Lab 02: VPC + EC2 기본 스택

terraform {
  required_version = ">= 1.0.0"

  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
}

provider "aws" {
  region = "ap-northeast-2" # 서울 리전
}

variable "project" {
  description = "프로젝트 이름"
  type        = string
  default     = "lab02"
}

variable "environment" {
  description = "배포 환경"
  type        = string
  default     = "dev"
}

variable "instance_type" {
  description = "EC2 인스턴스 타입"
  type        = string
  default     = "t2.micro"
}

locals {
  name_prefix = "${var.project}-${var.environment}"

  common_tags = {
    Project     = var.project
    Environment = var.environment
    ManagedBy   = "terraform"
  }
}

# VPC
resource "aws_vpc" "main" {
  cidr_block           = "10.0.0.0/16"
  enable_dns_hostnames = true
  enable_dns_support   = true

  tags = merge(local.common_tags, {
    Name = "${local.name_prefix}-vpc"
  })
}

# 퍼블릭 서브넷
resource "aws_subnet" "public" {
  vpc_id                  = aws_vpc.main.id   # VPC 참조 → 암시적 의존성
  cidr_block              = "10.0.1.0/24"
  availability_zone       = "ap-northeast-2a"
  map_public_ip_on_launch = true              # 퍼블릭 IP 자동 할당

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

# 인터넷 게이트웨이
resource "aws_internet_gateway" "main" {
  vpc_id = aws_vpc.main.id

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

# 라우팅 테이블
resource "aws_route_table" "public" {
  vpc_id = aws_vpc.main.id

  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = aws_internet_gateway.main.id
  }

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

# 라우팅 테이블 ↔ 서브넷 연결
resource "aws_route_table_association" "public" {
  subnet_id      = aws_subnet.public.id
  route_table_id = aws_route_table.public.id
}

# 최신 Ubuntu 22.04 AMI 조회 (data source)
data "aws_ami" "ubuntu" {
  most_recent = true
  owners      = ["099720109477"] # Canonical 공식 계정

  filter {
    name   = "name"
    values = ["ubuntu/images/hvm-ssd/ubuntu-jammy-22.04-amd64-server-*"]
  }

  filter {
    name   = "virtualization-type"
    values = ["hvm"]
  }
}

# 보안 그룹
resource "aws_security_group" "web" {
  name        = "${local.name_prefix}-sg"
  description = "Allow SSH and HTTP"
  vpc_id      = aws_vpc.main.id   # VPC 참조

  ingress {
    description = "SSH"
    from_port   = 22
    to_port     = 22
    protocol    = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }

  ingress {
    description = "HTTP"
    from_port   = 80
    to_port     = 80
    protocol    = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }

  egress {
    from_port   = 0
    to_port     = 0
    protocol    = "-1"
    cidr_blocks = ["0.0.0.0/0"]
  }

  tags = merge(local.common_tags, {
    Name = "${local.name_prefix}-sg"
  })
}

# EC2 인스턴스
resource "aws_instance" "web" {
  ami                    = data.aws_ami.ubuntu.id   # data source 참조
  instance_type          = var.instance_type
  subnet_id              = aws_subnet.public.id     # Subnet 참조
  vpc_security_group_ids = [aws_security_group.web.id]

  user_data = <<-EOF
              #!/bin/bash
              apt-get update -y
              apt-get install -y nginx
              echo "<h1>Hello from Terraform Lab 02</h1>" > /var/www/html/index.html
              systemctl start nginx
              systemctl enable nginx
              EOF

  tags = merge(local.common_tags, {
    Name = "${local.name_prefix}-web"
  })
}

output "vpc_id" {
  description = "생성된 VPC ID"
  value       = aws_vpc.main.id
}

output "public_subnet_id" {
  description = "퍼블릭 서브넷 ID"
  value       = aws_subnet.public.id
}

output "instance_id" {
  description = "EC2 인스턴스 ID"
  value       = aws_instance.web.id
}

output "public_ip" {
  description = "EC2 퍼블릭 IP"
  value       = aws_instance.web.public_ip
}

output "web_url" {
  description = "Nginx 웹서버 접근 URL"
  value       = "http://${aws_instance.web.public_ip}"
}