#!/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