#!/bin/bash

# specify registry as:
#  REGISTRY=my.secured.registry.com:5000
#  PROTOCOL=https
#  
#  REGISTRY=192.168.1.33:5000
#  PROTOCOL=http
#  
# If you don't have SSL, be sure to add the insecure 
# registry to docker configuration

REGISTRY=127.0.0.1:5000
PROTOCOL=http



IMAGE=$( echo "$1" | cut -f1 -d:)
if [ "$1" = "" ] ; then
  echo "You must specify which image to pull"
  exit 1
fi

TAG=$( echo "$1" | cut -s -f2 -d:)
TAG=${TAG:-latest}

## docker-search for upstream REGISTRY
# TODO: fix the grep part!
UPSTREAM=$( docker search --format="{{.Name}}" "${IMAGE}" | grep "^${IMAGE}$" )

if [ ! "${IMAGE}" = "${UPSTREAM}" ] ; then
  echo "Image doesn't exists on docker hub"
  exit 1
fi

# TODO: check if tag exists on upstream

## check if image exists on local registry
URL=${PROTOCOL}://${REGISTRY}/v2/${IMAGE}/tags/list
curl -sX GET "$URL" | grep '"NAME_UNKNOWN"' > /dev/null || {
  ## if so, check if tag exists on local registry
  URL=${PROTOCOL}://${REGISTRY}/v2/${IMAGE}/manifests/${TAG}
  curl -sX GET "$URL" | grep '"MANIFEST_UNKNOWN"' > /dev/null || {
    ## if so, download it
    docker pull ${REGISTRY}/${IMAGE}:${TAG}
  }
}

## then download from upstream
docker pull ${IMAGE}:${TAG}

## and update local registry 
docker tag ${IMAGE}:${TAG} ${REGISTRY}/${IMAGE}:${TAG}
docker push ${REGISTRY}/${IMAGE}:${TAG}
docker rmi ${REGISTRY}/${IMAGE}:${TAG}