# Data source to reference existing VCN in Korea region
data "oci_core_vcns" "existing_vcns" {
  compartment_id = var.compartment_id
}

# Use the specific existing VCN by filtering
locals {
  target_vcn = [
    for vcn in data.oci_core_vcns.existing_vcns.virtual_networks :
    vcn.id if vcn.display_name == "vcn-20220508-0033"
  ][0]
  default_dhcp_options_id = [
    for vcn in data.oci_core_vcns.existing_vcns.virtual_networks :
    vcn.default_dhcp_options_id if vcn.display_name == "vcn-20220508-0033"
  ][0]
  default_route_table_id = [
    for vcn in data.oci_core_vcns.existing_vcns.virtual_networks :
    vcn.default_route_table_id if vcn.display_name == "vcn-20220508-0033"
  ][0]
  default_security_list_id = [
    for vcn in data.oci_core_vcns.existing_vcns.virtual_networks :
    vcn.default_security_list_id if vcn.display_name == "vcn-20220508-0033"
  ][0]
}

# Find existing subnets in the target VCN
data "oci_core_subnets" "existing_subnets" {
  compartment_id = var.compartment_id
  vcn_id         = local.target_vcn
}

# Use an existing subnet or create a new one in the existing VCN
resource "oci_core_subnet" "kr_subnet" {
  count = length(data.oci_core_subnets.existing_subnets.subnets) == 0 ? 1 : 0  # Only create if no subnets exist

  availability_domain = var.availability_domain
  cidr_block          = "10.0.1.0/24"
  compartment_id      = var.compartment_id
  display_name        = "kr-subnet-tf"
  vcn_id              = local.target_vcn
  dhcp_options_id     = local.default_dhcp_options_id
  route_table_id      = local.default_route_table_id
  security_list_ids   = [local.default_security_list_id]
  dns_label           = "krtfsub"
}

# Define which subnet to use based on whether existing subnets are found
locals {
  subnet_to_use = length(data.oci_core_subnets.existing_subnets.subnets) > 0 ? data.oci_core_subnets.existing_subnets.subnets[0].id : oci_core_subnet.kr_subnet[0].id
}

# 实例 ch2 (将要终止的实例) - 仅在需要时创建用于模拟资源回收
resource "oci_core_instance" "ch2_instance" {
  count = var.ch2_enabled ? 1 : 0

  availability_domain = var.availability_domain
  compartment_id      = var.compartment_id
  display_name        = "ch2-instance"
  shape               = var.ch2_shape

  create_vnic_details {
    subnet_id        = local.subnet_to_use
    assign_public_ip = true
    hostname_label   = "ch2instance"
  }

  source_details {
    source_type = "image"
    source_id   = var.image_id
  }

  metadata = {
    ssh_authorized_keys = var.ssh_public_key
  }

  timeouts {
    create = "60m"
  }
}

# 实例 ch3 (保持不变的实例)
resource "oci_core_instance" "ch3_instance" {
  count = var.ch3_enabled ? 1 : 0

  availability_domain = var.availability_domain
  compartment_id      = var.compartment_id
  display_name        = "ch3-instance"
  shape               = var.ch3_shape

  create_vnic_details {
    subnet_id        = local.subnet_to_use
    assign_public_ip = true
    hostname_label   = "ch3instance"
  }

  source_details {
    source_type = "image"
    source_id   = var.image_id
  }

  metadata = {
    ssh_authorized_keys = var.ssh_public_key
  }

  timeouts {
    create = "60m"
  }
}

# A1 实例 (主要实例) - ARM架构实例
resource "oci_core_instance" "a1_instance" {
  availability_domain = var.availability_domain
  compartment_id      = var.compartment_id
  display_name        = "a1-instance"
  shape               = var.a1_shape

  create_vnic_details {
    subnet_id        = local.subnet_to_use
    assign_public_ip = true
    hostname_label   = "a1instance"
  }

  source_details {
    source_type = "image"
    source_id   = var.image_id
  }

  metadata = {
    ssh_authorized_keys = var.ssh_public_key
  }

  timeouts {
    create = "60m"
  }

  # 添加对 ch2 实例的依赖，确保在 ch2 被删除后才创建 A1
  depends_on = [oci_core_instance.ch2_instance]
}

# 为 A1 实例创建调整后的存储卷（代表从ch2释放的资源重新分配到A1，总共150GB）
resource "oci_core_volume" "a1_resize_storage" {
  availability_domain = var.availability_domain
  compartment_id      = var.compartment_id
  display_name        = "a1-resize-storage"  # 重命名以反映用途
  size_in_gbs         = var.a1_storage_size_gb  # 应该设置为150GB，代表A1的新存储大小

  # 确保ch2实例已禁用（模拟终止），以便我们可以重新分配其资源
  lifecycle {
    precondition {
      condition     = var.ch2_enabled == false
      error_message = "为了进行资源重新分配，请先设置 ch2_enabled = false 来模拟终止 ch2 实例."
    }
  }
}

# 将调整后的数据卷附加到 A1 实例
resource "oci_core_volume_attachment" "a1_resize_attachment" {
  count = var.ch2_enabled == false ? 1 : 0  # 仅在 ch2 被"终止"后附加

  attachment_type = "paravirtualized"
  instance_id     = oci_core_instance.a1_instance.id
  volume_id       = oci_core_volume.a1_resize_storage.id
}

# 实例配置变量
variable "compartment_id" {
  description = "OCI Compartment OCID for Korea region"
  type        = string
}

variable "availability_domain" {
  description = "Availability Domain for Korea region resources"
  type        = string
}

variable "image_id" {
  description = "OCID of the OS image to use for instances in Korea"
  type        = string
}

variable "ssh_public_key" {
  description = "SSH Public Key for instance access"
  type        = string
}

variable "ch2_shape" {
  description = "Shape for ch2 instance"
  type        = string
  default     = "VM.Standard2.1"  # 较小的实例
}

variable "ch3_shape" {
  description = "Shape for ch3 instance"
  type        = string
  default     = "VM.Standard2.1"  # 较小的实例
}

variable "a1_shape" {
  description = "Shape for A1 instance"
  type        = string
  default     = "VM.Standard.A1.Flex"  # ARM 架构实例
}

variable "ch2_enabled" {
  description = "Whether to enable ch2 instance (when false, simulates termination for resource reallocation)"
  type        = bool
  default     = false  # 默认不启用，以模拟已终止的状态
}

variable "ch3_enabled" {
  description = "Whether to enable ch3 instance"
  type        = bool
  default     = true  # 默认启用
}

variable "a1_storage_size_gb" {
  description = "Storage size in GB for A1 instance"
  type        = number
  default     = 150  # 默认150GB，代表A1实例的新存储大小（原有100GB + 新增50GB）
}