mon_simple.py

#!/usr/bin/env python3
"""
mon_simple.py -- Starter for the MON (Mission Object Notation) challenge.

Implement `canonicalize` below: parse a mission object from MON source
text and return its canonical form as a string. Raise MissionSyntaxError
(with a clear message) on any malformed input.

Full specification, grammar, examples, and error-message contract are in
README.md.

You may structure the implementation however you like -- tokenizer,
parser, single pass, whatever fits. There is no prescribed architecture.
The only hard constraints:

  - no parser generators or parsing libraries (see README, "Constraints")
  - the implementation must be written by hand
  - `canonicalize(source: str) -> str` is the interface graders call;
    keep its signature and behavior stable

Run it with:
    python3 mon_simple.py input1.mon
"""

import sys


class MissionSyntaxError(Exception):
    """Raise with a clear message for any malformed MON input."""


def canonicalize(source):
    """
    Parse `source` (MON text describing one mission object) and return its
    canonical form as a string. See README.md, "Canonical Output".

    Raise MissionSyntaxError on invalid input.
    """
    # TODO: implement tokenizing, parsing, validation, and canonical
    # formatting here, in whatever structure you prefer.
    raise NotImplementedError("canonicalize is not implemented yet")


def main():
    if len(sys.argv) != 2:
        print("Usage: python3 mon_simple.py <file.mon>", file=sys.stderr)
        sys.exit(1)

    try:
        with open(sys.argv[1], encoding="utf-8") as f:
            source = f.read()
    except OSError as exc:
        print(f"Error: cannot read file: {exc}", file=sys.stderr)
        sys.exit(1)

    try:
        print(canonicalize(source))
    except MissionSyntaxError as exc:
        print(f"Error: {exc}")
        sys.exit(1)


if __name__ == "__main__":
    main()