#!/bin/sh
set -eu

die() {
    echo "$1" >&2
    exit 1
}

cachedir="$HOME/.cache/llpp"
test -d "$cachedir" || die "cache directory '$cachedir' does not exist"

caspsuf=
type=

executable_p() { command -v "$1" >/dev/null 2>&1; }

missing() {
    executable_p $1 || \
        eval "$1() { die \"$2 is needed for \$type conversion\"; }"
}
trap 'test -n "${casp-}" && rm -f "$casp"' 0

while getopts s:c:m:t:fu opt; do
    case $opt in
        m) mime=$OPTARG;;
        t) type=$OPTARG;;
        f) force=true;;
        c) css="-s $OPTARG";;
        ?) die "usage: $0 [-c css] [-m mime/type] [-t filter] [-f] [path|url]";;
    esac
done
shift $(($OPTIND - 1))
test -z "$1" && die "usage $0: path"

origin="$1"
if ${force-test ! -e "$1"} && expr >/dev/null "$1" : "\(ftp\|https\?\)://";
then
    if executable_p wget; then
        dl() { wget -q $1 -O $2; }
    elif executable_p curl; then
        dl() { curl -L $1 -o $2; }
    else
        die "no program to fetch remote urls found"
    fi

    hashof="$cachedir/$(basename "$1")"
    dl "$1" "$hashof" || test -e "$md5of"
    shift
    set -- "$hashof" "$@"
else
    hashof="$1"
fi

test -z "$type" && {
    ft=$(file -L --mime-type -b "$1") || die "$ft";

    case $ft in
        application/x-gzip | application/x-compress) dc=zcat;;
        application/x-xz) dc=xzcat;;
        application/x-bzip2) dc=bzcat;;
        *) unset dc || true;;
    esac
}

filt='"${dc-cat}" "$1" |'

typeofmime() {
    case "$1" in
        application/postscript) type=ps;;
        application/pdf) type=pdf;;
        image/vnd.djvu) type=djvu;;
        text/html) type=html;;
        text/plain) type=text;;
        application/msword) type=word;;
        application/vnd.openxmlformats-officedocument.*  \
            | application/vnd.ms-powerpoint              \
            | application/vnd.ms-excel                   \
            | application/vnd.oasis.opendocument.*) type=uno;;
        image/svg+xml) type=svg;;
        image/png | image/jpeg)
            test -n "${dc-}" && type="image" || type="image2";;
        image/*) type=image;;
        application/x-dvi) type=dvi;;
        *) return 1;;
    esac
    return 0
}

if test -z "$type"; then
    test -z "${mime-}" &&                                          \
        mime=$(file -L --mime-type -b "$1" || die "$mime") ||   \
            $(file -L --mime-type -bz "$1" || die "$mime")
    typeofmime "$mime" || die "unhandled file type: '$mime'"
fi

caspsuf=".pdf"
case $type in
    ps)
        missing ps2pdf "ps2df(https://ghostscript.com/)"
        conv='ps2pdf - "$casp"'
        ;;
    image2|pdf) test -z "${dc-}" && exec llpp "$@" || conv='cat >"$casp"';;
    texi)
        missing texi2html "texi2html(http://www.nongnu.org/texi2html/)"
        conv='texi2html - -o $casp'
        caspsuf=.html
        ;;
    djvu)
        missing ddjvu "ddjvu(http://djvu.sourceforge.net/doc/man/ddjvu.html)"
        conv='ddjvu -format=pdf - "$casp"'
        ;;
    html)
        missing prince "Prince(http://www.princexml.com/)"
        conv='prince $css - -o "$casp"'
        ;;
    html2epub)
        missing pandoc "pandoc(http://pandoc.org)"
        caspsuf=".epub"
        conv='pandoc -r html - -w epub2 -o "$casp"'
        ;;
    word)
        missing unoconv "unoconv"
        filt=
        conv='unoconv -o "$casp" "$1"'
        ;;
    uno)
        test -n "$dc" && die "cannot convert compressed '$mime'"
        unset filt
        missing unoconv "unoconv(http://dag.wiee.rs/home-made/unoconv/)"
        conv='unoconv -o "$casp" "$1"'
        ;;
    svg)
        if executable_p inkscape && test -z "$dc"; then
            unset filt
            conv='inkscape -z -A "$casp" "$1"'
        else
            if executable_p rsvg-convert; then
                conv='rsvg-convert -f pdf -o "$casp"'
            else
                test -n "$dc" && die "cannot convert compressed '$mime'"
                unset filt
                missing unoconv "unoconv(http://dag.wiee.rs/home-made/unoconv/)"
                conv='unoconv -o "$casp" "$1"'
            fi
        fi
        ;;
    image)
        missing convert "convert(http://www.imagemagick.org/script/convert.php)"
        conv='convert - pdf:"$casp"'
    ;;
    dvi)
        test -n "$dc" && die "cannot convert compressed '$mime'"
        unset filt
        missing dvipdf "dvipdf(http://ghostscript.com/)"
        conv='dvipdf "$1" "$casp"'
    ;;
    text)
        missing pandoc "pandoc(http://pandoc.org/)"
        conv='pandoc -t epub2 - -o "$casp"'
        caspsuf=.epub
    ;;
    *) die "unhandled filter type: '$type'";;
esac

hash=$(cksum "$hashof") || die "$hash"
casp=$cachedir/${hash%% *}$caspsuf

{ test -n "${force-}" || test ! -e "$casp"; } && eval "$filt" "$conv"
shift

exec llpp -origin $origin "$@" "$casp"