vp-tree-node/server.js

const express = require('express');
const bodyParser = require('body-parser');
const vptree = require('vptree'); 
const similarity = require('compute-cosine-similarity');
const fs = require('fs');
const path = require('path');
const app = express();
const port = 2000;

app.use(bodyParser.json());

// Function to load JSON data
function loadJSON(filePath, callback) {
    fs.readFile(filePath, 'utf8', (err, data) => {
        if (err) {
            return callback(err, null);
        }
        try {
            const jsonData = JSON.parse(data);
            callback(null, jsonData);
        } catch (parseError) {
            callback(parseError, null);
        }
    });
}

function cosineDistanceMatching(vector1, vector2) {
    let cosineSimilarity = similarity(vector1, vector2);
    let distance = 2 * (1 - cosineSimilarity);
    return Math.sqrt(distance);
}

let tree, vectors, jsonEmbeddings

buildVPTree()
loadVPTree()

// Load tree endpoint
app.post('/search/', (req, res) => {
    const { vector } = req.body;

    if (!Array.isArray(vector) || vector.length !== 7 || !vector.every(num => typeof num === 'number')) {
        return res.status(400).send({ success: false, message: 'Invalid vector provided. It must be an array of 7 floating-point numbers.' });
    }

    let idx = queryVPTree(vector)

    // Retrieve the filename from the stored JSON data
    let filename = idx !== undefined && idx < jsonEmbeddings.length ? jsonEmbeddings[idx].filename : null;

    res.send({filename});
});

function queryVPTree(value){
    let nearest = tree.search(value)
    let index = nearest[0].i
    return index
}

function buildVPTree(){
    // Load JSON data from embeddings.json
    const jsonFilePath = path.join(__dirname, 'embeddings.json');
    loadJSON(jsonFilePath, (err, jsonData) => {
            if (err) {
                console.error('Error loading JSON:', err);
                return;
            }
        // Extract vectors from the JSON data
        jsonEmbeddings = jsonData
        vectors = jsonEmbeddings.map(item => item.vector);
        tree = vptree.build(vectors, cosineDistanceMatching)
        const treeString = tree.stringify();
        const fileName = "tree"
        const filePath = path.join(__dirname, `${fileName}.txt`);

        fs.writeFile(filePath, treeString, 'utf8', (err) => {
            if (err) {
                console.log("Tree did not save to file.")
                return
            }
            
            console.log("Tree saved successfully.")
        });
    });
    
}

function saveVPTree(fileName){

    const treeString = tree.stringify();

    const filePath = path.join(__dirname, `${fileName}.txt`);

    fs.writeFile(filePath, treeString, 'utf8', (err) => {
        if (err) {
            console.log("Tree did not save to file.")
            return
        }
        
        console.log("Tree saved successfully.")
    });
}

function loadVPTree(){
    loadTreeFromDisk("tree", (err, treeData) => {
        if (err) {
            console.error('Failed to load tree from disk:', err);
            return;
        }

        // Rebuild the VP-tree using the saved structure
        try {
            tree = vptree.load(vectors, cosineDistanceMatching, treeData);
            console.log('Tree loaded successfully.');

        } catch (loadError) {
            console.error('Error loading the VP-tree:', loadError);
        }
    });
}

function loadTreeFromDisk(fileName, callback){
    const filePath = path.join(__dirname, `${fileName}.txt`);

    fs.readFile(filePath, 'utf8', (err, data) => {
        if (err) {
            console.error('Error reading the file:', err);
            return callback(err, null);
        }

        // Parse the data as a JavaScript object
        try {
            const treeData = eval(`(${data})`); // Using eval to convert to object
            callback(null, treeData);
        } catch (parseError) {
            console.error('Error parsing the tree data:', parseError);
            callback(parseError, null);
        }
    });
}

app.listen(port, () => {
  console.log(`Server listening at http://localhost:${port}`);
});