arm-to-terraform-migration

Files (5)

• plugin.json · .claude-plugin/
• SKILL.md
• apm.yml
• arm-terraform-mapping.md · references/
• migrate-arm.js · scripts/

SKILL.md (first lines)

# ARM to Terraform Migration

You are an ARM template to Terraform migration expert. When this skill is invoked, you help users convert Azure Resource Manager (ARM) templates into equivalent Terraform configurations while preserving resource relationships, dependencies, and outputs.

## Your Task

When a user requests ARM to Terraform migration:

1. **Parse ARM Template**:
   - Extract resources from `template.json`
   - Parse parameters from `parameters.json`
   - Identify dependencies using `dependsOn`
   - Understand ARM expressions and functions

2. **Map Resources to Terraform**:
   - Convert ARM resource types to Terraform resources
   - Map ARM properties to Terraform arguments
   - Preserve resource naming (or create new names)
   - Maintain resource relationships

3. **Convert Expressions**:
   - ARM: `[parameters('name')]` → Terraform: `var.name`
   - ARM: `[variables('name')]` → Terraform: `local.name`
   - ARM: `[concat(...)]` → Terraform: String interpolation
   - ARM: `[reference(...)]` → Terraform: Resource attributes

4. **Generate Terraform Files**:
   - `main.tf`: Resource definitions
   - `variables.tf`: Converted parameters
   - `outputs.tf`: Converted outputs
   - `terraform.tf`: Provider configuration

## ARM to Terraform Resource Mapping

### Common Resource Types

| ARM Resource Type | Terraform Resource |
|------------------|-------------------|
| `Microsoft.Resources/resourceGroups` | `azurerm_resource_group` |
| `Microsoft.Storage/storageAccounts` | `azurerm_storage_account` |
| `Microsoft.Network/virtualNetworks` | `azurerm_virtual_network` |
| `Microsoft.Network/networkInterfaces` | `azurerm_network_interface` |
| `Microsoft.Network/publicIPAddresses` | `azurerm_public_ip` |
| `Microsoft.Network/networkSecurityGroups` | `azurerm_network_security_group` |
| `Microsoft.Compute/virtualMachines` | `azurerm_linux_virtual_machine` or `azurerm_windows_virtual_machine` |
| `Microsoft.Web/sites` | `azurerm_app_service` or `azurerm_linux_web_app` |
| `Microsoft.Web/serverfarms` | `azurerm_service_plan` |
| `Microsoft.Sql/servers` | `azurerm_mssql_server` |
| `Microsoft.Sql/servers/databases` | `azurerm_mssql_database` |
| `Microsoft.KeyVault/vaults` | `azurerm_key_vault` |
| `Microsoft.ContainerService/managedClusters` | `azurerm_kubernetes_cluster` |

### Nested Resources

ARM nested resources become separate Terraform resources with references:

**ARM**:
```json
{
  "type": "Microsoft.Sql/servers",
  "resources": [{
    "type": "databases",
    "name": "mydb"
  }]
}
```

**Terraform**:
```hcl
resource "azurerm_mssql_server" "main" {
  # ...
}

resource "azurerm_mssql_database" "main" {
  server_id = azurerm_mssql_server.main.id
  # ...
}
```

## Expression Conversion

### Parameters → Variables

**ARM parameters.json**:
```json
{
  "parameters": {
    "location": {
      "value": "eastus"
    },
    "vmSize": {
      "value": "Standard_D2s_v3"
    }
  }
}
```

**Terraform variables.tf**:
```hcl
variable "location" {
  description = "Azure region"
  type        = string
  default     = "eastus"
}

variable "vm_size" {
  description = "VM size"
  type        = string
  default     = "Standard_D2s_v3"
}
```

### ARM Functions → Terraform Interpolation

| ARM Function | Terraform Equivalent |
|-------------|---------------------|
| `[concat('a', 'b')]` | `"${a}${b}"` or `"a${b}"` |
| `[format('{0}-{1}', 'a', 'b')]` | `"${a}-${b}"` |
| `[parameters('name')]` | `var.name` |

From GuicedEE/ai-rules, Apache-2.0.

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