#!/usr/bin/env bash
set -euo pipefail

########################################
# Settings
########################################

# Directory where your docker-compose.yml lives
COMPOSE_DIR="/path/to/your/project"         # <-- CHANGE THIS

# Name of the replica service in docker-compose
REPLICA_SERVICE="mysql-replica"

# Monitoring DB user (created on PRIMARY, replicated to replica)
MONITOR_USER="monitor"
MONITOR_PASSWORD="monitor-password"        # <-- CHANGE THIS

########################################
# Colors
########################################

if [ -t 1 ]; then
  RED="$(printf '\e[31m')"
  GREEN="$(printf '\e[32m')"
  YELLOW="$(printf '\e[33m')"
  BOLD="$(printf '\e[1m')"
  RESET="$(printf '\e[0m')"
else
  RED=""; GREEN=""; YELLOW=""; BOLD=""; RESET=""
fi

########################################
# Helper
########################################

# Extract "Value" from lines like:
# "  Some_Field: Value"
get_field() {
  local key="$1"
  printf '%s\n' "$STATUS" \
    | sed -n "s/^[[:space:]]*${key}:[[:space:]]*//p" \
    | head -n1
}

########################################
# Main
########################################

cd "${COMPOSE_DIR}"

# Try SHOW REPLICA STATUS first (MySQL 8+), fall back to SHOW SLAVE STATUS (older)
STATUS=$(docker-compose -f "${COMPOSE_DIR}/docker-compose.yml" exec -T "${REPLICA_SERVICE}" \
  mysql -u"${MONITOR_USER}" -p"${MONITOR_PASSWORD}" -e "SHOW REPLICA STATUS\G" 2>/dev/null || true)

if [[ -z "${STATUS}" ]]; then
  STATUS=$(docker-compose -f "${COMPOSE_DIR}/docker-compose.yml" exec -T "${REPLICA_SERVICE}" \
    mysql -u"${MONITOR_USER}" -p"${MONITOR_PASSWORD}" -e "SHOW SLAVE STATUS\G" 2>/dev/null || true)
fi

if [[ -z "${STATUS}" ]]; then
  echo "${RED}${BOLD}ERROR:${RESET} No replication status found."
  echo "  - Is ${REPLICA_SERVICE} configured as a replica?"
  echo "  - Is MySQL running in that container?"
  exit 1
fi

# IO / SQL thread status (new names first, fall back to old)
IO_Running=$(get_field "Replica_IO_Running")
if [[ -z "${IO_Running}" ]]; then
  IO_Running=$(get_field "Slave_IO_Running")
fi

SQL_Running=$(get_field "Replica_SQL_Running")
if [[ -z "${SQL_Running}" ]]; then
  SQL_Running=$(get_field "Slave_SQL_Running")
fi

# Seconds behind (new name first, fall back)
Seconds_Behind=$(get_field "Seconds_Behind_Source")
if [[ -z "${Seconds_Behind}" ]]; then
  Seconds_Behind=$(get_field "Seconds_Behind_Master")
fi

# GTID sets – allow indent before the key
Executed_Gtid_Set=$(
  printf '%s\n' "${STATUS}" \
    | sed -n 's/^[[:space:]]*Executed_Gtid_Set:[[:space:]]*//p' \
    | head -n1
)
Retrieved_Gtid_Set=$(
  printf '%s\n' "${STATUS}" \
    | sed -n 's/^[[:space:]]*Retrieved_Gtid_Set:[[:space:]]*//p' \
    | head -n1
)

# Errors (names are the same on old/new)
Last_IO_Error=$(get_field "Last_IO_Error")
Last_SQL_Error=$(get_field "Last_SQL_Error")

########################################
# Determine overall status
########################################

overall_color="${GREEN}"
overall_text="OK"

if [[ "${IO_Running}" != "Yes" || "${SQL_Running}" != "Yes" ]]; then
  overall_color="${RED}"
  overall_text="ERROR"
elif [[ -z "${Seconds_Behind}" || "${Seconds_Behind}" == "NULL" ]]; then
  overall_color="${YELLOW}"
  overall_text="UNKNOWN_DELAY"
elif [[ "${Seconds_Behind}" =~ ^[0-9]+$ && "${Seconds_Behind}" -gt 300 ]]; then
  # More than 5 minutes behind -> warn
  overall_color="${YELLOW}"
  overall_text="LAGGING"
fi

########################################
# Output
########################################

echo
echo "${BOLD}Replica status for service '${REPLICA_SERVICE}':${RESET}"
echo "  Overall: ${overall_color}${overall_text}${RESET}"
echo

echo "  IO thread:   ${IO_Running:-<unknown>}"
echo "  SQL thread:  ${SQL_Running:-<unknown>}"

if [[ -z "${Seconds_Behind}" || "${Seconds_Behind}" == "NULL" ]]; then
  echo "  Delay:       (unknown / NULL)"
else
  echo "  Delay:       ${Seconds_Behind} seconds behind primary"
fi

echo
echo "  Retrieved GTID set:"
echo "    ${Retrieved_Gtid_Set:-<none>}"
echo "  Executed GTID set:"
echo "    ${Executed_Gtid_Set:-<none>}"
echo

if [[ -n "${Last_IO_Error}" && "${Last_IO_Error}" != " " ]]; then
  echo "${RED}  Last IO error:${RESET}"
  echo "    ${Last_IO_Error}"
  echo
fi

if [[ -n "${Last_SQL_Error}" && "${Last_SQL_Error}" != " " ]]; then
  echo "${RED}  Last SQL error:${RESET}"
  echo "    ${Last_SQL_Error}"
  echo
fi