var AWS = require('aws-sdk');
var dt = 'hrhub-prod1-Downloads';
var ddb = new AWS.DynamoDB({ apiVersion: '2012-08-10' });

exports.handler = async function(event, context, callback) {
    var srcKey = decodeURIComponent(event.Records[0].s3.object.key.replace(/\+/g, " "));
    var parts = srcKey.split('/');
    var fileName = srcKey;

    if (parts.length === 4 && parts[0] !== 'none') {
        var area = parts[0];
        var recipient = parts[1];
        var file = parts[2];
        var fileVersion = parts[3];

        await dltRecs(area, recipient, file, fileVersion, 'File');
        await dltRecs(area, recipient, file, fileVersion, 'Permission');
        console.log('File permissions deleted');

        if (!fileExists(area, '*', '*')) {
            await dltRecs(area, '*', '*', '*', 'Permission');
            await dltRecs(area, '*', '*', '*', 'FileRetention');
            await dltRecs(area, recipient, '*', '*', 'Permission');
            await dltRecs(area, recipient, '*', '*', 'FileRetention');
            await dltRecs(area, recipient, file, '*', 'Permission');
            await dltRecs(area, recipient, file, '*', 'FileRetention');

            return;
        }

        if (!fileExists(area, recipient, '*')) {
            await dltRecs(area, recipient, '*', '*', 'Permission');
            await dltRecs(area, recipient, '*', '*', 'FileRetention');
            await dltRecs(area, recipient, file, '*', 'Permission');
            await dltRecs(area, recipient, file, '*', 'FileRetention');

            return;
        }

        if (!fileExists(area, recipient, file)) {
            await dltRecs(area, recipient, file, '*', 'Permission');
            await dltRecs(area, recipient, file, '*', 'FileRetention');

            return;
        }
    }
};

async function fileExists(area, recipient, fileGroup) {
    var params = {
        TableName: dt,
        ProjectionExpression: 'ID',
        KeyConditionExpression: 'ID = :ID',
        FilterExpression: '(Recipient = :Recipient or :x = :Recipient) and (FileGroup = :FileGroup or :x = :FileGroup)',
        ExpressionAttributeValues: {
            ':ID': { S: area },
            ':Recipient': { S: recipient },
            ':FileGroup': { S: fileGroup },
            ':x': { S: '*' }
        }
    };
    var data = await ddb.query(params).promise();

    return data.Items.length < 0;
}

async function dltRecs(area, recipient, fileGroup, fileVersion, type) {
    var params = {
        TableName: dt,
        IndexName: 'RecordType-index',
        ProjectionExpression: 'ID, SortKey',
        KeyConditionExpression: 'RecordType = :RecordType',
        FilterExpression: 'Area = :Area and (Recipient = :Recipient or :x = :Recipient) and (FileGroup = :FileGroup or x: = :FileGroup) and (FileVersion = :FileVersion or x: = :FileVersion)',
        ExpressionAttributeValues: {
            ':RecordType': { S: type },
            ':Area': { S: area },
            ':Recipient': { S: recipient },
            ':FileGroup': { S: fileGroup },
            ':FileVersion': { S: fileVersion },
            ':x': { S: '*' }
        }
    };

    var data = await ddb.query(params).promise();
    var deleteItems = [];

    data.Items.forEach(function(item) {
        var id = item.ID.S;
        var sortKey = item.SortKey.S;
        var item = {
            DeleteRequest: {
                Key: {
                    'ID': { S: id },
                    'SortKey': { S: sortKey }
                }
            }
        };

        deleteItems.push(item);
    });

    do {
        await batchDelete(deleteItems.splice(0, 25));
    }
    while (deleteItems.length > 0)
}

async function batchDelete(deleteItems) {

    if (deleteItems.length > 0) {
        let params = {
            RequestItems: {
                [dt]: deleteItems
            }
        };

        do {
            var data = await ddb.batchWriteItem(params).promise();
            params = data.UnprocessedItems;
        }
        while (params.length > 0)
    }
}