#!/bin/sh

help() { echo "vartak-results-show - display results with names of students

USAGE:
	vartak-results-show [OPTION]... <FILE>

OPTIONS:
	-s FIELD  sort by FIELD name
	-S FIELD  sort by FIELD name (reversed)
	-N NAMES  path to file that has student names data
	-h        show this help message

FILE is the CSV file that contains scores of each student.
FIELD name is one of the field from CSV header.

NAMES data is the file containing the names of student. By default, it's
assumed that this file is named as 'names.csv' and is present in the current
directory. This file should have seat no in first column and names in the
second."; }

err() { printf 'vartak-results-show: %s\n' "$@" >&2; exit 1; }
while getopts 'ns:S:N:h' o; do case "$o" in
	s) SORTFIELD="$OPTARG" ;;
	S) SORTFIELD="$OPTARG" SORTOPTS="$SORTOPTS -r" ;;
	N) NAMEFILE="$OPTARG" ;;
	h) help; exit ;;
	*) err "invalid option -- '$OPTARG'" ;;
esac done
shift $((OPTIND - 1))

[ ! -f "${NAMEFILE:=names.csv}" ] && err "file not found: $NAMEFILE"

[ "$(awk -F, '{print NF; exit}' "$NAMEFILE")" != 2 ] &&
	err "NAMES data doesn't have exactly 2 columns"

[ "$#" -lt 1 ] && help >&2 && exit 1

data="$(awk -F, '
	FNR == NR { a[$1] = $2; next; }
	{
		printf("%s%s%s", $1, FS, a[$1])
		for (i = 2; i <= NF; i++) {
			printf("%s%s", FS, $i)
		}
		print ""
	}
	' "$NAMEFILE" "$1")"

header="$(echo "$data" | head -1)"
data="$(echo "$data" | tail +2)"

if [ -n "$SORTFIELD" ]; then
	FIELDINDEX="$(echo "$header" | sed -n 's/,/\n/gp' |
		grep -nx "$SORTFIELD" | cut -d: -f1)"
	data="$(echo "$data" | sort -n "$SORTOPTS" -t, -k "$FIELDINDEX")" || exit
fi

(printf "Sr. No,%s\n" "$header"; echo "$data" | nl -s, -w1) |
	column --table --separator ',' --table-right 1,2,4-20