#! /usr/bin/env bash
USAGE="Usage: ./download.sh [-hD] [-c <NUM>] <DUMP_DIR>

Download the latest Wikipedia Enterprise HTML dumps.

Arguments:
    <DUMP_DIR>  An existing directory to store dumps in. Dumps will be grouped
                into subdirectories by date, and a link 'latest' will point to
                the latest complete dump subdirectory, if it exists.

Options:
    -h          Print this help screen.
    -D          Delete all old dump subdirectories if the latest is downloaded.
    -c <NUM>    Number of concurrent downloads to allow. Ignored if wget2 is not
                present or MIRROR is not set. Defaults to 2.

Environment Variables:
    LANGUAGES   A whitespace-separated list of wikipedia language codes to
                download dumps of.
                Defaults to the languages in 'article_processing_config.json'.
                See <https://meta.wikimedia.org/wiki/List_of_Wikipedias>.
    MIRROR      A wikimedia dump mirror to use instead of the main wikimedia
                server. See <https://dumps.wikimedia.org/mirrors.html> for a
                list of available mirrors, note that many do not include the
                required Enterprise HTML dumps.
                For example: MIRROR=https://mirror.accum.se/mirror/wikimedia.org

Exit codes:
    0   The latest dumps are already present or were downloaded successfully.
    1   Argument error.
    16  Some of languages were not available to download. The latest dump may
        be in progress, some of the specified languages may not exist, or the
        chosen mirror may not host the files.
    _   Subprocess error.
"

set -euo pipefail
# set -x

build_user_agent() {
    # While the dump websites are not part of the API, it's still polite to identify yourself.
    # See https://meta.wikimedia.org/wiki/User-Agent_policy
    subcommand=$1
    name="OrganicMapsWikiparserDownloaderBot"
    version="1.0"
    url="https://github.com/organicmaps/wikiparser"
    email="hello@organicmaps.app"
    echo -n "$name/$version ($url; $email) $subcommand"
}

# Parse options.
DELETE_OLD_DUMPS=false
CONCURRENT_DOWNLOADS=
while getopts "hDc:" opt
do
    case $opt in
    h)  echo -n "$USAGE"; exit 0;;
    D)  DELETE_OLD_DUMPS=true;;
    c)  CONCURRENT_DOWNLOADS=$OPTARG;;
    ?)  echo "$USAGE" | head -n1 >&2; exit 1;;
    esac
done
shift $((OPTIND - 1))

if [ -z "${1:-}" ]; then
    echo "DUMP_DIR is required" >&2
    echo -n "$USAGE" >&2
    exit 1
fi

# The parent directory to store groups of dumps in.
DUMP_DIR=$(readlink -f "$1")
shift

if [ -n "${1:-}" ]; then
    echo "Unexpected extra argument: '$1'" >&2
    echo "$USAGE" | head -n1 >&2
    exit 1
fi

if [ ! -d "$DUMP_DIR" ]; then
    echo "DUMP_DIR does not exist: '$DUMP_DIR'" >&2
    exit 1
fi

if [ -n "$CONCURRENT_DOWNLOADS" ]; then
    if [ ! "$CONCURRENT_DOWNLOADS" -ge 1 ]; then
        echo "Number of concurrent downloads (-n) must be >= 1" >&2
        echo "$USAGE" | head -n1 >&2
        exit 1
    fi
    if [ -z "${MIRROR:-}" ]; then
        # NOTE: Wikipedia requests no more than 2 concurrent downloads.
        # See https://dumps.wikimedia.org/ for more info.
        echo "WARN: MIRROR is not set; ignoring -n" >&2
        CONCURRENT_DOWNLOADS=
    fi
fi

# Ensure we're running in the directory of this script.
SCRIPT_PATH=$(dirname "$0")
cd "$SCRIPT_PATH"
SCRIPT_PATH=$(pwd)

# Only load library after changing to script directory.
source lib.sh


if [ -n "${MIRROR:-}" ]; then
    log "Using mirror '$MIRROR'"
    BASE_URL=$MIRROR
else
    BASE_URL="https://dumps.wikimedia.org"
fi

if [ -z "${LANGUAGES:-}" ]; then
    # Load languages from config.
    LANGUAGES=$(jq -r '(.sections_to_remove | keys | .[])' article_processing_config.json)
fi
# shellcheck disable=SC2086 # LANGUAGES is intentionally expanded.
log "Selected languages:" $LANGUAGES

log "Fetching run index"
# The date of the latest dump, YYYYMMDD.
LATEST_DUMP=$(wget "$BASE_URL/other/enterprise_html/runs/" --no-verbose -O - \
            | grep -Po '(?<=href=")[^"]*' | grep -P '\d{8}' | sort -r | head -n1)
LATEST_DUMP="${LATEST_DUMP%/}"

log "Checking latest dump $LATEST_DUMP"

URLS=
MISSING_DUMPS=0
for lang in $LANGUAGES; do
    url="$BASE_URL/other/enterprise_html/runs/${LATEST_DUMP}/${lang}wiki-NS0-${LATEST_DUMP}-ENTERPRISE-HTML.json.tar.gz"
    if ! wget --no-verbose --method=HEAD "$url"; then
        MISSING_DUMPS=$(( MISSING_DUMPS + 1 ))
        log "Dump for '$lang' does not exist at '$url'"
        continue
    fi
    URLS="$URLS $url"
done

if [ -z "$URLS" ]; then
    log "No dumps available"
    exit 16
fi

# The subdir to store the latest dump in.
DOWNLOAD_DIR="$DUMP_DIR/$LATEST_DUMP"
if [ ! -e "$DOWNLOAD_DIR" ]; then
    mkdir "$DOWNLOAD_DIR"
fi

log "Downloading available dumps"
if type wget2 > /dev/null; then
    # shellcheck disable=SC2086 # URLS should be expanded on spaces.
    wget2 --verbose --progress=bar --continue \
        --user-agent "$(build_user_agent wget2)" \
        --max-threads "${CONCURRENT_DOWNLOADS:-2}" \
        --directory-prefix "$DOWNLOAD_DIR" \
        $URLS
else
    log "WARN: wget2 is not available, falling back to sequential downloads"
    # shellcheck disable=SC2086 # URLS should be expanded on spaces.
    wget --continue \
        --user-agent "$(build_user_agent wget)" \
        --directory-prefix "$DOWNLOAD_DIR" \
        $URLS
fi

if [ $MISSING_DUMPS -gt 0 ]; then
    log "$MISSING_DUMPS dumps not available yet"
    exit 16
fi

log "Linking 'latest' to '$LATEST_DUMP'"
LATEST_LINK="$DUMP_DIR/latest"
ln -sf -T "$LATEST_DUMP" "$LATEST_LINK"

if [ "$DELETE_OLD_DUMPS" = true ]; then
    # shellcheck disable=SC2010 # Only matching files with numeric names are used.
    mapfile -t OLD_DUMPS < <(ls "$DUMP_DIR" | grep -P '^\d{8}$' | grep -vF "$LATEST_DUMP")
    if [ "${#OLD_DUMPS[@]}" -gt 0 ]; then
        log "Deleting old dumps" "${OLD_DUMPS[@]}"
        for old_dump in "${OLD_DUMPS[@]}"; do
            rm -r "${DUMP_DIR:?}/${old_dump:?}/"
        done
    else
        log "No old dumps to delete"
    fi
fi