#!/bin/sh -u
# Answer file: Exercise #3 - myweather.sh
# show the current temperature/pressure/visibility/humidity for a city
#------------------------------------------------------------------
# Syntax:  $0  [ city_code [ weather_item ] ]
#------------------------------------------------------------------
# Purpose:
#  Display the current temperature/pressure/visibility/humidity for a
#  given city.  Print the result in a nice, readable format.
#  Prompt for any missing arguments if standard input is a terminal.
#  If not a terminal, a missing city code defaults to "YOW".
#  If not a terminal, a missing weather item defaults to "temperature".
#  Note: This script is not intended to be used as a CGI script;
#  since, it outputs no CGI header and errors print to standard error.
#------------------------------------------------------------------
# Student Name:                 Ian Allen
# Algonquin EMail Address:      alleni
# Student Number:               074-210-779 
# Course Number:                DAT2330  
# Lab Section Number:           010 
# Professor Name:               Ian Allen 
# Assignment Name/Number/Date:  Exercise #3 due November 23
# Comment:                      This is a sample solution.
#------------------------------------------------------------------

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

#-------------------------------------------------------------
# Input section.

# Exit the script if more than two arguments are supplied.
#
if [ $# -gt 2 ]; then
    echo 1>&2 "$0: Expecting city code and weather item; found $# args ($*)"
    exit 1
fi

# The user might have entered 0, 1, or 2 arguments.
# Prompt for missing arguments if standard input is a terminal.
# Use defaults for missing arguments if no terminal.
#
if [ $# -eq 0 ]; then
    if tty -s ; then
	echo 1>&2 "Enter city code and weather item:"
	read citycode weatheritem || exit $?
    else
	citycode=YOW
	weatheritem=temperature
	echo "Using default city code $citycode and weather item $weatheritem"
    fi
elif [ $# -eq 1 ]; then
    citycode="$1"     # first arg is citycode
    if tty -s ; then
	echo 1>&2 "Enter weatheritem:"
	read weatheritem || exit $?
    else
	weatheritem=temperature
	echo "Using default weather item $weatheritem"
    fi
else
    # we must have exactly two arguments on the command line
    #
    citycode="$1"     # first arg is citycode
    weatheritem="$2"  # second arg is weatheritem
fi
#
#-------------------------------------------------------------

#-------------------------------------------------------------
# Input validation section.

# Count the characters in the city code; make sure there are three.
# Subtract one to account for the newline at the end of the line.
#
count=$( echo "$citycode" | wc -c )
let count=count-1 
if [ "$count" -ne 3 ] ; then
    echo 1>&2 "$0: Expecting 3-character city code, found $count '$citycode'"
    exit 2
fi

# Check for one of the four weather items we know how to fetch.
# Choose a search pattern based on the item.
# Exit if the item is not one of the four we accept.
#
if [ "$weatheritem" = "temperature" ] ; then
    pattern="Temp.:"
elif [ "$weatheritem" = "pressure" ] ; then
    pattern="Pressure:"
elif [ "$weatheritem" = "visibility" ] ; then
    pattern="Visibility:"
elif [ "$weatheritem" = "humidity" ] ; then
    pattern="Humidity:"
else
    echo 1>&2 "$0: Unknown weather item '$weatheritem'"
    echo 1>&2 "$0: Expecting temperature, pressure, visibility, or humidity"
    exit 3
fi
#
#-------------------------------------------------------------

#-------------------------------------------------------------
# Processing section.
#

# Make the city code UPPER CASE.
#
citycode=$( echo "$citycode" | tr 'a-z' 'A-Z' )

# Fetch the page for the city code.
#
page=$( lynx -dump "http://weatheroffice.ec.gc.ca/forecast/city_e.html?$citycode" )

# Look for the string "Error" in the fetched page and exit if found.
#
if echo "$page" | grep "Error" >/dev/null ; then
    echo 1>&2 "$0: Cannot find weather for city code '$citycode'"
    exit 4
fi

# Extract the weather item and the city name.
# Note: the fields may have many extra blanks around them still.
# Note: looking for ": Issued" fails for some weather pages.
#
value=$( echo "$page" | grep -e "$pattern" | awk -F: '{print $2}' )
cityname=$( echo "$page" | grep -e "Issued" | awk -F: '{print $1}' )

#
#-------------------------------------------------------------

#-------------------------------------------------------------
# Output section.
#

# Generate nice output with multiple blanks squeezed down to one.
#
echo "The $weatheritem in $citycode - $cityname - is $value" | tr -s ' '

# script exits with the return code of the last command executed