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

usage() {
  cat <<'USAGE'
Usage:
  reconcile_from_plan.sh [--output-file <path>] [--] [terraform plan args...]

Description:
  Runs `terraform plan` with `-generate-config-out` and writes the generated
  configuration into a tracked Terraform file (default:
  `zz_generated_from_plan.auto.tf`).

  This is designed for import-first workflows where `import { ... }` blocks are
  present and Terraform can generate missing resource arguments from live
  infrastructure.

Options:
  --output-file <path>  Destination .tf/.auto.tf file to receive generated
                        configuration. Default: zz_generated_from_plan.auto.tf
  -h, --help            Show this help text.

Examples:
  ./reconcile_from_plan.sh
  ./reconcile_from_plan.sh --output-file generated_imports.auto.tf -- -var-file=terraform.tfvars
USAGE
}

output_file="zz_generated_from_plan.auto.tf"
plan_args=()

while (($# > 0)); do
  case "$1" in
    --output-file)
      if (($# < 2)); then
        echo "error: --output-file requires a value" >&2
        exit 1
      fi
      output_file="$2"
      shift 2
      ;;
    -h|--help)
      usage
      exit 0
      ;;
    --)
      shift
      plan_args=("$@")
      break
      ;;
    *)
      plan_args+=("$1")
      shift
      ;;
  esac
done

if ! command -v terraform >/dev/null 2>&1; then
  echo "error: terraform is not installed or not in PATH" >&2
  exit 1
fi

if [[ ! -f "main.tf" ]] && ! compgen -G "*.tf" >/dev/null; then
  echo "error: no Terraform configuration (*.tf) found in $(pwd)" >&2
  echo "run this script from a Terraform module directory" >&2
  exit 1
fi

generated_tmp_dir="$(mktemp -d -t terraform-generated-XXXXXX)"
generated_tmp="$generated_tmp_dir/generated.tf"
# terraform plan -generate-config-out requires a path that does not already exist
trap 'rm -rf "$generated_tmp_dir"' EXIT

echo "Running: terraform plan -generate-config-out=$generated_tmp ${plan_args[*]-}"
set +e
terraform plan -generate-config-out="$generated_tmp" "${plan_args[@]}"
plan_exit=$?
set -e

if [[ $plan_exit -ne 0 && $plan_exit -ne 2 ]]; then
  echo "error: terraform plan failed with exit code $plan_exit" >&2
  exit "$plan_exit"
fi

if [[ ! -s "$generated_tmp" ]]; then
  echo "No generated configuration was produced."
  echo "Tip: ensure you have import blocks and resources eligible for config generation."
  exit 0
fi

cat > "$output_file" <<EOF2
# -----------------------------------------------------------------------------
# AUTO-GENERATED BY reconcile_from_plan.sh
# Generated: $(date -u +"%Y-%m-%dT%H:%M:%SZ")
# Source: terraform plan -generate-config-out
# Review carefully before apply.
# -----------------------------------------------------------------------------

EOF2
cat "$generated_tmp" >> "$output_file"

terraform fmt "$output_file" >/dev/null

echo "Generated configuration written to: $output_file"
echo "Next step: review this file and run terraform plan again to confirm intent."