import * as ec2 from 'aws-cdk-lib/aws-ec2';
import * as cdk from 'aws-cdk-lib/core';
import { Construct } from 'constructs';
import {
  ClusterScalingConfig,
  LoadBalancerConfig,
  SpicyEcsCluster,
  SpicyEcsClusterTags,
  SpotConfig,
} from '../constructs/spicy-ecs-cluster';

/**
 * Props for SpicyEcsClusterStack
 */
export interface SpicyEcsClusterStackProps extends cdk.StackProps {
  /**
   * VPC stack name to import VPC details from (required)
   * All VPC details (VPC ID, CIDR, subnets, AZs) will be imported from VPC stack exports
   */
  readonly vpcStackName: string;

  /**
   * Number of availability zones (2-4) used by the VPC
   * Must match the VPC stack export to correctly import subnet IDs.
   */
  readonly numberOfAzs: number;

  /**
   * EC2 instance type
   * @default m5a.large
   */
  readonly instanceType?: string;

  /**
   * Additional instance types for mixed instances policy
   */
  readonly additionalInstanceTypes?: string[];

  /**
   * EC2 Key Pair name
   */
  readonly keyName?: string;

  /**
   * EBS volume size in GB
   * @default 100
   */
  readonly ebsVolumeSize?: number;

  /**
   * Enable Container Insights
   * @default true
   */
  readonly containerInsights?: boolean;

  /**
   * Minimum cluster size
   * @default 2
   */
  readonly minClusterSize?: number;

  /**
   * Maximum cluster size
   * @default 4
   */
  readonly maxClusterSize?: number;

  /**
   * Target capacity utilization percentage
   * @default 100
   */
  readonly targetCapacityPercent?: number;

  /**
   * Enable Spot instances
   * @default false
   */
  readonly spotEnabled?: boolean;

  /**
   * On-Demand percentage when Spot is enabled
   * @default 100
   */
  readonly onDemandPercentage?: number;

  /**
   * Spot allocation strategy
   * @default capacity-optimized
   */
  readonly spotAllocationStrategy?: 'lowest-price' | 'capacity-optimized' | 'capacity-optimized-prioritized';

  /**
   * Create external (internet-facing) load balancer
   * @default false
   */
  readonly createExternalLoadBalancer?: boolean;

  /**
   * Create internal load balancer
   * @default false
   */
  readonly createInternalLoadBalancer?: boolean;

  /**
   * SSL certificate ARN for HTTPS
   */
  readonly certificateArn?: string;

  /**
   * Enable Fargate capacity providers (adds both FARGATE and FARGATE_SPOT)
   * @default false
   */
  readonly enableFargate?: boolean;

  /**
   * Draining timeout in seconds
   * @default 900
   */
  readonly drainingTimeout?: number;

  /**
   * Max instance lifetime in seconds
   * @default 604800 (7 days)
   */
  readonly maxInstanceLifetime?: number;

  /**
   * Required cluster tags
   */
  readonly clusterTags: SpicyEcsClusterTags;
}

/**
 * Stack for deploying a SpicyEcsCluster
 */
export class SpicyEcsClusterStack extends cdk.Stack {
  public readonly cluster: SpicyEcsCluster;

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

    // Validate required inputs
    if (!props.vpcStackName) {
      throw new Error('vpcStackName is required for ECS Cluster stack.');
    }

    // Import all VPC details from VPC stack exports
    // VPC stack exports: ${vpcStackName}-VPCID, ${vpcStackName}-VPCCIDR, ${vpcStackName}-NumberOfAZs, etc.
    const vpcId = cdk.Fn.importValue(`${props.vpcStackName}-VPCID`);
    const vpcCidrBlock = cdk.Fn.importValue(`${props.vpcStackName}-VPCCIDR`).toString();
    if (!props.numberOfAzs || Number.isNaN(props.numberOfAzs)) {
      throw new Error('numberOfAzs is required and must be a number (2-4) to import subnets.');
    }
    const azs = ['A', 'B', 'C', 'D'].slice(0, Math.min(Math.max(props.numberOfAzs, 1), 4));

    // Import private subnet IDs (always needed for ECS instances)
    const privateSubnetIds = azs.map((az) =>
      cdk.Fn.importValue(`${props.vpcStackName}-PrivateSubnet${az}1ID`).toString()
    );

    // Import public subnet IDs if external load balancer is requested
    let publicSubnetIds: string[] | undefined;
    if (props.createExternalLoadBalancer) {
      publicSubnetIds = azs.map((az) => cdk.Fn.importValue(`${props.vpcStackName}-PublicSubnet${az}ID`).toString());
    }

    // Derive availability zones from region
    const region = cdk.Stack.of(this).region;
    const availabilityZones = azs.map((az) => `${region}${az.toLowerCase()}`);

    // Build VPC attributes for importing
    const vpcAttributes: ec2.VpcAttributes = {
      vpcId: vpcId.toString(),
      availabilityZones,
      privateSubnetIds,
      ...(publicSubnetIds && publicSubnetIds.length > 0 ? { publicSubnetIds } : {}),
    };

    const vpc = ec2.Vpc.fromVpcAttributes(this, 'ImportedVpc', vpcAttributes);

    // Parse instance types
    const instanceType = props.instanceType
      ? new ec2.InstanceType(props.instanceType)
      : ec2.InstanceType.of(ec2.InstanceClass.M5A, ec2.InstanceSize.LARGE);

    const additionalInstanceTypes = props.additionalInstanceTypes?.map((t) => new ec2.InstanceType(t));

    // Build scaling config
    const scaling: ClusterScalingConfig = {
      minCapacity: props.minClusterSize ?? 2,
      maxCapacity: props.maxClusterSize ?? 4,
      targetCapacityPercent: props.targetCapacityPercent ?? 100,
    };

    // Build spot config
    const spot: SpotConfig = {
      enabled: props.spotEnabled ?? false,
      onDemandPercentage: props.onDemandPercentage ?? 100,
      spotAllocationStrategy: props.spotAllocationStrategy ?? 'capacity-optimized',
    };

    // Build load balancer config
    const loadBalancer: LoadBalancerConfig = {
      createExternal: props.createExternalLoadBalancer ?? false,
      createInternal: props.createInternalLoadBalancer ?? false,
      certificateArn: props.certificateArn,
    };

    // Create the cluster
    this.cluster = new SpicyEcsCluster(this, 'EcsCluster', {
      vpc,
      vpcCidrBlock,
      vpcStackName: props.vpcStackName,
      instanceType,
      additionalInstanceTypes,
      keyName: props.keyName,
      ebsVolumeSize: props.ebsVolumeSize,
      containerInsights: props.containerInsights,
      scaling,
      spot,
      loadBalancer,
      enableFargate: props.enableFargate,
      drainingTimeout: props.drainingTimeout,
      maxInstanceLifetime: props.maxInstanceLifetime,
      tags: props.clusterTags,
      instanceSubnets: { subnetType: ec2.SubnetType.PRIVATE_WITH_EGRESS },
      externalSubnets: publicSubnetIds ? { subnetType: ec2.SubnetType.PUBLIC } : undefined,
      internalSubnets: { subnetType: ec2.SubnetType.PRIVATE_WITH_EGRESS },
    });
  }

  /**
   * Create stack from CDK context
   * Only requires vpcStackName - all VPC details are imported from VPC stack exports
   */
  static fromContext(scope: Construct, id: string, stackProps?: cdk.StackProps): SpicyEcsClusterStack {
    const app = scope.node.root as cdk.App;

    // Required: VPC stack name (all VPC details imported from exports)
    const vpcStackName = app.node.tryGetContext('vpcStackName');
    if (!vpcStackName) {
      throw new Error(
        'vpcStackName is required. Provide vpcStackName to import all VPC details from VPC stack exports.'
      );
    }
    const numberOfAzsRaw = app.node.tryGetContext('numberOfAzs');
    const numberOfAzs = numberOfAzsRaw ? parseInt(numberOfAzsRaw, 10) : NaN;
    if (!numberOfAzs || Number.isNaN(numberOfAzs)) {
      throw new Error('numberOfAzs is required in context (2-4) to import subnets from the VPC stack.');
    }

    // Tags
    const tags: SpicyEcsClusterTags = {
      owner: app.node.tryGetContext('ownerTag') ?? 'Unknown',
      product: app.node.tryGetContext('productTag') ?? 'Unknown',
      component: app.node.tryGetContext('componentTag') ?? 'ecs-cluster',
      environment: app.node.tryGetContext('environment') ?? 'dev',
      build: app.node.tryGetContext('build'),
    };

    // Optional context values
    const instanceType = app.node.tryGetContext('instanceType');
    const additionalInstanceTypes = app.node.tryGetContext('additionalInstanceTypes')?.split(',');
    const keyName = app.node.tryGetContext('keyName');
    const ebsVolumeSize = app.node.tryGetContext('ebsVolumeSize')
      ? parseInt(app.node.tryGetContext('ebsVolumeSize'))
      : undefined;
    const containerInsights = app.node.tryGetContext('containerInsights') !== 'false';

    // Scaling
    const minClusterSize = app.node.tryGetContext('minClusterSize')
      ? parseInt(app.node.tryGetContext('minClusterSize'))
      : undefined;
    const maxClusterSize = app.node.tryGetContext('maxClusterSize')
      ? parseInt(app.node.tryGetContext('maxClusterSize'))
      : undefined;
    const targetCapacityPercent = app.node.tryGetContext('targetCapacityPercent')
      ? parseInt(app.node.tryGetContext('targetCapacityPercent'))
      : undefined;

    // Spot
    const spotEnabled = app.node.tryGetContext('spotEnabled') === 'true';
    const onDemandPercentage = app.node.tryGetContext('onDemandPercentage')
      ? parseInt(app.node.tryGetContext('onDemandPercentage'))
      : undefined;
    const spotAllocationStrategy = app.node.tryGetContext('spotAllocationStrategy') as
      | 'lowest-price'
      | 'capacity-optimized'
      | 'capacity-optimized-prioritized'
      | undefined;

    // Load balancers
    const createExternalLoadBalancer = app.node.tryGetContext('createExternalLoadBalancer') === 'true';
    const createInternalLoadBalancer = app.node.tryGetContext('createInternalLoadBalancer') === 'true';
    const certificateArn = app.node.tryGetContext('certificateArn');

    // Fargate
    const enableFargate = app.node.tryGetContext('enableFargate') === 'true';

    // Timeouts
    const drainingTimeout = app.node.tryGetContext('drainingTimeout')
      ? parseInt(app.node.tryGetContext('drainingTimeout'))
      : undefined;
    const maxInstanceLifetime = app.node.tryGetContext('maxInstanceLifetime')
      ? parseInt(app.node.tryGetContext('maxInstanceLifetime'))
      : undefined;

    return new SpicyEcsClusterStack(scope, id, {
      ...stackProps,
      vpcStackName,
      instanceType,
      additionalInstanceTypes,
      keyName,
      ebsVolumeSize,
      containerInsights,
      minClusterSize,
      maxClusterSize,
      targetCapacityPercent,
      spotEnabled,
      onDemandPercentage,
      spotAllocationStrategy,
      createExternalLoadBalancer,
      createInternalLoadBalancer,
      certificateArn,
      enableFargate,
      drainingTimeout,
      maxInstanceLifetime,
      numberOfAzs,
      clusterTags: tags,
    });
  }
}