#!/bin/bash

# exit on any non-zero exit code:
set -e

# keep track of the last executed command
trap 'last_command=$current_command; current_command=$BASH_COMMAND' DEBUG
# echo an error message before exiting
trap 'echo "\"${last_command}\" command filed with exit code $?."' EXIT

if [[ -z "${GCP_GCS_BUCKET}" ]]; then
    echo "GCP_GCS_BUCKET env var not set"
    exit 1
fi

if [[ -z "${MYSQL_ROOT_PASSWORD}" ]]; then
    echo "MYSQL_ROOT_PASSWORD env var not set"
    exit 1
fi

if [[ -z "${GOOGLE_APPLICATION_CREDENTIALS}" ]]; then
    echo "GOOGLE_APPLICATION_CREDENTIALS env var not set"
    exit 1
fi

if [[ ! -f "$GOOGLE_APPLICATION_CREDENTIALS" ]]; then
    echo "File $GOOGLE_APPLICATION_CREDENTIALS doesn't exist!"
    exit 1
fi

gcloud auth activate-service-account \
    --key-file $GOOGLE_APPLICATION_CREDENTIALS
verificationDate=$(date +"%Y-%m-%d")

# extract last filename from listing:
#   1. list all files in bucket
#   2. sort by date (2nd column) ascending
#   3. get last 2 lines and remove the last one (it consists of summary)

OUT=$(gsutil ls -l gs://$GCP_GCS_BUCKET/$BACKUPS_PATH | sort -k 2 | tail -2 | head -1)
BFILE=$(echo $OUT | grep $verificationDate | cut -f3 -d ' ')

if [ "${BFILE}" == "" ]; then
    echo -e "Can't extract filename (date: $verificationDate) from:\n\n$OUT"
    exit 1
fi

echo "Fetching $BFILE"
gsutil cp $BFILE /home/svc/backup.sql.gz

echo "Extracting..."
gunzip /home/svc/backup.sql.gz

MYSQL_CONN="-h 127.0.0.1 --port=3306 --user=root \
       --password="$MYSQL_ROOT_PASSWORD""

echo "Importing databases"
mysql $MYSQL_CONN < /home/svc/backup.sql

echo "Databases imported. Starting verification"

# based on https://dba.stackexchange.com/a/60774
SQL="SET SESSION group_concat_max_len = 1048576;"
SQL="${SQL} SELECT CONCAT('CHECK TABLE ',dbtblist,';') FROM"
SQL="${SQL} (SELECT GROUP_CONCAT(table_schema,'.',table_name) dbtblist FROM"
SQL="${SQL} information_schema.tables WHERE table_schema NOT IN"
SQL="${SQL} ('information_schema','performance_schema','mysql')) A"

mysql $MYSQL_CONN -ANe"${SQL}" | mysql ${MYSQL_CONN}

echo "Shutting down the server"
mysql $MYSQL_CONN -e "SHUTDOWN"

echo "Verification finished. Looks good."