thesoftwarehouse/copilot-collections/tsh-implementing-terraform-modules

terraform-modules/
├── aws/
│   ├── vpc/
│   ├── eks/
│   ├── rds/
│   └── s3/
├── azure/
│   ├── vnet/
│   ├── aks/
│   └── storage/
└── gcp/
    ├── vpc/
    ├── gke/
    └── cloud-sql/

module-name/
├── main.tf          # Main resources
├── variables.tf     # Input variables
├── outputs.tf       # Output values
├── versions.tf      # Provider versions
├── README.md        # Documentation
├── examples/        # Usage examples
│   └── complete/
│       ├── main.tf
│       └── variables.tf
└── tests/           # Terratest files
    └── module_test.go

resource "aws_vpc" "main" {
  cidr_block           = var.cidr_block
  enable_dns_hostnames = var.enable_dns_hostnames
  enable_dns_support   = var.enable_dns_support
 
  tags = merge(
    {
      Name = var.name
    },
    var.tags
  )
}
 
resource "aws_subnet" "private" {
  count             = length(var.private_subnet_cidrs)
  vpc_id            = aws_vpc.main.id
  cidr_block        = var.private_subnet_cidrs[count.index]
  availability_zone = var.availability_zones[count.index]
 
  tags = merge(
    {
      Name = "${var.name}-private-${count.index + 1}"
      Tier = "private"
    },
    var.tags
  )
}
 
resource "aws_internet_gateway" "main" {
  count  = var.create_internet_gateway ? 1 : 0
  vpc_id = aws_vpc.main.id
 
  tags = merge(
    {
      Name = "${var.name}-igw"
    },
    var.tags
  )
}

variable "name" {
  description = "Name of the VPC"
  type        = string
}
 
variable "cidr_block" {
  description = "CIDR block for VPC"
  type        = string
  validation {
    condition     = can(cidrnetmask(var.cidr_block))
    error_message = "CIDR block must be valid IPv4 CIDR notation."
  }
}
 
variable "availability_zones" {
  description = "List of availability zones"
  type        = list(string)
}
 
variable "private_subnet_cidrs" {
  description = "CIDR blocks for private subnets"
  type        = list(string)
  default     = []
}
 
variable "enable_dns_hostnames" {
  description = "Enable DNS hostnames in VPC"
  type        = bool
  default     = true
}
 
variable "enable_dns_support" {
  description = "Enable DNS support in VPC"
  type        = bool
  default     = true
}
 
variable "create_internet_gateway" {
  description = "Whether to create an Internet Gateway"
  type        = bool
  default     = true
}
 
variable "tags" {
  description = "Additional tags"
  type        = map(string)
  default     = {}
}

output "vpc_id" {
  description = "ID of the VPC"
  value       = aws_vpc.main.id
}
 
output "private_subnet_ids" {
  description = "IDs of private subnets"
  value       = aws_subnet.private[*].id
}
 
output "vpc_cidr_block" {
  description = "CIDR block of VPC"
  value       = aws_vpc.main.cidr_block
}

infrastructure/
├── terragrunt.hcl              # Root config (remote_state, generate provider)
├── _envcommon/                  # Shared module references
│   ├── vpc.hcl
│   ├── eks.hcl
│   └── rds.hcl
├── dev/
│   ├── env.hcl                 # Environment-level vars
│   ├── vpc/terragrunt.hcl
│   └── eks/terragrunt.hcl
├── staging/
│   └── ...
└── prod/
    └── ...