/**
 * Shared CDK construct: VPN-accessible EC2 instance on the Sea Haven private subnet.
 *
 * Encapsulates the repeating pattern from file-share and forgejo stacks:
 * - Looks up the Sea Haven VPC and private subnet
 * - Creates a security group with VPN (10.10.0.0/16) and VPC (10.20.0.0/16) ingress
 * - Creates an IAM role with SSM and Secrets Manager access
 * - Launches a t4g ARM64 AL2023 instance with encrypted EBS
 * - Sets up DLM daily snapshots with 30-day retention
 * - Exports InstanceId and PrivateIp as CloudFormation outputs
 *
 * Copy this file into your project's lib/constructs/ directory and import it.
 */

import * as cdk from "aws-cdk-lib";
import * as ec2 from "aws-cdk-lib/aws-ec2";
import * as iam from "aws-cdk-lib/aws-iam";
import * as dlm from "aws-cdk-lib/aws-dlm";
import { Construct } from "constructs";

export interface IngressPort {
  readonly port: number;
  readonly description: string;
}

export interface VpnEc2InstanceProps {
  readonly name: string;
  readonly instanceType?: ec2.InstanceType;
  readonly rootVolumeSize?: number;
  readonly dataVolumeSize?: number;
  readonly ingressPorts: IngressPort[];
  readonly secretsPrefix: string;
  readonly userData?: ec2.UserData;
  readonly additionalPolicies?: iam.PolicyStatement[];
  readonly snapshotRetentionDays?: number;
}

const VPC_ID = "vpc-0d3d4b67bd0cf8a68";
const PRIVATE_SUBNET_ID = "subnet-04e38c507e96f1926";
const PRIVATE_SUBNET_AZ = "us-east-1a";
const ACCOUNT_ID = "328440206208";
const REGION = "us-east-1";
const VPN_CIDR = "10.10.0.0/16";
const VPC_CIDR = "10.20.0.0/16";

export class VpnEc2Instance extends Construct {
  public readonly instance: ec2.Instance;
  public readonly securityGroup: ec2.SecurityGroup;
  public readonly role: iam.Role;

  constructor(scope: Construct, id: string, props: VpnEc2InstanceProps) {
    super(scope, id);

    const vpc = ec2.Vpc.fromLookup(this, "Vpc", { vpcId: VPC_ID });

    const subnet = ec2.Subnet.fromSubnetAttributes(this, "PrivateSubnet", {
      subnetId: PRIVATE_SUBNET_ID,
      availabilityZone: PRIVATE_SUBNET_AZ,
    });

    this.securityGroup = new ec2.SecurityGroup(this, "SecurityGroup", {
      vpc,
      securityGroupName: props.name,
      description: `${props.name} — VPN and VPC access`,
      allowAllOutbound: true,
    });

    for (const ingress of props.ingressPorts) {
      this.securityGroup.addIngressRule(
        ec2.Peer.ipv4(VPN_CIDR),
        ec2.Port.tcp(ingress.port),
        `${ingress.description} from VPN`
      );
      this.securityGroup.addIngressRule(
        ec2.Peer.ipv4(VPC_CIDR),
        ec2.Port.tcp(ingress.port),
        `${ingress.description} from VPC`
      );
    }

    this.role = new iam.Role(this, "InstanceRole", {
      roleName: `${props.name}-instance`,
      assumedBy: new iam.ServicePrincipal("ec2.amazonaws.com"),
      managedPolicies: [
        iam.ManagedPolicy.fromAwsManagedPolicyName("AmazonSSMManagedInstanceCore"),
      ],
    });

    this.role.addToPolicy(
      new iam.PolicyStatement({
        actions: ["secretsmanager:GetSecretValue"],
        resources: [
          `arn:aws:secretsmanager:${REGION}:${ACCOUNT_ID}:secret:${props.secretsPrefix}/*`,
        ],
      })
    );

    if (props.additionalPolicies) {
      for (const policy of props.additionalPolicies) {
        this.role.addToPolicy(policy);
      }
    }

    const blockDevices: ec2.BlockDevice[] = [
      {
        deviceName: "/dev/xvda",
        volume: ec2.BlockDeviceVolume.ebs(props.rootVolumeSize ?? 20, {
          volumeType: ec2.EbsDeviceVolumeType.GP3,
          encrypted: true,
        }),
      },
    ];

    if (props.dataVolumeSize) {
      blockDevices.push({
        deviceName: "/dev/xvdf",
        volume: ec2.BlockDeviceVolume.ebs(props.dataVolumeSize, {
          volumeType: ec2.EbsDeviceVolumeType.GP3,
          encrypted: true,
        }),
      });
    }

    this.instance = new ec2.Instance(this, "Instance", {
      instanceName: props.name,
      vpc,
      vpcSubnets: { subnets: [subnet] },
      instanceType:
        props.instanceType ??
        ec2.InstanceType.of(ec2.InstanceClass.T4G, ec2.InstanceSize.SMALL),
      machineImage: ec2.MachineImage.latestAmazonLinux2023({
        cpuType: ec2.AmazonLinuxCpuType.ARM_64,
      }),
      securityGroup: this.securityGroup,
      role: this.role,
      userData: props.userData,
      blockDevices,
    });

    const backupTag = `${props.name}-backup`;
    cdk.Tags.of(this.instance).add(backupTag, "true");

    const dlmRole = new iam.Role(this, "DlmRole", {
      roleName: `${props.name}-dlm`,
      assumedBy: new iam.ServicePrincipal("dlm.amazonaws.com"),
      managedPolicies: [
        iam.ManagedPolicy.fromAwsManagedPolicyName(
          "service-role/AWSDataLifecycleManagerServiceRole"
        ),
      ],
    });

    new dlm.CfnLifecyclePolicy(this, "SnapshotPolicy", {
      description: `Nightly EBS snapshots for ${props.name}`,
      state: "ENABLED",
      executionRoleArn: dlmRole.roleArn,
      policyDetails: {
        resourceTypes: ["INSTANCE"],
        targetTags: [{ key: backupTag, value: "true" }],
        schedules: [
          {
            name: `${props.name}-nightly`,
            createRule: { interval: 24, intervalUnit: "HOURS", times: ["06:00"] },
            retainRule: { count: props.snapshotRetentionDays ?? 30 },
            copyTags: true,
            tagsToAdd: [{ key: backupTag, value: "true" }],
          },
        ],
      },
    });

    new cdk.CfnOutput(this, "InstanceId", {
      value: this.instance.instanceId,
    });

    new cdk.CfnOutput(this, "PrivateIp", {
      value: this.instance.instancePrivateIp,
      description: `Private IP for ${props.name}`,
    });
  }
}