#!/bin/bash

##
# AutoFS user-folder indirect Automounter for S3 using either FUSE goofyfs or s3fs
#
# Requirements
# - AWS CLI installed
# - JQ installed
# - Either FUSE goofyfs or s3fs installed
#
# Usage
#  - place config to $S3FS_CONFIG directory using s3fs config format (ACCESS_KEY:ACCESS_SECRET)
#  - place this file to /etc/auto.s3 and make it executable
#  - add to /etc/auto.master: /home/<user>/Remote/S3 /etc/auto.s3 --timeout=3000
#  - choose backend by config section in this file (NOTE: goofyfs needs )
#  - cd <mountpoint>/<aws-profile>/<bucket>
#
# Debugging
# - Stop system service by:
#   systemctl stop autofs
# - Execute as process (use --debug to see mount commands)
#   automount -f -v
#
# Clean up mountpoints (when autofs hangs or mountpoints are still used)
#   mount | grep autofs | cut -d' ' -f 3 | xargs umount -l
#
# Logging
# - Logs go to syslog except you are running automount within TTY
#
# Notes
# - goofyfs makes sometimes trouble - use s3fs!
# - Daemon needs to run by root since we only root has access to all mount options
# - Additional entries can be defined with the -Dvariable=Value map-option to automount(8).
# - Alternative fuse style mount can be done by -fstype=fuse,allow_other :sshfs#user@example.com:/path/to/mount
# - We do not read out .aws/config since not all credentials do necessary have S3-access
# - https://github.com/kahing/goofys/pull/91/commits/07dffdbda4ff7fc3c538cb07e58ad12cc464b628
# - goofyfs catfs cache is not activated by default
# - chown/chmod is not that nice but works ;9
# - other backends not planned at the moment
#
# AWS Commands
# - aws s3api list-buckets
# - aws s3api list-objects --bucket <bucket>
#
# FAQ
# -  https://github.com/s3fs-fuse/s3fs-fuse/wiki/FAQ
#
# Autofs provides additional variables that are set based on the user requesting the mount:
#
#   USER   The user login name
#   UID    The user login ID
#   GROUP  The user group name
#   GID    The user group ID
#   HOME   The user home directory
#   HOST   Hostname (uname -n)
#
# From exports
#
#   AUTOFS_GID="1000"
#   AUTOFS_GROUP="ctang"
#   AUTOFS_HOME="/home/ctang"
#   AUTOFS_SHOST="refpad-16"
#   AUTOFS_UID="1000"
#   AUTOFS_USER="ctang"
#

# Strict mode
set -euo pipefail -o errtrace

# Config
S3FS_CONFIG="${AUTOFS_HOME:-$HOME}/.autofs/s3fs" # user directory
BACKEND="goofyfs" # s3fs|goofyfs - not goofyfs requires goofyfs-fuse!
DEBUG=0 # 0|1 where 1 is on - output will go to syslog or journald
UMASK="750" # Umask for mountpoint placeholder directories
OPTS="defaults,noatime" # mount options
if [[ -z "${GID:-}" ]]; then
    GID="$(id -g)"
fi

# We ensure every command output can be parsed in neutral form
export LC_ALL=C
export AWS_SDK_LOAD_CONFIG=0

# Const
PWD="$(pwd)"
SCRIPT_NAME=`basename "$0"`
LOGGER_CMD="logger -i -t ${SCRIPT_NAME}"
if test -t 1; then 
    # if tty
    LOGGER_CMD="${LOGGER_CMD}  --no-act --stderr"
fi
PROFILES=()

if ! which jq 1>/dev/null 2>&1; then
     $LOGGER_CMD "Cannot find jq binary"
     exit 1
fi

if ! which aws 1>/dev/null 2>&1; then
     $LOGGER_CMD "Cannot find aws binary"
     exit 1
fi

# If use is already in a mount point this script will be called by root
# so we need to remap some stuff
if [[ ! "${HOME:-}" == "${PWD}/"* ]] && [[ "${PWD}" =~ ^(/home/[^/]+) ]]; then
    S3FS_CONFIG=${S3FS_CONFIG/${AUTOFS_HOME:-$HOME}/${BASH_REMATCH[1]}}
    HOME="${BASH_REMATCH[1]}"
    USER="${HOME##*/}"
    AUTOFS_UID="$(id -u ${USER})"
    AUTOFS_GID="$(id -g ${USER})"
    $LOGGER_CMD "Initializing. Remapping home to ${HOME}, user=${USER}, config=${S3FS_CONFIG}"
fi

# Prevent errors
if [[ ! -d ${S3FS_CONFIG} ]]; then
     $LOGGER_CMD "Config directory ${S3FS_CONFIG} not found."
     exit 1
fi

# Mountpoint needs to be owned by user 
chown -R ${AUTOFS_UID:-$UID}:${AUTOFS_GID:-$GID} "${S3FS_CONFIG}"
chmod -R 700 "${S3FS_CONFIG}"

# Create indirect mount points for s3 profiles
PROFILES=($(ls -1 ${S3FS_CONFIG}))
if [[ -z "${PROFILES[*]}" ]]; then
    $LOGGER_CMD "No profiles found within ${S3FS_CONFIG}"
else
    for profile in "${PROFILES[@]}"; do
        chmod 600 ${S3FS_CONFIG}/${profile}
        if [[ ! -d "${PWD}/${profile}" ]]; then
            $LOGGER_CMD "Creating ${PWD}/${profile}"
            mkdir -p "${PWD}/${profile}"  || true > /dev/null
            chmod ${UMASK} "${PWD}/${profile}"
            chown ${AUTOFS_UID:-$UID}:${AUTOFS_GID:-$GID} "${PWD}/${profile}"
        fi
    done
fi

# Requested profile
PROFILE="${1:-}"
if [[ ! -e "${S3FS_CONFIG}/${PROFILE}" ]]; then
    $LOGGER_CMD "No valid profile=${PROFILE} given! "
    exit 1
fi
$LOGGER_CMD "Profile: $@"
if [[ -z "${PROFILE}" ]]; then
    $LOGGER_CMD "No profile given" 
    exit 1
fi

if [[ "${BACKEND}" == "s3fs" ]]; then
    if ! which s3fs 1>/dev/null 2>&1; then
        $LOGGER_CMD "Cannot find s3fs installation"
        exit 1
    fi
    OPTS="-fstype=fuse.s3fs,uid=${AUTOFS_UID:-${UID}},gid=${AUTOFS_UID:-${GID}},umask=000,${OPTS},_netdev,allow_other,default_permissions,passwd_file=${S3FS_CONFIG}/${PROFILE},use_cache=$(mktemp -d)"
    if [[ "$DEBUG" -eq 1 ]]; then
        OPTS="${OPTS},dbglevel=info,curldbg"
    fi
elif [[ "${BACKEND}" == "goofyfs" ]]; then
    if ! which goofyfs 1>/dev/null 2>&1; then
        $LOGGER_CMD "Cannot find goofyfs installation"
        exit 1
    fi
    OPTS="-fstype=fuse.goofyfs-fuse,${OPTS},_netdev,nonempty,allow_other,passwd_file=${S3FS_CONFIG}/${PROFILE},--file-mode=0666,nls=utf8"
    if [[ "${DEBUG}" -eq 1 ]]; then
        OPTS="${OPTS},--debug_s3,--debug_fuse"
    fi
else
    $LOGGER_CMD "Unsupported backend ${BACKEND}"
    exit 1
fi

read  -r -d '' CREDENTIALS < ${S3FS_CONFIG}/${PROFILE}
export AWS_ACCESS_KEY_ID="${CREDENTIALS%%:*}"
export AWS_SECRET_ACCESS_KEY="${CREDENTIALS##*:}"
BUCKETS=($(aws s3api list-buckets --output json | jq -r '.Buckets[].Name'))
printf "%s\n" "${BUCKETS[@]}" | awk -v "opts=${OPTS}" -F '|' -- \
    '\
    BEGIN { ORS=""; first=1 }
    { 
          if (first)
            print opts; first=0
          bucket = $1
          # Enclose mount dir and location in quotes
          # Double quote "$" in location as it is special
          gsub(/\$\$/, "\\\$\",loc)
          gsub(/&amp;/, "\\&amp;",loc)
          print " \
\t \"/" bucket "\"", ":"bucket "\""
          # print " \
\t " bucket, ":"bucket
        }
    END { if (!first) print "\n"; else exit 1 }'