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

POSTGRES_EXPORTER_VERSION="0.20.1"
POSTGRES_EXPORTER_SHA256_ARM64="d5d86fb98bb1f26b088d1a6fda07fd6b6f035cb5d40492f75ec3bfebb5ddfe9d"
REDIS_EXPORTER_VERSION="1.89.0"
REDIS_EXPORTER_SHA256_ARM64="1a70d42cd1d96a9388f8b528f55ad5bdc2c3cbd911c1dff3875fcb9ac01fa28a"
NGINX_EXPORTER_VERSION="1.5.3"
NGINX_EXPORTER_SHA256_ARM64="a0b1a5f5bba09483bd2e04c759c1a75fffe46ca72c0314ee2bb925d1742ff23b"
MONITORING_RELEASE_CACHE_DIR="${MONITORING_RELEASE_CACHE_DIR:-}"

if [[ "$(id -u)" -ne 0 ]]; then echo "Run as root." >&2; exit 1; fi
for command_name in systemctl nginx curl install ss; do command -v "$command_name" >/dev/null || { echo "Missing command: $command_name" >&2; exit 1; }; done

log() { printf '\n[%s] %s\n' "$(date '+%F %T')" "$*"; }

install_release_binary() {
  local url="$1" expected_sha256="$2" archive_member="$3" destination="$4"
  local work_dir archive asset_name
  work_dir="$(mktemp -d /tmp/cmpp-monitoring.XXXXXX)"
  archive="$work_dir/release.tar.gz"
  asset_name="${url##*/}"
  if [[ -n "$MONITORING_RELEASE_CACHE_DIR" && -f "$MONITORING_RELEASE_CACHE_DIR/$asset_name" ]]; then
    cp "$MONITORING_RELEASE_CACHE_DIR/$asset_name" "$archive"
  else
    curl -fL --retry 5 --retry-delay 2 --connect-timeout 15 -o "$archive" "$url"
  fi
  printf '%s  %s\n' "$expected_sha256" "$archive" | sha256sum -c -
  tar -xzf "$archive" -C "$work_dir"
  install -o root -g root -m 0755 "$work_dir/$archive_member" "$destination"
  rm -rf -- "$work_dir"
}

write_base_unit() {
  local unit="$1" description="$2" executable="$3"
  cat >"/etc/systemd/system/${unit}.service" <<EOF
[Unit]
Description=${description}
Wants=network-online.target
After=network-online.target

[Service]
Type=simple
User=prometheus
Group=prometheus
Restart=on-failure
RestartSec=5s
ExecStart=${executable}

[Install]
WantedBy=multi-user.target
EOF
}

install_official_arm64_releases() {
  [[ "$(uname -m)" == "aarch64" ]] || {
    echo "Official-binary installation currently supports Linux aarch64 only." >&2
    exit 1
  }
  for command_name in sha256sum tar; do
    command -v "$command_name" >/dev/null || { echo "Missing command: $command_name" >&2; exit 1; }
  done
  getent group prometheus >/dev/null || groupadd --system prometheus
  id prometheus >/dev/null 2>&1 || useradd --system --gid prometheus --home-dir /var/lib/prometheus --shell /sbin/nologin prometheus

  log "Installing checksum-pinned official service exporter ARM64 releases"
  install_release_binary \
    "https://github.com/prometheus-community/postgres_exporter/releases/download/v${POSTGRES_EXPORTER_VERSION}/postgres_exporter-${POSTGRES_EXPORTER_VERSION}.linux-arm64.tar.gz" \
    "$POSTGRES_EXPORTER_SHA256_ARM64" \
    "postgres_exporter-${POSTGRES_EXPORTER_VERSION}.linux-arm64/postgres_exporter" \
    /usr/local/bin/prometheus-postgres-exporter
  install_release_binary \
    "https://github.com/oliver006/redis_exporter/releases/download/v${REDIS_EXPORTER_VERSION}/redis_exporter-v${REDIS_EXPORTER_VERSION}.linux-arm64.tar.gz" \
    "$REDIS_EXPORTER_SHA256_ARM64" \
    "redis_exporter-v${REDIS_EXPORTER_VERSION}.linux-arm64/redis_exporter" \
    /usr/local/bin/prometheus-redis-exporter
  install_release_binary \
    "https://github.com/nginx/nginx-prometheus-exporter/releases/download/v${NGINX_EXPORTER_VERSION}/nginx-prometheus-exporter_${NGINX_EXPORTER_VERSION}_linux_arm64.tar.gz" \
    "$NGINX_EXPORTER_SHA256_ARM64" \
    nginx-prometheus-exporter \
    /usr/local/bin/prometheus-nginx-exporter

  write_base_unit prometheus-postgres-exporter "Prometheus PostgreSQL Exporter" /usr/local/bin/prometheus-postgres-exporter
  write_base_unit prometheus-redis-exporter "Prometheus Redis Exporter" /usr/local/bin/prometheus-redis-exporter
  write_base_unit prometheus-nginx-exporter "Prometheus Nginx Exporter" /usr/local/bin/prometheus-nginx-exporter
}

backup_dir="/etc/prometheus/cmpp-backups/$(date '+%Y%m%d-%H%M%S')-service-exporters"
mkdir -p "$backup_dir"

for config_file in /etc/cmpp-platform/minio.env /etc/nginx/conf.d/cmpp-monitoring-status.conf /etc/cmpp-platform/monitoring-exporters.env; do
  [[ -f "$config_file" ]] && cp --preserve=mode,timestamps "$config_file" "$backup_dir/$(basename "$config_file")"
done

if command -v apt-get >/dev/null 2>&1; then
  log "Installing bounded service exporter packages"
  apt-get update
  DEBIAN_FRONTEND=noninteractive apt-get install -y prometheus-postgres-exporter prometheus-redis-exporter prometheus-nginx-exporter
else
  install_official_arm64_releases
fi

[[ -f /etc/cmpp-platform/cmpp-platform.env ]] || { echo "Missing platform environment file." >&2; exit 1; }
set -a
# shellcheck disable=SC1091
. /etc/cmpp-platform/cmpp-platform.env
set +a
database_base="${DATABASE_URL%%\?*}"
cat >/etc/cmpp-platform/monitoring-exporters.env <<EOF
DATA_SOURCE_NAME=${database_base}?sslmode=disable
REDIS_ADDR=redis://${REDIS_HOST:-127.0.0.1}:${REDIS_PORT:-6379}
EOF
chown root:prometheus /etc/cmpp-platform/monitoring-exporters.env
chmod 0640 /etc/cmpp-platform/monitoring-exporters.env

write_override() {
  local unit="$1" executable="$2" arguments="$3" environment_file="${4:-}"
  local directory="/etc/systemd/system/${unit}.service.d"
  mkdir -p "$directory"
  [[ -f "$directory/cmpp-monitoring.conf" ]] && cp --preserve=mode,timestamps "$directory/cmpp-monitoring.conf" "$backup_dir/${unit}-override.conf"
  cat >"$directory/cmpp-monitoring.conf" <<EOF
[Service]
ExecStart=
ExecStart=${executable} ${arguments}
EOF
  if [[ -n "$environment_file" ]]; then
    sed -i "/^\[Service\]$/a EnvironmentFile=${environment_file}" "$directory/cmpp-monitoring.conf"
  fi
}

postgres_exporter="$(command -v prometheus-postgres-exporter)"
redis_exporter="$(command -v prometheus-redis-exporter)"
nginx_exporter="$(command -v prometheus-nginx-exporter)"
write_override prometheus-postgres-exporter "$postgres_exporter" '--web.listen-address=127.0.0.1:9187' /etc/cmpp-platform/monitoring-exporters.env
write_override prometheus-redis-exporter "$redis_exporter" '--web.listen-address=127.0.0.1:9121' /etc/cmpp-platform/monitoring-exporters.env

cat >/etc/nginx/conf.d/cmpp-monitoring-status.conf <<'EOF'
server {
  listen 127.0.0.1:8088;
  server_name localhost;
  access_log off;
  location = /stub_status {
    stub_status;
    allow 127.0.0.1;
    allow ::1;
    deny all;
  }
}
EOF
write_override prometheus-nginx-exporter "$nginx_exporter" '--web.listen-address=127.0.0.1:9113 --nginx.scrape-uri=http://127.0.0.1:8088/stub_status'

# MinIO exposes only operational aggregates and listens on loopback; public auth here does not expose objects or credentials.
grep -q '^MINIO_PROMETHEUS_AUTH_TYPE=' /etc/cmpp-platform/minio.env \
  && sed -i 's/^MINIO_PROMETHEUS_AUTH_TYPE=.*/MINIO_PROMETHEUS_AUTH_TYPE=public/' /etc/cmpp-platform/minio.env \
  || printf '\nMINIO_PROMETHEUS_AUTH_TYPE=public\n' >>/etc/cmpp-platform/minio.env

nginx -t
systemctl daemon-reload
systemctl enable prometheus-postgres-exporter prometheus-redis-exporter prometheus-nginx-exporter
systemctl restart prometheus-postgres-exporter prometheus-redis-exporter prometheus-nginx-exporter
systemctl restart cmpp-minio
systemctl reload nginx

wait_for_http() {
  local endpoint="$1" attempt
  for attempt in $(seq 1 30); do
    curl -fsS "$endpoint" >/dev/null 2>&1 && return 0
    sleep 1
  done
  echo "Monitoring endpoint did not become ready: $endpoint" >&2
  return 1
}
for endpoint in 127.0.0.1:9187 127.0.0.1:9121 127.0.0.1:9113; do wait_for_http "http://${endpoint}/metrics"; done
wait_for_http http://127.0.0.1:9000/minio/v2/metrics/cluster
if ss -lnt | grep -Eq '(^|[[:space:]])(0\.0\.0\.0|\[::\]):(9187|9121|9113)([[:space:]]|$)'; then
  echo "A service exporter unexpectedly listens on a wildcard address." >&2
  exit 1
fi
log "Service exporters are ready on loopback only; backup: $backup_dir"