terraform-module-builder

What this skill does

# Terraform Module Builder

Generates production-ready, reusable Terraform modules with best practices for multi-cloud infrastructure as code.

## When to Use

- "Create Terraform module"
- "Generate infrastructure module"
- "Setup Terraform for AWS/Azure/GCP"
- "Create reusable IaC module"
- "Generate Terraform boilerplate"

## Instructions

### 1. Module Structure

```
terraform-aws-vpc/
├── 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
    └── vpc_test.go
```

### 2. AWS VPC Module Example

**main.tf:**
```hcl
# main.tf
locals {
  name = var.name != "" ? var.name : "${var.environment}-vpc"

  common_tags = merge(
    var.tags,
    {
      Environment = var.environment
      ManagedBy   = "Terraform"
      Module      = "terraform-aws-vpc"
    }
  )
}

resource "aws_vpc" "this" {
  cidr_block           = var.vpc_cidr
  enable_dns_hostnames = var.enable_dns_hostnames
  enable_dns_support   = var.enable_dns_support

  tags = merge(
    local.common_tags,
    {
      Name = local.name
    }
  )
}

resource "aws_subnet" "public" {
  count = length(var.public_subnet_cidrs)

  vpc_id                  = aws_vpc.this.id
  cidr_block              = var.public_subnet_cidrs[count.index]
  availability_zone       = var.availability_zones[count.index]
  map_public_ip_on_launch = true

  tags = merge(
    local.common_tags,
    {
      Name = "${local.name}-public-${var.availability_zones[count.index]}"
      Type = "public"
    }
  )
}

resource "aws_subnet" "private" {
  count = length(var.private_subnet_cidrs)

  vpc_id            = aws_vpc.this.id
  cidr_block        = var.private_subnet_cidrs[count.index]
  availability_zone = var.availability_zones[count.index]

  tags = merge(
    local.common_tags,
    {
      Name = "${local.name}-private-${var.availability_zones[count.index]}"
      Type = "private"
    }
  )
}

resource "aws_internet_gateway" "this" {
  count = length(var.public_subnet_cidrs) > 0 ? 1 : 0

  vpc_id = aws_vpc.this.id

  tags = merge(
    local.common_tags,
    {
      Name = "${local.name}-igw"
    }
  )
}

resource "aws_eip" "nat" {
  count = var.enable_nat_gateway ? length(var.availability_zones) : 0

  domain = "vpc"

  tags = merge(
    local.common_tags,
    {
      Name = "${local.name}-nat-${var.availability_zones[count.index]}"
    }
  )

  depends_on = [aws_internet_gateway.this]
}

resource "aws_nat_gateway" "this" {
  count = var.enable_nat_gateway ? length(var.availability_zones) : 0

  allocation_id = aws_eip.nat[count.index].id
  subnet_id     = aws_subnet.public[count.index].id

  tags = merge(
    local.common_tags,
    {
      Name = "${local.name}-nat-${var.availability_zones[count.index]}"
    }
  )

  depends_on = [aws_internet_gateway.this]
}

resource "aws_route_table" "public" {
  count = length(var.public_subnet_cidrs) > 0 ? 1 : 0

  vpc_id = aws_vpc.this.id

  tags = merge(
    local.common_tags,
    {
      Name = "${local.name}-public"
    }
  )
}

resource "aws_route" "public_internet_gateway" {
  count = length(var.public_subnet_cidrs) > 0 ? 1 : 0

  route_table_id         = aws_route_table.public[0].id
  destination_cidr_block = "0.0.0.0/0"
  gateway_id             = aws_internet_gateway.this[0].id

  timeouts {
    create = "5m"
  }
}

resource "aws_route_table_association" "public" {
  count = length(var.public_subnet_cidrs)

  subnet_id      = aws_subnet.public[count.index].id
  route_table_id = aws_route_table.public[0].id
}

resource "aws_route_table" "private" {
  count = length(var.private_subnet_cidrs)

  vpc_id = aws_vpc.this.id

  tags = merge(
    local.common_tags,
    {
      Name = "${local.name}-private-${var.availability_zones[count.index]}"
    }
  )
}

resource "aws_route" "private_nat_gateway" {
  count = var.enable_nat_gateway ? length(var.private_subnet_cidrs) : 0

  route_table_id         = aws_route_table.private[count.index].id
  destination_cidr_block = "0.0.0.0/0"
  nat_gateway_id         = aws_nat_gateway.this[count.index].id

  timeouts {
    create = "5m"
  }
}

resource "aws_route_table_association" "private" {
  count = length(var.private_subnet_cidrs)

  subnet_id      = aws_subnet.private[count.index].id
  route_table_id = aws_route_table.private[count.index].id
}

resource "aws_flow_log" "this" {
  count = var.enable_flow_logs ? 1 : 0

  iam_role_arn    = aws_iam_role.flow_logs[0].arn
  log_destination = aws_cloudwatch_log_group.flow_logs[0].arn
  traffic_type    = "ALL"
  vpc_id          = aws_vpc.this.id

  tags = merge(
    local.common_tags,
    {
      Name = "${local.name}-flow-logs"
    }
  )
}

resource "aws_cloudwatch_log_group" "flow_logs" {
  count = var.enable_flow_logs ? 1 : 0

  name              = "/aws/vpc/${local.name}"
  retention_in_days = var.flow_logs_retention_days

  tags = local.common_tags
}

resource "aws_iam_role" "flow_logs" {
  count = var.enable_flow_logs ? 1 : 0

  name = "${local.name}-flow-logs"

  assume_role_policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Action = "sts:AssumeRole"
        Effect = "Allow"
        Principal = {
          Service = "vpc-flow-logs.amazonaws.com"
        }
      }
    ]
  })

  tags = local.common_tags
}

resource "aws_iam_role_policy" "flow_logs" {
  count = var.enable_flow_logs ? 1 : 0

  name = "flow-logs"
  role = aws_iam_role.flow_logs[0].id

  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Action = [
          "logs:CreateLogGroup",
          "logs:CreateLogStream",
          "logs:PutLogEvents",
          "logs:DescribeLogGroups",
          "logs:DescribeLogStreams"
        ]
        Effect   = "Allow"
        Resource = "*"
      }
    ]
  })
}
```

**variables.tf:**
```hcl
# variables.tf
variable "name" {
  description = "Name to be used on all resources as prefix"
  type        = string
  default     = ""
}

variable "environment" {
  description = "Environment name"
  type        = string
  validation {
    condition     = contains(["dev", "staging", "production"], var.environment)
    error_message = "Environment must be dev, staging, or production."
  }
}

variable "vpc_cidr" {
  description = "CIDR block for VPC"
  type        = string
  default     = "10.0.0.0/16"

  validation {
    condition     = can(cidrhost(var.vpc_cidr, 0))
    error_message = "VPC CIDR must be a valid IPv4 CIDR block."
  }
}

variable "availability_zones" {
  description = "List of availability zones"
  type        = list(string)
}

variable "public_subnet_cidrs" {
  description = "CIDR blocks for public subnets"
  type        = list(string)
  default     = []
}

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 "enable_nat_gateway" {
  description = "Enable NAT Gateway for private subnets"
  type        = bool
  default     = true
}

variable "enable_flow_logs" {
  description = "Enable VPC Flow Logs"
  type        = bool
  default     = false
}

variable "flow_logs_retention_days" {
  description = "Flow logs retention in days"
  type        = number
  default     = 7
}

variable "tags" {
  description = "Additional tags for all resources"
  type        = map(string)
  default     = {}
}
```

**outputs.tf:**
```hcl
# outputs.tf
output "vpc_id" {
  description = "ID of the VPC"
  value       = aws_vpc.this.id
}

output "vpc_cidr" {
  description = "CIDR block of the VPC"
  value       = aws_vpc.this.cidr_block
}

output "public_subnet_id