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// @flow
const debug = require('debug')('api:thread-message-connection');
import type { DBThread } from 'shared/types';
import type { PaginationOptions } from '../../utils/paginate-arrays';
import UserError from '../../utils/UserError';
import { encode, decode } from '../../utils/base64';
import { getMessages } from '../../models/message';
export default (
{ id }: DBThread,
{
first,
after,
last,
before,
}: { ...PaginationOptions, last: number, before: string }
) => {
// Make sure users don't provide bonkers arguments that paginate in both directions at the same time
if (
(first && last) ||
(after && before) ||
(first && before) ||
(after && last)
) {
debug('invalid pagination options provided:');
debug(
'first:',
first,
' last:',
last,
' after:',
after,
' before:',
before
);
return new UserError(
'Cannot paginate back- and forwards at the same time. Please only ask for the first messages after a certain point or the last messages before a certain point.'
);
}
debug(`get messages for ${id}`);
let cursor = after || before;
try {
cursor = decode(cursor);
if (cursor) cursor = parseInt(cursor, 10);
} catch (err) {
console.error('❌ Error in job:\n');
console.error(err);
return new UserError('Invalid cursor passed to thread.messageConnection.');
}
if (cursor) debug(`cursor: ${cursor}`);
let options = {
// Default first/last to 25 if their counterparts after/before are provided
// so users can query messageConnection(after: "cursor") or (before: "cursor")
// without any more options
first: first ? first : after ? 25 : null,
last: last ? last : before ? 25 : null,
// Set after/before to the cursor depending on which one was requested by the user
after: after ? cursor : null,
before: before ? cursor : null,
};
// If we didn't get any arguments at all (i.e messageConnection {})
// then just fetch the first 25 messages
// $FlowIssue
if (Object.keys(options).every(key => !options[key])) {
options = {
first: 25,
};
}
debug('pagination options for query:', options);
// Load one message too much so that we know whether there's
// a next or previous page
options.first && options.first++;
options.last && options.last++;
return getMessages(id, options).then(result => {
let messages = result;
// Check if more messages were returned than were requested, which would mean
// there's a next/previous page. (depending on the direction of the pagination)
const loadedMoreFirst = options.first && result.length > options.first - 1;
const loadedMoreLast = options.last && result.length > options.last - 1;
// Get rid of the extranous message if there is one
if (loadedMoreFirst) {
debug('not sending extranous message loaded first');
messages = result.slice(0, result.length - 1);
} else if (loadedMoreLast) {
debug('not sending extranous message loaded last');
messages = result.reverse().slice(1, result.length);
}
return {
pageInfo: {
// Use the extranous message that was maybe loaded to figure out whether
// there is a next/previous page, otherwise just try and guess based on
// if a cursor was provided
// $FlowIssue
hasNextPage: loadedMoreFirst || !!options.before,
// $FlowIssue
hasPreviousPage: loadedMoreLast || !!options.after,
},
edges: messages.map(message => ({
cursor: encode(message.timestamp.getTime().toString()),
node: message,
})),
};
});
};
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