#!/usr/bin/env python3
"""Idempotently inject the HomeDash stylesheet and script into Dashy's index.html.

Dashy's index.html does not always contain a `</body>` tag. A naive
`sed s#</body>#...#` therefore silently drops the injected script (and the
`</body>` marker itself). This script inserts before `</head>`/`</body>` when
those exist, otherwise before `</html>`, and restores a missing `</body>`.
"""
import re
import sys

CSS_TAG = '<link rel="stylesheet" href="/navi.css">'
JS_TAG = '<script src="/navi.js"></script>'


def patch(html: str) -> str:
    html = re.sub(r'[ \t]*<link rel="stylesheet" href="/navi\.css">\s*', '', html)
    html = re.sub(r'[ \t]*<script src="/navi\.js"></script>\s*', '', html)

    if '</head>' in html:
        html = html.replace('</head>', CSS_TAG + '</head>', 1)

    if '</body>' in html:
        html = html.replace('</body>', JS_TAG + '</body>', 1)
    elif '</html>' in html:
        html = html.replace('</html>', JS_TAG + '\n</body>\n</html>', 1)
    else:
        html = html + '\n' + JS_TAG + '\n'
    return html


def main(path: str) -> int:
    with open(path, encoding='utf-8') as fh:
        original = fh.read()
    patched = patch(original)
    if 'href="/navi.css"' not in patched or 'src="/navi.js"' not in patched:
        print('patch failed: tags missing after patch', file=sys.stderr)
        return 1
    with open(path, 'w', encoding='utf-8') as fh:
        fh.write(patched)
    print('patched %s (%s)' % (path, 'changed' if patched != original else 'unchanged'))
    return 0


if __name__ == '__main__':
    raise SystemExit(main(sys.argv[1] if len(sys.argv) > 1 else '/app/dashy/index.html'))