Downloads a Minecraft skin using Mojang's player API

download-minecraft-skin.ts

// https://davidglymph.com/blog/https-api-fetch-with-promises/
// To run script, make sure you have ts-node installed "npm i -g ts-node",
// replace {USERNAME} with a valid Minecraft account
// 
// ts-node download-minecraft-skin.ts {USERNAME}

import https from 'https';
import http from 'http';
import fs from 'fs';

getUuid(process.argv[2])
    .then(getProfile)
    .then(saveSkin)
    .then(console.log)
    .catch(console.log);

function getUuid(profileName: string) {
    const getUuidUrl = (profileName: string) => `https://api.mojang.com/users/profiles/minecraft/${profileName}`;
    
    return new Promise<string>((resolve, reject) => {
        if(profileName === undefined) reject(`Invalid or missing command argument`);

        https.get(getUuidUrl(profileName), response => {
            if(response.statusCode === 200) {
                let chunk = '';
                response.on('data', data => chunk += data);
                response.on('end', () => resolve(JSON.parse(chunk).id));
            }
            else {
                reject(`UUID fetch was invalid with status code ${response.statusCode}`);
            }
        }).on('error', reject);
    });
}

function getProfile(uuid: string) {
    const getProfileUrl = (uuid: string) => `https://sessionserver.mojang.com/session/minecraft/profile/${uuid}`;

    return new Promise((resolve, reject) => {
        https.get(getProfileUrl(uuid), response => {
            if(response.statusCode === 200) {
                let chunk = '';
                response.on('data', data => chunk += data);
                response.on('end', () => resolve(JSON.parse(chunk)));
            }
            else {
                reject(`Profile fetch was invalid with status code ${response.statusCode}`);
            }
        }).on('error', reject);
    });
}

function saveSkin(profile: any) {
    const textureObjectBuffer = Buffer.from(profile.properties[0].value, 'base64url');
    const textureObject = JSON.parse(textureObjectBuffer.toString('ascii'));

    const profileName = textureObject.profileName;
    const skinUrl = textureObject.textures.SKIN.url;

    return downloadImageFromUrl(skinUrl, `./${profileName}.png`);
}

function downloadImageFromUrl(url: string, filepath: string) {
    return new Promise((resolve, reject) => {
        http.get(url, response => {
            if(response.statusCode === 200)
                response.pipe(fs.createWriteStream(filepath))
                .on('error', reject)
                .on('close', () => resolve(`File saved to ${filepath}`));
            
            else
                response.resume()
                .on('end', () => reject(`Downloading image failed with status code ${response.statusCode}`));
            
        }).on('error', reject);
    });
}