VPC avec Terraform & AWS

# create a VPC
resource "aws_vpc" "main" {
  cidr_block = var.vpc_cidr
  tags       = { Name = var.vpc_tag } # utilise vpc_tag
}

# subnet public
resource "aws_subnet" "pub" {
  count             = length(var.vpc_subnet_pub)
  vpc_id            = aws_vpc.main.id
  cidr_block        = var.vpc_subnet_pub[count.index]
  availability_zone = var.azs[count.index]
  tags = {
    Name = "subnet_${var.vpc_subnet_pub[count.index]}"
  }
}

# subnet private
resource "aws_subnet" "priv" {
  count             = length(var.vpc_subnet_priv)
  vpc_id            = aws_vpc.main.id
  cidr_block        = var.vpc_subnet_priv[count.index]
  availability_zone = var.azs[count.index]
  tags = {
    Name = "subnet_${var.vpc_subnet_priv[count.index]}"
  }
}

# IGW / internet gateway
resource "aws_internet_gateway" "igw" {
  vpc_id = aws_vpc.main.id
  tags   = { Name = "IGW" }
}

# EIP pour NAT
resource "aws_eip" "nat_eip" {
  domain = "vpc"
}

#NAT GW dans SUB1 publique
resource "aws_nat_gateway" "nat" {
  allocation_id = aws_eip.nat_eip.id
  subnet_id     = aws_subnet.pub[0].id
  tags          = { Name = "NAT-GW" }
}

# table routage publique (0.0.0/0 -> IGW)
resource "aws_route_table" "public" {
  vpc_id = aws_vpc.main.id
  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = aws_internet_gateway.igw.id
  }
  tags = { Name = "RT-public" }
}

# association RT publique aux sub public 1&2
resource "aws_route_table_association" "pub" {
  count          = length(var.vpc_subnet_pub)
  subnet_id      = aws_subnet.pub[count.index].id
  route_table_id = aws_route_table.public.id
}

# table routage private (0.0.0/0 → IGW)
resource "aws_route_table" "private" {
  vpc_id = aws_vpc.main.id
  route {
    cidr_block     = "0.0.0.0/0"
    nat_gateway_id = aws_nat_gateway.nat.id
  }
  tags = { Name = "RT-private" }
}

# association RT privée aux sub privés 3&4
resource "aws_route_table_association" "priv" {
  count          = length(var.vpc_subnet_priv)
  subnet_id      = aws_subnet.priv[count.index].id # public → priv
  route_table_id = aws_route_table.private.id      # public → private
}

# EC2 dans subnets privés
resource "aws_instance" "web" {
  count                  = 2
  ami                    = var.web_ami_id
  instance_type          = "t3.micro"
  subnet_id              = aws_subnet.priv[count.index].id
  vpc_security_group_ids = [aws_security_group.web_sg.id]
  user_data = base64encode(<<-EOF
              #!/bin/bash
              apt update -y 
              apt upgrade
              apt-get install -y apache2
              systemctl start apache2
              systemctl enable apache2
              echo "Bienvenue sur le serveur web privé # ${count.index}" > /var/www/html/index.html
              EOF
  )

  tags = { Name = "lab-web-${count.index + 1}" }
}

#load balancer + target group
resource "aws_lb" "alb" {
  name               = "lab-alb"
  load_balancer_type = "application"
  subnets            = aws_subnet.pub[*].id
  security_groups    = [aws_security_group.alb_sg.id]
}

resource "aws_lb_target_group" "tg" {
  name     = "lab-tg"
  port     = 80
  protocol = "HTTP"
  vpc_id   = aws_vpc.main.id
}

resource "aws_lb_target_group_attachment" "tg_attachment" {
  count            = length(aws_instance.web)
  target_group_arn = aws_lb_target_group.tg.arn
  target_id        = aws_instance.web[count.index].id
  port             = 80
}

resource "aws_lb_listener" "http" {
  load_balancer_arn = aws_lb.alb.arn
  port              = 80
  protocol          = "HTTP"

  default_action {
    type             = "forward"
    target_group_arn = aws_lb_target_group.tg.arn
  }
}

#security groups
#pour l’ALB
resource "aws_security_group" "alb_sg" {
  name   = "lab-alb-sg"
  vpc_id = aws_vpc.main.id

  ingress { #inbound : HTTP/HTTPS depuis 0.0.0.0/0
    from_port   = 80
    to_port     = 80
    protocol    = "tcp"
    cidr_blocks = ["0.0.0.0/0"]
  }

  egress { #Outbound : vers SG des serveurs
    from_port   = 0
    to_port     = 0
    protocol    = "-1"
    cidr_blocks = ["0.0.0.0/0"]
  }
}

#pour EC2 privés
resource "aws_security_group" "web_sg" {
  name   = "lab-web-sg"
  vpc_id = aws_vpc.main.id

  ingress {
    from_port       = 80
    to_port         = 80
    protocol        = "tcp"
    security_groups = [aws_security_group.alb_sg.id]
    description     = "HTTP from ALB"
  }

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

variable "vpc_cidr" {
  description = "Plage CIDR du VPC"
  type        = string
  default     = "10.0.0.0/16"
}

variable "vpc_subnet_pub" {
  description = "CIDRs des subnets publics"
  type        = list(string)
  default     = ["10.0.1.0/24", "10.0.11.0/24"]
}

variable "vpc_subnet_priv" {
  description = "CIDRs des subnets privés"
  type        = list(string)
  default     = ["10.0.2.0/24", "10.0.21.0/24"]
}

variable "vpc_tag" {
  description = "Tag name du VPC"
  type        = string
  default     = "cesi"
}

variable "web_ami_id" {
  description = "AMI pour les EC2 web"
  type        = string
  default     = "ami-0c02fb55956c7d316" # Amazon Linux 2 us-east-1
}
variable "azs" {
  description = "Availability Zones"
  type        = list(string)
  default     = ["us-east-1a", "us-east-1b"] #region diff
}

# URL pour tester ALB
output "alb_dns_name" {
  description = "URL du Load Balancer"
  value       = aws_lb.alb.dns_name
}

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

# subnets
output "subnet_pub_ids" {
  description = "IDs des subnets publics"
  value       = aws_subnet.pub[*].id
}

output "subnet_priv_ids" {
  description = "IDs des subnets privés"
  value       = aws_subnet.priv[*].id
}

# NAT GW
output "nat_gateway_ip" {
  description = "IP publique du NAT Gateway"
  value       = aws_eip.nat_eip.public_ip
}

# EC2
output "web_instance_ids" {
  description = "IDs des instances web"
  value       = aws_instance.web[*].id
}

output "web_private_ips" {
  description = "IPs privées des serveurs web"
  value       = aws_instance.web[*].private_ip
}