Support basic query operations without eval

erithmetic · erithmetic · commit 79ce2e1a6d11 · 2011-10-07T11:45:28.000-04:00
diff --git a/lib/environment.js b/lib/environment.js
@@ -111,12 +111,74 @@ Environment.prototype.slice = function(segment, expression, object, path) {
    }
 };
 
-Environment.prototype.match = function(segment, _v, _vname) {
-   try {
-     var $ = this.jsonObject;
-     return _v && eval(segment.replace(/@/g, "_v"));
-   }
-   catch(e) {
-     throw new SyntaxError("jsonPath: " + e.message + ": " + segment.replace(/@/g, "_v").replace(/\^/g, "_a"));
-   }
+Environment.prototype.match = function(expression, object, _vname) {
+  if(object === null) return object;
+
+  if(/[>=<]/.test(expression))
+    return this.compareValue(expression, object);
+  else if(/[-+*\/]/.test(expression))
+    return this.computeValue(expression, object);
+  else if(/\./.test(expression))
+    return this.getProperty(expression, object);
+  else
+    throw new SyntaxError("jsonPath: invalid query syntax: " + expression);
+};
+
+Environment.prototype.compareValue = function(expression, object) {
+  return this.operate(object, expression, '>=<');
+};
+
+Environment.prototype.getProperty = function(expression, object) {
+  var parts = expression.match(/\.([^\s]+)/);
+  var rhs;
+  try {
+    rhs = JSON.parse('"' + parts[1] + '"');
+  }
+  catch(e) {
+    throw new SyntaxError("jsonPath: invalid property name: " + parts[1]);
+  }
+  return object[rhs];
+};
+
+Environment.prototype.getValue = function(expression) {
+  try {
+    return JSON.parse(expression);
+  }
+  catch(e) {
+    throw new SyntaxError("jsonPath: invalid right-hand-side value: " + expression);
+  }
+};
+
+Environment.prototype.computeValue = function(expression, object) {
+  return this.operate(object, expression, '-+*/');
+};
+
+Environment.prototype.operate = function(object, expression, operators) {
+  var regex = new RegExp("([^\(\)" + operators + "]+)([" + operators + "]+)([^\(\)]+)");
+  var parts = expression.match(regex);
+  var lhs = this.getProperty(parts[1], object);
+  var rhs = this.getValue(parts[3]);
+
+  switch(parts[2]) {
+  case '==':
+    return lhs == rhs;
+  case '>=':
+    return lhs >= rhs;
+  case '<=':
+    return lhs <= rhs;
+  case '>':
+    return lhs > rhs;
+  case '<':
+    return lhs < rhs;
+  case '-':
+    return lhs - rhs;
+  case '+':
+    return lhs + rhs;
+  case '*':
+    return lhs * rhs;
+  case '/':
+    return lhs / rhs;
+  default:
+    throw new SyntaxError("jsonPath: invalid query syntax: " + expression);
+  }
 };
diff --git a/test/environment-test.js b/test/environment-test.js
@@ -0,0 +1,42 @@
+var assert = require('assert'),
+    vows = require('vows'),
+    Environment = require("../lib/environment");
+
+vows.describe('JSONPath').addBatch({
+  '#match': {
+    topic: new Environment({}, '', {}),
+
+    'matches (@.length-1)': function(env) {
+      var obj = [1,2,3];
+      assert.equal(env.match('(@.length-1)', obj), 2);
+    },
+    'matches @.isbn': function(env) {
+      var obj = { isbn: 'abc123' };
+      assert.equal(env.match('@.isbn', obj), 'abc123');
+    },
+    'matches @.price<10 true': function(env) {
+      var obj = { price: 5 };
+      assert.isTrue(env.match('@.price<10', obj));
+    },
+    'matches @.price<10 false': function(env) {
+      var obj = { price: 10 };
+      assert.isFalse(env.match('@.price<10', obj));
+    },
+    'matches @.price==10 true': function(env) {
+      var obj = { price: 10 };
+      assert.isTrue(env.match('@.price==10', obj));
+    },
+    'matches @.price==10 false': function(env) {
+      var obj = { price: 11 };
+      assert.isFalse(env.match('@.price==10', obj));
+    },
+    'returns null if there is nothing to match against': function(env) {
+      assert.isNull(env.match('something', null));
+    },
+    'throws a syntax error for invalid statements': function(env) {
+      assert.throws(function() {
+        env.match('oogabooga', {});
+      });
+    }
+  }
+}).export(module);
