#!/bin/bash

# Copyright 2012 Hewlett-Packard Development Company, L.P.
# Copyright 2013 Red Hat, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.

set -eu
set -o pipefail

# Download a URL to a local cache
# e.g. cache-url http://.../foo ~/.cache/image-create/foo

url=$1
dest=$2
time_cond=

if [ -p $dest ]; then
    type="fifo"
    tmp=$(mktemp --tmpdir download.XXXXXXXX)
else
    type="normal"
    mkdir -p $(dirname $dest)
    tmp=$(mktemp $(dirname $dest)/.download.XXXXXXXX)
fi

if [ -f $dest -a -s $dest ] ; then
    time_cond="-z $dest"
    success="Server copy has changed. Using server version of $url"
else
    success="Downloaded and cached $url for the first time"
fi

rcode=$(curl -L -o $tmp -w '%{http_code}' $url $time_cond)
if [ "$rcode" == "200" -o "${url:0:7}" == "file://" ] ; then
    # In cases where servers ignore the Modified time,
    # curl cancels the download, outputs a 200 and leaves
    # the output file untouched, we don't want this empty file.
    if [ -n "$time_cond" -a ! -s $tmp ] ; then
        echo "Ignoring empty file returned by curl. Using locally cached $url"
        rm -f $tmp
    else
        echo $success
        if [ "fifo" = "$type" ]; then
            cp $tmp $dest
            rm $tmp
        else
            mv $tmp $dest
        fi
    fi
    # 213 is the response to a ftp MDTM command, curl outputs a 213 as the status
    # if the url redirected to a ftp server and Not-Modified
elif [ "$rcode" = "304" -o "$rcode" = "213" ] ; then
    echo "Server copy has not changed. Using locally cached $url"
    rm -f $tmp
else
    echo "Server returned an unexpected response code. [$rcode]"
    rm -f $tmp
    # expose some error codes so the calling process might know what happened
    if [ "$rcode" = "404" ] ; then
        exit 44
    fi
    exit 1
fi