feat: basic snake addon implementation

addon/atoms.js

@@ -1,6 +1,6 @@
 'use strict';
 
-var atoms = {
+var atoms = exports.atoms = {
     d:      'display',
 
     mar:    'margin',

addon/snake.js

@@ -0,0 +1,75 @@
+'use strict';
+
+var atoms = require('./atoms').atoms;
+
+var createSnake = function (renderer, rules) {
+    rules = rules || {};
+
+    var defaultRules = renderer.assign({}, atoms, {
+        bgWhite: function () {
+            defaultRules.bg.call(this, '#fff');
+        },
+
+        bgBlack: function () {
+            defaultRules.bg.call(this, '#000');
+        },
+    });
+
+    rules = renderer.assign({}, defaultRules, rules);
+
+    var snake = {
+        start: function () {
+            var instance = Object.create(snake);
+
+            instance.obj = {};
+            instance.toString = function () {
+                return renderer.cache(instance.obj);
+            };
+
+            return instance;
+        }
+    };
+
+    var onRule = function (name) {
+        var rule = rules[name];
+
+        if (typeof rule === 'function') {
+            if (!rule.length) {
+                Object.defineProperty(snake, name, {
+                    get: function () {
+                        rule.call(this.obj);
+                        return this;
+                    }
+                });
+            } else {
+                snake[name] = function () {
+                    rule.apply(this.obj, arguments);
+                    return this;
+                };
+            }
+        } else {
+            snake[name] = function (value) {
+                this.obj['' + rule] = value;
+                return this;
+            };
+        }
+    };
+
+    for (var name in rules) onRule(name);
+
+    return snake;
+};
+
+exports.addon = function (renderer) {
+    if (process.env.NODE_ENV !== 'production') {
+        require('./__dev__/warnOnMissingDependencies')('sheet', renderer, ['cache']);
+    }
+
+    var snake = createSnake(renderer);
+
+    Object.defineProperty(renderer, 's', {
+        get: function () {
+            return snake.start();
+        }
+    });
+};