Merge pull request #22 from 0xPolygonID/update-docs

update verifier docs

docs/verifier/verification-library/verifier-set-up.md

@@ -424,8 +424,175 @@ The Verifier Client must fetch the Auth Request generated by the Server (`/api/s
 
 > To display the QR code inside your frontend, you can use this [Code Sandbox](https://codesandbox.io/s/yp1pmpjo4z?file=/index.js).
 
-The same request can also be delivered to users via Deep Linking. In order to do so, it is necessary to encode the `request` file to Base64 Format. The related deep link would be `iden3comm://?i_m={{base64EncodedRequestHere}}`.
+A Verifier can show a QR code that contains one of the following data structures:
 
+* Raw JSON - message will be treated as one of the [IDEN3 Protocol messages](https://iden3-communication.io/credentials/overview/).
+* Link with base64 encoded message or shortened request URI (encoded URL) in case base64-encoded message is too large. Possible formats of links are: 
+    1. `iden3comm://?i_m={{base64EncodedRequestHere}}`
+    2. `iden3comm://?request_uri={{shortenedUrl}}`
+
+
+If both params are present `i_m` is prioritized and `request_uri` is ignored.
+
+The same request can also be delivered to users via Deep Linking. The same format for links must be used.
+
+:::note "Polygon ID wallet"
+
+Polygon ID wallet will support handling of `request_uri` in the next release, while your client can already implement this specification.
+
+:::
+
+***Shortened URL algorithm***
+
+While it's not strictly restricted how you can perform URL shortage algorithm, it is recommended to follow these instructions:
+
+1. Generate a UUID for a particular request (or use ID of the message itself)
+2. Implement an endpoint to fetch messages by UUID.
+3. Encode URL to fetch messages to `the request_uri`.
+
+Example of URL shortage logic:
+
+<Tabs>
+<TabItem value= "Golang">
+
+```go
+package handlers
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"time"
+	"github.com/gofrs/uuid"
+	"github.com/patrickmn/go-cache"
+)
+
+var cacheStorage = cache.New(60*time.Minute, 60*time.Minute)	
+
+func HandleQRData(w http.ResponseWriter, r *http.Request) {
+	switch r.Method {
+
+	// create url for the message
+	case http.MethodPost:
+
+		// get json data from request body
+		var data interface{}
+		body, err := io.ReadAll(r.Body)
+		if err != nil {
+			http.Error(w, "Failed to read request body", http.StatusInternalServerError)
+			return
+		}
+		defer r.Body.Close()
+
+		err = json.Unmarshal(body, &data)
+		if err != nil {
+			http.Error(w, "Failed to unmarshal body data", http.StatusInternalServerError)
+			return
+		}
+
+		// generate random key
+		uv, err := uuid.NewV4()
+
+		if err != nil {
+			http.Error(w, "Failed to generate uuid", http.StatusInternalServerError)
+			return
+		}
+
+		// store data in map
+		cacheStorage.Set(uv.String(), data, 1*time.Hour)
+
+		hostURL := os.Getenv("HOST_URL") // e.g. https://verifier.com
+		// write key to response
+		fmt.Fprintf(w, "%s%s?id=%s", hostURL, "api/qr-store", uv.String())
+		return	
+
+	// get message by identifier	
+	case http.MethodGet:
+
+		// get path param
+		id := r.URL.Query().Get("id")
+		if id == "" {
+			http.Error(w, "Failed to get id", http.StatusNotFound)
+			return
+		}
+		// get data from map
+		data, ok := cacheStorage.Get(id)
+
+		if !ok {
+			http.Error(w, fmt.Sprintf("Failed to retrieve QR data by %s", id), http.StatusNotFound)
+			return
+		}
+
+		jsonData, err := json.Marshal(data)
+		if err != nil {
+			http.Error(w, "Failed to encode JSON", http.StatusInternalServerError)
+			return
+		}
+
+		// write data to response
+		w.WriteHeader(http.StatusOK)
+		w.Header().Set("Content-Type", "application/json")
+		w.Write(jsonData)
+		return
+	}
+}
+
+```
+
+</TabItem>
+<TabItem value= "Javascript">
+
+```js
+const express = require('express');
+const { v4: uuidv4 } = require('uuid');
+const Cache = require('cache-manager');
+const HttpStatus = require('http-status-codes');
+
+const app = express();
+app.use(express.json());
+
+const cPromise = Cache.caching('memory', {
+	max: 100,
+	ttl: 10 * 1000 /*milliseconds*/,
+});
+app.get('/api/qr-store', async (req, res) => {
+const id = req.query.id;
+const cacheManager = await cPromise;
+const data = await cacheManager.get(id);
+
+if (!data) {
+	return res.status(HttpStatus.NOT_FOUND).json({ error: `item not found ${id}` });
+}
+
+return res.status(HttpStatus.OK).json(data);
+});
+
+app.post('/api/qr-store', async (req, res) => {
+const body = req.body;
+const uuid = uuidv4();
+const cacheManager = await cPromise;
+
+console.log(cacheManager);
+
+await cacheManager.set(uuid, body, { ttl: 3600 });
+
+const hostUrl = process.env.HOST_URL;
+const qrUrl = `${hostUrl}/api/qr-store?id=${uuid}`;
+
+return res.status(HttpStatus.OK).json({ qrUrl });
+});
+
+app.listen(3000, () => {
+console.log('Express server is running on port 3000');
+
+});
+```  
+
+</TabItem>
+</Tabs>
+	
 **Implement Further Logic**
 
 This tutorial showcased a minimalistic application that leverages Polygon ID libraries for authentication purposes. Developers can leverage the broad set of existing Credentials held by users to set up any customized Query using our [ZK Query Language](./zk-query-language.md) to unleash the full potential of the framework.