#!/usr/bin/env bash
# ct302-self-health.sh — CT 302 (claude-runner) disk self-check → Discord
#
# Monitors disk usage on CT 302 itself and alerts to Discord when any
# filesystem exceeds the threshold. Closes the blind spot where the
# monitoring system cannot monitor itself via external health checks.
#
# Designed to run silently when healthy (no Discord spam on green).
# Only posts when a filesystem is at or above THRESHOLD.
#
# Usage:
#   ct302-self-health.sh [--discord-webhook URL] [--threshold N] [--dry-run] [--always-post]
#
# Environment overrides:
#   DISCORD_WEBHOOK   Discord webhook URL (required unless --dry-run)
#   DISK_THRESHOLD    Disk usage % alert threshold (default: 80)
#
# Install on CT 302 (daily, 07:00 UTC):
#   0 7 * * * /root/scripts/ct302-self-health.sh >> /var/log/ct302-self-health.log 2>&1

set -uo pipefail

DISK_THRESHOLD="${DISK_THRESHOLD:-80}"
DISCORD_WEBHOOK="${DISCORD_WEBHOOK:-}"
DRY_RUN=0
ALWAYS_POST=0

while [[ $# -gt 0 ]]; do
  case "$1" in
    --discord-webhook)
      if [[ $# -lt 2 ]]; then
        echo "Error: --discord-webhook requires a value" >&2
        exit 1
      fi
      DISCORD_WEBHOOK="$2"
      shift 2
      ;;
    --threshold)
      if [[ $# -lt 2 ]]; then
        echo "Error: --threshold requires a value" >&2
        exit 1
      fi
      DISK_THRESHOLD="$2"
      shift 2
      ;;
    --dry-run)
      DRY_RUN=1
      shift
      ;;
    --always-post)
      ALWAYS_POST=1
      shift
      ;;
    *)
      echo "Unknown option: $1" >&2
      exit 1
      ;;
  esac
done

if [[ "$DRY_RUN" -eq 0 && -z "$DISCORD_WEBHOOK" ]]; then
  echo "Error: DISCORD_WEBHOOK not set. Use --discord-webhook URL or set env var." >&2
  exit 1
fi

log() { echo "[$(date '+%Y-%m-%d %H:%M:%S')] $*"; }

# ---------------------------------------------------------------------------
# Check disk usage on all real filesystems
# ---------------------------------------------------------------------------
# df output: Filesystem Use% Mounted-on (skipping tmpfs, devtmpfs, overlay)
TRIGGERED=()
ALL_FS=()

while IFS= read -r line; do
  fs=$(echo "$line" | awk '{print $1}')
  pct=$(echo "$line" | awk '{print $5}' | tr -d '%')
  mount=$(echo "$line" | awk '{print $6}')
  ALL_FS+=("${pct}% ${mount} (${fs})")
  if [[ "$pct" -ge "$DISK_THRESHOLD" ]]; then
    TRIGGERED+=("${pct}% used — ${mount} (${fs})")
  fi
done < <(df -h --output=source,size,used,avail,pcent,target |
  tail -n +2 |
  awk '$1 !~ /^(tmpfs|devtmpfs|overlay|udev)/' |
  awk '{print $1, $5, $6}')

HOSTNAME=$(hostname -s)
TRIGGERED_COUNT=${#TRIGGERED[@]}

log "Disk check complete: ${TRIGGERED_COUNT} filesystem(s) above ${DISK_THRESHOLD}%"

# Exit cleanly with no Discord post if everything is healthy
if [[ "$TRIGGERED_COUNT" -eq 0 && "$ALWAYS_POST" -eq 0 && "$DRY_RUN" -eq 0 ]]; then
  log "All filesystems healthy — no alert needed."
  exit 0
fi

# ---------------------------------------------------------------------------
# Build Discord payload
# ---------------------------------------------------------------------------
if [[ "$TRIGGERED_COUNT" -gt 0 ]]; then
  EMBED_COLOR=15548997 # 0xED4245 red
  TITLE="🔴 ${HOSTNAME}: Disk usage above ${DISK_THRESHOLD}%"
  alert_lines=$(printf '⚠️ %s\n' "${TRIGGERED[@]}")
  FIELDS=$(jq -n \
    --arg name "Filesystems Over Threshold" \
    --arg value "$alert_lines" \
    '[{"name": $name, "value": $value, "inline": false}]')
else
  EMBED_COLOR=5763719 # 0x57F287 green
  TITLE="🟢 ${HOSTNAME}: All filesystems healthy"
  FIELDS='[]'
fi

# Add summary of all filesystems
all_lines=$(printf '%s\n' "${ALL_FS[@]}")
FIELDS=$(echo "$FIELDS" | jq \
  --arg name "All Filesystems" \
  --arg value "$all_lines" \
  '. + [{"name": $name, "value": $value, "inline": false}]')

FOOTER="$(date -u '+%Y-%m-%d %H:%M UTC') · CT 302 self-health · threshold: ${DISK_THRESHOLD}%"

PAYLOAD=$(jq -n \
  --arg title "$TITLE" \
  --argjson color "$EMBED_COLOR" \
  --argjson fields "$FIELDS" \
  --arg footer "$FOOTER" \
  '{
    "embeds": [{
      "title": $title,
      "color": $color,
      "fields": $fields,
      "footer": {"text": $footer}
    }]
  }')

if [[ "$DRY_RUN" -eq 1 ]]; then
  log "DRY RUN — Discord payload:"
  echo "$PAYLOAD" | jq .
  exit 0
fi

log "Posting to Discord..."
HTTP_STATUS=$(curl -s -o /tmp/ct302-self-health-discord.out \
  -w "%{http_code}" \
  -X POST "$DISCORD_WEBHOOK" \
  -H "Content-Type: application/json" \
  -d "$PAYLOAD")

if [[ "$HTTP_STATUS" -ge 200 && "$HTTP_STATUS" -lt 300 ]]; then
  log "Discord notification sent (HTTP ${HTTP_STATUS})."
else
  log "Warning: Discord returned HTTP ${HTTP_STATUS}."
  cat /tmp/ct302-self-health-discord.out >&2
  exit 1
fi