import * as ec2 from 'aws-cdk-lib/aws-ec2';
import * as ecs from 'aws-cdk-lib/aws-ecs';
import * as cdk from 'aws-cdk-lib/core';
import { Construct } from 'constructs';
import {
  CapacityProviderStrategyItem,
  ContainerConfig,
  DeploymentConfig,
  DnsConfig,
  HealthCheckConfig,
  LoadBalancerRoutingConfig,
  ServiceScalingConfig,
  SpicyEcsService,
  SpicyEcsServiceTags,
} from '../constructs/spicy-ecs-service';

/**
 * Props for SpicyEcsServiceStack
 */
export interface SpicyEcsServiceStackProps extends cdk.StackProps {
  /** ECS Cluster name to import */
  readonly clusterName: string;

  /** VPC ID */
  readonly vpcId: string;

  /** VPC CIDR block */
  readonly vpcCidrBlock?: string;

  /** Number of availability zones (2-4) */
  readonly numberOfAzs: number;

  /** Availability zones */
  readonly availabilityZones: string[];

  /** Private subnet IDs */
  readonly privateSubnetIds: string[];

  /** Service name */
  readonly serviceName: string;

  /** Docker image URI */
  readonly image: string;

  /** Container port */
  readonly containerPort: number;

  /** CPU units */
  readonly cpu?: number;

  /** Memory in MiB */
  readonly memory?: number;

  /** Environment variables (JSON string) */
  readonly environment?: string;

  /** Secrets (JSON string: { "ENV_VAR": "secret-arn" }) */
  readonly secrets?: string;

  /** Desired task count */
  readonly desiredCount?: number;

  /** Capacity provider strategy (JSON string) */
  readonly capacityProviderStrategy?: string;

  /** Scaling configuration */
  readonly scaling?: ServiceScalingConfig;

  /** Health check path */
  readonly healthCheckPath?: string;

  /** Routing configuration */
  readonly routing?: LoadBalancerRoutingConfig;

  /** External ALB listener ARN (for cluster ALB mode) */
  readonly externalListenerArn?: string;

  /** Internal ALB listener ARN (for cluster ALB mode) */
  readonly internalListenerArn?: string;

  /** Public subnet IDs (for individual ALB) */
  readonly publicSubnetIds?: string[];

  /** Cluster logs bucket name (for individual ALB access logs) */
  readonly clusterLogsBucketName?: string;

  /** DNS configuration */
  readonly dns?: DnsConfig;

  /** Deployment configuration */
  readonly deployment?: DeploymentConfig;

  /** Service tags */
  readonly serviceTags: SpicyEcsServiceTags;
}

/**
 * Stack for deploying an ECS Service
 */
export class SpicyEcsServiceStack extends cdk.Stack {
  public readonly service: SpicyEcsService;

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

    // Import VPC
    const vpc = ec2.Vpc.fromVpcAttributes(this, 'ImportedVpc', {
      vpcId: props.vpcId,
      availabilityZones: props.availabilityZones,
      privateSubnetIds: props.privateSubnetIds,
      ...(props.publicSubnetIds && { publicSubnetIds: props.publicSubnetIds }),
    });

    // Import Cluster
    const cluster = ecs.Cluster.fromClusterAttributes(this, 'ImportedCluster', {
      clusterName: props.clusterName,
      vpc,
      securityGroups: [],
    });

    // Parse JSON configs
    const environment = props.environment ? JSON.parse(props.environment) : undefined;
    const secrets = props.secrets ? JSON.parse(props.secrets) : undefined;
    const capacityProviderStrategy: CapacityProviderStrategyItem[] | undefined = props.capacityProviderStrategy
      ? JSON.parse(props.capacityProviderStrategy)
      : undefined;

    // Build container config
    const container: ContainerConfig = {
      image: props.image,
      port: props.containerPort,
      cpu: props.cpu,
      memory: props.memory,
      environment,
      secrets,
    };

    // Build health check config
    const healthCheck: HealthCheckConfig | undefined = props.healthCheckPath
      ? { path: props.healthCheckPath }
      : undefined;

    // Create the service
    this.service = new SpicyEcsService(this, 'EcsService', {
      cluster,
      vpc,
      serviceName: props.serviceName,
      container,
      capacityProviderStrategy,
      desiredCount: props.desiredCount,
      scaling: props.scaling,
      healthCheck,
      routing: props.routing,
      externalListenerArn: props.externalListenerArn,
      internalListenerArn: props.internalListenerArn,
      dns: props.dns,
      deployment: props.deployment,
      tags: props.serviceTags,
    });
  }

  /**
   * Create stack from CDK context
   * Only requires clusterStackName - VPC stack name imported from cluster export, then all VPC details imported from VPC stack
   */
  static fromContext(scope: Construct, id: string, stackProps?: cdk.StackProps): SpicyEcsServiceStack {
    const app = scope.node.root as cdk.App;

    // Required: clusterStackName (VPC stack name imported from cluster export, then VPC details imported from VPC stack)
    const clusterStackName = app.node.tryGetContext('clusterStackName') || app.node.tryGetContext('clusterName');
    if (!clusterStackName) {
      throw new Error(
        'clusterStackName is required. Provide clusterStackName to import VPC stack name from cluster export, then import VPC details from VPC stack.'
      );
    }

    // Required service config
    const serviceName = app.node.tryGetContext('serviceName');
    const image = app.node.tryGetContext('image');
    const containerPort = parseInt(app.node.tryGetContext('containerPort') ?? '3000');

    // Import VPC stack name from cluster stack (cluster exports: ${clusterStackName}-VPCStackName)
    const vpcStackName = cdk.Fn.importValue(`${clusterStackName}-VPCStackName`).toString();

    // Import VPC ID from cluster stack (cluster exports: ${clusterStackName}-VPC)
    const vpcId = cdk.Fn.importValue(`${clusterStackName}-VPC`);

    // Import all VPC details from VPC stack exports
    const vpcCidrBlock = cdk.Fn.importValue(`${vpcStackName}-VPCCIDR`).toString();
    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 VPC subnets.');
    }
    const azs = ['A', 'B', 'C', 'D'].slice(0, Math.min(Math.max(numberOfAzs, 1), 4));

    // Import private subnet IDs from VPC stack
    const privateSubnetIds = azs.map((az) => cdk.Fn.importValue(`${vpcStackName}-PrivateSubnet${az}1ID`).toString());

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

    // ALB stack name is derived from service stackName: ${baseStackName}-alb
    // Remove -blue/-green suffix and add -alb
    const serviceStackName = app.node.tryGetContext('stackName') || id;
    const baseStackName = serviceStackName.replace(/-blue$|-green$/, '');
    const albStackName = `${baseStackName}-alb`;

    // Tags
    const serviceTags: SpicyEcsServiceTags = {
      owner: app.node.tryGetContext('ownerTag') ?? 'Unknown',
      product: app.node.tryGetContext('productTag') ?? 'Unknown',
      component: app.node.tryGetContext('componentTag') ?? serviceName,
      environment: app.node.tryGetContext('environment') ?? 'dev',
      build: app.node.tryGetContext('build'),
    };

    // Optional container config
    const cpu = app.node.tryGetContext('cpu') ? parseInt(app.node.tryGetContext('cpu')) : undefined;
    const memory = app.node.tryGetContext('memory') ? parseInt(app.node.tryGetContext('memory')) : undefined;
    const environment = app.node.tryGetContext('environment_vars'); // JSON string
    const secrets = app.node.tryGetContext('secrets'); // JSON string
    const desiredCount = app.node.tryGetContext('desiredCount')
      ? parseInt(app.node.tryGetContext('desiredCount'))
      : undefined;

    // Capacity provider strategy (JSON string)
    const capacityProviderStrategy = app.node.tryGetContext('capacityProviderStrategy');

    // Scaling
    const minCapacity = app.node.tryGetContext('minCapacity')
      ? parseInt(app.node.tryGetContext('minCapacity'))
      : undefined;
    const maxCapacity = app.node.tryGetContext('maxCapacity')
      ? parseInt(app.node.tryGetContext('maxCapacity'))
      : undefined;
    const targetCpuUtilization = app.node.tryGetContext('targetCpuUtilization')
      ? parseInt(app.node.tryGetContext('targetCpuUtilization'))
      : undefined;
    const targetMemoryUtilization = app.node.tryGetContext('targetMemoryUtilization')
      ? parseInt(app.node.tryGetContext('targetMemoryUtilization'))
      : undefined;
    const targetRequestsPerTarget = app.node.tryGetContext('targetRequestsPerTarget')
      ? parseInt(app.node.tryGetContext('targetRequestsPerTarget'))
      : undefined;

    const scaling: ServiceScalingConfig | undefined =
      minCapacity && maxCapacity
        ? {
            minCapacity,
            maxCapacity,
            targetCpuUtilization,
            targetMemoryUtilization,
            targetRequestsPerTarget,
          }
        : undefined;

    // Health check
    const healthCheckPath = app.node.tryGetContext('healthCheckPath');

    // Routing - ALB details (resolved by pipeline from cluster or ALB stack)
    // Pipeline sets: albLoadBalancerArn, albHttpsListenerArn, albHttpListenerArn in context
    // If not provided in context, fall back to importing from exports (backward compatibility)
    const useClusterAlb = app.node.tryGetContext('useClusterAlb') !== 'false'; // default true

    let existingAlbArn: string | undefined = app.node.tryGetContext('albLoadBalancerArn');
    let existingAlbHttpsListenerArn: string | undefined = app.node.tryGetContext('albHttpsListenerArn');
    let existingAlbHttpListenerArn: string | undefined = app.node.tryGetContext('albHttpListenerArn');

    // If not provided in context, import from exports (backward compatibility)
    if (!existingAlbArn && !useClusterAlb) {
      const albScheme = app.node.tryGetContext('albScheme') || 'internet-facing';
      const prefix = albScheme === 'internet-facing' ? 'internet-facing' : 'internal';
      existingAlbArn = cdk.Fn.importValue(`${albStackName}-${prefix}-arn`).toString();
      existingAlbHttpsListenerArn = cdk.Fn.importValue(`${albStackName}-${prefix}-https-listener`).toString();
      existingAlbHttpListenerArn = cdk.Fn.importValue(`${albStackName}-${prefix}-http-listener`).toString();
    }

    // ALB listeners (for cluster ALB mode) - import from cluster stack (backward compatibility)
    // Cluster exports: ${clusterStackName}-internet-facing-https-listener, ${clusterStackName}-internal-https-listener
    let externalListenerArn = app.node.tryGetContext('externalListenerArn');
    let internalListenerArn = app.node.tryGetContext('internalListenerArn');

    // Auto-import listener ARNs from cluster stack if clusterStackName provided and listeners not explicitly set
    // This matches the old pattern: Fn::ImportValue: !Sub "${ClusterName}-internet-facing-https-listener"
    // Only used if albLoadBalancerArn is not provided (backward compatibility)
    if (!existingAlbArn && clusterStackName && !externalListenerArn && !internalListenerArn) {
      const useExternal = app.node.tryGetContext('useExternalALB') === 'true';
      const useInternal = app.node.tryGetContext('useInternalALB') === 'true';
      const albScheme =
        app.node.tryGetContext('albScheme') ||
        (useExternal ? 'internet-facing' : useInternal ? 'internal' : 'internet-facing');

      // Try HTTPS listener first (most common), fall back to HTTP if needed
      if (albScheme === 'internet-facing' || useExternal) {
        externalListenerArn = cdk.Fn.importValue(`${clusterStackName}-internet-facing-https-listener`).toString();
      } else if (albScheme === 'internal' || useInternal) {
        internalListenerArn = cdk.Fn.importValue(`${clusterStackName}-internal-https-listener`).toString();
      }
    }
    const hostHeader = app.node.tryGetContext('hostHeader');
    const pathPatterns = app.node.tryGetContext('pathPatterns')?.split(',');
    const priority = app.node.tryGetContext('priority') ? parseInt(app.node.tryGetContext('priority')) : undefined;
    const useExternal = app.node.tryGetContext('useExternalALB') === 'true';
    const useInternal = app.node.tryGetContext('useInternalALB') === 'true';

    let routing: LoadBalancerRoutingConfig | undefined;

    // Use unified ALB parameters if provided (from pipeline resolveAlbDetails)
    // Otherwise fall back to cluster ALB mode (backward compatibility)
    const useBgCommonAlb = existingAlbArn != null;

    if (useBgCommonAlb) {
      // ALB details are provided by pipeline (resolved from cluster or ALB stack)
      // Pipeline sets: albLoadBalancerArn, albHttpsListenerArn, albHttpListenerArn
      if (!hostHeader && (!pathPatterns || pathPatterns.length === 0)) {
        throw new Error('When using ALB, either hostHeader or pathPatterns must be provided for routing');
      }
      // Use unified ALB parameters (from cluster or ALB stack, resolved by pipeline)
      routing = {
        existingALB: existingAlbArn!, // ALB ARN (from cluster or ALB stack)
        httpsListenerArn: existingAlbHttpsListenerArn, // HTTPS listener ARN (if certificate provided)
        httpListenerArn: existingAlbHttpListenerArn, // HTTP listener ARN (if no certificate or for redirect)
        hostHeader,
        pathPatterns,
        priority,
        stickiness: app.node.tryGetContext('stickiness') !== 'false',
        stickinessDuration: app.node.tryGetContext('stickinessDuration')
          ? parseInt(app.node.tryGetContext('stickinessDuration'))
          : undefined,
        deregistrationDelay: app.node.tryGetContext('deregistrationDelay')
          ? parseInt(app.node.tryGetContext('deregistrationDelay'))
          : undefined,
      };

      // Blue/Green DNS configuration (for bg-common ALB)
      // Note: Both DNS records are created and point to the same ALB.
      // Routing is controlled by listener rule priorities, not DNS changes.
      // The isActive flag is informational - both records are always created.
      const activeHostname = app.node.tryGetContext('activeHostname');
      const inactiveHostname = app.node.tryGetContext('inactiveHostname');
      const bgHostedZoneId = app.node.tryGetContext('bgHostedZoneId') || app.node.tryGetContext('hostedZoneId');
      const isActive = app.node.tryGetContext('isActive') !== 'false'; // default true

      if (activeHostname && inactiveHostname && bgHostedZoneId) {
        routing.blueGreenDns = {
          activeHostname,
          inactiveHostname,
          hostedZoneId: bgHostedZoneId,
          isActive, // Informational only - both DNS records are always created
        };
      }
    } else if (hostHeader || pathPatterns) {
      // Cluster ALB mode (existing behavior)
      // Validate required parameters for cluster ALB
      // Note: externalListenerArn/internalListenerArn were declared above and may have been imported if clusterStackName was provided

      if (!externalListenerArn && !internalListenerArn) {
        throw new Error('When using cluster ALB, either externalListenerArn or internalListenerArn must be provided');
      }
      if (externalListenerArn && internalListenerArn) {
        throw new Error(
          'Cannot use both externalListenerArn and internalListenerArn. Choose either external OR internal, not both'
        );
      }
      if (useExternal && useInternal) {
        throw new Error(
          'Cannot use both useExternalALB and useInternalALB. Choose either external OR internal, not both'
        );
      }
      if (useExternal && !externalListenerArn) {
        throw new Error('useExternalALB=true requires externalListenerArn to be provided');
      }
      if (useInternal && !internalListenerArn) {
        throw new Error('useInternalALB=true requires internalListenerArn to be provided');
      }
      // Auto-detect if not explicitly set
      const detectedExternal = externalListenerArn ? true : false;
      const detectedInternal = internalListenerArn ? true : false;

      // Use explicit flags if set, otherwise auto-detect from listener ARNs
      routing = {
        external: useExternal || (detectedExternal && !useInternal),
        internal: useInternal || (detectedInternal && !useExternal),
        hostHeader,
        pathPatterns,
        priority: priority ?? 100,
        stickiness: app.node.tryGetContext('stickiness') === 'true',
        stickinessDuration: app.node.tryGetContext('stickinessDuration')
          ? parseInt(app.node.tryGetContext('stickinessDuration'))
          : undefined,
        deregistrationDelay: app.node.tryGetContext('deregistrationDelay')
          ? parseInt(app.node.tryGetContext('deregistrationDelay'))
          : undefined,
      };
    } else {
      // No routing configured - this is valid for services without ALB (e.g., workers, pub/sub)
      // No validation needed - service can run without ALB
    }

    // DNS (for cluster ALB mode)
    const hostedZoneId = app.node.tryGetContext('hostedZoneId');
    const zoneName = app.node.tryGetContext('zoneName');
    const recordName = app.node.tryGetContext('recordName');

    const dns: DnsConfig | undefined =
      hostedZoneId && zoneName && recordName
        ? {
            hostedZoneId,
            zoneName,
            recordName,
          }
        : undefined;

    // Deployment
    const circuitBreaker = app.node.tryGetContext('circuitBreaker') !== 'false';
    const enableExecuteCommand = app.node.tryGetContext('enableExecuteCommand') !== 'false';

    const deployment: DeploymentConfig = {
      circuitBreaker,
      enableExecuteCommand,
    };

    // Public subnet IDs (for individual ALB)
    const publicSubnetIds = app.node.tryGetContext('publicSubnetIds')?.split(',');

    // Auto-import logs bucket from cluster stack if not explicitly provided
    // This matches the old pattern: Fn::ImportValue: !Sub "${ClusterName}-logs-s3-bucket"
    // Cluster exports: ${clusterStackName}-logs-s3-bucket
    let clusterLogsBucketName = app.node.tryGetContext('clusterLogsBucketName');
    if (!clusterLogsBucketName && clusterStackName) {
      clusterLogsBucketName = cdk.Fn.importValue(`${clusterStackName}-logs-s3-bucket`).toString();
    }
    // Note: clusterLogsBucketName is optional (only needed for bg-common ALB access logs)
    // We don't fail if it's missing - it's only used if provided

    return new SpicyEcsServiceStack(scope, id, {
      ...stackProps,
      clusterName: clusterStackName,
      vpcId: vpcId.toString(),
      vpcCidrBlock,
      numberOfAzs,
      availabilityZones,
      privateSubnetIds,
      serviceName,
      image,
      containerPort,
      cpu,
      memory,
      environment,
      secrets,
      desiredCount,
      capacityProviderStrategy,
      scaling,
      healthCheckPath,
      routing,
      externalListenerArn,
      internalListenerArn,
      publicSubnetIds,
      clusterLogsBucketName,
      dns,
      deployment,
      serviceTags,
    });
  }
}