#!/usr/bin/env bash
set -e

RUNID=$(openssl rand -hex 16)
function log {
  echo -e "${RUNID}\t$(date -Is)\t$@"
}

if [ $# -lt 4 ]; then
  echo "Usage: ssync KEY_FILE REMOTE REMOTE_DIR SRC_DIR"
  exit 1
fi

# opts
KEY_FILE=$1
REMOTE=$2
REMOTE_DIR=$3
SRC_DIR=$4

# constants
PARALLEL=5
SSYNC_DIR=$HOME/.local/share/ssync
FETCHED_FILE=$SSYNC_DIR/fetched
FETCH_FILE=$SSYNC_DIR/fetch
LASTRAN_FILE=$SSYNC_DIR/lastran
NEXT_RUN_DATE=$(date -u -Is -d '5 minutes ago')
RUN_DIR=$SSYNC_DIR/.runs/
CURGET_FILE=$RUN_DIR/$RUNID
if [ ! -f $LASTRAN_FILE ]; then
  mkdir -p $SSYNC_DIR
  echo $NEXT_RUN_DATE > $LASTRAN_FILE
  log "No run existed marking next run for files newer than: $NEXT_RUN_DATE"
  exit 0;
fi
PREV_RUN_DATE=$(cat $LASTRAN_FILE)

# main

if [[ $PREV_RUN_DATE ==  "" ]]; then
  echo $NEXT_RUN_DATE > $LASTRAN_FILE
  log "No run existed marking next run for files newer than: $NEXT_RUN_DATE"
  exit 0;
fi

if [ ! -f $FETCHED_FILE ]; then
  touch $FETCHED_FILE
fi


log "Failsafe - Running at: $NEXT_RUN_DATE - if failed to write use this timestamp in $LASTRAN_FILE"
log "Syncing files since: $PREV_RUN_DATE"


log "Fetching files"
mkdir -p $RUN_DIR
ssh -i $KEY_FILE $REMOTE "find ${REMOTE_DIR} -type f -newermt ${PREV_RUN_DATE} -exec realpath --relative-to ${REMOTE_DIR} {} \;" >> $CURGET_FILE
GET_COUNT=$(wc -l $CURGET_FILE | cut -d' ' -f1)

if [ $GET_COUNT -gt 0 ]; then
  comm -23 <(sort -u $CURGET_FILE) <(sort -u $FETCHED_FILE) > $FETCH_FILE
  COUNT=$(wc -l $FETCH_FILE | cut -d' ' -f1)

  if [ $COUNT -gt 0 ]; then
    #
    # Syncing
    #
    log "Found ${COUNT} files to fetch"

    cat $FETCH_FILE >> $FETCHED_FILE
    log "Wrote files to fetched files"
    log "Syncing now"
    cat $FETCH_FILE | xargs -n1 -P$PARALLEL -I '{}' rsync -e "ssh -i $KEY_FILE" \
      -av \
      $REMOTE:"${REMOTE_DIR}/'{}'" ${SRC_DIR}
  else
    log "No new files to sync - found $GET_COUNT existing files" 
  fi
else
  log "No new files found - deleting $CURGET_FILE"
  rm -f $CURGET_FILE
fi

echo $NEXT_RUN_DATE > $LASTRAN_FILE
log "Done syncing"