#!/usr/bin/env bash
set -euo pipefail

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
# Workspace root containing train/ and test/ outputs; override via MVEB_ROOT.
ROOT_DIR="${MVEB_ROOT:-$(cd "${SCRIPT_DIR}/../../.." && pwd)}"
GDRIVE_FOLDER_ID="18EunmjOJsbE5Lh9zA0cZ4wKV6Um46dkg"
GDRIVE_URL="https://drive.google.com/drive/folders/${GDRIVE_FOLDER_ID}"
DOWNLOAD_DIR="${ROOT_DIR}/downloads/compcars"
EXTRACT_DIR="${ROOT_DIR}/source/compcars"
PASSWORD="d89551fd190e38"

need_cmd() {
    command -v "$1" >/dev/null 2>&1 || {
        echo "Missing command: $1" >&2
        exit 1
    }
}

need_cmd gdown
need_cmd zip
need_cmd unzip
need_cmd python3

mkdir -p "${DOWNLOAD_DIR}" "${EXTRACT_DIR}"

download_from_gdrive() {
    echo "==> Downloading files from Google Drive folder: ${GDRIVE_URL}"
    echo "    Save to: ${DOWNLOAD_DIR}"
    # --remaining-ok: skip files that already exist (resume-friendly).
    gdown --folder "${GDRIVE_URL}" -O "${DOWNLOAD_DIR}" --remaining-ok
}

check_split_parts() {
    local prefix="$1"
    local zipfile="${DOWNLOAD_DIR}/${prefix}.zip"

    if [[ ! -f "${zipfile}" ]]; then
        echo "[warn] ${prefix}.zip not found under ${DOWNLOAD_DIR}"
        return 1
    fi

    local missing=0
    local part
    for part in "${DOWNLOAD_DIR}/${prefix}".z*; do
        [[ -e "${part}" ]] || continue
        :
    done

    # data.z01 - data.z22
    if [[ "${prefix}" == "data" ]]; then
        local i
        for i in $(seq -w 1 22); do
            if [[ ! -f "${DOWNLOAD_DIR}/${prefix}.z${i}" ]]; then
                echo "[warn] missing ${prefix}.z${i}"
                missing=1
            fi
        done
    fi

    if [[ "${missing}" -eq 1 ]]; then
        echo "[warn] split archive for ${prefix} is incomplete; zip -F may still work if only a few parts are absent."
    fi
    return 0
}

check_truncated_parts() {
    # gdown --remaining-ok skips any existing file without size checks, so a
    # part truncated by a broken run would silently survive re-runs. Split
    # volumes (.zNN) are all cut at the same size, so any part smaller than
    # the largest one is truncated and must be deleted before re-running.
    local prefix="$1"
    local max_size=0 size part
    local bad_parts=()

    for part in "${DOWNLOAD_DIR}/${prefix}".z[0-9]*; do
        [[ -f "${part}" ]] || continue
        size=$(stat -c %s "${part}")
        if (( size > max_size )); then
            max_size=${size}
        fi
    done
    for part in "${DOWNLOAD_DIR}/${prefix}".z[0-9]*; do
        [[ -f "${part}" ]] || continue
        size=$(stat -c %s "${part}")
        if (( size < max_size )); then
            bad_parts+=("${part} (${size} < ${max_size} bytes)")
        fi
    done
    if [[ -f "${DOWNLOAD_DIR}/${prefix}.zip" ]] && [[ ! -s "${DOWNLOAD_DIR}/${prefix}.zip" ]]; then
        bad_parts+=("${DOWNLOAD_DIR}/${prefix}.zip (0 bytes)")
    fi

    if [[ ${#bad_parts[@]} -gt 0 ]]; then
        echo "[error] Truncated download detected (likely an interrupted gdown run):" >&2
        printf '    %s\n' "${bad_parts[@]}" >&2
        echo "Delete the file(s) above and re-run this script to re-download them." >&2
        exit 1
    fi
}

extract_split_archive() {
    local prefix="$1"
    local out_dir="$2"
    local zipfile="${DOWNLOAD_DIR}/${prefix}.zip"
    local combined="${DOWNLOAD_DIR}/combined_${prefix}.zip"
    local marker="${out_dir}/.extracted"

    if [[ -f "${marker}" ]]; then
        echo "==> Skip ${prefix}: already extracted (${marker})"
        return 0
    fi

    if [[ ! -f "${zipfile}" ]]; then
        echo "==> Skip ${prefix}: ${zipfile} not found"
        return 0
    fi

    check_split_parts "${prefix}" || true
    check_truncated_parts "${prefix}"

    echo "==> Combining ${prefix}.zip + ${prefix}.z* -> $(basename "${combined}")"
    (
        cd "${DOWNLOAD_DIR}"
        zip -F "${prefix}.zip" --out "$(basename "${combined}")"
    )

    echo "==> Extracting ${combined} -> ${out_dir}"
    mkdir -p "${out_dir}"
    unzip -o -P "${PASSWORD}" "${combined}" -d "${out_dir}"
    touch "${marker}"
    echo "==> Done: ${out_dir}"
}

main() {
    download_from_gdrive

    extract_split_archive "data" "${EXTRACT_DIR}/data"

    if [[ -f "${DOWNLOAD_DIR}/README.txt" ]]; then
        cp -f "${DOWNLOAD_DIR}/README.txt" "${ROOT_DIR}/README.txt"
        echo "==> Copied README.txt to ${ROOT_DIR}/README.txt"
    fi

    echo "==> Pack CompCars to parquet"
    python3 "${SCRIPT_DIR}/process_compcars.py" --overwrite \
        --image-root "${EXTRACT_DIR}/data/image" \
        --output-root "${ROOT_DIR}"

    echo "==> All done."
    echo "    downloads: ${DOWNLOAD_DIR}"
    echo "    extracted: ${EXTRACT_DIR}"
    echo "    output:    ${MVEB_TRAIN_DIR:-${ROOT_DIR}/MVEB-train}/CompCars , ${MVEB_TEST_DIR:-${ROOT_DIR}/MVEB-test}/CompCars"
}

main "$@"