#!/usr/bin/env bash
#
# cfn-stack-decommission.sh — safely retire a CloudFormation/CDK stack.
#
# Reports first (default), acts only with --execute. The value is the pre-flight:
# it predicts what will ORPHAN (DeletionPolicy: Retain resources survive a stack
# delete) and what will BLOCK the delete (consumed exports, non-empty buckets),
# so you don't discover surviving tables/buckets after the fact.
#
# Built from the Day 4 LedgerFlow decommission, where 4 of 5 DynamoDB tables +
# 2 of 3 S3 buckets were RemovalPolicy.RETAIN and orphaned. See feedback memory
# `feedback_cfn_decommission_and_remediation`.
#
# Usage:
#   scripts/cfn-stack-decommission.sh [--profile NAME] [--execute] STACK
#
#   (no --execute)  REPORT only: termination protection, consumed exports,
#                   Retain resources (orphans-to-be), in-stack S3 buckets.
#   --execute       Disable termination protection, empty Delete-policy buckets,
#                   delete the stack, wait, then delete the Retain orphans.
#
set -euo pipefail
PROFILE_ARG=(); EXECUTE=0; STACK=""
while [[ $# -gt 0 ]]; do
  case "$1" in
    --profile) PROFILE_ARG=(--profile "$2"); shift 2 ;;
    --execute) EXECUTE=1; shift ;;
    -h|--help) sed -n '2,22p' "$0"; exit 0 ;;
    -*) echo "unknown flag: $1" >&2; exit 2 ;;
    *) STACK="$1"; shift ;;
  esac
done
[[ -z "$STACK" ]] && { echo "usage: $0 [--profile NAME] [--execute] STACK" >&2; exit 2; }
aws_() { aws "${PROFILE_ARG[@]}" "$@"; }
R="us-east-1"

echo "== stack: $STACK =="
aws_ cloudformation describe-stacks --stack-name "$STACK" --region "$R" \
  --query 'Stacks[0].{Status:StackStatus,TermProt:EnableTerminationProtection}' --output table

echo "-- consumed exports (any import BLOCKS the delete) --"
BLOCKED=0
for e in $(aws_ cloudformation list-exports --region "$R" \
            --query "Exports[?ExportingStackId && contains(ExportingStackId,':stack/$STACK/')].Name" --output text 2>/dev/null); do
  imp=$(aws_ cloudformation list-imports --export-name "$e" --region "$R" --query 'Imports' --output text 2>/dev/null || true)
  if [[ -n "$imp" && "$imp" != "None" ]]; then echo "  BLOCK: export $e imported by: $imp"; BLOCKED=1; fi
done
[[ $BLOCKED -eq 0 ]] && echo "  none"

echo "-- DeletionPolicy: Retain resources (these ORPHAN, survive the delete) --"
TMP="$(aws_ cloudformation get-template --stack-name "$STACK" --region "$R" --query TemplateBody --output json)"
echo "$TMP" | python3 -c '
import json,sys
res=json.load(sys.stdin).get("Resources",{})
orphans=[(r.get("Type"),lid,r.get("Properties",{}).get("TableName") or r.get("Properties",{}).get("BucketName") or "")
         for lid,r in res.items() if r.get("DeletionPolicy")=="Retain"]
[print(f"  {t:<28} {lid}  {name}") for t,lid,name in sorted(orphans)] or print("  none")
'

echo "-- in-stack S3 buckets (non-empty Delete-policy buckets block; check auto-delete) --"
for b in $(aws_ cloudformation list-stack-resources --stack-name "$STACK" --region "$R" \
            --query "StackResourceSummaries[?ResourceType=='AWS::S3::Bucket'].PhysicalResourceId" --output text 2>/dev/null); do
  n=$(aws_ s3api list-objects-v2 --bucket "$b" --max-items 1 --query 'KeyCount' --output text 2>/dev/null || echo "?")
  v=$(aws_ s3api get-bucket-versioning --bucket "$b" --query 'Status' --output text 2>/dev/null || echo "-")
  echo "  $b  objects~=$n  versioning=$v"
done

if [[ $EXECUTE -eq 0 ]]; then
  echo; echo "REPORT ONLY. Re-run with --execute to delete (after reviewing the orphans + blocks above)."
  exit 0
fi
[[ $BLOCKED -eq 1 ]] && { echo "ABORT: a consumed export blocks the delete (see above)." >&2; exit 1; }

read -r -p "EXECUTE decommission of '$STACK'? [y/N] " ans; [[ "$ans" =~ ^[Yy]$ ]] || { echo "aborted"; exit 0; }
aws_ cloudformation update-termination-protection --stack-name "$STACK" --no-enable-termination-protection --region "$R" >/dev/null 2>&1 || true
echo "deleting stack..."
aws_ cloudformation delete-stack --stack-name "$STACK" --region "$R"
aws_ cloudformation wait stack-delete-complete --stack-name "$STACK" --region "$R"
echo "stack deleted. Review the Retain orphans above and remove them with delete-table / delete-bucket"
echo "(versioned buckets: purge all versions + delete-markers first — see the iam-user-delete sibling pattern)."