import { ResourceConstants } from './ResourceConstants';
import DataSource from 'cloudform-types/types/appSync/dataSource';
import IAM from 'cloudform-types/types/iam';

import cloudform, { Fn, StringParameter, Refs } from 'cloudform';
import Template from 'cloudform-types/types/template';
import { TemplateContext } from './RelationalDBSchemaTransformer';
import { RelationalDBResolverGenerator } from './RelationalDBResolverGenerator';

/**
 * This is the Class responsible for generating and managing the CloudForm template
 * provided a TemplateContext object, which is generated by the RelationalDBSchemaTransformer.
 *
 * It will generate the basic CloudForm template needed for getting the AppSync API and
 * RDS DataSource provisioned. It also allows for adding the CRUDL+Q Resolvers upon need.
 */
export class RelationalDBTemplateGenerator {
  context: TemplateContext;

  constructor(context: TemplateContext) {
    this.context = context;
  }

  /**
   * Creates and returns the basic Cloudform template needed for setting
   * up an AppSync API pointing at the RDS DataSource.
   *
   * @returns the created CloudFormation template.
   */
  public createTemplate(context: any): Template {
    const template = {
      AWSTemplateFormatVersion: '2010-09-09',
      Parameters: this.makeParameters(this.context.databaseName),
      Resources: {
        [ResourceConstants.RESOURCES.RelationalDatabaseDataSource]: this.makeRelationalDataSource(context),
        [ResourceConstants.RESOURCES.RelationalDatabaseAccessRole]: this.makeIAMDataSourceRole(),
      },
    };

    return template;
  }

  /**
   * Provided a Cloudform Template, this method adds Resolver Resources to the
   * Template.
   *
   * @param template - the Cloudform template
   * @returns the given template, updated with new resolvers.
   */
  public addRelationalResolvers(template: Template, resolverFilePath: string): Template {
    let resolverGenerator = new RelationalDBResolverGenerator(this.context);
    template.Resources = { ...template.Resources, ...resolverGenerator.createRelationalResolvers(resolverFilePath) };
    return template;
  }

  /**
   * Provided a Cloudform Template, this method returns the cfn json template as a string
   *
   * @param template - the Cloudform template
   * @returns the json, string form of the template given.
   */
  public printCloudformationTemplate(template: Template): string {
    return cloudform(template);
  }

  /*
   * Private Helper Methods for Generating the Necessary CFN Specs for the CFN Template
   */

  /**
   * Creates any Parmaters needed for the CFN Template
   *
   * @param databaseName - the name of the database being parsed.
   * @returns the parameters for the template.
   */
  private makeParameters(databaseName: string) {
    return {
      [ResourceConstants.PARAMETERS.AppSyncApiName]: new StringParameter({
        Description: `The name of the AppSync API generated from database ${databaseName}`,
        Default: `AppSyncSimpleTransform`,
      }),
      [ResourceConstants.PARAMETERS.Env]: new StringParameter({
        Description: 'The environment name. e.g. Dev, Test, or Production',
        Default: 'NONE',
      }),
      [ResourceConstants.PARAMETERS.S3DeploymentBucket]: new StringParameter({
        Description: 'The S3 bucket containing all deployment assets for the project.',
      }),
      [ResourceConstants.PARAMETERS.S3DeploymentRootKey]: new StringParameter({
        Description: 'An S3 key relative to the S3DeploymentBucket that points to the root of the deployment directory.',
      }),
      [ResourceConstants.PARAMETERS.AppSyncApiId]: new StringParameter({
        Description: 'The id of the AppSync API associated with this project.',
      }),
      [ResourceConstants.PARAMETERS.rdsRegion]: new StringParameter({
        Description: 'The region that the RDS Cluster is located in.',
      }),
      [ResourceConstants.PARAMETERS.rdsClusterIdentifier]: new StringParameter({
        Description: 'The ARN identifier denoting the RDS cluster.',
      }),
      [ResourceConstants.PARAMETERS.rdsSecretStoreArn]: new StringParameter({
        Description: 'The ARN for the Secret containing the access for the RDS cluster.',
      }),
      [ResourceConstants.PARAMETERS.rdsDatabaseName]: new StringParameter({
        Description: 'The name of the database within the RDS cluster to use.',
      }),
    };
  }

  /*
   * Resources
   */

  /**
   * Creates the IAM Role CFN Spec to allow AppSync to interact with the RDS cluster
   *
   * @returns the IAM role CloudFormation resource.
   */
  private makeIAMDataSourceRole() {
    return new IAM.Role({
      RoleName: Fn.Join('-', ['role', Fn.Ref(ResourceConstants.PARAMETERS.AppSyncApiId), Fn.Ref(ResourceConstants.PARAMETERS.Env)]),

      AssumeRolePolicyDocument: {
        Version: '2012-10-17',
        Statement: [
          {
            Effect: 'Allow',
            Principal: {
              Service: 'appsync.amazonaws.com',
            },
            Action: 'sts:AssumeRole',
          },
        ],
      },
      Policies: [
        new IAM.Role.Policy({
          PolicyName: 'RelationalDatabaseAccessPolicy',
          PolicyDocument: {
            Version: '2012-10-17',
            Statement: [
              {
                Effect: 'Allow',
                Action: [
                  'rds-data:ExecuteSql',
                  'rds-data:ExecuteStatement',
                  'rds-data:DeleteItems',
                  'rds-data:GetItems',
                  'rds-data:InsertItems',
                  'rds-data:UpdateItems',
                ],
                Resource: [Fn.Ref(ResourceConstants.PARAMETERS.rdsClusterIdentifier)],
              },
              {
                Effect: 'Allow',
                Action: ['secretsmanager:GetSecretValue'],
                Resource: [Fn.Ref(ResourceConstants.PARAMETERS.rdsSecretStoreArn)],
              },
            ],
          },
        }),
      ],
    });
  }

  /**
   * Creates the AppSync DataSource CFN Spec pointing at the provided RDS Cluster
   *
   * @param cliContext - the Amplify context, used to load environment variables.
   * @returns the data source CloudFormation resource.
   */
  private makeRelationalDataSource(cliContext: any): DataSource {
    return new DataSource({
      Type: 'RELATIONAL_DATABASE',
      Name: `${this.context.databaseName}_rds_DataSource`,
      Description: `RDS Data Source Provisioned for ${this.context.databaseName}`,
      ApiId: Fn.Ref(ResourceConstants.PARAMETERS.AppSyncApiId),
      ServiceRoleArn: Fn.GetAtt(ResourceConstants.RESOURCES.RelationalDatabaseAccessRole, 'Arn'),
      RelationalDatabaseConfig: {
        RelationalDatabaseSourceType: 'RDS_HTTP_ENDPOINT',
        RdsHttpEndpointConfig: {
          AwsRegion: Fn.Ref(ResourceConstants.PARAMETERS.rdsRegion),
          DbClusterIdentifier: Fn.Ref(ResourceConstants.PARAMETERS.rdsClusterIdentifier),
          DatabaseName: Fn.Ref(ResourceConstants.PARAMETERS.rdsDatabaseName),
          Schema: this.context.databaseSchema,
          AwsSecretStoreArn: Fn.Ref(ResourceConstants.PARAMETERS.rdsSecretStoreArn),
        },
      },
    }).dependsOn([ResourceConstants.RESOURCES.RelationalDatabaseAccessRole]);
  }
}