""" Make links in HTML pages relative to a root """

import os
import fileinput

from ext.html5_petsc import PETSC_DOC_OUT_ROOT_PLACEHOLDER

def make_links_relative(root, placeholder=PETSC_DOC_OUT_ROOT_PLACEHOLDER):
    """ For all generated .html files in directory root and descendants replace placeholder with a relative path back up to root
        Exclude a specific set of subdirectories.
    """
    excludes = ["_static", "_sources", "_images"]
    root_level = os.fspath(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 = os.fspath(dirpath).count(os.path.sep) - root_level
        if level == 0: relpath = "."
        else: 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