#!/usr/bin/env python
#
# Dumps output generated by Mercurial's command server in a formatted style to a
# given file or stderr if '-' is specified. Output is also written in its raw
# format to stdout.
#
# $ ./hg serve --cmds pipe | ./contrib/debugcmdserver.py -
# o, 52   -> 'capabilities: getencoding runcommand\nencoding: UTF-8'

from __future__ import absolute_import, print_function

import struct
import sys


if len(sys.argv) != 2:
    print("usage: debugcmdserver.py FILE")
    sys.exit(1)

outputfmt = ">cI"
outputfmtsize = struct.calcsize(outputfmt)

if sys.argv[1] == "-":
    log = sys.stderr
else:
    log = open(sys.argv[1], "a")


def read(size):
    data = sys.stdin.read(size)
    if not data:
        raise EOFError
    sys.stdout.write(data)
    sys.stdout.flush()
    return data


try:
    while True:
        header = read(outputfmtsize)
        channel, length = struct.unpack(outputfmt, header)
        log.write("%s, %-4d" % (channel, length))
        if channel in "IL":
            log.write(" -> waiting for input\n")
        else:
            data = read(length)
            log.write(" -> %r\n" % data)
        log.flush()
except EOFError:
    pass
finally:
    if log != sys.stderr:
        log.close()