#!/bin/sh

# Requires: rofi, bc, xclip

# Calculator. The rofi-calc plugin wants libqalculate; this needs nothing but

# bc, at the cost of results arriving on Enter rather than as you type:

#   type an expression, Enter   evaluate it (the result becomes a row)

#   Enter on a result row       copy it to the clipboard

# Past results stay listed until cleared, so earlier answers can be copied or

# pasted back into a new expression.

set -u

HIST="${XDG_CACHE_HOME:-$HOME/.cache}/rofi-calc-history"

HIST_MAX=${ROFI_CALC_HISTORY_MAX:-50}

SCALE=${ROFI_CALC_SCALE:-10}

if [ -z "${ROFI_RETV:-}" ]; then

    exec rofi -show calc -modes "calc:$0"

fi

US=$(printf '\037')

touch "$HIST"

list() {

    printf '\0prompt%scalc\n' "$US"

    printf '\0message%sType an expression and press Enter. + - * / ^%%, sqrt(), s()/c()/a() trig, l()/e() log.\n' "$US"

    printf '\0keep-selection%strue\n' "$US"

    while IFS='	' read -r expr result; do

        [ -n "$result" ] || continue

        printf '%s = %s\0info%s%s\n' "$expr" "$result" "$US" "$result"

    done < "$HIST"

    [ -s "$HIST" ] && printf 'clear history\0info%s@clear\n' "$US"

    return 0

}

evaluate() {

    # -l pulls in the math library (sqrt, s, c, a, l, e) and sets scale=20,

    # so scale has to be set after it to control the printed precision.

    result=$(printf 'scale=%s\n%s\n' "$SCALE" "$1" | bc -l 2>/dev/null | tail -n1)

    [ -n "$result" ] || return 1

    # bc pads to the full scale (2/1 = .5000000000) and leads with a bare dot;

    # trim both so results look like results.

    result=$(printf '%s' "$result" | sed -e 's/\([.][0-9]*[1-9]\)0*$/\1/' -e 's/[.]0*$//' -e 's/^\([-]\{0,1\}\)[.]/\10./')

    printf '%s' "$result"

}

case "$ROFI_RETV" in

    0) list ;;

    1)

        info=${ROFI_INFO:-}

        if [ "$info" = "@clear" ]; then

            : > "$HIST"

            list

        elif [ -n "$info" ]; then

            # Redirect: xclip backgrounds itself still holding the pipe rofi

            # reads this script on, and rofi hangs with the keyboard grabbed

            # until it sees EOF there.

            printf '%s' "$info" | xclip -selection clipboard -i >/dev/null 2>&1

        fi

        ;;

    2)

        expr=${1:-}

        [ -n "$expr" ] || { list; exit 0; }

        if result=$(evaluate "$expr") && [ -n "$result" ]; then

            tmp="$HIST.$$"

            printf '%s\t%s\n' "$expr" "$result" > "$tmp"

            grep -v "^$(printf '%s' "$expr" | sed 's/[][\.*^$/]/\\&/g')	" "$HIST" >> "$tmp" 2>/dev/null

            head -n "$HIST_MAX" "$tmp" > "$HIST"

            rm -f "$tmp"

        else

            printf '\0message%s<span foreground="#bf616a">Not a valid expression</span>\n' "$US"

        fi

        list

        ;;

    3)

        expr=$(printf '%s' "${1:-}" | sed 's/ = .*$//')

        if [ -n "$expr" ]; then

            grep -v "^$(printf '%s' "$expr" | sed 's/[][\.*^$/]/\\&/g')	" "$HIST" > "$HIST.$$" 2>/dev/null

            mv "$HIST.$$" "$HIST"

        fi

        list

        ;;

esac