provider "aws" {
  region = local.region
}

data "aws_availability_zones" "available" {}

locals {
  name   = "ex-${basename(path.cwd)}"
  region = "eu-west-1"

  db_username = random_pet.users.id # using random here due to secrets taking at least 7 days before fully deleting from account
  db_password = random_password.password.result

  vpc_cidr = "10.0.0.0/16"
  azs      = slice(data.aws_availability_zones.available.names, 0, 3)

  tags = {
    Example    = local.name
    GithubRepo = "terraform-aws-rds-proxy"
    GithubOrg  = "terraform-aws-modules"
  }
}

################################################################################
# RDS Proxy
################################################################################

module "rds_proxy" {
  source = "../../"

  name                   = local.name
  iam_role_name          = local.name
  vpc_subnet_ids         = module.vpc.private_subnets
  vpc_security_group_ids = [module.rds_proxy_sg.security_group_id]

  endpoints = {
    read_write = {
      name                   = "read-write-endpoint"
      vpc_subnet_ids         = module.vpc.private_subnets
      vpc_security_group_ids = [module.rds_proxy_sg.security_group_id]
      tags                   = local.tags
    },
    read_only = {
      name                   = "read-only-endpoint"
      vpc_subnet_ids         = module.vpc.private_subnets
      vpc_security_group_ids = [module.rds_proxy_sg.security_group_id]
      target_role            = "READ_ONLY"
      tags                   = local.tags
    }
  }

  auth = {
    (local.db_username) = {
      description = aws_secretsmanager_secret.superuser.description
      secret_arn  = aws_secretsmanager_secret.superuser.arn
    }
  }

  engine_family = "POSTGRESQL"
  debug_logging = true

  # Target RDS instance
  target_db_instance     = true
  db_instance_identifier = module.rds.db_instance_identifier

  tags = local.tags
}

################################################################################
# Supporting Resources
################################################################################

resource "random_pet" "users" {
  length    = 2
  separator = "_"
}

resource "random_password" "password" {
  length  = 16
  special = false
}

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "~> 6.0"

  name = local.name
  cidr = local.vpc_cidr

  azs              = local.azs
  public_subnets   = [for k, v in local.azs : cidrsubnet(local.vpc_cidr, 8, k)]
  private_subnets  = [for k, v in local.azs : cidrsubnet(local.vpc_cidr, 8, k + 3)]
  database_subnets = [for k, v in local.azs : cidrsubnet(local.vpc_cidr, 8, k + 6)]

  tags = local.tags
}

module "rds" {
  source  = "terraform-aws-modules/rds/aws"
  version = "~> 6.0"

  username = local.db_username
  password = local.db_password

  # When using RDS Proxy w/ IAM auth - Database must be username/password auth, not IAM
  iam_database_authentication_enabled = false

  identifier           = local.name
  engine               = "postgres"
  engine_version       = "14"
  family               = "postgres14" # DB parameter group
  major_engine_version = "14"         # DB option group
  instance_class       = "db.t4g.large"
  allocated_storage    = 20
  port                 = 5432
  apply_immediately    = true

  db_subnet_group_name   = module.vpc.database_subnet_group
  vpc_security_group_ids = [module.rds_sg.security_group_id]
  multi_az               = true

  backup_retention_period = 0
  deletion_protection     = false

  tags = local.tags
}

module "rds_sg" {
  source  = "terraform-aws-modules/security-group/aws"
  version = "~> 5.0"

  name        = "rds"
  description = "PostgreSQL RDS example security group"
  vpc_id      = module.vpc.vpc_id

  revoke_rules_on_delete = true

  ingress_with_cidr_blocks = [
    {
      description = "Private subnet PostgreSQL access"
      rule        = "postgresql-tcp"
      cidr_blocks = join(",", module.vpc.private_subnets_cidr_blocks)
    }
  ]

  tags = local.tags
}

module "rds_proxy_sg" {
  source  = "terraform-aws-modules/security-group/aws"
  version = "~> 5.0"

  name        = "rds_proxy"
  description = "PostgreSQL RDS Proxy example security group"
  vpc_id      = module.vpc.vpc_id

  revoke_rules_on_delete = true

  ingress_with_cidr_blocks = [
    {
      description = "Private subnet PostgreSQL access"
      rule        = "postgresql-tcp"
      cidr_blocks = join(",", module.vpc.private_subnets_cidr_blocks)
    }
  ]

  egress_with_cidr_blocks = [
    {
      description = "Database subnet PostgreSQL access"
      rule        = "postgresql-tcp"
      cidr_blocks = join(",", module.vpc.database_subnets_cidr_blocks)
    },
  ]

  tags = local.tags
}

################################################################################
# Secrets - DB user passwords
################################################################################

data "aws_kms_alias" "secretsmanager" {
  name = "alias/aws/secretsmanager"
}

resource "aws_secretsmanager_secret" "superuser" {
  name        = local.db_username
  description = "Database superuser, ${local.db_username}, database connection values"
  kms_key_id  = data.aws_kms_alias.secretsmanager.id

  tags = local.tags
}

resource "aws_secretsmanager_secret_version" "superuser" {
  secret_id = aws_secretsmanager_secret.superuser.id
  secret_string = jsonencode({
    username = local.db_username
    password = local.db_password
  })
}