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server.js
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server.js
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const express = require('express');
const axios = require('axios');
const bodyParser = require('body-parser');
const app = express();
if(process.env.ES_HOST === undefined) {
console.log("FATAL ERROR: ES_HOST environment variable is not set.");
process.exit(1);
}
/**
* Creates the elasticsearch query for aggregating tag data.
*/
function queryForFetchingTags(size) {
return {
"aggs": {
"byTag": {
"terms": {
"field": "tag_nested.name.keyword",
"size": size
}
}
},
"size": 0
};
}
/**
* Creates the book search elasticsearch query.
*/
function queryForSearchingBooks(size, title, select_with, select_without) {
var with_list = [];
var without_list = [];
var query = {"from" : 0, "size" : size, "query":{"bool": {}}};
// search by title
if(title !== '') {
query['query']['bool']['filter'] = {
"match" : {
"title": {
"query": title,
"operator": "and"
}
}
}
}
// if there are tags to be searched, add them to the query
if(select_with !== "") {
select_with.split(',').map((item) => {
with_list.push({"match": {"tag_nested.name.keyword": item}})
})
query['query']['bool']['must'] = with_list;
}
// if there are tags to be ommited, add them to the query
if(select_without !== "") {
select_without.split(',').map((item) => {
without_list.push({"match": {"tag_nested.name.keyword": item}})
})
query['query']['bool']['must_not'] = without_list;
}
return query;
}
/**
* Creates a query to do search-as-you-type with book titles.
* Prefix is a straing, fuzziness is an integer that goes from
* 0 (no fuzziness at all) up, increasing the number of characters
* of distance that are allowed from the given prefix.
*/
function queryForBookTitleSearchAsYouType(prefix, fuzziness) {
return {
"suggest": {
"book-suggest-fuzzy": {
"prefix": prefix,
"completion": {
"field": "title.completion",
"fuzzy": {
"fuzziness": fuzziness
}
}
}
}
}
}
function getTags(req, res) {
const endpoint = process.env.ES_HOST + '/goodbooks10k/books/_search';
const size = req.params.size;
const params = {
params: {
source: JSON.stringify(queryForFetchingTags(size)),
source_content_type: 'application/json'
}
}
axios.get(endpoint, params).then((res2) => {
var title_list = [];
var count_list = [];
res2.data.aggregations.byTag.buckets.map((bucket) => {
title_list.push(bucket.key);
count_list.push(bucket.doc_count);
});
res.send({
success: true,
title_list: title_list,
count_list: count_list
})
}).catch((error) => {
console.log("Error 500 on getAllTags called with size=" + size);
console.log(error);
res.status(500);
res.send({
success: false
})
});
}
/**
* Request handler for book search.
*
* Remeember that select_with and select_without are passed by the React
* UI as comma-separated strings like tag1,tag2,tag3.
*/
function searchBooks(req, res) {
const endpoint = process.env.ES_HOST + '/goodbooks10k/books/_search';
var title_search = req.body.title_search;
var select_with = req.body.select_with;
var select_without = req.body.select_without;
const size = 100;
if(title_search === undefined) { title_search = ""};
if(select_with === undefined) { select_with = ""};
if(select_without === undefined) { select_without = ""};
if(typeof(title_search) !== 'string') {
res.status(400);
res.send({success: false, error: 'title_search must be a string'});
}
if(typeof(select_with) !== 'string') {
res.status(400);
res.send({success: false, error: 'select_with must be a string'});
}
if(typeof(select_without) !== 'string') {
res.status(400);
res.send({success: false, error: 'select_without must be a string'});
}
const params = {
params: {
source: JSON.stringify(queryForSearchingBooks(
size, title_search, select_with, select_without)),
source_content_type: 'application/json'
}
};
axios.get(endpoint, params).then((res2) => {
var results = [];
res2.data.hits.hits.map((hit) => {
results.push(hit._source);
});
res.send(res2.data);
}).catch((error) => {
console.log("Error 500 on searchBooks called with payload:");
console.log(payload);
console.log(error);
res.status(500);
res.send({success: false});
});
}
/**
* Redirects unmatched requests to the elasticsearch host
* for GET requests, acting as a proxy for reading data.
*/
function redirectUnmatchedGetToElasticsearch(req, res) {
if (req.method == "GET") {
const url = process.env.ES_HOST + req.originalUrl;
// console.log(req.body);
// console.log(req.params);
// console.log(req.query);
if(typeof(req.body) === "object" && req.body.params !== undefined) {
var promise = axios.get(url, {
params: {
source: JSON.stringify(req.body),
source_content_type: 'application/json'
}
});
} else {
var promise = axios.get(url);
}
promise.then((response) => {
res.send(response.data);
}).catch((error) => {
console.log("ERROR:");
console.log(error);
res.send({'error': 'check output'});
});
} else {
res.setHeader('Content-Type', 'application/json');
res.send(JSON.stringify({ error: 'ONLY_GET_REQUESTS_ALLOWED' }));
}
}
// set CORS headers
app.all('/*', function(req, res, next) {
res.header("Access-Control-Allow-Origin", "*");
res.header("Access-Control-Allow-Headers", "X-Requested-With");
next();
});
app.use(express.static(__dirname + '/build'));
app.use(bodyParser.json());
app.get('/api/v1/tags/:size(\\d+)/', getTags);
app.get('/api/v1/search_books', searchBooks);
app.use(redirectUnmatchedGetToElasticsearch);
app.listen(process.env.PORT || 8080);
console.log("Server.js started.");