#!/bin/sh

# The MIT License (MIT)
#
# Copyright © 2020-2025 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.


# dtsv [column names...]
#
# Drop Tab Separated-Values, ignoring all columns given, and keeping all the
# others. The column names given are matched using the first line from stdin.
# Matching works by first trying exact matching, then by case-insensitive
# matching, when there's no exact match, finally giving up when there's no
# match either way.


case "$1" in
    -h|--h|-help|--help)
        awk '/^# +dtsv /, /^$/ { gsub(/^# ?/, ""); print }' "$0"
        exit 0
    ;;
esac

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

command="awk"
if [ -p 1 ] || [ -t 1 ]; then
    command="stdbuf -oL awk"
fi

${command} -F "\t" '
    BEGIN {
        for (i = 1; i < ARGC; i++) {
            colnames[++n] = ARGV[i]
            lownames[n] = tolower(ARGV[i])
            delete ARGV[i]
        }
    }

    function findcol(name, lowname, i) {
        for (i = 1; i <= NF; i++) if (name == $i) return i
        for (i = 1; i <= NF; i++) if (lowname == tolower($i)) return i

        if (1 <= name && name <= NF) return name + 0
        if (name < 0 && -name <= NF) return NF + name + 1

        return 0
    }

    { gsub(/\r$/, "") }

    NR == 1 {
        numcols = NF
        for (i = 1; i <= numcols; i++) keep[i] = 1

        colsused = numcols
        for (i = 1; i <= n; i++) {
            j = findcol(colnames[i], lownames[i])
            if (j > 0) {
                keep[j] = 0
                colsused--
            }

            if (j == 0) {
                fmt = "\x1b[31mno column match for \"%s\"\x1b[0m\n"
                printf(fmt, colnames[i]) > "/dev/stderr"
                errors++
            }
        }

        if (errors > 0) exit 1
        if (colsused == 0) exit
    }

    {
        c = 0
        for (i = 1; i <= numcols; i++) {
            if (keep[i] == 1) {
                if (c > 0) printf "\t"
                printf "%s", $i
                c++
            }
        }

        printf "\n"
    }
' "$@"