resource "aws_rds_cluster" "aurora_cluster" {
  cluster_identifier      = var.cluster_identifier
  engine                  = var.engine
  engine_version          = var.engine_version
  availability_zones      = data.aws_availability_zones.available.names
  database_name           = var.database_name
  master_username         = var.master_username
  master_password         = var.master_password
  backup_retention_period = var.backup_retention_period
  preferred_backup_window = var.preferred_backup_window
  vpc_security_group_ids  = [aws_security_group.aurora_sg.id]
  db_subnet_group_name    = aws_db_subnet_group.aurora_subnet_group.name
  skip_final_snapshot     = var.skip_final_snapshot

  tags = var.tags
}

resource "aws_rds_cluster_instance" "aurora_instances" {
  count              = var.instance_count
  identifier         = "${var.cluster_identifier}-${count.index + 1}"
  cluster_identifier = aws_rds_cluster.aurora_cluster.id
  instance_class     = var.instance_class
  engine             = aws_rds_cluster.aurora_cluster.engine
  engine_version     = aws_rds_cluster.aurora_cluster.engine_version

  tags = var.tags
}

resource "aws_db_subnet_group" "aurora_subnet_group" {
  name       = "${var.cluster_identifier}-subnet-group"
  subnet_ids = var.subnet_ids

  tags = var.tags
}

resource "aws_security_group" "aurora_sg" {
  name_prefix = "${var.cluster_identifier}-sg"
  vpc_id      = var.vpc_id

  ingress {
    from_port   = 3306
    to_port     = 3306
    protocol    = "tcp"
    cidr_blocks = var.allowed_cidr_blocks
  }

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

  tags = var.tags
}

data "aws_availability_zones" "available" {
  state = "available"
}

variable "cluster_identifier" {
  description = "The cluster identifier for the Aurora cluster"
  type        = string
}

variable "engine" {
  description = "The name of the database engine to be used for this DB cluster"
  type        = string
  default     = "aurora-mysql"
}

variable "engine_version" {
  description = "The database engine version"
  type        = string
}

variable "instance_class" {
  description = "The instance class to use for the Aurora instances"
  type        = string
}

variable "instance_count" {
  description = "The number of instances to create in the cluster"
  type        = number
  default     = 2
}

variable "database_name" {
  description = "Name for an automatically created database on cluster creation"
  type        = string
}

variable "master_username" {
  description = "Username for the master DB user"
  type        = string
}

variable "master_password" {
  description = "Password for the master DB user"
  type        = string
}

variable "vpc_id" {
  description = "VPC ID to create the cluster in"
  type        = string
}

variable "subnet_ids" {
  description = "A list of VPC subnet IDs to create the cluster in"
  type        = list(string)
}

variable "allowed_cidr_blocks" {
  description = "A list of CIDR blocks that are allowed to access the database"
  type        = list(string)
  default     = []
}

variable "backup_retention_period" {
  description = "The days to retain backups for"
  type        = number
  default     = 7
}

variable "preferred_backup_window" {
  description = "The daily time range during which automated backups are created"
  type        = string
  default     = "02:00-03:00"
}

variable "skip_final_snapshot" {
  description = "Determines whether a final DB snapshot is created before the DB cluster is deleted"
  type        = bool
  default     = false
}

variable "tags" {
  description = "A map of tags to add to all resources"
  type        = map(string)
  default     = {}
}

output "cluster_endpoint" {
  description = "The cluster endpoint"
  value       = aws_rds_cluster.aurora_cluster.endpoint
}

output "cluster_reader_endpoint" {
  description = "The cluster reader endpoint"
  value       = aws_rds_cluster.aurora_cluster.reader_endpoint
}

output "cluster_id" {
  description = "The ID of the cluster"
  value       = aws_rds_cluster.aurora_cluster.id
}

output "cluster_resource_id" {
  description = "The Resource ID of the cluster"
  value       = aws_rds_cluster.aurora_cluster.cluster_resource_id
}

output "cluster_instances" {
  description = "A list of all cluster instance IDs"
  value       = aws_rds_cluster_instance.aurora_instances[*].id
}

output "security_group_id" {
  description = "The ID of the security group created for the Aurora cluster"
  value       = aws_security_group.aurora_sg.id
}

output "db_subnet_group_name" {
  description = "The name of the DB subnet group created for the Aurora cluster"
  value       = aws_db_subnet_group.aurora_subnet_group.name
}