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

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
PROMETHEUS_RETENTION_TIME="${PROMETHEUS_RETENTION_TIME:-30d}"
PROMETHEUS_RETENTION_SIZE="${PROMETHEUS_RETENTION_SIZE:-8GB}"
PROMETHEUS_VERSION="3.14.0"
PROMETHEUS_SHA256_ARM64="077f3781ab7245dc04c9a3c9b78ba120fc8e41aa0dc97489b0af67247e50ba83"
NODE_EXPORTER_VERSION="1.12.1"
NODE_EXPORTER_SHA256_ARM64="ad35b605f9954b9f1ffddf5ba054bdc5a98d790b9eae5291e1eeb83f1ecbd0e7"

if [[ "$(id -u)" -ne 0 ]]; then
  echo "Run as root." >&2
  exit 1
fi
log() { printf '\n[%s] %s\n' "$(date '+%F %T')" "$*"; }

install_release_binary() {
  local url="$1" expected_sha256="$2" archive_member="$3" destination="$4"
  local work_dir archive
  work_dir="$(mktemp -d /tmp/cmpp-monitoring.XXXXXX)"
  archive="$work_dir/release.tar.gz"
  curl -fL --retry 5 --retry-delay 2 --connect-timeout 15 -o "$archive" "$url"
  printf '%s  %s\n' "$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"
}

install_official_arm64_releases() {
  [[ "$(uname -m)" == "aarch64" ]] || {
    echo "Official-binary installation currently supports Linux aarch64 only." >&2
    exit 1
  }
  for command_name in curl sha256sum tar; do
    command -v "$command_name" >/dev/null || { echo "Missing command: $command_name" >&2; exit 1; }
  done

  log "Installing checksum-pinned official Prometheus ARM64 releases"
  install_release_binary \
    "https://github.com/prometheus/prometheus/releases/download/v${PROMETHEUS_VERSION}/prometheus-${PROMETHEUS_VERSION}.linux-arm64.tar.gz" \
    "$PROMETHEUS_SHA256_ARM64" \
    "prometheus-${PROMETHEUS_VERSION}.linux-arm64/prometheus" \
    /usr/local/bin/prometheus
  install_release_binary \
    "https://github.com/prometheus/prometheus/releases/download/v${PROMETHEUS_VERSION}/prometheus-${PROMETHEUS_VERSION}.linux-arm64.tar.gz" \
    "$PROMETHEUS_SHA256_ARM64" \
    "prometheus-${PROMETHEUS_VERSION}.linux-arm64/promtool" \
    /usr/local/bin/promtool
  install_release_binary \
    "https://github.com/prometheus/node_exporter/releases/download/v${NODE_EXPORTER_VERSION}/node_exporter-${NODE_EXPORTER_VERSION}.linux-arm64.tar.gz" \
    "$NODE_EXPORTER_SHA256_ARM64" \
    "node_exporter-${NODE_EXPORTER_VERSION}.linux-arm64/node_exporter" \
    /usr/local/bin/prometheus-node-exporter

  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
  install -d -o root -g root -m 0755 /etc/prometheus
  install -d -o prometheus -g prometheus -m 0750 /var/lib/prometheus/metrics2

  cat >/etc/systemd/system/prometheus.service <<'EOF'
[Unit]
Description=Prometheus monitoring server
Wants=network-online.target
After=network-online.target

[Service]
Type=simple
User=prometheus
Group=prometheus
Restart=on-failure
RestartSec=5s
ExecStart=/usr/local/bin/prometheus

[Install]
WantedBy=multi-user.target
EOF
  cat >/etc/systemd/system/prometheus-node-exporter.service <<'EOF'
[Unit]
Description=Prometheus Node Exporter
Wants=network-online.target
After=network-online.target

[Service]
Type=simple
User=prometheus
Group=prometheus
Restart=on-failure
RestartSec=5s
ExecStart=/usr/local/bin/prometheus-node-exporter

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

for command_name in systemctl install awk curl ss; do
  command -v "$command_name" >/dev/null || { echo "Missing command: $command_name" >&2; exit 1; }
done

if command -v apt-get >/dev/null 2>&1; then
  log "Installing Prometheus and Node Exporter packages"
  apt-get update
  DEBIAN_FRONTEND=noninteractive apt-get install -y prometheus prometheus-node-exporter curl iproute2
else
  install_official_arm64_releases
fi

prometheus_bin="$(command -v prometheus)"
node_exporter_bin="$(command -v prometheus-node-exporter)"
promtool_bin="$(command -v promtool)"
backup_dir="/etc/prometheus/cmpp-backups/$(date '+%Y%m%d-%H%M%S')"
mkdir -p "$backup_dir" /etc/systemd/system/prometheus.service.d /etc/systemd/system/prometheus-node-exporter.service.d /etc/systemd/system/cmpp-api.service.d

for config_file in /etc/prometheus/prometheus.yml /etc/prometheus/cmpp-alerts.yml /etc/prometheus/cmpp-alerts-source.yml; do
  if [[ -f "$config_file" ]]; then
    cp --preserve=mode,timestamps "$config_file" "$backup_dir/$(basename "$config_file")"
  fi
done
if [[ -f /etc/systemd/system/prometheus.service.d/cmpp-monitoring.conf ]]; then
  cp --preserve=mode,timestamps /etc/systemd/system/prometheus.service.d/cmpp-monitoring.conf "$backup_dir/prometheus-service-override.conf"
fi
if [[ -f /etc/systemd/system/prometheus-node-exporter.service.d/cmpp-monitoring.conf ]]; then
  cp --preserve=mode,timestamps /etc/systemd/system/prometheus-node-exporter.service.d/cmpp-monitoring.conf "$backup_dir/node-exporter-service-override.conf"
fi
if [[ -f /etc/systemd/system/cmpp-api.service.d/monitoring-storage.conf ]]; then
  cp --preserve=mode,timestamps /etc/systemd/system/cmpp-api.service.d/monitoring-storage.conf "$backup_dir/cmpp-api-monitoring-storage.conf"
fi

log "Installing platform-owned scrape and alert configuration"
install -o root -g root -m 0644 "$SCRIPT_DIR/prometheus.yml" /etc/prometheus/prometheus.yml
install -o root -g root -m 0644 "$SCRIPT_DIR/cmpp-alerts.yml" /etc/prometheus/cmpp-alerts-source.yml
# 可配置规则由 API 管理；基础规则必须排除同名项，否则 Prometheus 会同时计算旧阈值和新阈值。
awk '
BEGIN {
  split("HostCpuUsageWarning HostCpuUsageCritical HostMemoryUsageWarning HostMemoryUsageCritical HostRootDiskUsageWarning HostRootDiskUsageCritical CmppApiHttpErrorRateWarning CmppApiHttpErrorRateCritical CmppApiLatencyWarning CmppApiLatencyCritical CmppApiEventLoopLagWarning CmppApiEventLoopLagCritical CmppGatewayQueueDelayedWarning CmppGatewayQueueDelayedCritical PostgresConnectionsWarning PostgresConnectionsCritical RedisMemoryWarning RedisMemoryCritical MinioCapacityWarning MinioCapacityCritical", names, " ")
  for (i in names) dropped[names[i]] = 1
}
/^  - name:/ { skip = 0 }
/^      - alert:/ { skip = ($3 in dropped) }
!skip { print }
' "$SCRIPT_DIR/cmpp-alerts.yml" > /etc/prometheus/cmpp-alerts.yml
chown root:root /etc/prometheus/cmpp-alerts.yml
chmod 0644 /etc/prometheus/cmpp-alerts.yml
# SGID ensures API原子rename生成的新规则继续继承prometheus组，否则reload会因不可读返回500。
install -d -o cmpp-api -g prometheus -m 2750 /var/lib/cmpp-platform/monitoring
if [[ ! -f /var/lib/cmpp-platform/monitoring/cmpp-managed-alerts.yml ]]; then
  install -o cmpp-api -g prometheus -m 0640 "$SCRIPT_DIR/cmpp-managed-alerts.yml" /var/lib/cmpp-platform/monitoring/cmpp-managed-alerts.yml
fi
chown cmpp-api:prometheus /var/lib/cmpp-platform/monitoring/cmpp-managed-alerts.yml
chmod 0640 /var/lib/cmpp-platform/monitoring/cmpp-managed-alerts.yml

# The API writes managed rules atomically. Its hardened unit otherwise sees /var/lib as read-only.
cat >/etc/systemd/system/cmpp-api.service.d/monitoring-storage.conf <<'EOF'
[Service]
ReadWritePaths=/var/lib/cmpp-platform/monitoring
EOF

cat >/etc/systemd/system/prometheus.service.d/cmpp-monitoring.conf <<EOF
[Service]
ExecStart=
ExecStart=${prometheus_bin} --config.file=/etc/prometheus/prometheus.yml --storage.tsdb.path=/var/lib/prometheus/metrics2 --storage.tsdb.retention.time=${PROMETHEUS_RETENTION_TIME} --storage.tsdb.retention.size=${PROMETHEUS_RETENTION_SIZE} --web.listen-address=127.0.0.1:9090 --web.enable-lifecycle
EOF

cat >/etc/systemd/system/prometheus-node-exporter.service.d/cmpp-monitoring.conf <<EOF
[Service]
ExecStart=
ExecStart=${node_exporter_bin} --web.listen-address=127.0.0.1:9100 --collector.systemd --collector.systemd.unit-include='cmpp-api\\.service|cmpp-send-worker\\.service|cmpp-gateway\\.service|postgresql\\.service|redis(-server)?\\.service|cmpp-minio\\.service|nginx\\.service' --collector.filesystem.mount-points-exclude='^/(dev|proc|run/credentials/.+|sys|var/lib/docker/.+)($|/)'
EOF

log "Validating Prometheus configuration before restart"
"$promtool_bin" check rules /etc/prometheus/cmpp-alerts.yml
"$promtool_bin" check rules /var/lib/cmpp-platform/monitoring/cmpp-managed-alerts.yml
"$promtool_bin" check config /etc/prometheus/prometheus.yml

systemctl daemon-reload
systemctl enable prometheus prometheus-node-exporter
systemctl restart prometheus-node-exporter
systemctl restart prometheus

for _ in $(seq 1 30); do
  if curl -fsS http://127.0.0.1:9090/-/ready >/dev/null; then
    break
  fi
  sleep 1
done
curl -fsS http://127.0.0.1:9090/-/ready >/dev/null
curl -fsS http://127.0.0.1:9100/metrics >/dev/null

if ss -lnt | grep -Eq '(^|[[:space:]])(0\.0\.0\.0|\[::\]):(9090|9100)([[:space:]]|$)'; then
  echo "Prometheus monitoring ports unexpectedly listen on a wildcard address." >&2
  exit 1
fi

log "Prometheus monitoring is ready on loopback only"
echo "Configuration backup: $backup_dir"
echo "The CMPP API and Gateway were not restarted. Restart the API after setting PROMETHEUS_URL."