""" Helper to make links in HTML pages relative to a root """

import os
import fileinput

def make_links_relative(root, placeholder="PETSC_DOC_OUT_ROOT_PLACEHOLDER"):
    """ For .html files in root, replace placeholder with a relative path back up to root """
    excludes = ["_static", "_sources", "_images", "docs", "src", "include"]
    root_level = root.count(os.path.sep)
    for dirpath, dirnames, filenames in os.walk(root, topdown=True):
        dirnames[:] = [dirname for dirname in dirnames if dirname not in excludes]
        level = dirpath.count(os.path.sep) - root_level
        relpath = os.path.sep.join([".."] * level)
        for filename in filenames:
            if filename.endswith(".html"):
                filename_from_root = os.path.join(dirpath, filename)
                with fileinput.FileInput(filename_from_root, inplace=True) as file:
                    for line in file:
                        print(line.replace(placeholder, relpath), end='')  # prints to file