Implement debug.stringify service (#125)

src/__test__/unit/builtInHandler.spec.ts

@@ -5,6 +5,18 @@ import { KeyPair } from '../../internal/KeyPair';
 import { Sig, defaultSigGuard, allowServiceFn } from '../../internal/builtins/Sig';
 import { toUint8Array } from 'js-base64';
 
+const a10b20 = `{
+    "a": 10,
+    "b": 20
+}`;
+
+const oneTwoThreeFour = `[
+    1,
+    2,
+    3,
+    4
+]`;
+
 describe('Tests for default handler', () => {
     // prettier-ignore
     each`
@@ -49,6 +61,10 @@ describe('Tests for default handler', () => {
   ${'peer'}     | ${'timeout'}         | ${[]}                           | ${1}    | ${'timeout accepts exactly two arguments: timeout duration in ms and a message string'}}
   ${'peer'}     | ${'timeout'}         | ${[200, 'test', 1]}             | ${1}    | ${'timeout accepts exactly two arguments: timeout duration in ms and a message string'}}
 
+  ${'debug'}    | ${'stringify'}       | ${[]}                           | ${0}    | ${'"<empty argument list>"'}}
+  ${'debug'}    | ${'stringify'}       | ${[{a: 10, b: 20}]}             | ${0}    | ${a10b20}}
+  ${'debug'}    | ${'stringify'}       | ${[1, 2, 3, 4]}                 | ${0}    | ${oneTwoThreeFour}}
+  
   `.test(
         //
         '$fnName with $args expected retcode: $retCode and result: $result',

src/internal/builtins/common.ts

@@ -18,6 +18,7 @@ import { CallServiceResult } from '@fluencelabs/avm-runner-interface';
 import { encode, decode } from 'bs58';
 import { sha256 } from 'multiformats/hashes/sha2';
 import { ResultCodes } from '../commonTypes';
+import { jsonify } from '../utils'
 import Buffer from '../Buffer';
 
 const success = (result: any): CallServiceResult => {
@@ -128,6 +129,22 @@ export const builtInServices = {
         },
     },
 
+    debug: {
+        stringify: (req) => {
+            let out;
+
+            if (req.args.length === 0) {
+                out = '<empty argument list>';
+            } else if (req.args.length === 1) {
+                out = req.args[0];
+            } else {
+                out = req.args;
+            }
+
+            return success(jsonify(out));
+        },
+    },
+
     peer: {
         timeout: (req) => {
             if (req.args.length !== 2) {