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@Nxtra

Nxtra/index.js

Last active Dec 6, 2020
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A lambda function to resolve the editPostAndComments mutation.
const AWS = require("aws-sdk");
const docClient = new AWS.DynamoDB.DocumentClient();
const POSTTABLE = process.env.POSTTABLE;
const COMMENTTABLE = process.env.COMMENTTABLE;
const resolvers = {
Mutation: {
deletePostAndComments: (event) => {
return deletePostAndComments(event);
},
},
};
exports.handler = async function (event, context) {
console.log(event);
console.log(context);
const typeHandler = resolvers[event.typeName];
if (typeHandler) {
const resolver = typeHandler[event.fieldName];
if (resolver) {
return await resolver(event);
}
}
throw new Error("Resolver not found.");
};
async function deletePostAndComments(event) {
const removeCommentsProm = removeCommentsOfPost(event.arguments.postId);
const removePostProm = removePost(event.arguments.postId);
const [_, deletedPost] = await Promise.all([
removeCommentsProm,
removePostProm,
]);
return { id: deletedPost.id };
}
async function removePost(postId) {
const deletedPost = await deletePost(postId);
console.log("Deleted post is: ", deletedPost);
console.log("Deleted post with id: ", deletedPost.id);
return deletedPost;
}
async function removeCommentsOfPost(postId) {
const comments = await listCommentsForPost(postId);
await deleteComments(comments);
}
async function listCommentsForPost(postId) {
var params = {
TableName: COMMENTTABLE,
IndexName: "byPost",
KeyConditionExpression: "postID = :postId",
ExpressionAttributeValues: { ":postId": postId },
};
try {
const data = await docClient.query(params).promise();
return data.Items;
} catch (err) {
return err;
}
}
async function deleteComments(comments) {
// format data for docClient
const seedData = comments.map((item) => {
return { DeleteRequest: { Key: { id: item.id } } };
});
/* We can only batch-write 25 items at a time,
so we'll store both the quotient, as well as what's left.
*/
let quotient = Math.floor(seedData.length / 25);
const remainder = seedData.length % 25;
/* Delete in increments of 25 */
let batchMultiplier = 1;
while (quotient > 0) {
for (let i = 0; i < seedData.length - 1; i += 25) {
await docClient
.batchWrite(
{
RequestItems: {
[COMMENTTABLE]: seedData.slice(i, 25 * batchMultiplier),
},
},
(err, data) => {
if (err) {
console.log(err);
console.log("something went wrong...");
}
}
)
.promise();
++batchMultiplier;
--quotient;
}
}
/* Upload the remaining items (less than 25) */
if (remainder > 0) {
await docClient
.batchWrite(
{
RequestItems: {
[COMMENTTABLE]: seedData.slice(seedData.length - remainder),
},
},
(err, data) => {
if (err) {
console.log(err);
console.log("something went wrong...");
}
}
)
.promise();
}
}
async function deletePost(id) {
var params = {
TableName: POSTTABLE,
Key: { id },
ReturnValues: "ALL_OLD",
};
try {
const data = await docClient.delete(params).promise();
const response = data.Attributes;
return response;
} catch (err) {
return err;
}
}
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