chain4all-service/app.js

import fetch from "node-fetch"
import express from "express"
import bodyParser from "body-parser"

const app = express();
app.use(bodyParser.json());

const CHAIN4ALL_SERVICE_PORT = process.env.CHAIN4ALL_SERVICE_PORT || 3000;
const IROHA_API_HOST = process.env.IROHA_API_HOST || "http://localhost";
const IROHA_API_PORT = process.env.IROHA_API_PORT || 5000;

const IROHA_DOMAIN = process.env.IROHA_DOMAIN || "test";
const IROHA_ASSET = process.env.IROHA_ASSET || "coin";
const DATA_OWNER = process.env.DATA_OWNER || "admin"
const PRICE_MODIFIER = process.env.PRICE_MODIFIER || 0.5;

app.get("/", (req, res) => {
    res.send("Chain4All Blockchain service");
});

app.post("/price", (req, res) => {
    if (req.body && req.body.extent) {
        res.send({ price: getPrice(req.body.extent) });
    }
    else {
        res.status(400);
        throw Error(JSON.stringify({ error: { name: "Error, request has no body with \"extent\" property!" } }));
    }
});

app.get("/users/:userId/assets", async (req, res) => {
    let irohaResponse = await fetchUsersAssets(req.params.userId);

    res.status(irohaResponse.status);

    if (irohaResponse.headers.get("content-length") < 1) {
        res.send();
    }
    else {
        res.send(await irohaResponse.json());
    }
});

app.get("/users/:userId/assets/:assetId", async (req, res) => {
    let assets = (await fetchUsersAssets(req.params.userId)).assets;

    let parsedAssetName = "";
    let i = 0;
    for (i; i < assets.length; i++) {
        parsedAssetName = assets[i].assetId.split('#')[0];
        if (parsedAssetName === req.params.assetId) {
            res.status(200);
            res.send(assets[i]);
            return;
        }
    }

    res.status(204);
    res.send();
});

app.post("/buy", async (req, res) => {

    if (!req.body) {
        res.status(400);
        throw Error(JSON.stringify({ error: { name: "Error, request has no body!" } }));
    }

    if (!req.body.extent) {
        res.status(400);
        throw Error(JSON.stringify({ error: { name: "Error, request body has no \"extent\" property!" } }));
    }

    if (!req.body.user) {
        res.status(400);
        throw Error(JSON.stringify({ error: { name: "Error, request body has no \"user\" property!" } }));
    }

    let price = getPrice(req.body.extent);

    let irohaResponse = await forwardBuyRequest(
        {
            transfers: [
                {
                    asset: IROHA_ASSET + "#" + IROHA_DOMAIN,
                    source: req.body.user + "@" + IROHA_DOMAIN,
                    destination: DATA_OWNER + "@" + IROHA_DOMAIN,
                    description: "test", //TODO: compose uniform description
                    amount: price
                }
            ]
        }
    );

    let data = "test - to be implemented"; //TODO implement data extraction 

    res.status(irohaResponse.status);

    if(!irohaResponse.ok){
        res.send(irohaResponse);
    }

    let irohaResponseJson = await irohaResponse.json();

    console.log("tx hash: " + irohaResponseJson.transactionHash);   

    res.send({
        data : data,
        transactionHash : irohaResponseJson.transactionHash
    });
});

async function forwardBuyRequest(body) {
    return await fetch(IROHA_API_HOST + ':' + IROHA_API_PORT + '/assets/transfer/',
        {
            method: 'POST',
            body: JSON.stringify(body),
            headers: { 'Content-Type': 'application/json' }
        }
    );
}

async function fetchUsersAssets(userId) {
    return await fetch(IROHA_API_HOST + ':' + IROHA_API_PORT + '/accounts/' + userId + '@' + IROHA_DOMAIN + '/assets/');
}

function getArea(extent) {
    let y1 = extent[0][1];
    let y4 = extent[3][1];

    let x1 = extent[0][0];
    let x2 = extent[1][0];

    let height = Math.abs(y1 - y4);
    let width = Math.abs(x1 - x2);

    return height * width;
}

function getPrice(extent) {
    return getArea(extent) * PRICE_MODIFIER;
}

function error(err, req, res, next) { //TODO: add custom Exception class
    console.log(err);

    if (!res.status) {
        res.status(500);
    }

    res.send(err.message);
}

app.use(error);

app.listen(CHAIN4ALL_SERVICE_PORT, () => {
    console.log(`Listening at http://localhost:${CHAIN4ALL_SERVICE_PORT}`)
});