#!/bin/bash
# Script to manage MariaDB events during replication role changes.
#
# Author: Xavi Lleó & GhatGPT ®
# Copyright (c) 2025 Verdnatura S.L. All rights reserved.
# Version: 1.4.0
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
#
# Description:
# This script toggles MariaDB events during replication role changes.
# It supports three modes:
#   --promote : Re-enable events previously marked SLAVESIDE_DISABLED
#   --demote  : Disable currently ENABLED events using DISABLE ON SLAVE
#   --status  : Display current status of all events
# All actions are logged to /var/log/mariadb_admin.log.

set -euo pipefail

LOG_FILE="/var/log/mariadb_admin.log"
TIMESTAMP="$(date '+%F %T')"

log() {
    echo "$TIMESTAMP - $1" | tee -a "$LOG_FILE"
}

disable_scheduler() {
    log "Disabling event_scheduler..."
    if mysql -e "SET GLOBAL event_scheduler = OFF"; then
        log "Successfully disabled event_scheduler"
    else
        log "ERROR: Failed to disable event_scheduler"
        exit 1
    fi
}

enable_scheduler() {
    log "Re-enabling event_scheduler..."
    if mysql -e "SET GLOBAL event_scheduler = ON"; then
        log "Successfully re-enabled event_scheduler"
    else
        log "ERROR: Failed to re-enable event_scheduler"
        exit 1
    fi
}

final_status() {
    log "Final event_scheduler status:"
    mysql --table -e "SHOW VARIABLES LIKE 'event_scheduler';" | tee -a "$LOG_FILE"

    log "Final state of all events:"
    mysql --table -e "SELECT db, name, status FROM mysql.event;" | tee -a "$LOG_FILE"
}

if [[ $# -ne 1 ]]; then
    echo "Usage: $0 --promote | --demote | --status"
    exit 1
fi

MODE="$1"

case "$MODE" in
    --status)
        log "Fetching current event_scheduler status:"
        mysql --table -e "SHOW VARIABLES LIKE 'event_scheduler';" | tee -a "$LOG_FILE"

        log "Fetching current event status:"
        mysql --table -e "SELECT db, name, status FROM mysql.event;" | tee -a "$LOG_FILE"
        ;;
    
    --promote)
        disable_scheduler

        log "Promoting: Enabling events with SLAVESIDE_DISABLED status..."
        mysql --raw --silent -e "SELECT db, name FROM mysql.event WHERE status = 'SLAVESIDE_DISABLED'" | \
        awk '{ gsub("`", "``", $1); gsub("`", "``", $2); print "`"$1"`.`"$2"`" }' | \
        while read -r event; do
            if mysql -e "ALTER EVENT $event ENABLE"; then
                log "Enabled event: $event"
            else
                log "ERROR: Failed to enable event: $event"
            fi
        done

        enable_scheduler
        final_status
        ;;

    --demote)
        disable_scheduler

        log "Demoting: Disabling events currently ENABLED..."
        mysql --raw --silent -e "SELECT db, name FROM mysql.event WHERE status = 'ENABLED'" | \
        awk '{ gsub("`", "``", $1); gsub("`", "``", $2); print "`"$1"`.`"$2"`" }' | \
        while read -r event; do
            if mysql -e "ALTER EVENT $event DISABLE ON SLAVE"; then
                log "Disabled event: $event"
            else
                log "ERROR: Failed to disable event: $event"
            fi
        done

        enable_scheduler
        final_status
        ;;

    *)
        echo "Invalid mode: $MODE"
        echo "Usage: $0 --promote | --demote | --status"
        exit 1
        ;;
esac