HP smart contract nodejs library. (#101)

examples/nodejs_contract/echo_contract.js

@@ -0,0 +1,30 @@
+const { HotPocketContract } = require("./hp-contract-lib");
+const fs = require('fs');
+
+const hpc = new HotPocketContract();
+
+//console.log("===Echo contract started===");
+
+// We just save execution timestamp as an example state file change.
+if (!hpc.readonly)
+    fs.appendFileSync("exects.txt", "ts:" + hpc.timestamp + "\n");
+
+Object.keys(hpc.users).forEach(function (key) {
+
+    const user = hpc.users[key];
+    const inputBuf = user.readInput();
+    if (inputBuf) {
+        const userInput = inputBuf.toString("utf8");
+
+        // Append user input to a state file if not in read only mode.
+        if (!hpc.readonly)
+            fs.appendFileSync("userinputs.txt", userInput + "\n");
+
+        if (userInput == "ts")
+            user.sendOutput(fs.readFileSync("exects.txt"));
+        else
+            user.sendOutput("Echoing: " + userInput);
+    }
+});
+
+//console.log("===Echo contract ended===");