# Terraform Template for Azure

## Overview

Template for deploying Azure resources using Terraform.

---

## Project Structure

```
terraform/
├── main.tf
├── variables.tf
├── outputs.tf
├── providers.tf
├── terraform.tfvars
└── modules/
    ├── network/
    │   ├── main.tf
    │   ├── variables.tf
    │   └── outputs.tf
    ├── compute/
    │   ├── main.tf
    │   ├── variables.tf
    │   └── outputs.tf
    └── database/
        ├── main.tf
        ├── variables.tf
        └── outputs.tf
```

---

## Base Configuration

### providers.tf

```hcl
terraform {
  required_version = ">= 1.5.0"

  required_providers {
    azurerm = {
      source  = "hashicorp/azurerm"
      version = "~> 3.0"
    }
  }

  backend "azurerm" {
    resource_group_name  = "rg-terraform-state"
    storage_account_name = "stterraformstate"
    container_name       = "tfstate"
    key                  = "prod.terraform.tfstate"
  }
}

provider "azurerm" {
  features {}
}
```

### variables.tf

```hcl
variable "environment" {
  type        = string
  description = "Environment name (dev, staging, prod)"
  default     = "dev"
}

variable "location" {
  type        = string
  description = "Azure region"
  default     = "eastus"
}

variable "project_name" {
  type        = string
  description = "Project name used in resource naming"
}

variable "tags" {
  type        = map(string)
  description = "Tags to apply to all resources"
  default     = {}
}

locals {
  common_tags = merge(var.tags, {
    environment = var.environment
    project     = var.project_name
    managed_by  = "terraform"
  })
}
```

---

## Network Module

### modules/network/main.tf

```hcl
resource "azurerm_resource_group" "main" {
  name     = "rg-${var.project_name}-${var.environment}"
  location = var.location
  tags     = var.tags
}

resource "azurerm_virtual_network" "main" {
  name                = "vnet-${var.project_name}-${var.environment}"
  resource_group_name = azurerm_resource_group.main.name
  location            = azurerm_resource_group.main.location
  address_space       = ["10.0.0.0/16"]
  tags                = var.tags
}

resource "azurerm_subnet" "web" {
  name                 = "snet-web"
  resource_group_name  = azurerm_resource_group.main.name
  virtual_network_name = azurerm_virtual_network.main.name
  address_prefixes     = ["10.0.1.0/24"]

  delegation {
    name = "webapp-delegation"
    service_delegation {
      name = "Microsoft.Web/serverFarms"
    }
  }
}

resource "azurerm_subnet" "db" {
  name                                          = "snet-db"
  resource_group_name                           = azurerm_resource_group.main.name
  virtual_network_name                          = azurerm_virtual_network.main.name
  address_prefixes                              = ["10.0.2.0/24"]
  private_endpoint_network_policies_enabled     = false
}

resource "azurerm_network_security_group" "web" {
  name                = "nsg-web-${var.environment}"
  resource_group_name = azurerm_resource_group.main.name
  location            = azurerm_resource_group.main.location
  tags                = var.tags

  security_rule {
    name                       = "Allow-HTTPS"
    priority                   = 100
    direction                  = "Inbound"
    access                     = "Allow"
    protocol                   = "Tcp"
    source_port_range          = "*"
    destination_port_range     = "443"
    source_address_prefix      = "*"
    destination_address_prefix = "*"
  }
}

resource "azurerm_subnet_network_security_group_association" "web" {
  subnet_id                 = azurerm_subnet.web.id
  network_security_group_id = azurerm_network_security_group.web.id
}
```

---

## Compute Module

### modules/compute/main.tf

```hcl
resource "azurerm_service_plan" "main" {
  name                = "plan-${var.project_name}-${var.environment}"
  resource_group_name = var.resource_group_name
  location            = var.location
  os_type             = "Linux"
  sku_name            = var.environment == "prod" ? "P1v3" : "B1"
  tags                = var.tags
}

resource "azurerm_linux_web_app" "main" {
  name                = "app-${var.project_name}-${var.environment}"
  resource_group_name = var.resource_group_name
  location            = var.location
  service_plan_id     = azurerm_service_plan.main.id
  tags                = var.tags

  site_config {
    application_stack {
      node_version = "18-lts"
    }

    always_on = var.environment == "prod" ? true : false
  }

  app_settings = {
    "WEBSITE_NODE_DEFAULT_VERSION" = "~18"
    "DATABASE_URL"                 = "@Microsoft.KeyVault(SecretUri=${var.database_url_secret_id})"
  }

  identity {
    type = "SystemAssigned"
  }
}

resource "azurerm_app_service_virtual_network_swift_connection" "main" {
  app_service_id = azurerm_linux_web_app.main.id
  subnet_id      = var.subnet_id
}
```

---

## Database Module

### modules/database/main.tf

```hcl
resource "azurerm_postgresql_flexible_server" "main" {
  name                   = "psql-${var.project_name}-${var.environment}"
  resource_group_name    = var.resource_group_name
  location               = var.location
  version                = "14"
  delegated_subnet_id    = var.subnet_id
  private_dns_zone_id    = azurerm_private_dns_zone.postgres.id
  administrator_login    = "adminuser"
  administrator_password = var.db_password
  zone                   = "1"
  storage_mb             = 32768
  sku_name               = var.environment == "prod" ? "GP_Standard_D2s_v3" : "B_Standard_B1ms"
  tags                   = var.tags
}

resource "azurerm_postgresql_flexible_server_database" "main" {
  name      = "appdb"
  server_id = azurerm_postgresql_flexible_server.main.id
  charset   = "UTF8"
  collation = "en_US.utf8"
}

resource "azurerm_private_dns_zone" "postgres" {
  name                = "privatelink.postgres.database.azure.com"
  resource_group_name = var.resource_group_name
  tags                = var.tags
}

resource "azurerm_private_dns_zone_virtual_network_link" "postgres" {
  name                  = "postgres-dns-link"
  private_dns_zone_name = azurerm_private_dns_zone.postgres.name
  virtual_network_id    = var.vnet_id
  resource_group_name   = var.resource_group_name
}
```

---

## Main Configuration

### main.tf

```hcl
module "network" {
  source = "./modules/network"

  project_name = var.project_name
  environment  = var.environment
  location     = var.location
  tags         = local.common_tags
}

module "compute" {
  source = "./modules/compute"

  project_name        = var.project_name
  environment         = var.environment
  location            = var.location
  resource_group_name = module.network.resource_group_name
  subnet_id           = module.network.web_subnet_id
  tags                = local.common_tags
}

module "database" {
  source = "./modules/database"

  project_name        = var.project_name
  environment         = var.environment
  location            = var.location
  resource_group_name = module.network.resource_group_name
  subnet_id           = module.network.db_subnet_id
  vnet_id             = module.network.vnet_id
  db_password         = var.db_password
  tags                = local.common_tags
}
```

---

## Outputs

### outputs.tf

```hcl
output "resource_group_name" {
  description = "Name of the resource group"
  value       = module.network.resource_group_name
}

output "web_app_url" {
  description = "URL of the web application"
  value       = "https://${module.compute.web_app_hostname}"
}

output "database_server" {
  description = "Database server FQDN"
  value       = module.database.server_fqdn
  sensitive   = true
}
```

---

## Terraform Commands

```bash
# Initialize
terraform init

# Plan
terraform plan -var-file="environments/prod.tfvars"

# Apply
terraform apply -var-file="environments/prod.tfvars"

# Destroy
terraform destroy -var-file="environments/prod.tfvars"
```