#!/usr/bin/env bash

set -euo pipefail

usage() {
    cat <<EOF
$0
Downloads the latest version of the Zipkin Server executable jar

$0 GROUP:ARTIFACT:CLASSIFIER TARGET
Downloads the latest version of GROUP:ARTIFACT with classifier "CLASSIFIER"
to path "TARGET" on the local file system. For example:

$0 io.zipkin.java:zipkin-autoconfigure-collector-kafka10:module kafka10.jar
downloads the latest version of the artifact with group "io.zipkin.java",
artifact id "zipkin-autoconfigure-collector-kafka10", and classifier "module"
to PWD/kafka10.jar
EOF
}

welcome() {
    cat <<EOF
Thank you for trying OpenZipkin!

This installer is provided as a quick-start helper, so you can try Zipkin out
without a lengthy installation process.

EOF
}

farewell() {
    local artifact_classifier="$1"; shift
    local filename="$1"; shift
    if [ "$artifact_classifier" = 'exec' ]; then
        cat <<EOF

You can now run the downloaded executable jar:

    java -jar $filename

EOF
    else
        cat << EOF

The downloaded artifact is now available at $filename.
EOF
    fi
}

handle_shutdown() {
    local status=$?
    local base_filename="$1"; shift
    if [ $status -eq 0 ]; then
        rm -f "$base_filename"{.asc,.md5,.md5.asc}
    else
        cat <<EOF

It looks like quick-start setup has failed. Please run the command again
with the debug flag like below, and open an issue on
https://github.com/openzipkin/zipkin/issues/new. Make sure to include the
full output of the run.

    \curl -sSL http://zipkin.io/quickstart.sh | bash -sx $@

In the meanwhile, you can manually download and run the latest executable jar
from the following URL:

https://dl.bintray.com/openzipkin/maven/io/zipkin/java/zipkin-server/

EOF
    fi
}

extract_latest_version() {
    local package_data="$1"
    if \which jq >/dev/null 2>&1; then
        echo "$package_data" | jq '.latest_version' -r
    else
        echo "$package_data" | sed 's/^.*"latest_version" *: *"*\([^"]*\)".*$/\1/'
    fi
}

artifact_part() {
    local index="$1"; shift
    local default="$1"; shift
}

verify_version_number() {
    if ! echo "$1" | grep -E '^[0-9]+\.[0-9]+\.[0-9]+$' >/dev/null 2>&1; then
        cat <<EOF
It looks like the current version number is "$1". That doesn't look like a
valid Zipkin release version number; this script is confused. Bailing out.

EOF
        exit 1
    fi
}

verify_checksum() {
    local url="$1"; shift
    local filename="$1"; shift

    if \which md5sum >/dev/null 2>&1; then
        echo
        echo "Verifying checksum..."
        curl -sL -o "$filename.md5" "$url.md5"
        echo "$(cat $filename.md5)  $filename" | md5sum --check
    else
        echo "md5sum not found on path, skipping checksum verification"
    fi
}

verify_signature() {
    local url="$1"; shift
    local filename="$1"; shift

    local bintray_gpg_key='D401AB61'

    if \which gpg >/dev/null 2>&1; then
        echo
        echo "Verifying signature of $filename..."
        curl -sL -o "$filename.asc" "$url.asc"
        if gpg --list-keys "$bintray_gpg_key" >/dev/null 2>&1; then
            gpg --verify "$filename.asc" "$filename"
        else
            cat <<EOF

JFrog BinTray GPG signing key is not known, skipping signature verification.
You can import it, then verify the signature of $filename, using the following
commands:

    gpg --keyserver keyserver.ubuntu.com --recv $bintray_gpg_key
    # Optionally trust the key via 'gpg --edit-key $bintray_gpg_key', then typing 'trust',
    # choosing a trust level, and exiting the interactive GPG session by 'quit'
    gpg --verify $filename.asc $filename

EOF
        fi
    else
        echo "gpg not found on path, skipping checksum verification"
    fi
}

main() {
    local artifact_group=io.zipkin.java
    local artifact_id=zipkin-server
    local artifact_classifier=exec
    if [ $# -eq 0 ]; then
        local filename="zipkin.jar"
        trap "handle_shutdown \"$filename\" $*" EXIT
    elif [ "$1" = '-h' ] || [ "$1" = '--help' ]; then
        usage
        exit
    elif [ $# -eq 2 ]; then
        local filename="$2"
        trap "handle_shutdown \"$filename\" $*" EXIT
        local artifact_parts=(${1//:/ })
        local artifact_group="${artifact_parts[0]}"
        local artifact_id="${artifact_parts[1]}"
        local artifact_classifier="${artifact_parts[2]}"
    else
        usage
        exit 1
    fi

    if [ -n "$artifact_classifier" ]; then
        artifact_classifier_suffix="-$artifact_classifier"
    else
        artifact_classifier_suffix=''
    fi

    welcome
    echo 'Fetching version number of latest Zipkin release...'
    local package_data="$(curl -fsL  https://bintray.com/api/v1/packages/openzipkin/maven/zipkin)"
    local latest_version="$(extract_latest_version "$package_data")"
    verify_version_number "$latest_version"

    echo "Downloading $artifact_group:$artifact_id:$latest_version:$artifact_classifier to $filename..."
    local url="https://dl.bintray.com/openzipkin/maven/${artifact_group//./\/}/${artifact_id}/$latest_version/${artifact_id}-${latest_version}${artifact_classifier_suffix}.jar"
    echo "$url -> $filename"
    curl -L -o "$filename" "$url"
    verify_checksum "$url" "$filename"
    verify_signature "$url" "$filename"
    verify_signature "$url.md5" "$filename.md5"

    farewell "$artifact_classifier" "$filename"

}

main "$@"