#!/bin/bash

# pycalc

# usage:
# pycalc        # interactive, 
#                 last result will be in ~/.pans.txt 
#                 and log will be in ~/.pcalc.txt
# pycalc -n 1+1 # non-interactive

# what py modules to load by default
modules="sys,math"

# get ans if there is one and it's number
test -f "$HOME/.pans.txt" && ans=$(cat "$HOME/.pans.txt")

#set -x
# function
shopt -s extglob
isNumber() {
var="$1"
# ˇ will fail for numbers like 4.044676226059745e-17 (so called scientific notation)
if [[ $var = @(*[0-9]*|!([+-]|)) && $var = ?([+-])*([0-9])?(.*([0-9])) ]]; then 
  #echo "fine"
  ans="$var"
  true  # return 0
else 
  #echo "bad"
  ans="0"
  false # return 1
fi
}

isNumber "$ans"
# ^ if things went fine, py3 interpreter will have variable 'ans' assigned to old ~/.pans.txt

if [ "$1" == "-i" ] || [ "$1" == "" ]; then

    # interactive python shell action
    script -q -a "$HOME/.pcalc.txt" -c "python3 -ic \"import $modules; sys.ps1=''; ans=$ans\""

    # latest valid numeral result to file ~/.pans.txt
    ans=$(grep -E '[[:digit:]]' "$HOME/.pcalc.txt" | tail -1 | tr -d '\r')
    if isNumber "$ans"; then
        echo "storing ans $ans to $HOME/.pans.txt"
        echo "$ans" > "$HOME/.pans.txt"
    fi
    
elif [ "$1" == "-n" ]; then

    shift
    ans=$(python3 -c "import $modules; print($*);") # this isn't user safe, can run any python.
    if isNumber "$ans"; then
        #echo "storing $ans to $HOME/.pans.txt"
        echo "$ans" > "$HOME/.pans.txt"
        
    fi
    echo "$ans"
fi

# crop log
file="$HOME/.pcalc.txt"
if [ -f "$file" ]; then
    tail -n 100 "$file" > "$file.tmp" && mv "$file.tmp" "$file"
fi

# alias ans='cat ~/.pans.txt'