#!/usr/bin/env python3

import difflib
import email.parser
import email.policy
import itertools
import mailbox
import sys


def flexible_eq(expected, got):
    """Compare two strings, supporting wildcards.

    This functions compares two strings, but supports wildcards on the
    expected string. The following characters have special meaning:

     - ?  matches any character.
     - *  matches anything until the end of the line.

    Returns True if equal (considering wildcards), False otherwise.
    """
    posG = 0
    for c in expected:
        if posG >= len(got):
            return False

        if c == "?":
            posG += 1
            continue
        if c == "*":
            while posG < len(got) and got[posG] != "\t":
                posG += 1
                continue
            continue

        if c != got[posG]:
            return False

        posG += 1

    if posG != len(got):
        # We got more than we expected.
        return False

    return True


def msg_equals(expected, msg):
    """Compare two messages recursively, using flexible_eq()."""
    diff = False
    for h, val in expected.items():
        if h not in msg:
            print("Header missing: %r" % h)
            diff = True
            continue

        if expected[h] == "*":
            continue

        msg_hdr_vals = msg.get_all(h, [])
        if len(msg_hdr_vals) == 1:
            if not flexible_eq(val, msg[h]):
                print("Header %r differs:" % h)
                print("Exp: %r" % val)
                print("Got: %r" % msg[h])
                diff = True
        else:
            # We have multiple values for this header, so we need to check each
            # one, and only return a diff if none of them match.
            # Note this will result in a false positive if two headers match
            # the same expected one, but this is good enough for now.
            for msg_hdr_val in msg_hdr_vals:
                if flexible_eq(val, msg_hdr_val):
                    break
            else:
                print("Header %r differs, no matching header found" % h)
                print("Exp: %r" % val)
                for i, msg_hdr_val in enumerate(msg_hdr_vals):
                    print("Got %d: %r" % (i, msg_hdr_val))
                diff = True

    if diff:
        return False

    if expected.is_multipart() != msg.is_multipart():
        print(
            "Multipart differs, expected %s, got %s"
            % (expected.is_multipart(), msg.is_multipart())
        )
        return False

    if expected.is_multipart():
        for exp, got in itertools.zip_longest(
            expected.get_payload(), msg.get_payload()
        ):
            if not msg_equals(exp, got):
                return False
    else:
        if not flexible_eq(expected.get_payload(), msg.get_payload()):
            exp = expected.get_payload().splitlines()
            got = msg.get_payload().splitlines()
            print("Payload differs:")
            for l in difflib.ndiff(exp, got):
                print(l)
            return False

    return True


if __name__ == "__main__":
    f1, f2 = sys.argv[1:3]

    # We use a custom strict policy to do more strict content validation.
    policy = email.policy.EmailPolicy(
        utf8=True, linesep="\r\n", refold_source="none", raise_on_defect=True
    )

    expected = email.parser.Parser(policy=policy).parse(open(f1))
    msg = email.parser.Parser(policy=policy).parse(open(f2))

    sys.exit(0 if msg_equals(expected, msg) else 1)