#!/bin/zsh
q=$1
url='http://danbooru.donmai.us/posts.xml'
de=--data-urlencode

curl=(curl -sS -m 32 --connect-timeout 8 --retry 3 --retry-delay 1)

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

push() {
    if [ -z $md5 ] || [ -z $ext ] || [ -z $size ]; then
        print missing value >&2
        return
    fi
    local fn=$md5.$ext
    local s="$(find . -name $fn -print -quit 2>/dev/null)"
    [ -n "$s" ] && print $s || print \#$fn
    md5= ext= size=
}

page=1
while; do
    once=0
    ${curl[@]} -G -d limit=100 -d page=$page $de tags=$q $url \
      | xml2 2>/dev/null \
      | while IFS== read -r tree val; do
        [ $tree = /posts/post ] && push && continue
        [ ${tree:0:12} = /posts/post/ ] && tree=${tree:12} || continue
        once=1

        case $tree in
          (md5) md5=$val ;;
          (file-ext) ext=$val ;;
          (file-size) size=$val ;;
        esac
    done
    [[ ${PIPESTATUS[1]} -eq 0 ]] || die "curl failed on page $page"
    [[ $once -eq 0 ]] && exit 0 # no posts left, well done
    push
    let page++
done