#!/usr/bin/env python
# A Python function for overlaying a source directory on top of a destination dir

import os
import re

from conda_build.utils import merge_tree, _copy_with_shell_fallback

def build_absolute_paths(src, dest, dest_prefix):
    abs_src = os.path.abspath(src)
    abs_dest = os.path.join(dest_prefix, re.sub(r'^/+', '', dest))
    return abs_src, abs_dest

def overlay(src, dest, dest_prefix):
    abs_src, abs_dest = build_absolute_paths(src, dest, dest_prefix)
    if os.path.isfile(abs_src):
        os.makedirs(os.path.dirname(abs_dest))
        _copy_with_shell_fallback(abs_src, abs_dest)
    elif os.path.isdir(abs_src):
        merge_tree(abs_src, abs_dest)

if __name__ == "__main__":
    # The conda-build dir is overlaid on PREFIX/
    overlay("/Users/sodre/git/conda/conda-build", "/", "/tmp/tmp0")

    # The overlay-dir.py file is copied to PREFIX/overlay-dir.py
    overlay('overlay-dir.py', '/', '/tmp/tmp1')
    assert(os.path.isfile('/tmp/tmp1/overlay-dir.py'))

    # The overlay-dir.py file is copied to PREFIX/bin/overlay-dir.py
    overlay('overlay-dir.py', '/bin/', "/tmp/tmp2")
    assert(os.path.isfile('/tmp/tmp2/bin/overlay-dir.py'))

    # The overlay-dir.py file is copied to PREFIX/bin/overlay
    overlay('overlay-dir.py', '/bin/overlay', "/tmp/tmp3")
    assert(os.path.isfile('/tmp/tmp3/bin/overlay'))