terraform {
  required_version = ">= 1.0"

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

provider "azurerm" {
  features {}
}

# Resource Group
resource "azurerm_resource_group" "main" {
  name     = var.resource_group_name
  location = var.location

  tags = var.tags
}

# Virtual Network
resource "azurerm_virtual_network" "main" {
  name                = "${var.resource_group_name}-vnet"
  address_space       = [var.vnet_address_space]
  location            = azurerm_resource_group.main.location
  resource_group_name = azurerm_resource_group.main.name

  tags = var.tags
}

# Subnet
resource "azurerm_subnet" "main" {
  name                 = "default"
  resource_group_name  = azurerm_resource_group.main.name
  virtual_network_name = azurerm_virtual_network.main.name
  address_prefixes     = [var.subnet_address_prefix]
}

# Network Security Group
resource "azurerm_network_security_group" "main" {
  name                = "${var.vm_name}-nsg"
  location            = azurerm_resource_group.main.location
  resource_group_name = azurerm_resource_group.main.name

  security_rule {
    name                       = "SSH"
    priority                   = 1001
    direction                  = "Inbound"
    access                     = "Allow"
    protocol                   = "Tcp"
    source_port_range          = "*"
    destination_port_range     = "22"
    source_address_prefix      = var.allowed_ssh_source
    destination_address_prefix = "*"
  }

  tags = var.tags
}

# Public IP
resource "azurerm_public_ip" "main" {
  name                = "${var.vm_name}-pip"
  location            = azurerm_resource_group.main.location
  resource_group_name = azurerm_resource_group.main.name
  allocation_method   = "Static"
  sku                 = "Standard"

  tags = var.tags
}

# Network Interface
resource "azurerm_network_interface" "main" {
  name                = "${var.vm_name}-nic"
  location            = azurerm_resource_group.main.location
  resource_group_name = azurerm_resource_group.main.name

  ip_configuration {
    name                          = "internal"
    subnet_id                     = azurerm_subnet.main.id
    private_ip_address_allocation = "Dynamic"
    public_ip_address_id          = azurerm_public_ip.main.id
  }

  tags = var.tags
}

# Associate NSG with Network Interface
resource "azurerm_network_interface_security_group_association" "main" {
  network_interface_id      = azurerm_network_interface.main.id
  network_security_group_id = azurerm_network_security_group.main.id
}

# Linux Virtual Machine
resource "azurerm_linux_virtual_machine" "main" {
  name                            = var.vm_name
  resource_group_name             = azurerm_resource_group.main.name
  location                        = azurerm_resource_group.main.location
  size                            = var.vm_size
  admin_username                  = var.admin_username
  admin_password                  = var.admin_password
  disable_password_authentication = false

  network_interface_ids = [
    azurerm_network_interface.main.id,
  ]

  os_disk {
    caching              = "ReadWrite"
    storage_account_type = "Standard_LRS"
  }

  source_image_reference {
    publisher = "Canonical"
    offer     = "0001-com-ubuntu-server-jammy"
    sku       = "22_04-lts-gen2"
    version   = "latest"
  }

  tags = var.tags
}