "w") as _dest:
        _dest.writelines(head)
        _dest.writelines(body)
        _dest.writelines(tail)