#!/usr/bin/env bash
# Blue/Green deploy for neuron-mcp
# Usage: ./blue-green-deploy.sh <new-image-tag>
# Example: ./blue-green-deploy.sh v0.8.4
#
# PVC is ReadWriteOnce — only ONE pod can hold it at a time.
# Process: scale IDLE slot to 1 (new image, it waits for PVC) →
#          scale ACTIVE slot to 0 (releases PVC) → idle pod claims PVC + starts →
#          verify health → switch service selector → done.
# Rollback: re-run with old tag, slots flip back.
set -euo pipefail

KUBECONFIG="${KUBECONFIG:-$HOME/.kube/legion-config}"
NS="neuron-prod"
SVC="neuron-mcp"
IMAGE_BASE="registry.neuralplatform.ai/neuron-technologies/neuron-mcp"
TAG="${1:-}"

if [[ -z "$TAG" ]]; then
  echo "Usage: $0 <image-tag>"
  exit 1
fi

KC="kubectl --kubeconfig=$KUBECONFIG -n $NS"

# Determine active and idle slots
ACTIVE_SLOT=$($KC get svc $SVC -o jsonpath='{.spec.selector.slot}')
if [[ "$ACTIVE_SLOT" == "blue" ]]; then
  IDLE_SLOT="green"
else
  IDLE_SLOT="blue"
fi

echo "→ Active slot: $ACTIVE_SLOT | Deploying to: $IDLE_SLOT | Image: $IMAGE_BASE:$TAG"

# 1. Update idle deployment with new image (still scaled to 0)
echo "→ Updating neuron-mcp-$IDLE_SLOT image..."
$KC set image deployment/neuron-mcp-$IDLE_SLOT neuron-mcp=$IMAGE_BASE:$TAG

# 2. Scale active down — releases the PVC
echo "→ Scaling neuron-mcp-$ACTIVE_SLOT to 0 (releases PVC)..."
$KC scale deployment/neuron-mcp-$ACTIVE_SLOT --replicas=0
$KC rollout status deployment/neuron-mcp-$ACTIVE_SLOT --timeout=60s || true

# 3. Scale idle up — claims PVC, starts with new image
echo "→ Scaling neuron-mcp-$IDLE_SLOT to 1..."
$KC scale deployment/neuron-mcp-$IDLE_SLOT --replicas=1

# 4. Wait for readiness (up to 3 min for JVM startup)
echo "→ Waiting for neuron-mcp-$IDLE_SLOT to be ready..."
$KC rollout status deployment/neuron-mcp-$IDLE_SLOT --timeout=180s

# 5. Health check
POD=$($KC get pod -l app=neuron-mcp,slot=$IDLE_SLOT -o jsonpath='{.items[0].metadata.name}')
HEALTH=$($KC exec "$POD" -- wget -qO- http://localhost:8080/actuator/health/readiness 2>/dev/null || echo '{"status":"DOWN"}')
STATUS=$(echo "$HEALTH" | python3 -c "import sys,json; print(json.load(sys.stdin).get('status','UNKNOWN'))" 2>/dev/null || echo "UNKNOWN")

if [[ "$STATUS" != "UP" ]]; then
  echo "✗ Health check failed (status=$STATUS). Rolling back — scaling $IDLE_SLOT back to 0, $ACTIVE_SLOT back to 1."
  $KC scale deployment/neuron-mcp-$IDLE_SLOT --replicas=0
  $KC scale deployment/neuron-mcp-$ACTIVE_SLOT --replicas=1
  $KC rollout status deployment/neuron-mcp-$ACTIVE_SLOT --timeout=180s
  echo "✓ Rollback complete. Still on $ACTIVE_SLOT ($IMAGE_BASE:$(kubectl --kubeconfig=$KUBECONFIG -n $NS get deployment neuron-mcp-$ACTIVE_SLOT -o jsonpath='{.spec.template.spec.containers[0].image}' | cut -d: -f2))."
  exit 1
fi

echo "✓ Health OK — switching service selector to $IDLE_SLOT..."

# 6. Switch service selector
$KC patch svc $SVC \
  -p "{\"spec\":{\"selector\":{\"app\":\"neuron-mcp\",\"slot\":\"$IDLE_SLOT\"}},\"metadata\":{\"annotations\":{\"neuron.ai/active-slot\":\"$IDLE_SLOT\"}}}"

echo "✓ Traffic now on neuron-mcp-$IDLE_SLOT ($IMAGE_BASE:$TAG)"
echo "  Previous slot neuron-mcp-$ACTIVE_SLOT is scaled to 0 (kept for instant rollback)."
echo ""
echo "  To rollback: $0 <previous-tag>   (will swap slots back)"