#!/bin/bash

set -eux
set -o pipefail

write_entries() {
    local file="$1"
    local entries="$2"

    # Don't do anything if the file isn't there
    if [ ! -f "$file" ]; then
        return
    fi

    if grep -q "^# HEAT_HOSTS_START" "$file"; then
        temp=$(mktemp)
        (
        sed '/^# HEAT_HOSTS_START/,$d' "$file"
        echo -ne "# HEAT_HOSTS_START - Do not edit manually within this section!\n"
        echo "$entries"
        echo -ne "# HEAT_HOSTS_END\n"
        sed '1,/^# HEAT_HOSTS_END/d' "$file"
        ) > "$temp"
        echo "INFO: Updating hosts file $file, check below for changes"
        diff "$file" "$temp" || true
        cat "$temp" > "$file"
    else
        echo -ne "\n# HEAT_HOSTS_START - Do not edit manually within this section!\n" >> "$file"
        echo "$entries" >> "$file"
        echo -ne "# HEAT_HOSTS_END\n\n" >> "$file"
    fi

}

ENTRIES=$(os-apply-config --key hosts --type raw --key-default '' | tr '[A-Z]' '[a-z]' | sed -e 's/\\n/\n/g' -e '/^$/d')
if [ ! -z "$ENTRIES" ]; then
    # cloud-init files are /etc/cloud/templates/hosts.OSNAME.tmpl
    DIST=$(lsb_release -is | tr -s '[A-Z]' '[a-z]')
    case $DIST in
        fedora|redhatenterpriseserver)
            name="redhat"
            ;;
        *)
            name="$DIST"
            ;;
    esac
    write_entries "/etc/cloud/templates/hosts.${name}.tmpl" "$ENTRIES"
    write_entries "/etc/hosts" "$ENTRIES"
else
    echo "No hosts in Heat, nothing written."
fi