# Phase 2: ECS Fargate + Application Load Balancer
# File: infrastructure/services/main.tf

terraform {
  required_version = ">= 1.0"
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
}

provider "aws" {
  region = var.aws_region
  default_tags {
    tags = var.common_tags
  }
}

# Data sources to reference Foundation Layer outputs
data "terraform_remote_state" "foundation" {
  backend = "s3"
  config = {
    bucket = "nvhi-atsila-microservice-terraform-state-c4ae0f80"
    key    = "foundation/terraform.tfstate"
    region = var.aws_region
  }
}

# Enterprise naming convention with AWS resource limits
locals {
  # Shortened base name for AWS resource naming limits
  base_name = "nvhi-atsila"
  
  # Computed names ensuring AWS limits compliance
  # Target Groups (32 char limit): "nvhi-atsila-blue-tg" = 17 chars ✅
  blue_tg_name  = "${local.base_name}-blue-tg"
  green_tg_name = "${local.base_name}-green-tg"
  
  # ALB name (32 char limit): "nvhi-atsila-alb" = 15 chars ✅  
  alb_name = "${local.base_name}-alb"
  
  # ECS names for consistency
  ecs_cluster_name = "${local.base_name}-cluster"
  ecs_service_name = "${local.base_name}-service"
  
  # ECR name  
  ecr_repo_name = "${local.base_name}-app"
  
  # Common resource prefix for tagging and organization
  resource_prefix = local.base_name
}

# ECR Repository for container images
resource "aws_ecr_repository" "app" {
  name                 = local.ecr_repo_name
  image_tag_mutability = "MUTABLE"
  force_delete         = true # For demo purposes

  image_scanning_configuration {
    scan_on_push = true
  }

  tags = {
    Name        = "${var.project_name}-ecr"
    Environment = var.environment
    Project     = var.project_name
  }
}

# ECR Lifecycle Policy
resource "aws_ecr_lifecycle_policy" "app" {
  repository = aws_ecr_repository.app.name
  policy = jsonencode({
    rules = [
      {
        rulePriority = 1
        description  = "Keep last 10 images"
        selection = {
          tagStatus     = "tagged"
          tagPrefixList = ["v"]
          countType     = "imageCountMoreThan"
          countNumber   = 10
        }
        action = {
          type = "expire"
        }
      },
      {
        rulePriority = 2
        description  = "Delete untagged images older than 1 day"
        selection = {
          tagStatus   = "untagged"
          countType   = "sinceImagePushed"
          countUnit   = "days"
          countNumber = 1
        }
        action = {
          type = "expire"
        }
      }
    ]
  })
}

# ECS Cluster
resource "aws_ecs_cluster" "main" {
  name = local.ecs_cluster_name

  configuration {
    execute_command_configuration {
      logging = "OVERRIDE"
      log_configuration {
        cloud_watch_log_group_name = aws_cloudwatch_log_group.ecs_cluster.name
      }
    }
  }

  setting {
    name  = "containerInsights"
    value = "enabled"
  }

  tags = {
    Name        = "${var.project_name}-ecs-cluster"
    Environment = var.environment
    Project     = var.project_name
  }
}

# CloudWatch Log Group for ECS
resource "aws_cloudwatch_log_group" "ecs_cluster" {
  name              = "/aws/ecs/${local.ecs_cluster_name}"
  retention_in_days = 7 # Free tier friendly
  skip_destroy      = false

  tags = {
    Name        = "${local.ecs_cluster_name}-logs"
    Environment = var.environment
    Project     = var.project_name
  }
}

resource "aws_cloudwatch_log_group" "app" {
  name              = "/aws/ecs/${local.ecr_repo_name}"
  retention_in_days = 7 # Free tier friendly
  skip_destroy      = false

  tags = {
    Name        = "${local.ecr_repo_name}-logs"
    Environment = var.environment
    Project     = var.project_name
  }
}

# Application Load Balancer
resource "aws_lb" "main" {
  name               = local.alb_name
  internal           = false
  load_balancer_type = "application"
  security_groups    = [data.terraform_remote_state.foundation.outputs.alb_security_group_id]
  subnets            = data.terraform_remote_state.foundation.outputs.public_subnet_ids

  enable_deletion_protection = false # For demo purposes

  tags = {
    Name        = "${var.project_name}-alb"
    Environment = var.environment
    Project     = var.project_name
  }
}

# ALB Target Group for Blue Environment
resource "aws_lb_target_group" "blue" {
  name        = local.blue_tg_name
  port        = 8080
  protocol    = "HTTP"
  vpc_id      = data.terraform_remote_state.foundation.outputs.vpc_id
  target_type = "ip"

  health_check {
    enabled             = true
    healthy_threshold   = 2
    interval            = 30
    matcher             = "200"
    path                = "/health"
    port                = "traffic-port"
    protocol            = "HTTP"
    timeout             = 5
    unhealthy_threshold = 3
  }

  deregistration_delay = 30 # Fast for demo

  tags = {
    Name        = "${var.project_name}-blue-tg"
    Environment = var.environment
    Project     = var.project_name
  }
}

# ALB Target Group for Green Environment (Blue/Green Deployment)
resource "aws_lb_target_group" "green" {
  name        = local.green_tg_name
  port        = 8080
  protocol    = "HTTP"
  vpc_id      = data.terraform_remote_state.foundation.outputs.vpc_id
  target_type = "ip"

  health_check {
    enabled             = true
    healthy_threshold   = 2
    interval            = 30
    matcher             = "200"
    path                = "/health"
    port                = "traffic-port"
    protocol            = "HTTP"
    timeout             = 5
    unhealthy_threshold = 3
  }

  deregistration_delay = 30 # Fast for demo

  tags = {
    Name        = "${var.project_name}-green-tg"
    Environment = var.environment
    Project     = var.project_name
  }
}

# ALB Listener (defaults to Blue)
resource "aws_lb_listener" "main" {
  load_balancer_arn = aws_lb.main.arn
  port              = "80"
  protocol          = "HTTP"

  default_action {
    type             = "forward"
    forward {
    target_group { 
      arn = aws_lb_target_group.blue.arn
    }
  }
}

  tags = {
    Name        = "${var.project_name}-alb-listener"
    Environment = var.environment
    Project     = var.project_name
  }
}

# IAM Role for ECS Task Execution
resource "aws_iam_role" "ecs_task_execution" {
  name = "${var.project_name}-ecs-task-execution-role"

  assume_role_policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Action = "sts:AssumeRole"
        Effect = "Allow"
        Principal = {
          Service = "ecs-tasks.amazonaws.com"
        }
      }
    ]
  })

  tags = {
    Name        = "${var.project_name}-ecs-task-execution-role"
    Environment = var.environment
    Project     = var.project_name
  }
}

# IAM Role Policy Attachment for ECS Task Execution
resource "aws_iam_role_policy_attachment" "ecs_task_execution" {
  role       = aws_iam_role.ecs_task_execution.name
  policy_arn = "arn:aws:iam::aws:policy/service-role/AmazonECSTaskExecutionRolePolicy"
}

# Additional IAM Policy for ECR and CloudWatch
resource "aws_iam_role_policy" "ecs_task_execution_custom" {
  name = "${var.project_name}-ecs-task-execution-custom"
  role = aws_iam_role.ecs_task_execution.id

  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Effect = "Allow"
        Action = [
          "ecr:GetAuthorizationToken",
          "ecr:BatchCheckLayerAvailability",
          "ecr:GetDownloadUrlForLayer",
          "ecr:BatchGetImage"
        ]
        Resource = "*"
      },
      {
        Effect = "Allow"
        Action = [
          "logs:CreateLogStream",
          "logs:PutLogEvents"
        ]
        Resource = "${aws_cloudwatch_log_group.app.arn}:*"
      }
    ]
  })
}

# IAM Role for ECS Task (application permissions)
resource "aws_iam_role" "ecs_task" {
  name = "${var.project_name}-ecs-task-role"

  assume_role_policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Action = "sts:AssumeRole"
        Effect = "Allow"
        Principal = {
          Service = "ecs-tasks.amazonaws.com"
        }
      }
    ]
  })

  tags = {
    Name        = "${var.project_name}-ecs-task-role"
    Environment = var.environment
    Project     = var.project_name
  }
}

# ECS Task Definition
resource "aws_ecs_task_definition" "app" {
  family                   = local.ecr_repo_name
  network_mode             = "awsvpc"
  requires_compatibilities = ["FARGATE"]
  cpu                      = var.task_cpu
  memory                   = var.task_memory
  execution_role_arn       = aws_iam_role.ecs_task_execution.arn
  task_role_arn           = aws_iam_role.ecs_task.arn

  container_definitions = jsonencode([
    {
      name      = "app"
      image     = "${aws_ecr_repository.app.repository_url}:${var.image_tag}"
      essential = true

      portMappings = [
        {
          containerPort = 8080
          protocol      = "tcp"
        }
      ]

      logConfiguration = {
        logDriver = "awslogs"
        options = {
          awslogs-group         = aws_cloudwatch_log_group.app.name
          awslogs-region        = var.aws_region
          awslogs-stream-prefix = "ecs"
        }
      }

      environment = [
        {
          name  = "ENV"
          value = var.environment
        },
        {
          name  = "PROJECT_NAME"
          value = var.project_name
        }
      ]
    }
  ])

  tags = {
    Name        = "${var.project_name}-task-definition"
    Environment = var.environment
    Project     = var.project_name
  }
}

# ECS Service (Blue Environment)
resource "aws_ecs_service" "app" {
  name            = local.ecs_service_name
  cluster         = aws_ecs_cluster.main.id
  task_definition = aws_ecs_task_definition.app.arn
  desired_count   = var.desired_count
  launch_type     = "FARGATE"

  network_configuration {
    subnets          = data.terraform_remote_state.foundation.outputs.app_subnet_ids
    security_groups  = [data.terraform_remote_state.foundation.outputs.ecs_tasks_security_group_id]
    assign_public_ip = true # Required for public subnets without NAT gateway
  }

  load_balancer {
    target_group_arn = aws_lb_target_group.blue.arn
    container_name   = "app"
    container_port   = 8080
  }

  depends_on = [aws_lb_listener.main]

  # Blue/Green deployment configuration
    deployment_maximum_percent         = 200
    deployment_minimum_healthy_percent = 50
  
  deployment_circuit_breaker {
      enable   = true
      rollback = true
  }


  enable_execute_command = true

  tags = {
    Name        = "${var.project_name}-ecs-service"
    Environment = var.environment
    Project     = var.project_name
  }
}

# CloudWatch Alarms for monitoring
resource "aws_cloudwatch_metric_alarm" "high_cpu" {
  alarm_name          = "${var.project_name}-high-cpu"
  comparison_operator = "GreaterThanThreshold"
  evaluation_periods  = "2"
  metric_name         = "CPUUtilization"
  namespace           = "AWS/ECS"
  period              = "300"
  statistic           = "Average"
  threshold           = "80"
  alarm_description   = "This metric monitors ECS service CPU utilization"
  alarm_actions       = [] # Add SNS topic ARN for notifications

  dimensions = {
    ServiceName = aws_ecs_service.app.name
    ClusterName = aws_ecs_cluster.main.name
  }

  tags = {
    Name        = "${var.project_name}-high-cpu-alarm"
    Environment = var.environment
    Project     = var.project_name
  }
}

resource "aws_cloudwatch_metric_alarm" "high_memory" {
  alarm_name          = "${var.project_name}-high-memory"
  comparison_operator = "GreaterThanThreshold"
  evaluation_periods  = "2"
  metric_name         = "MemoryUtilization"
  namespace           = "AWS/ECS"
  period              = "300"
  statistic           = "Average"
  threshold           = "80"
  alarm_description   = "This metric monitors ECS service memory utilization"
  alarm_actions       = [] # Add SNS topic ARN for notifications

  dimensions = {
    ServiceName = aws_ecs_service.app.name
    ClusterName = aws_ecs_cluster.main.name
  }

  tags = {
    Name        = "${var.project_name}-high-memory-alarm"
    Environment = var.environment
    Project     = var.project_name
  }
}