96 lines
3.1 KiB
Python
Executable File
96 lines
3.1 KiB
Python
Executable File
#!/usr/bin/env python3
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"""
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short.py generates unique short URLs.
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This script reads lines from stdin or files named as arguments, then:
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1. retrieves or creates new short URLs, taking into account existing RedirectTemp
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directives in custom.htaccess or short.htaccess;
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2. appends RedirectTemp directives for newly created short URLs to short.htaccess;
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3. outputs the list of (short, long) URLs retrieved or created.
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"""
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import fileinput
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import itertools
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from collections.abc import Iterator
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from time import strftime
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HTACCESS_CUSTOM = 'custom.htaccess'
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HTACCESS_SHORT = 'short.htaccess'
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HTACCESS_FILES = (HTACCESS_CUSTOM, HTACCESS_SHORT)
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BASE_DOMAIN = 'fpy.li'
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def load_redirects() -> tuple[dict, dict]:
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redirects = {}
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targets = {}
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for filename in HTACCESS_FILES:
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with open(filename) as fp:
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for line in fp:
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if line.startswith('RedirectTemp'):
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_, short, long = line.split()
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short = short[1:] # Remove leading slash
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assert short not in redirects, f'{filename}: duplicate redirect from {short}'
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# htaccess.custom is live since 2022, we can't change it remove duplicate targets
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if filename != HTACCESS_CUSTOM:
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assert long not in targets, f'{filename}: duplicate redirect to {long}'
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redirects[short] = long
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targets[long] = short
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return redirects, targets
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SDIGITS = '23456789abcdefghjkmnpqrstvwxyz'
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def gen_short(start_len=1) -> Iterator[str]:
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"""Generate every possible sequence of SDIGITS, starting with start_len"""
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length = start_len
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while True:
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for short in itertools.product(SDIGITS, repeat=length):
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yield ''.join(short)
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length += 1
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def gen_unused_short(redirects: dict) -> Iterator[str]:
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"""Generate next available short URL of len >= 2."""
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for short in gen_short(2):
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if short not in redirects:
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yield short
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def shorten(urls: list[str]) -> list[tuple[str, str]]:
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"""Return (short, long) pairs, appending directives to HTACCESS_SHORT as needed."""
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redirects, targets = load_redirects()
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iter_short = gen_unused_short(redirects)
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pairs = []
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timestamp = strftime('%Y-%m-%d %H:%M:%S')
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with open(HTACCESS_SHORT, 'a') as fp:
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for long in urls:
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assert BASE_DOMAIN not in long, f'{long} is a {BASE_DOMAIN} URL'
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if long in targets:
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short = targets[long]
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else:
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short = next(iter_short)
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redirects[short] = long
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targets[long] = short
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if timestamp:
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fp.write(f'\n# appended: {timestamp}\n')
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timestamp = None
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fp.write(f'RedirectTemp /{short} {long}\n')
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pairs.append((short, long))
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return pairs
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def main() -> None:
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"""read URLS from filename arguments or stdin"""
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urls = [line.strip() for line in fileinput.input(encoding='utf-8')]
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for short, long in shorten(urls):
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print(f'{BASE_DOMAIN}/{short}\t{long}')
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if __name__ == '__main__':
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main()
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