# Input:  Docker image in ECR, VPC/subnet IDs
# Output: Complete ECS Fargate service with ALB, auto-scaling

resource "aws_ecs_cluster" "main" {
  name = "myapp-cluster"
}

resource "aws_ecs_task_definition" "app" {
  family                   = "myapp"
  network_mode             = "awsvpc"
  requires_compatibilities = ["FARGATE"]
  cpu                      = "256"   # 0.25 vCPU (≈ Heroku standard-1x)
  memory                   = "512"   # 512 MB
  execution_role_arn       = aws_iam_role.ecs_execution.arn

  container_definitions = jsonencode([{
    name      = "myapp"
    image     = "${aws_ecr_repository.app.repository_url}:latest"
    essential = true
    portMappings = [{ containerPort = 3000, protocol = "tcp" }]
    environment = [
      { name = "PORT", value = "3000" },
      { name = "NODE_ENV", value = "production" }
    ]
    secrets = [
      { name = "DATABASE_URL", valueFrom = aws_ssm_parameter.db_url.arn }
    ]
    logConfiguration = {
      logDriver = "awslogs"
      options = {
        awslogs-group         = "/ecs/myapp"
        awslogs-region        = var.region
        awslogs-stream-prefix = "ecs"
      }
    }
  }])
}

resource "aws_ecs_service" "app" {
  name            = "myapp-service"
  cluster         = aws_ecs_cluster.main.id
  task_definition = aws_ecs_task_definition.app.arn
  desired_count   = 2
  launch_type     = "FARGATE"

  network_configuration {
    subnets          = var.private_subnets
    security_groups  = [aws_security_group.ecs.id]
    assign_public_ip = false
  }

  load_balancer {
    target_group_arn = aws_lb_target_group.app.arn
    container_name   = "myapp"
    container_port   = 3000
  }
}

# Auto-scaling (replaces Heroku dyno scaling)
resource "aws_appautoscaling_target" "ecs" {
  max_capacity       = 10
  min_capacity       = 2
  resource_id        = "service/${aws_ecs_cluster.main.name}/${aws_ecs_service.app.name}"
  scalable_dimension = "ecs:service:DesiredCount"
  service_namespace  = "ecs"
}