# Generate Phase: Billing Skeleton Artifact Generation

> Loaded by generate.md when generation-billing.json and aws-design-billing.json exist.

**Execute ALL steps in order. Do not skip or optimize.**

## Overview

Generate **skeleton Terraform** with TODO markers for billing-only migrations. These configurations are NOT deployable as-is — they require manual configuration refinement based on actual infrastructure discovery.

Every resource block includes TODO markers indicating what is missing and where to get it.

## Prerequisites

Read from `$MIGRATION_DIR/`:

- `aws-design-billing.json` (REQUIRED) — Billing-based service mapping from Phase 3
- `generation-billing.json` (REQUIRED) — Conservative migration plan from Stage 1

If any required file is missing: **STOP**. Output: "Missing required artifact: [filename]. Complete the prior phase that produces it."

## Output Structure

| File           | When                                 | Contains                               |
| -------------- | ------------------------------------ | -------------------------------------- |
| `main.tf`      | Only if infra track didn't create it | Provider config, backend, data sources |
| `variables.tf` | Only if infra track didn't create it | Inferred variables with TODO markers   |
| `skeleton.tf`  | Always                               | Resource stubs with TODO markers       |

Do NOT overwrite existing `main.tf` or `variables.tf` if the infrastructure track already generated them.

## Step 0: Read Design Inputs

From `aws-design-billing.json`: `services[]` (mapped), `unknowns[]` (unmapped), `metadata.total_services`, `metadata.confidence_note`.

From `generation-billing.json`: migration timeline (for header comments), risk level (for confidence tags).

## Step 1: Generate main.tf (if not present)

**Requirements:**

- Header comment block: "SKELETON TERRAFORM — BILLING-ONLY MIGRATION", WARNING about TODO markers, confidence LOW, action required note
- `terraform` block: `required_version >= 1.5.0`, `hashicorp/aws ~> 5.0`, commented S3 backend
- `provider "aws"` block: `region = var.aws_region`, `default_tags` with Project, Environment, ManagedBy, `Confidence = "billing-only-skeleton"`
- Data sources: `aws_caller_identity`, `aws_region`, `aws_availability_zones`

## Step 2: Generate variables.tf (if not present)

**Global variables:** `aws_region` (from preferences.json), `project_name`, `environment`.

**Per-service variables:** For each mapped service in `aws-design-billing.json.services[]`, create variables with:

- **Known defaults** get a `# Verify` comment
- **Unknown values** get a `# TODO` comment with placeholder
- Use billing SKU hints to inform reasonable defaults where possible

Header comment: "Many values are placeholders. Search for TODO to find values needing manual configuration."

## Step 3: Generate skeleton.tf

For each mapped service in `aws-design-billing.json.services[]`, generate a resource stub.

**Every resource block must include:**

- Header comment: AWS service name, GCP source, confidence level, monthly GCP cost, SKU hints
- `# TODO: Verify all configuration values against actual GCP resource settings`
- At least one `# TODO` per configurable attribute
- Tags: Name, GCPSource, `Confidence = "billing-inferred"`

**Resource generation by GCP service type:**

| GCP Service          | AWS Resource Type                   | Key TODO Attributes                                  |
| -------------------- | ----------------------------------- | ---------------------------------------------------- |
| Cloud Run, GCE, GKE  | ECS cluster + task def              | CPU, memory, container image, port, auto-scaling     |
| Cloud SQL            | RDS instance                        | Engine, version, instance class, storage, networking |
| Spanner, Firestore   | DynamoDB / Aurora                   | Capacity, schema, access patterns                    |
| Cloud Storage        | S3 bucket + versioning + encryption | Bucket count, storage classes, lifecycle policies    |
| Cloud Load Balancing | VPC + ALB                           | CIDR, subnets, security groups, listeners            |
| Cloud DNS            | Route 53                            | Zone names, record types                             |
| Cloud NAT            | NAT Gateway                         | Subnet associations                                  |

For compute stubs: include ECS cluster + task definition with `FARGATE` compatibility, `awsvpc` network mode, `awslogs` log configuration.

For database stubs: include `storage_encrypted = true`, `skip_final_snapshot = true # TODO: Set to false for production`.

For storage stubs: include bucket with account ID suffix, versioning enabled, SSE-KMS encryption.

**Unmapped services:** At the bottom of `skeleton.tf`, add a comment block for each service in `unknowns[]` with: service name, monthly cost, reason unmapped, possible AWS target suggestion, TODO marker.

## Step 4: Self-Check

- [ ] Every mapped service has a resource stub in `skeleton.tf`
- [ ] Every resource has at least one `# TODO` comment
- [ ] No resource is presented as production-ready — all have confidence markers
- [ ] Skeleton warning header present at top of `main.tf` and `skeleton.tf`
- [ ] No hardcoded credentials
- [ ] Tags include `Confidence = "billing-inferred"` on every resource
- [ ] Unmapped services from `unknowns[]` listed at bottom
- [ ] Did not overwrite existing `main.tf` or `variables.tf` from infrastructure track

## Phase Completion

Report generated files to the parent orchestrator. **Do NOT update `.phase-status.json`** — the parent `generate.md` handles phase completion.

```
Generated billing skeleton artifacts:
- terraform/skeleton.tf (with TODO markers)
- terraform/main.tf (if not already present)
- terraform/variables.tf (if not already present)

WARNING: These are SKELETON configurations generated from billing data only.
They are NOT deployable without manual configuration.
TODO markers: [N] items requiring manual configuration
Unmapped services: [N] services need manual AWS target assignment

Recommendation: Provide Terraform files and re-run discovery for deployable configurations.
```