#!/bin/bash -e
    #For course FYD500, exam 2020
    #No warranty provided
    
    # Price checker for imaginary items, has fake discount for elderly.
    #   CTRL+C (SIGINT) enters admin mode which shows some host information,
    #   assuming the correct password is supplied (read from file techpasswd)"
    
    ### PROVIDED FUNCTIONS ###
    function user_mode {
        #terminal location provided by customer
        LOCATION=$1
        OPTION_1="Price Information"
        OPTION_2="Senior Rebate"
    
        echo "
            1) $OPTION_1
            2) $OPTION_2"
    
        #select output gets sent to stderr for some reason?
        select OPTION in "$OPTION_1" "$OPTION_2"
        do
            case $OPTION in
                "$OPTION_1")
                    price_info
                    #break
                    ;;
                "$OPTION_2")
                    senior_rebate
                    #break
                    ;;
                *)  ;;
            esac
        done
    }
    
    function price_info {
        while :
        do
            echo -e "Enter an article number: "
            read  ARTICLE
    
            #article code length (includes '\n')
            ARTICLE_LEN="$(echo "$ARTICLE" | wc -m )"
            if [ ! $ARTICLE_LEN -eq "8" ]; then
                echo "Invalid length of article code"
                echo "Expected 7, got $ARTICLE_LEN" 1>&2
                echo
                continue
            fi
    
            LOCATION_CODE="${ARTICLE:0:1}"
            PRICE_CODE="${ARTICLE:1:5}"
            CHECKSUM="${ARTICLE:6:6}"
    
            #Check if item location matches store location
            ERROR=0
            PRICE_MULTIPLIER="1"
            if [ "$LOCATION" = "G" ]; then
                if [ ! "$LOCATION_CODE" = "1" ]; then ERROR=1; fi
            elif [ "$LOCATION" = "S" ]; then
                #Stockholm tax
                PRICE_MULTIPLIER="1.15"
                if [ ! "$LOCATION_CODE" = "2" ]; then ERROR=1; fi
            elif [ "$LOCATION" = "M" ]; then
                if [ ! "$LOCATION_CODE" = "3" ]; then ERROR=1; fi
            else
                ERROR=1
            fi
    
            if [ "$ERROR" -eq "1" ]; then
                echo "Invalid location article code combination!"
                continue
            fi
    
            #checksum should be sum of digits modulus 7
            EXPECTED_CHECKSUM=$(echo "$PRICE_CODE" |\
                awk 'BEGIN{FIELDWIDTHS="1 1 1 1 1"}{print ($1+$2+$3+$4+$5)%7}')
    
            if [ ! $CHECKSUM -eq $EXPECTED_CHECKSUM ]; then
                echo "Invalid checksum!" 1>&2 #error
                echo -e "Invalid article\n"
                continue
            fi
    
            case "$PRICE_CODE" in
                "64964")
                    PRICE=$(awk "BEGIN {print 120*${PRICE_MULTIPLIER}}")
                    echo -e "$ARTICLE (USB stick): $PRICE kronor\n"
                    #break
                    ;;
                "59457")
                    PRICE=$(awk "BEGIN {print 400*${PRICE_MULTIPLIER}}")
                    echo -e "$ARTICLE (headset): $PRICE kronor\n"
                    #break
                    ;;
                *)
                    echo -e "Hm, well I can't seem to find the product ($ARTICLE) in our system!\n"
                    #break
                    ;;
            esac
        done
    }
    
    #TODO the age calculation is probably not exact!
    function senior_rebate {
        BIRTHDAY=""
    
        #Require 8 chars AND all digits
        while [ ! ${#BIRTHDAY} -eq 8 ] || [ ! -z "${BIRTH_YEAR##*[!0-9]*}" ]
        do
            echo -e "Enter your birthday (YYYYMMDD)"
            read BIRTHDAY
        done
    
        CURRENT_DATE=$(date +"%Y%m%d")
        let AGE=$CURRENT_DATE-$BIRTHDAY
        #Age in years
        AGE=${AGE:0:2}
    
        if [ $AGE -gt 64 ]; then
            echo "CONGRATULATIONS YOU ARE SENIOR REBATE ELIGABLE!"
        else
            echo "Good try kid, come back later"
        fi
    }
    
    
    #tech_mode is entered by a Trap
    #(as long as we are in a trap no additional traps can be made)
    function tech_mode {
        #Reset errors to tty
        exec 2>/dev/tty
        #Errors and warnings goes to both TTY and file
        exec > >(tee admin.log)
    
        FILE="techpasswd"
    
        if [[ ! -f "$FILE" ]]; then
            echo "ERROR: password file not found" 1>&2
            sleep 10
            return
        fi
    
        echo "Enter secret password:"
        read PASSWORD
    
        if [ "$PASSWORD" = "$( cat $FILE )" ]; then
            echo "CPU Model: $(  lscpu | awk -F:  '/Model name/ { print $2 }' | sed 's/^ *//g'  )"
    
            echo "Processes over 5000kB RSS: $(ps -eo rss --sort=-rss | awk '{ if ( $1 > 5000 ) {sum+=1}} {print sum}' | tail -n 1)"
    
            echo "System was last updated: $( stat /etc/redhat-release | awk '/Modify/ { print $2 " " $3 " (" $4 ")" }' )"
    
        else
            echo "Incorrect password" 1>&2
            sleep 10
        fi
    
        return
    }
    
    function help {
        echo -e "\\033[1m${0}\\033[0m usage:
        \\e[0;31m-h\\e[0m             Prints this help
        \\e[0;31m-shop G/S/M\\e[0m    Enter shop by specifying city Gothenburg, Stockholm, Malmo. Exactly one additional argument is required G, S, or M.
    
        Any other input will result in the printing of this help screen."
    }
    
    
    ### PROGRAM STARTS HERE ###
    
    #Hide errors from user, send to log file
    exec 2>file.log
    
    #CTRL+C triggers admin mode (requires password)
    trap tech_mode SIGINT
    
    #0-1 arguments always shows help
    if [ $# -lt 2 ]; then
        help
    #2 arguments check whether user wants to enter shop
    elif [ $# -eq 2 ]; then
        case $1 in
            "-shop")
                user_mode $2
                #break
                ;;
            *)
                help
                #break
                ;;
        esac
    #Too many arguments show help
    else
        help
    fi