#!/usr/bin/env bash

usage() {
    cat <<EOF
Usage: $0 -s </path/to/wdl> -t </path/to/wdl-mount> [-o <max-ring-overworld>] [-n <max-ring-nether>] [-e <max-ring-end>]
Options:
  -s </path/to/wdl>         Path to source directory containing overworld, nether, and end directories (required)
  -t </path/to/extracted>   Path to target directory to extract all rings into (required)
  -o <max-ring-overworld>   Maximum ring for overworld (default: 33, set to 0 for none)
  -n <max-ring-nether>      Maximum ring for nether (default: 23, set to 0 for none)
  -e <max-ring-end>         Maximum ring for end (default: 8, set to 0 for none)
  -h                        Show this help message
EOF
    exit 1
}

SRC=""
DST=""

MAX_RING_OVERWORLD=33
MAX_RING_NETHER=23
MAX_RING_END=8

while getopts "s:t:o:n:e:h" opt; do
    case "$opt" in
        s) SRC="$OPTARG" ;;
        t) DST="$OPTARG" ;;
        o) MAX_RING_OVERWORLD="$OPTARG" ;;
        n) MAX_RING_NETHER="$OPTARG" ;;
        e) MAX_RING_END="$OPTARG" ;;
        h) usage ;;
        *) usage ;;
    esac
done

if [[ -z "$SRC" ]]; then
    echo "Error: -s </path/to/wdl> is required." >&2
    usage
fi

[[ -d "$SRC" ]] || {
    echo "Error: $SRC is not a directory." >&2
    exit 1
}

DST="$(realpath -m "$DST")"

extract_ring() {
    local max="$1"
    local dim="$2"

    for ((r=1; r<=max; r++)); do
        local img="$SRC/$dim/ring$r.squashfs"
        if [[ ! -f "$img" ]]; then
            echo "Skipping missing ring $img"
            continue
        fi

        local tmp_dir="$SRC/$dim/.tmp_ring$r"
        unsquashfs -d "$tmp_dir" "$img"

        pushd "$tmp_dir" || exit 1
        find . -type d -exec mkdir -p "$DST/"{} \;
        find . -type f -exec mv -n {} "$DST/"{} \;
        popd || exit 1

        find "$tmp_dir" -type d -empty -delete
    done
}

extract_ring "$MAX_RING_OVERWORLD" "overworld"
extract_ring "$MAX_RING_NETHER" "nether"
extract_ring "$MAX_RING_END" "end"