#!/usr/bin/env bash

# SPDX-License-Identifier: MIT
# Copyright (c) 2026 Frost

set -u

if [ "$#" -eq 0 ]; then
    echo "Usage: get <url1> [url2 ...]"
    exit 1
fi

download_to_file() {
    local url="$1"
    local outfile="$2"
    local tmpfile

    tmpfile="$(mktemp)" || return 1
    if wget -q -O "$tmpfile" "$url"; then
        mv -f "$tmpfile" "$outfile"
    else
        rm -f "$tmpfile"
        return 1
    fi
}

get_konachan_post_id() {
    local url="$1"
    if [[ "$url" =~ %20-%20([0-9]+)%20 ]]; then
        printf '%s\n' "${BASH_REMATCH[1]}"
        return 0
    fi
    return 1
}

get_danbooru_post_id() {
    local md5="$1"
    local id

    id="$(wget -qO- "https://danbooru.donmai.us/posts.json?tags=md5:${md5}&limit=1" \
        | jq -r '.[0].id // empty')" || return 1

    [ -n "$id" ] && printf '%s\n' "$id"
}

process_url() {
    local url="$1"
    local clean_url="${url%%\?*}"

    if [[ "$clean_url" =~ konachan\.(com|net) ]]; then
        local download_url="${clean_url/konachan.com/konachan.net}"
        local filename="${clean_url##*/}"
        local ext="${filename##*.}"
        local post_id final_file

        if post_id="$(get_konachan_post_id "$clean_url")"; then
            final_file="${post_id}k.${ext}"
            printf "Downloading: %s ... " "$final_file"
            if download_to_file "$download_url" "$final_file"; then
                echo "[OK]"
            else
                echo "[FAILED]"
            fi
        else
            echo "Could not extract Konachan post ID: $url"
        fi

    elif [[ "$clean_url" =~ (danbooru\.donmai\.us|cdn\.donmai\.us) ]]; then
        local filename="${clean_url##*/}"
        local ext="${filename##*.}"
        local md5 post_id final_file

        if [[ "$clean_url" =~ ([0-9a-f]{32})\.[A-Za-z0-9]+$ ]]; then
            md5="${BASH_REMATCH[1]}"

            if post_id="$(get_danbooru_post_id "$md5")"; then
                final_file="${post_id}d.${ext}"
                printf "Downloading: %s ... " "$final_file"
                if download_to_file "$clean_url" "$final_file"; then
                    echo "[OK]"
                else
                    echo "[FAILED]"
                fi
            else
                echo "Could not find Danbooru ID for MD5: $md5"
            fi
        else
            echo "Could not extract MD5: $url"
        fi

    else
        printf "Downloading: %s ... " "$url"
        if wget -q "$url"; then
            echo "[OK]"
        else
            echo "[FAILED]"
        fi
    fi
}

# ----------------------
# PARALLEL CONTROL
# ----------------------

max_jobs=$(( $# < 5 ? $# : 5 ))

pids=()
outputs=()

for url in "$@"; do
    tmp_out="$(mktemp)"
    outputs+=("$tmp_out")

    (
        process_url "$url"
    ) >"$tmp_out" 2>&1 &

    pids+=($!)

    # limit parallel jobs
    if (( ${#pids[@]} >= max_jobs )); then
        wait "${pids[0]}"
        cat "${outputs[0]}"
        rm -f "${outputs[0]}"
        pids=("${pids[@]:1}")
        outputs=("${outputs[@]:1}")
    fi
done

# wait remaining
for I in "${!pids[@]}"; do
    wait "${pids[$I]}"
    cat "${outputs[$I]}"
    rm -f "${outputs[$I]}"
done