import * as cdk from 'aws-cdk-lib';
import * as ec2 from 'aws-cdk-lib/aws-ec2';
import * as rds from 'aws-cdk-lib/aws-rds';
import * as s3 from 'aws-cdk-lib/aws-s3';
import * as sqs from 'aws-cdk-lib/aws-sqs';
import * as cognito from 'aws-cdk-lib/aws-cognito';
import * as logs from 'aws-cdk-lib/aws-logs';
import * as secretsmanager from 'aws-cdk-lib/aws-secretsmanager';
import * as sns from 'aws-cdk-lib/aws-sns';
import * as snsSubscriptions from 'aws-cdk-lib/aws-sns-subscriptions';
import * as cloudwatch from 'aws-cdk-lib/aws-cloudwatch';
import * as cloudwatchActions from 'aws-cdk-lib/aws-cloudwatch-actions';
import { Construct } from 'constructs';
import { EnvConfig } from './config';

export interface FoundationStackProps extends cdk.StackProps {
  config: EnvConfig;
}

export class FoundationStack extends cdk.Stack {
  public readonly vpc: ec2.IVpc;
  public readonly lambdaSecurityGroup: ec2.ISecurityGroup;
  public readonly dbSecret: secretsmanager.ISecret;
  public readonly dbCluster: rds.IDatabaseCluster;
  public readonly uploadsBucket: s3.IBucket;
  public readonly generatedBucket: s3.IBucket;
  public readonly libraryBucket: s3.IBucket;
  public readonly jobsQueue: sqs.IQueue;
  public readonly userPool: cognito.IUserPool;
  public readonly alarmTopic: sns.ITopic;
  public readonly webClientId: string;
  public readonly mobileClientId: string;

  constructor(scope: Construct, id: string, props: FoundationStackProps) {
    super(scope, id, props);
    const { config } = props;

    // VPC: 2 AZs, public + private subnets, single NAT Gateway
    this.vpc = new ec2.Vpc(this, 'Vpc', {
      vpcName: `proposal-system-vpc${config.stackSuffix}`,
      maxAzs: 2,
      natGateways: 1,
      subnetConfiguration: [
        {
          name: 'public',
          subnetType: ec2.SubnetType.PUBLIC,
          cidrMask: 24,
        },
        {
          name: 'private',
          subnetType: ec2.SubnetType.PRIVATE_WITH_EGRESS,
          cidrMask: 24,
        },
      ],
    });

    // VPC Endpoints
    this.vpc.addGatewayEndpoint('S3Endpoint', {
      service: ec2.GatewayVpcEndpointAwsService.S3,
    });

    this.vpc.addInterfaceEndpoint('SecretsManagerEndpoint', {
      service: ec2.InterfaceVpcEndpointAwsService.SECRETS_MANAGER,
    });

    // Security Groups
    this.lambdaSecurityGroup = new ec2.SecurityGroup(this, 'LambdaSg', {
      vpc: this.vpc,
      securityGroupName: `proposal-system-lambda-sg${config.stackSuffix}`,
      description: 'Security group for proposal system Lambda functions',
      allowAllOutbound: true,
    });

    const rdsSg = new ec2.SecurityGroup(this, 'RdsSg', {
      vpc: this.vpc,
      securityGroupName: `proposal-system-rds-sg${config.stackSuffix}`,
      description: 'Security group for proposal system RDS instance',
      allowAllOutbound: false,
    });

    rdsSg.addIngressRule(
      this.lambdaSecurityGroup,
      ec2.Port.tcp(5432),
      'Allow PostgreSQL from Lambda SG'
    );

    // Aurora PostgreSQL Serverless v2 — pgvector store for the Bedrock Knowledge Base.
    // PR3: replaced the RDS instance + OpenSearch Serverless with Aurora + pgvector
    // (kills the AOSS OCU floor; scales toward 0 ACU when idle). Data API is required
    // by Bedrock Knowledge Bases to query the vector table.
    // Construct ID is 'AuroraCluster' (not 'Database') so CloudFormation gets a NEW
    // logical ID for the cluster — the old RDS DBInstance shared logical ID 'Database*'
    // and CFN forbids changing a resource's type in place ("Update of resource type is
    // not permitted"). A distinct ID makes it a clean replace instead.
    const dbCluster = new rds.DatabaseCluster(this, 'AuroraCluster', {
      clusterIdentifier: `proposal-system-db${config.stackSuffix}`,
      // 15.17 = latest available aurora-postgresql 15.x (15.4 was retired by RDS —
      // "Cannot find version 15.4"). Stays on major 15 for pgvector / ADR 0001 compat.
      engine: rds.DatabaseClusterEngine.auroraPostgres({
        version: rds.AuroraPostgresEngineVersion.VER_15_17,
      }),
      vpc: this.vpc,
      vpcSubnets: { subnetType: ec2.SubnetType.PRIVATE_WITH_EGRESS },
      securityGroups: [rdsSg],
      writer: rds.ClusterInstance.serverlessV2('writer'),
      serverlessV2MinCapacity: 0.5,
      serverlessV2MaxCapacity: 4,
      enableDataApi: true,
      storageEncrypted: true,
      // Aurora native automated backups (PITR). 14-day retention for the prod tenant;
      // a dedicated AWS Backup vault + cross-account restore test is a tracked follow-up
      // (no org central-backup design exists yet — see the prod-deploy plan Phase 4 fallback).
      backup: { retention: cdk.Duration.days(14), preferredWindow: '07:00-08:00' },
      deletionProtection: config.retainData,
      removalPolicy: config.retainData ? cdk.RemovalPolicy.RETAIN : cdk.RemovalPolicy.DESTROY,
      defaultDatabaseName: 'proposals',
      credentials: rds.Credentials.fromGeneratedSecret('proposalsadmin', {
        secretName: `proposal-system/db-credentials${config.stackSuffix}`,
      }),
    });

    this.dbSecret = dbCluster.secret!;
    this.dbCluster = dbCluster;

    // S3 Buckets
    // Fix: INF-M5 — enforce HTTPS-only access on all S3 buckets
    this.uploadsBucket = new s3.Bucket(this, 'UploadsBucket', {
      bucketName: `proposal-system-uploads-${this.account}${config.stackSuffix}`,
      encryption: s3.BucketEncryption.S3_MANAGED,
      enforceSSL: true,
      versioned: true,
      blockPublicAccess: s3.BlockPublicAccess.BLOCK_ALL,
      lifecycleRules: [
        {
          transitions: [
            {
              storageClass: s3.StorageClass.INFREQUENT_ACCESS,
              transitionAfter: cdk.Duration.days(90),
            },
          ],
        },
      ],
      cors: [
        {
          allowedMethods: [s3.HttpMethods.PUT, s3.HttpMethods.POST],
          allowedOrigins: config.s3CorsOrigins,
          allowedHeaders: ['*'],
          maxAge: 3600,
        },
      ],
      removalPolicy: config.retainData ? cdk.RemovalPolicy.RETAIN : cdk.RemovalPolicy.DESTROY,
    });
    cdk.Tags.of(this.uploadsBucket).add('Purpose', 'Vendor PDFs and dispatcher attachments');
    cdk.Tags.of(this.uploadsBucket).add('ManagedBy', 'proposal-system');

    this.generatedBucket = new s3.Bucket(this, 'GeneratedBucket', {
      bucketName: `proposal-system-generated-${this.account}${config.stackSuffix}`,
      encryption: s3.BucketEncryption.S3_MANAGED,
      enforceSSL: true, // Fix: INF-M5
      versioned: true,
      blockPublicAccess: s3.BlockPublicAccess.BLOCK_ALL,
      removalPolicy: config.retainData ? cdk.RemovalPolicy.RETAIN : cdk.RemovalPolicy.DESTROY,
    });
    cdk.Tags.of(this.generatedBucket).add('Purpose', 'Generated proposal PDFs');
    cdk.Tags.of(this.generatedBucket).add('ManagedBy', 'proposal-system');

    this.libraryBucket = new s3.Bucket(this, 'LibraryBucket', {
      bucketName: `proposal-system-library-${this.account}${config.stackSuffix}`,
      encryption: s3.BucketEncryption.S3_MANAGED,
      enforceSSL: true, // Fix: INF-M5
      versioned: true,
      blockPublicAccess: s3.BlockPublicAccess.BLOCK_ALL,
      removalPolicy: config.retainData ? cdk.RemovalPolicy.RETAIN : cdk.RemovalPolicy.DESTROY,
    });
    cdk.Tags.of(this.libraryBucket).add('Purpose', 'Historical proposal library for RAG');
    cdk.Tags.of(this.libraryBucket).add('ManagedBy', 'proposal-system');

    // SQS Queue + DLQ
    const dlq = new sqs.Queue(this, 'JobsDlq', {
      queueName: `proposal-system-jobs-dlq${config.stackSuffix}`,
      retentionPeriod: cdk.Duration.days(14),
    });

    this.jobsQueue = new sqs.Queue(this, 'JobsQueue', {
      queueName: `proposal-system-jobs${config.stackSuffix}`,
      visibilityTimeout: cdk.Duration.seconds(720),
      deadLetterQueue: {
        queue: dlq,
        maxReceiveCount: 3,
      },
    });

    // Cognito User Pool
    const userPool = new cognito.UserPool(this, 'UserPool', {
      userPoolName: `proposal-system-auth${config.stackSuffix}`,
      selfSignUpEnabled: false,
      signInAliases: { email: true },
      standardAttributes: {
        email: { required: true, mutable: true },
        fullname: { required: true, mutable: true },
      },
      passwordPolicy: {
        minLength: 12,
        requireUppercase: true,
        requireLowercase: true,
        requireDigits: true,
        requireSymbols: false,
      },
      accountRecovery: cognito.AccountRecovery.EMAIL_ONLY,
      removalPolicy: config.retainData ? cdk.RemovalPolicy.RETAIN : cdk.RemovalPolicy.DESTROY,
    });

    this.userPool = userPool;

    // Cognito Groups
    new cognito.CfnUserPoolGroup(this, 'DispatchersGroup', {
      userPoolId: userPool.userPoolId,
      groupName: 'dispatchers',
      description: 'Dispatchers who submit proposal requests',
    });

    new cognito.CfnUserPoolGroup(this, 'AdminsGroup', {
      userPoolId: userPool.userPoolId,
      groupName: 'admins',
      description: 'Admins who review and approve proposals',
    });

    new cognito.CfnUserPoolGroup(this, 'SysadminsGroup', {
      userPoolId: userPool.userPoolId,
      groupName: 'sysadmins',
      description: 'System administrators',
    });

    // Cognito Domain
    userPool.addDomain('CognitoDomain', {
      cognitoDomain: { domainPrefix: config.cognitoDomainPrefix },
    });

    // Web App Client (PKCE)
    const webClient = userPool.addClient('WebClient', {
      userPoolClientName: 'proposal-system-web',
      generateSecret: false,
      authFlows: {
        userSrp: true,
      },
      oAuth: {
        flows: { authorizationCodeGrant: true },
        scopes: [
          cognito.OAuthScope.OPENID,
          cognito.OAuthScope.EMAIL,
          cognito.OAuthScope.PROFILE,
        ],
        callbackUrls: config.webCallbackUrls,
        logoutUrls: config.webLogoutUrls,
      },
    });

    this.webClientId = webClient.userPoolClientId;

    // Mobile App Client (PKCE)
    const mobileClient = userPool.addClient('MobileClient', {
      userPoolClientName: 'proposal-system-mobile',
      generateSecret: false,
      authFlows: {
        userSrp: true,
      },
      oAuth: {
        flows: { authorizationCodeGrant: true },
        scopes: [
          cognito.OAuthScope.OPENID,
          cognito.OAuthScope.EMAIL,
          cognito.OAuthScope.PROFILE,
        ],
        callbackUrls: ['com.seahavenind.proposals://auth/callback'],
        logoutUrls: ['com.seahavenind.proposals://auth/logout'],
      },
    });

    this.webClientId = webClient.userPoolClientId;
    this.mobileClientId = mobileClient.userPoolClientId;

    // SNS Alarm Topic
    const alarmTopic = new sns.Topic(this, 'AlarmTopic', {
      topicName: `proposal-system-alarms${config.stackSuffix}`,
      displayName: 'Proposal System Alarms',
    });
    alarmTopic.addSubscription(
      new snsSubscriptions.EmailSubscription(config.alarmsEmail),
    );
    this.alarmTopic = alarmTopic;

    const alarmAction = new cloudwatchActions.SnsAction(alarmTopic);

    // DLQ Alarm: any message landing in DLQ indicates a processing failure
    const dlqAlarm = new cloudwatch.Alarm(this, 'DlqDepthAlarm', {
      alarmName: `proposal-system-dlq-depth${config.stackSuffix}`,
      alarmDescription: 'Messages in DLQ — SQS processing failures',
      metric: dlq.metricApproximateNumberOfMessagesVisible({
        period: cdk.Duration.minutes(1),
      }),
      threshold: 0,
      comparisonOperator: cloudwatch.ComparisonOperator.GREATER_THAN_THRESHOLD,
      evaluationPeriods: 1,
      treatMissingData: cloudwatch.TreatMissingData.NOT_BREACHING,
    });
    dlqAlarm.addAlarmAction(alarmAction);

    // RDS Alarms
    const rdsAlarms = [
      new cloudwatch.Alarm(this, 'RdsCpuAlarm', {
        alarmName: `proposal-system-rds-cpu${config.stackSuffix}`,
        alarmDescription: 'RDS CPU utilization above 80%',
        metric: dbCluster.metricCPUUtilization({ period: cdk.Duration.minutes(5) }),
        threshold: 80,
        evaluationPeriods: 3,
        treatMissingData: cloudwatch.TreatMissingData.BREACHING,
      }),
      new cloudwatch.Alarm(this, 'RdsConnectionsAlarm', {
        alarmName: `proposal-system-rds-connections${config.stackSuffix}`,
        alarmDescription: 'RDS database connections above 80',
        metric: dbCluster.metricDatabaseConnections({ period: cdk.Duration.minutes(5) }),
        threshold: 80,
        evaluationPeriods: 2,
        treatMissingData: cloudwatch.TreatMissingData.NOT_BREACHING,
      }),
      // Aurora storage auto-scales (no FreeStorageSpace); freeable memory is the
      // meaningful health signal for a Serverless v2 cluster.
      new cloudwatch.Alarm(this, 'RdsLowMemoryAlarm', {
        alarmName: `proposal-system-rds-low-memory${config.stackSuffix}`,
        alarmDescription: 'Aurora freeable memory below 256 MB',
        metric: dbCluster.metricFreeableMemory({ period: cdk.Duration.minutes(5) }),
        threshold: 256_000_000,
        comparisonOperator: cloudwatch.ComparisonOperator.LESS_THAN_THRESHOLD,
        evaluationPeriods: 3,
        treatMissingData: cloudwatch.TreatMissingData.NOT_BREACHING,
      }),
    ];
    for (const alarm of rdsAlarms) {
      alarm.addAlarmAction(alarmAction);
    }

    // CloudWatch Log Groups
    const logGroupNames = [
      'proposal-system-api',
      'proposal-system-pdf-extract',
      'proposal-system-pdf-generate',
      'proposal-system-library-ingest',
    ];

    for (const name of logGroupNames) {
      new logs.LogGroup(this, `LogGroup-${name}`, {
        logGroupName: `/aws/lambda/${name}${config.stackSuffix}`,
        retention: logs.RetentionDays.TWO_MONTHS,
        removalPolicy: cdk.RemovalPolicy.DESTROY,
      });
    }

    // Outputs
    new cdk.CfnOutput(this, 'VpcId', { value: this.vpc.vpcId });
    new cdk.CfnOutput(this, 'UserPoolId', { value: userPool.userPoolId });
    new cdk.CfnOutput(this, 'UserPoolArn', { value: userPool.userPoolArn });
    new cdk.CfnOutput(this, 'UploadsBucketName', { value: this.uploadsBucket.bucketName });
    new cdk.CfnOutput(this, 'GeneratedBucketName', { value: this.generatedBucket.bucketName });
    new cdk.CfnOutput(this, 'LibraryBucketName', { value: this.libraryBucket.bucketName });
    new cdk.CfnOutput(this, 'JobsQueueUrl', { value: this.jobsQueue.queueUrl });
    new cdk.CfnOutput(this, 'DbSecretArn', { value: this.dbSecret.secretArn });
    new cdk.CfnOutput(this, 'WebClientId', { value: webClient.userPoolClientId });
    new cdk.CfnOutput(this, 'MobileClientId', { value: mobileClient.userPoolClientId });
    new cdk.CfnOutput(this, 'AlarmTopicArn', { value: alarmTopic.topicArn });
  }
}