#!/bin/bash 

# Title......: calc
# Description: bash calculator with history and readline support
# Author.....: Mitchell Johnston - uid 0
# Contact....: mitch@crn.hopto.org
# Updated....: Sat May 16 09:56:35 AM CDT 2026
#----------------------------------

# Sections: Changes variables functions setup main 
# use '#' in vi/vim to jump to word under cursor

: ' Changes:
Sat May 16 2026 Added option to start with formula i.e. calc 5+9
Sat May 16 2026 Cleaning up formating and comments
Sat May 16 2026 First upload
'


# variables
#----------------------------------
[ "$1" == "-D" ] && DEBUG=1 && shift 1     # -D to turn on debug mode
[ "$DEBUG" == 1 ] && echo "---Variables---" && set -x
PS4='$SECONDS $LINENO: '                   # debug prompt
DOW=$(date +%a)                            # day of week: Thu
TODAY=$(date +%m/%d)                       # month/day: 03/25
DOM=$(date +%d)                            # day of month: 25
OS=$(uname -s)                             # OS type: SunOS Linux
NAME=${0##*/}                              # name of the script
DIR="$(basename $PWD)"                     # location started
PDIR="$(cd ..;basename $PWD)"              # parrent dir

# Configuration
HISTORY_FILE="$HOME/.calculator_tape.txt"
DECIMALS=2

# Colors - uncomment if needed
R=$(tput setaf 1)                          # red
BR=$(tput setaf 1; tput bold)              # bold red
G=$(tput setaf 2)                          # green
BG=$(tput setaf 2; tput bold)              # bold green
Y=$(tput setaf 3)                          # yellow
BY=$(tput setaf 3; tput bold)              # bold yellow
B=$(tput setaf 4)                          # blue
BM=$(tput setaf 5; tput bold)              # bold magenta
BC=$(tput setaf 6; tput bold)              # bold cyan
C=$(tput setaf 6)                          # cyan
BL=$(tput setaf 7; tput bold)              # bold light grey
BLD=$(tput bold)                           # bold
N=$(tput sgr0)                             # normal
SIT=$(tput sitm)                           # italics
RIT=$(tput ritm)                           # remove italics
UL=$(tput smul)                            # turn underline on
NL=$(tput rmul)                            # turn underline off
RV=$(tput rev)                             # turn on reverse mode
ROWS=$(tput lines)
COLS=$(tput cols)

[ "$DEBUG" == 1 ] && set +x && read -p "${N}-Continue-" -n 1 x

# functions
#----------------------------------
#
bl(){ ## blank line
    echo ""
}

html(){ ## mark up code
    vim -f +"syn on" +"set nonu" +"set foldenable!" +"set nospell" +"run! syntax/2html.vim" +"wq" +"q" $1
}

log(){ ## creates a basic log entry $LOG must be defined
    # Use: log {entry}  
    [ "$DEBUG" == "1" ] && set -x
    logger -i -t "$NAME" "$*"
}

pause(){ ## simple pause routine
    # Use: pause  {optional number of seconds} or "-nt" for no time out 
    [ "$DEBUG" == "1" ] && set -x
    [ "$1" == "-nt" ] && TMOUT="" && shift
    echo "$BY";
    if [ $# -gt 0 ]
    then
        read -t $1 -r -p "${C}Hit any key (${BY}$1${C} second timeout)${N}" -n 1 FOO;
    else
        read -r -p "${C}Hit any key${N}" -n 1 FOO;
    fi;
    bl
}

strip-tags(){ ## remove HTML tags
  # Use: curl https://linuxhint.com/bash_cut_command/ --silent | strip-tags
  sed -e 's/<[^>]*.//g' -
}

xtitle(){ ## set window title
    # Use: xtitle "Text to display"
    printf "\033]0;%s\007" "$*"
}


# setup
#----------------------------------

# this provides a quick way to edit all my scripts on the fly
if [ "$1" == "-E" ]
then
    vim $0
    sed -i -e "7s/.*/# Updated....: $(date)/" $0
    log "Updated $0"
    html $0
    cp $0 /var/www/unix
    mv $0.html /var/www/unix
    exit
fi

# display help if needed
if [ "$1" == "-h" ] || [ "$1" == "--help" ]
then
fmt -s -w $(tput cols) <<END
$NAME

No options

END
exit
fi

# listing of required apps
command -v bash >/dev/null || sudo apt install bash -qyy
command -v rlwrap >/dev/null || sudo apt install rlwrap -qyy

# display version and change history
if [[ "$1" == "-v" ||  "$1" == "--version" ]]
then
    grep -E '^# Updated' $0
    bl
    sed -n "/' Changes/,/^ *$/p" <$0 |head -n 7
    read -p "View source (y|n)? " -n 1 ANS
    set -x
    [ "$ANS" == "y" ] && bat $0
    exit 0
fi

# Initialize history file if it doesn't exist
touch "$HISTORY_FILE"

# main
#--------------------------- 
[ "$DEBUG" == 1 ] && echo "---Functions---" && typeset -F && read -p "${N}-Continue-" -n 1 x
[ "$DEBUG" == 1 ] && echo "---Main---" && set -x

if [[ "$#" = 0 ]] # don't display help if you passed it a problem
then
    echo "${BG}===${N}${BLD}Bash Calculator with History Tape${N}${BG}===${N}"
    echo "Type your math equation (e.g., 22 / 7) or ${SIT}'history'${RIT} to view the tape."
    echo "${BR}q${BC} to exit. ${BLD}Enter will clear last result in stack.${N}"
fi

# Interactive loop
while true; do
    if [[ $# = 0 ]] # check  to see command line options
    then
        input=$(rlwrap -S '> ' -H HISTORY -P "$a" -o cat) # readline wrapper
    else
        input="$@"
        shift "$#"   # clear to break loop
    fi

    # Check for history command
    if [[ "$input" == "history" || "$input" == "h" ]]; then
        echo "--- History Tape ---${BC}"
        cat "$HISTORY_FILE"
        echo "${N}--------------------"
        continue
    fi

    # Ignore empty inputs
    if [[ -z "$input" ]]; then
        continue
    fi

    # clear last run with return
    if [[ "$input" = "$a" ]]; then
        a=""
        continue
    fi

    [[ "$input" = "q" ]] && exit # exit run

    # Calculate using 'bc' (Basic Calculator) and preserve decimals
    result=$(echo "scale=$DECIMALS; $input" | bc -l 2>/dev/null)
    a=$result

    # Check if the calculation was valid
    if [[ -z "$result" ]]; then
        echo "${BR}Error:${BY}${SIT} Invalid mathematical expression.${RIT}${N}"
    else
        # Print the result
        echo "= ${BG}$result${N}"
        # Append to history tape
        echo "$input = $result" >> "$HISTORY_FILE"
    fi
done

exit

# Code snippets
#--------------------------- 

# vim: nospell ft=sh
#