#!/bin/sh

# The MIT License (MIT)
#
# Copyright (c) 2026 pacman64
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.


# decap [options...] [max lines...] [command...] [command args...]
#
# DECAPitate emits the first n lines from the standard input, handing the rest
# (if any) to the command given. If a leading number isn't given, the default
# is to `decapitate` just the first line.
#
# The only option available is to show this help message, using any of
# `-h`, `--h`, `-help`, or `--help`, without the quotes.


buffered=0

case "$1" in
    -b|--b|-buffered|--buffered)
        buffered=1
        shift
    ;;

    -h|--h|-help|--help)
        awk '/^# +decap /, /^$/ { gsub(/^# ?/, ""); print }' "$0"
        exit 0
    ;;
esac

lines=1
if echo "$1" | grep -q -E '^[+-]?[0-9]+$'; then
    lines="$1"
    shift
fi

[ "$1" = '--' ] && shift

flush=0
if [ "${buffered}" -eq 0 ] && { [ -p /dev/stdout ] || [ -t 1 ]; }; then
    flush=1
fi

if [ $# -eq 0 ]; then
    awk -v flush="${flush}" -v n="${lines}" '
        NR > n { exit }
        { print; if (flush) fflush() }
        NR >= n { exit }
    '
else
    awk -v flush="${flush}" -v n="${lines}" -v command="$*" '
        NR > n { print | command; next }
        { print; if (flush) fflush() }
    '
fi