#!/bin/sh

# bv, short for bible verse, is a simple program for helping to learn and 
# remember bible verses from a minimal X environment and the command line.

# make sure needed dirs exist
conf="${XDG_CONFIG_DIR:-$HOME/.config}/bv"
cache="${XDG_CACHE_DIR:-$HOME/.cache}/bv"
[ -d "$conf" ] || mkdir -p "$conf"
[ -d "$cache" ] || mkdir -p "$cache"


help_msg() {
    printf "Usage:\\n\
 -s \t set new bible verse to given string or path to file\\n\
 -l \t list current bible verse \\n\
 -u \t update media (do this after changing your wallpaper)\\n\
 -a \t ask for bible verse via stdin and mark mistakes if found\\n\
 -h \t show this help message\\n"
}

generate_assets() {
    # fetch infos
    bgpath="$(tail -n 1 "${XDG_CACHE_DIR:-$HOME/.cache}/.fehbg" | rev | \
        awk '{print $1}' | rev | sed 's/.$//;s/^.//' )"
    dim="$(mediainfo "$bgpath" | grep "Width\|Height" | sed 's/^.*\: //;s/pixels//' \
        | tr -d ' ' | tr '\n' x | sed s'/x$/\n/')"
    width="$(echo "$dim" | sed 's/x.*//')"
    #height="$(echo "$dim" | sed 's/.*x//')"
    bgext="${bgpath##*.}"
    savedpath="$(cat "$cache/bg-orig.path")"
    savedext="${savedpath##*.}"

    # clunky path parsing ...

    [ -f "$cache/bg-orig.path" ] || echo "$bgpath" > "$cache/bg-orig.path"

    if ! echo "${bgpath##*/}" | grep -q "bv-bg.png"; then
        echo "$bgpath" > "$cache/bg-orig.path"
    fi

    echo "$savedpath" | grep -q "bv-bg.png" && savedpath=""

    if [ ! -s "$savedpath" ]; then
        if [ -n "$savedpath" ]; then
            cp "$cache/bg-orig.$savedext" "$savedpath" && 
            echo "original file moved or deleted: restoring ..."
        fi
    fi

    # check if new background should be generated
    if diff "$cache/bg-orig.$savedext" "$(cat "$cache/bg-orig.path")" > /dev/null 2> /dev/null &&
        diff "$cache/verse" "$conf/verse" > /dev/null 2> /dev/null; then
        echo "Everything already up to date, skipping Asset Generation ..."
    else
        # cache new bg incl. its source path
        cp "$bgpath" "$cache/bg-orig.$bgext"
        echo "$bgpath" > "$cache/bg-orig.path"

        # cache new verse
        cat "$conf/verse" > "$cache/verse"

        echo "Generating Background ..."

        # calculate text scaling accordingly to the resolution
        : $((scal = width / 128))
        : $((dens = 300 * 15 / scal))
        : $((pntr = scal * scal * 16 / 225))
        : $((strk = scal * 2 / 15))

        # generate text and merge w/ background
        magick -gravity center -background transparent -density "$dens" \
            -pointsize "$pntr" -fill white -size "$dim" -stroke black -strokewidth "$strk" \
            -font "/usr/share/fonts/adobe-source-code-pro/SourceCodePro-BlackIt.otf" \
            caption:@- "$cache/bv-verse.png" < "$conf/verse"
        composite -gravity center "$cache/bv-verse.png" \
            "$bgpath" "$cache/bv-bg.png"
    fi
}

update_assets() {
    # set bg
    echo "Setting Background ..."
    feh --bg-scale "$cache/bv-bg.png"
    mv "$HOME/.fehbg" "${XDG_CACHE_DIR:-$HOME/.cache}"
}

exit_when_no_verse() {
    [ ! -s "$conf/verse" ] && echo "Error: No bible verse set." && exit 1
}

verse_diff() {
    git -c color.diff.new='bold reverse green' \
        -c color.diff.old='bold reverse red' diff --no-index -U0 --no-color \
        --word-diff=color --word-diff-regex=. \
        "$cache/guessed-verse" "$cache/stripped-verse" | tail -n +3 |
        grep -v '\-\-\-\|+++'
}

# parse arguments
while getopts ":s:ahlu" option; do case "${option}" in
    h)  help_msg; exit 0;;
    s)  newbv="${OPTARG}"
        if [ -s "$newbv" ]; then
            cat "$newbv" > "$conf/verse"
            cp "$conf/verse" "$cache/verse"
        elif [ -n "$newbv" ]; then
            echo "$newbv" > "$conf/verse"
            cp "$conf/verse" "$cache/verse"
        fi

        generate_assets; update_assets; exit 0;;
    l)  exit_when_no_verse; cat "$conf/verse"; exit 0;;
    u)  generate_assets; update_assets; exit 0;;
    a)  exit_when_no_verse; printf "bible verse: "; read -r ask_input
        echo "$ask_input" > "$cache/guessed-verse"
        tr '\n' ' ' < "$conf/verse" | sed 's/.$/\n/; s/  / /g' > "$cache/stripped-verse"
        verse_diff; exit 0;;
    *)  printf "Invalid option: -%s\\n\\n" "$OPTARG"; help_msg; exit 1 ;;
esac done

# when no arguments are given, print help message
help_msg