#!/bin/sh -u
# Sorts three integers on the command line; prompts for missing numbers.
#------------------------------------------------------------
# Syntax:
#    $0 [ int1 [ int2 [ int3 ] ] ]
#------------------------------------------------------------
# Purpose:
#    Get three integers from the command line or by prompting and reading.
#    Output the numbers in ascending order.
#    Save the numbers in a file.
#    Exit zero if the numbers were already sorted; exit 1 otherwise.
#    Print an error message and exit non-zero on any errors.
#-------------------------------------------------------------
# Student Name:                  Ian! D. Allen
# Algonquin EMail Address:       alleni
# Student Number:                000-000-000
# Course Number:                 DAT2330
# Lab Section Number:            010
# Professor Name:                Ian! D. Allen
# Assignment Name/Number/Date:   Exercise 5, due March 21
# Comment:                       This is a sample assignment label.
# see http://idallen.com/teaching/assignment_standards.html
#-------------------------------------------------------------

# Set standard search path and umask.
#
PATH=/bin:/usr/bin ; export PATH
umask 022

# The name of the output file we will be writing.
#
outfile='out.txt'

# Pick up any missing arguments by prompting on stderr and reading
# them from standard input.  Accept only zero, one, two, or three arguments.
# If more than three, echo the count and incorrect input on stderr and exit.
#
if [ $# -eq 0 ]; then
    echo 1>&2 "Enter three integers:"
    read int1 int2 int3 || exit $?
else
    if [ $# -eq 1 ]; then
	int1="$1"               # first arg on command line becomes int1
	echo 1>&2 "Enter two integers:"
	read int2 int3 || exit $?
    else
	if [ $# -eq 2 ]; then
	    int1="$1"           # first arg on command line becomes int1
	    int2="$2"           # second arg on command line becomes int2
	    echo 1>&2 "Enter third integer:"
	    read int3 || exit $?
	else
	    if [ $# -eq 3 ]; then
		int1="$1"       # first arg on command line becomes int1
		int2="$2"       # second arg on command line becomes int2
		int3="$3"       # third arg on command line becomes int3
	    else
		echo 1>&2 "$0: Expecting three integers; found $# args ($*)"
		exit 2
	    fi
	fi
    fi
fi

# We have collected the three arguments into $int1 $int2 and $int3.
# Echo the user's input back to the user, as specified.
#
echo "You entered these inputs: '$int1' '$int2' '$int3'"

# Print a nice message if any input number was empty.
#
if [ -z "$int1" -o -z "$int2" -o -z "$int3" ] ; then
    echo 1>&2 "$0: Empty integer input; nothing done.  Bye."
    exit 2
fi

# At this point, we should verify that each of the three inputs is
# actually a valid integer (not letters); but, doing so is a bit messy.
# See CST8129 for a way to write a shell function to do this nicely.
# In DAT2330, we will just have to hope the data is good!  -IAN!

# Transfer the inputs to other variables and then bubble sort them.
#
sorted1="$int1"
sorted2="$int2"
sorted3="$int3"

# Two compares and swaps make sorted3 the largest integer.
#
if [ "$sorted1" -gt "$sorted2" ] ; then
    tmp="$sorted1"
    sorted1="$sorted2"
    sorted2="$tmp"
fi
if [ "$sorted2" -gt "$sorted3" ] ; then
    tmp="$sorted2"
    sorted2="$sorted3"
    sorted3="$tmp"
fi

# sorted3 now has the biggest integer; sort the remaining two.
#
if [ "$sorted1" -gt "$sorted2" ] ; then
    tmp="$sorted1"
    sorted1="$sorted2"
    sorted2="$tmp"
fi

echo "The numbers are, from smallest to largest: $sorted1 $sorted2 $sorted3"

# Put the sorted numbers into the $outfile output file, if the file
# doesn't exist.  (Exit the script if the file exists.)
#
if [ -e "$outfile" ] ; then
    echo 1>&2 "$0: File '$outfile' already exists.  No output saved."
    exit 2
fi

# BONUS: A writable, empty file is okay.
#
#if [ -s "$outfile" ] ; then
#   echo 1>&2 "$0: Non-empty file '$outfile' already exists.  No output saved."
#   exit 2
#fi
#if [ -e "$outfile" -a ! -w "$outfile" ] ; then
#   echo 1>&2 "$0: Existing file '$outfile' is not writable.  No output saved."
#   exit 2
#fi

echo "$sorted1"  >"$outfile"
echo "$sorted2" >>"$outfile"
echo "$sorted3" >>"$outfile"

count=$( wc -c <"$outfile" )
echo "The file '$outfile' contains $count characters."

# Return 0 if the numbers were already sorted
#
if [ "$int1" -eq "$sorted1" \
  -a "$int2" -eq "$sorted2" \
  -a "$int3" -eq "$sorted3" ] ; then
    return=0
else
    return=1
fi

exit $return