#!/usr/bin/python3

import mailbox
import re
import sys

for f in sys.argv[1:]:
    print("F", f)
    mb = mailbox.mbox(f)

    for m in mb:
        try:
            for match in re.findall(r'<(.*?)>', m["Message-ID"]):
                print('M', match)
            if "In-Reply-To" in m:
                h = str(m["In-Reply-To"]) # sometimes it's a string,
                # sometimes an email.header.Header. But the latter's
                # __str__ method returns something sensible, so let's just
                # force it to be a string
                for match in re.findall(r'<(.*?)>', h):
                    print('I', match)
            if "References" in m:
                for match in re.findall(r'<(.*?)>', m["References"]):
                    print('R', match)
        except:
            print("Error in message:", file=sys.stderr)
            print(m.as_string(), file=sys.stderr)
            sys.exit(1)