Add example helpers

src/helpers/echo.js

@@ -0,0 +1,3 @@
+module.exports = async (node, repeat = 1) => {
+  return { type: 'string', value: node.value.repeat(repeat) }
+}

src/helpers/formatDate.js

@@ -0,0 +1,3 @@
+module.exports = async (timestamp, format='MM-DD-YYYY') => {
+  return { type: 'string', value: timestamp } // TODO
+}

src/helpers/index.js

@@ -0,0 +1,17 @@
+const formatDate = require('./formatDate')
+const echo = require('./echo')
+
+module.exports = {
+  helpers: {
+    formatDate,
+    echo,
+  },
+
+  exists (helper) {
+    return !!this.helpers[helper]
+  },
+
+  execute (helper, inputs) {
+    return this.helpers[helper](...inputs)
+  }
+}

test/examples/examples.js

@@ -27,6 +27,13 @@ const bytes32 = (value) => ({
   value
 })
 
+const helperCases = [
+  [{
+    source: 'helper `@echo(@echo(\'hi\', 2), 9 / 3)`',
+    bindings: { }
+  }, 'helper hihihihihihi'],
+]
+
 const cases = [
   // Bindings
   [{
@@ -108,7 +115,9 @@ const cases = [
   [{
     source: '`_bool ? \'h\' + _var + \'o\' : \'damn\'`',
     bindings: { _bool: bool(true), _var: string('ell') }
-  }, 'hello']
+  }, 'hello'],
+
+  ...helperCases,
 ]
 
 for (let [input, expected] of cases) {