Tools/peg_generator/scripts/joinstats.py

#!/usr/bin/env python3.8

"""Produce a report about the most-memoable types.

Reads a list of statistics from stdin.  Each line must be two numbers,
being a type and a count.  We then read some other files and produce a
list sorted by most frequent type.

There should also be something to recognize left-recursive rules.
"""

import os
import re
import sys

from typing import Dict

reporoot = os.path.dirname(os.path.dirname(__file__))
parse_c = os.path.join(reporoot, "peg_extension", "parse.c")


class TypeMapper:
    """State used to map types to names."""

    def __init__(self, filename: str) -> None:
        self.table: Dict[int, str] = {}
        with open(filename) as f:
            for line in f:
                match = re.match(r"#define (\w+)_type (\d+)", line)
                if match:
                    name, type = match.groups()
                    if "left" in line.lower():
                        name += " // Left-recursive"
                    self.table[int(type)] = name

    def lookup(self, type: int) -> str:
        return self.table.get(type, str(type))


def main() -> None:
    mapper = TypeMapper(parse_c)
    table = []
    filename = sys.argv[1]
    with open(filename) as f:
        for lineno, line in enumerate(f, 1):
            line = line.strip()
            if not line or line.startswith("#"):
                continue
            parts = line.split()
            # Extra fields ignored
            if len(parts) < 2:
                print(f"{lineno}: bad input ({line!r})")
                continue
            try:
                type, count = map(int, parts[:2])
            except ValueError as err:
                print(f"{lineno}: non-integer input ({line!r})")
                continue
            table.append((type, count))
    table.sort(key=lambda values: -values[1])
    for type, count in table:
        print(f"{type:4d} {count:9d} {mapper.lookup(type)}")


if __name__ == "__main__":
    main()