generator

#!/usr/bin/env python3

import re
from pathlib import Path
import datetime

class GeneratorException(Exception):
    pass

DAY_TEMPLATE = """#[allow(unused_variables)]
pub fn parse_input(input: &str) -> Vec<String> {
	vec![]
}

#[allow(unused_variables)]
pub fn part1(input: &[String]) -> usize {
	0
}

#[allow(unused_variables)]
pub fn part2(input: &[String]) -> usize {
	0
}

#[cfg(test)]
mod tests {
	use super::*;

	const EXAMPLE: &str = "";

	#[test]
	fn example_part1() {
		assert_eq!(part1(&parse_input(EXAMPLE)), 0);
	}

	#[test]
	fn example_part2() {
		assert_eq!(part2(&parse_input(EXAMPLE)), 0);
	}
}
"""


def generate_mod_file(year: int, max_day: int, extra_mods: list) -> str:
    mods = ""
    if extra_mods:
        mods += "\n".join(extra_mods)
        mods += "\n\n"
    mods += "\n".join(f"mod d{i:02};" for i in range(1, max_day + 1))
    run_braces = "\n".join(
        f"\t\t{i} => run_day!(y{year:02}, d{i:02}),"
        for i in range(1, max_day + 1)
    )


    return """use crate::run_day;

{}

pub fn run(day: u8) {{
	match day {{
{}
		_ => unimplemented!(),
	}}
}}

pub fn run_all() {{
	(1..={}).for_each(run)
}}
""".format(mods, run_braces, max_day)

def get_next_day(year_folder: Path) -> int:
    next_day = len(list(year_folder.glob("d*.rs"))) + 1
    if next_day > 25:
        raise GeneratorException("Year is done")
    return next_day

DAY_MOD_RE = re.compile(r"mod d\d{2};")

def is_extra_mod(line: str) -> bool:
    if not line.startswith("mod "):
        return False
    if DAY_MOD_RE.match(line):
        return False
    return True


def generate(year: int):
    year_folder = Path(f"./src/y{year}")
    if not year_folder.exists():
        year_folder.mkdir(parents=True)
        next_day = 1
    else:
        next_day = get_next_day(year_folder)
        
    day_file = year_folder / f"d{next_day:02}.rs"
    day_file.write_text(DAY_TEMPLATE)
    mod_file = year_folder / "mod.rs"
    if mod_file.exists():
        extra_mods = [line for line in mod_file.read_text().splitlines() if is_extra_mod(line)]
    else:
        extra_mods = []
    mod_file.write_text(generate_mod_file(year, next_day, extra_mods))

def get_last_year() -> int:
    now = datetime.datetime.now(tz=datetime.timezone.utc)
    release = datetime.datetime(year=now.year, month=12, day=1, hour=5, tzinfo=datetime.timezone.utc)
    if now < release:
        return now.year - 1
    else:
        return now.year


if __name__ == "__main__":
    import sys
    
    if len(sys.argv) != 2:
        print(f"usage: {sys.argv[0]} <year>")
        sys.exit(1)
    
    try:
        year = int(sys.argv[1])
    except ValueError:
        print(f"error: {sys.argv[1]} is not an int")
        sys.exit(1)

    min_year = 2015
    max_year = get_last_year()
    if not (min_year <= year <= max_year):
        print(f"error: year must be between {min_year} and {max_year}")
        sys.exit(1)

    try:
        generate(year)
    except GeneratorException as e:
        print(f"error: {e}")
        sys.exit(1)