const AWS = require("aws-sdk");
const csv = require("csv-parser");
const { Readable } = require("stream");
const simpleParser = require("mailparser").simpleParser;

const s3 = new AWS.S3();
const documentClient = new AWS.DynamoDB.DocumentClient();

const TableName = process.env.TABLE;

exports.handler = async (event) => {
    const Bucket = event.Records[0].s3.bucket.name;
    const Key = event.Records[0].s3.object.key;

    const eml = await s3
        .getObject({
            Bucket,
            Key,
        })
        .promise();

    const parsed = await simpleParser(eml.Body);

    const csvAttachments = parsed.attachments.filter(
        (attachment) => attachment.contentType === "text/csv"
    );

    if (csvAttachments) {
        const content = csvAttachments[0].content;
        const stream = Readable.from(content.toString("utf-8"));
        const promises = [];
        stream
            .pipe(csv())
            .on("data", (data) => {
                var promise = documentClient
                    .put({
                        TableName,
                        Item: data,
                    })
                    .promise();
                promises.push(promise);
            })
            .on("end", () => {
                Promise.all(promises).then(() => {
                    console.log(
                        `Email from ${parsed.from.value.address} processed successfully`
                    );
                });
            });
    }
};