From 1050b712bbf36550f6cfbad4ac186d6511aa1eae Mon Sep 17 00:00:00 2001
From: Dana Sulit <dana.sulit@mapbox.com>
Date: Mon, 30 Oct 2017 11:45:25 -0400
Subject: [PATCH] Start writing expressions with jsep

---
 package-lock.json              |  5 +++++
 package.json                   |  3 +++
 src/ast-to-expression.js       | 11 +++++++++++
 src/index.js                   |  5 -----
 src/string-to-ast.js           |  7 +++++++
 test/ast-to-expression.test.js | 24 ++++++++++++++++++++++++
 test/index.test.js             |  7 -------
 test/string-to-ast.test.js     | 23 +++++++++++++++++++++++
 8 files changed, 73 insertions(+), 12 deletions(-)
 create mode 100644 src/ast-to-expression.js
 delete mode 100644 src/index.js
 create mode 100644 src/string-to-ast.js
 create mode 100644 test/ast-to-expression.test.js
 delete mode 100644 test/index.test.js
 create mode 100644 test/string-to-ast.test.js

diff --git a/package-lock.json b/package-lock.json
index b2b2214..16ab23d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -3785,6 +3785,11 @@
         }
       }
     },
+    "jsep": {
+      "version": "0.3.2",
+      "resolved": "https://registry.npmjs.org/jsep/-/jsep-0.3.2.tgz",
+      "integrity": "sha512-b/QP7Apx3EEvFk5/O+bp8BmMP97EypcxqTXWs8nK+Mr9DKhxLX/EWlxERtCZ7mwWIssnOLGCGMoJ08oMiwrjIw=="
+    },
     "jsesc": {
       "version": "1.3.0",
       "resolved": "https://registry.npmjs.org/jsesc/-/jsesc-1.3.0.tgz",
diff --git a/package.json b/package.json
index b076a54..992d68b 100644
--- a/package.json
+++ b/package.json
@@ -46,5 +46,8 @@
     "jest": "^21.2.1",
     "lint-staged": "^4.3.0",
     "prettier": "^1.7.4"
+  },
+  "dependencies": {
+    "jsep": "^0.3.2"
   }
 }
diff --git a/src/ast-to-expression.js b/src/ast-to-expression.js
new file mode 100644
index 0000000..21fcc1a
--- /dev/null
+++ b/src/ast-to-expression.js
@@ -0,0 +1,11 @@
+function astToExpression(input) {
+  if (input.value) return input.value;
+  if (input.type === 'BinaryExpression') {
+    const left = astToExpression(input.left);
+    const right = astToExpression(input.right);
+
+    return [input.operator, left, right];
+  }
+}
+
+export default astToExpression;
diff --git a/src/index.js b/src/index.js
deleted file mode 100644
index 4b1a58c..0000000
--- a/src/index.js
+++ /dev/null
@@ -1,5 +0,0 @@
-function returnTrue() {
-  return true;
-}
-
-export default returnTrue;
diff --git a/src/string-to-ast.js b/src/string-to-ast.js
new file mode 100644
index 0000000..1fd6b73
--- /dev/null
+++ b/src/string-to-ast.js
@@ -0,0 +1,7 @@
+import jsep from 'jsep';
+
+function stringToAst(input) {
+  return jsep(input);
+}
+
+export default stringToAst;
diff --git a/test/ast-to-expression.test.js b/test/ast-to-expression.test.js
new file mode 100644
index 0000000..0fa078e
--- /dev/null
+++ b/test/ast-to-expression.test.js
@@ -0,0 +1,24 @@
+import stringToAst from '../src/string-to-ast';
+import astToExpression from '../src/ast-to-expression';
+
+describe('astToExpression', () => {
+  test('3', () => {
+    const actual = astToExpression(stringToAst('3'));
+    expect(actual).toBe(3);
+  });
+
+  test('3 + 4', () => {
+    const actual = astToExpression(stringToAst('3 + 4'));
+    expect(actual).toEqual(['+', 3, 4]);
+  });
+
+  test('(3 + 4) / 7', () => {
+    const actual = astToExpression(stringToAst('(3 + 4) / 7'));
+    expect(actual).toEqual(['/', ['+', 3, 4], 7]);
+  });
+
+  test('((3 + 4) * 2) / 7', () => {
+    const actual = astToExpression(stringToAst('((3 + 4) * 2) / 7'));
+    expect(actual).toEqual(['/', ['*', ['+', 3, 4], 2], 7]);
+  });
+});
diff --git a/test/index.test.js b/test/index.test.js
deleted file mode 100644
index 1dc338b..0000000
--- a/test/index.test.js
+++ /dev/null
@@ -1,7 +0,0 @@
-import returnTrue from '../src/index';
-
-describe('returnTrue', function() {
-  test('returns true', function() {
-    expect(returnTrue()).toBe(true);
-  });
-});
diff --git a/test/string-to-ast.test.js b/test/string-to-ast.test.js
new file mode 100644
index 0000000..ca47638
--- /dev/null
+++ b/test/string-to-ast.test.js
@@ -0,0 +1,23 @@
+import stringToAst from '../src/string-to-ast';
+
+describe('stringToAst', () => {
+  test('3 + 4', () => {
+    const actual = stringToAst('3 + 4');
+    const output = {
+      type: 'BinaryExpression',
+      operator: '+',
+      left: {
+        type: 'Literal',
+        value: 3,
+        raw: '3'
+      },
+      right: {
+        type: 'Literal',
+        value: 4,
+        raw: '4'
+      }
+    };
+
+    expect(actual).toEqual(output);
+  });
+});