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Permission is hereby granted, free of charge, to any person obtaining a copy of this
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
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package com.amazonaws.partners.saasfactory.metering.onboarding;

import com.amazonaws.partners.saasfactory.metering.common.TenantOnboardingException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.RequestStreamHandler;

import software.amazon.awssdk.services.dynamodb.DynamoDbClient;
import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
import software.amazon.awssdk.services.dynamodb.model.InternalServerErrorException;
import software.amazon.awssdk.services.dynamodb.model.ResourceNotFoundException;
import software.amazon.awssdk.services.dynamodb.model.TransactionCanceledException;
import software.amazon.awssdk.services.dynamodb.model.UpdateItemRequest;

import com.amazonaws.partners.saasfactory.metering.common.TableConfiguration;
import com.amazonaws.partners.saasfactory.metering.common.OnboardingEvent;
import com.amazonaws.partners.saasfactory.metering.common.EventBridgeOnboardTenantEvent;
import static com.amazonaws.partners.saasfactory.metering.common.Constants.ATTRIBUTE_DELIMITER;
import static com.amazonaws.partners.saasfactory.metering.common.Constants.CONFIG_SORT_KEY_VALUE;
import static com.amazonaws.partners.saasfactory.metering.common.Constants.EXTERNAL_SUBSCRIPTION_IDENTIFIER_ATTRIBUTE_NAME;
import static com.amazonaws.partners.saasfactory.metering.common.Constants.EXTERNAL_SUBSCRIPTION_IDENTIFIER_EXPRESSION_NAME;
import static com.amazonaws.partners.saasfactory.metering.common.Constants.EXTERNAL_SUBSCRIPTION_IDENTIFIER_EXPRESSION_VALUE;
import static com.amazonaws.partners.saasfactory.metering.common.Constants.PRIMARY_KEY_NAME;
import static com.amazonaws.partners.saasfactory.metering.common.Constants.SORT_KEY_NAME;
import static com.amazonaws.partners.saasfactory.metering.common.Constants.TENANT_PREFIX;
import static com.amazonaws.partners.saasfactory.metering.common.Constants.initializeDynamoDBClient;
import static com.amazonaws.partners.saasfactory.metering.common.Constants.initializeTableConfiguration;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;

public class OnboardNewTenant implements RequestStreamHandler {

    private final DynamoDbClient ddb;
    private final Gson gson;
    private final Logger logger;
    private final TableConfiguration tableConfig;

    public OnboardNewTenant() {
        this.ddb = initializeDynamoDBClient();
        this.logger = LoggerFactory.getLogger(OnboardNewTenant.class);
        this.gson = new GsonBuilder().setPrettyPrinting().create();
        this.tableConfig = initializeTableConfiguration(this.logger);
    }

    // Used for testing, need to inject the mock DDB client
    public OnboardNewTenant(DynamoDbClient ddb, TableConfiguration tableConfig) {
        this.ddb = ddb;
        this.logger = LoggerFactory.getLogger(OnboardNewTenant.class);
        this.gson = new GsonBuilder().setPrettyPrinting().create();
        this.tableConfig = tableConfig;
    }

    private UpdateItemRequest buildUpdateStatement(OnboardingEvent onboardingEvent) {
        HashMap<String, AttributeValue> compositeKey = new HashMap<>();

        AttributeValue primaryKeyValue = AttributeValue.builder()
                .s(String.format("%s%s%s",
                                    TENANT_PREFIX,
                                    ATTRIBUTE_DELIMITER,
                                    onboardingEvent.getTenantID()))
                .build();

        compositeKey.put(PRIMARY_KEY_NAME, primaryKeyValue);

        AttributeValue sortKeyValue = AttributeValue.builder()
                .s(CONFIG_SORT_KEY_VALUE)
                .build();
        compositeKey.put(SORT_KEY_NAME, sortKeyValue);

        HashMap<String, String> expressionAttributeNames = new HashMap<>();
        expressionAttributeNames.put(EXTERNAL_SUBSCRIPTION_IDENTIFIER_EXPRESSION_NAME, EXTERNAL_SUBSCRIPTION_IDENTIFIER_ATTRIBUTE_NAME);

        HashMap<String, AttributeValue> expressionAttributeValues = new HashMap<>();
        AttributeValue externalProductCodeValue = AttributeValue.builder()
                .s(onboardingEvent.getExternalSubscriptionIdentifier())
                .build();

        expressionAttributeValues.put(EXTERNAL_SUBSCRIPTION_IDENTIFIER_EXPRESSION_VALUE, externalProductCodeValue);

        String updateStatement = String.format("SET %s = %s",
                EXTERNAL_SUBSCRIPTION_IDENTIFIER_EXPRESSION_NAME,
                EXTERNAL_SUBSCRIPTION_IDENTIFIER_EXPRESSION_VALUE);

        return UpdateItemRequest.builder()
                .tableName(this.tableConfig.getTableName())
                .key(compositeKey)
                .updateExpression(updateStatement)
                .expressionAttributeNames(expressionAttributeNames)
                .expressionAttributeValues(expressionAttributeValues)
                .build();

    }

    private void putTenant(OnboardingEvent onboardingEvent) {
        // This needs to be an update; there may already be an existing value in the subscription mapping attribute
        UpdateItemRequest subscriptionMappingUpdate = buildUpdateStatement(onboardingEvent);

        try {
            this.ddb.updateItem(subscriptionMappingUpdate);
        } catch (ResourceNotFoundException|InternalServerErrorException|TransactionCanceledException e) {
            this.logger.error("{}", e.toString());
            throw e;
        }
    }

    @Override
    public void handleRequest(InputStream inputStream, OutputStream outputStream, Context context) {
        if (this.tableConfig.getTableName().isEmpty() || this.tableConfig.getIndexName().isEmpty()) {
            return;
        }

        BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, StandardCharsets.UTF_8));
        EventBridgeOnboardTenantEvent event = gson.fromJson(reader, EventBridgeOnboardTenantEvent.class);

        // Create onboarding event
        OnboardingEvent onboardingEvent = OnboardingEvent.createOnboardingEvent(event);
        if (onboardingEvent == null) {
            if (event.getDetail().getTenantID() == null) {
                this.logger.error("Failed to create a new tenant because tenant ID unspecified");
                throw new TenantOnboardingException("Failed to create a new tenant because tenant ID unspecified");
            }
            if (event.getDetail().getExternalSubscriptionIdentifier() == null) {
                this.logger.error("Failed to create a new tenant because external subscription identifier unspecified");
                throw new TenantOnboardingException("Failed to create a new tenant because external subscription identifier unspecified");
            }
            return;
        }

        // Put the onboarding event into DynamoDB
        putTenant(onboardingEvent);
        this.logger.info("Created tenant with ID {}", onboardingEvent.getTenantID());
    }

}